Rework/update ARM semihosting

In 2016, ARM released the second edition of the semihosting specs
("Semihosting for AArch32 and AArch64"), adding support for 64-bits.

To ease the reuse of the semihosting logic for other platforms
(like RISC-V), the semihosting code was isolated from the ARM
target and updated to the latest specs.

The new code is already in use since January (in GNU MCU Eclipse
OpenOCD) and no problems were reported, neither for ARM nor for
RISC-V targets, after more than 7K downloads.

The 2 new files were formatted with uncrustify.

Change-Id: Ie84dbd86a547323bb8a5d24eab68fc7dad013d96
Signed-off-by: Liviu Ionescu <ilg@livius.net>
Reviewed-on: http://openocd.zylin.com/4518
Tested-by: jenkins
Reviewed-by: Matthias Welwarsky <matthias@welwarsky.de>

12 files changed, 1871 insertions, 747 deletions

diff --git a/src/server/gdb_server.c b/src/server/gdb_server.c
index d329bfe..f54db9e 100644
--- a/src/server/gdb_server.c
+++ b/src/server/gdb_server.c
@@ -793,64 +793,64 @@ static void gdb_fileio_reply(struct target *target, struct connection *connectio
 	bool program_exited = false;
 
 	if (strcmp(target->fileio_info->identifier, "open") == 0)
-		sprintf(fileio_command, "F%s,%" PRIx32 "/%" PRIx32 ",%" PRIx32 ",%" PRIx32, target->fileio_info->identifier,
+		sprintf(fileio_command, "F%s,%" PRIx64 "/%" PRIx64 ",%" PRIx64 ",%" PRIx64, target->fileio_info->identifier,
 				target->fileio_info->param_1,
 				target->fileio_info->param_2,
 				target->fileio_info->param_3,
 				target->fileio_info->param_4);
 	else if (strcmp(target->fileio_info->identifier, "close") == 0)
-		sprintf(fileio_command, "F%s,%" PRIx32, target->fileio_info->identifier,
+		sprintf(fileio_command, "F%s,%" PRIx64, target->fileio_info->identifier,
 				target->fileio_info->param_1);
 	else if (strcmp(target->fileio_info->identifier, "read") == 0)
-		sprintf(fileio_command, "F%s,%" PRIx32 ",%" PRIx32 ",%" PRIx32, target->fileio_info->identifier,
+		sprintf(fileio_command, "F%s,%" PRIx64 ",%" PRIx64 ",%" PRIx64, target->fileio_info->identifier,
 				target->fileio_info->param_1,
 				target->fileio_info->param_2,
 				target->fileio_info->param_3);
 	else if (strcmp(target->fileio_info->identifier, "write") == 0)
-		sprintf(fileio_command, "F%s,%" PRIx32 ",%" PRIx32 ",%" PRIx32, target->fileio_info->identifier,
+		sprintf(fileio_command, "F%s,%" PRIx64 ",%" PRIx64 ",%" PRIx64, target->fileio_info->identifier,
 				target->fileio_info->param_1,
 				target->fileio_info->param_2,
 				target->fileio_info->param_3);
 	else if (strcmp(target->fileio_info->identifier, "lseek") == 0)
-		sprintf(fileio_command, "F%s,%" PRIx32 ",%" PRIx32 ",%" PRIx32, target->fileio_info->identifier,
+		sprintf(fileio_command, "F%s,%" PRIx64 ",%" PRIx64 ",%" PRIx64, target->fileio_info->identifier,
 				target->fileio_info->param_1,
 				target->fileio_info->param_2,
 				target->fileio_info->param_3);
 	else if (strcmp(target->fileio_info->identifier, "rename") == 0)
-		sprintf(fileio_command, "F%s,%" PRIx32 "/%" PRIx32 ",%" PRIx32 "/%" PRIx32, target->fileio_info->identifier,
+		sprintf(fileio_command, "F%s,%" PRIx64 "/%" PRIx64 ",%" PRIx64 "/%" PRIx64, target->fileio_info->identifier,
 				target->fileio_info->param_1,
 				target->fileio_info->param_2,
 				target->fileio_info->param_3,
 				target->fileio_info->param_4);
 	else if (strcmp(target->fileio_info->identifier, "unlink") == 0)
-		sprintf(fileio_command, "F%s,%" PRIx32 "/%" PRIx32, target->fileio_info->identifier,
+		sprintf(fileio_command, "F%s,%" PRIx64 "/%" PRIx64, target->fileio_info->identifier,
 				target->fileio_info->param_1,
 				target->fileio_info->param_2);
 	else if (strcmp(target->fileio_info->identifier, "stat") == 0)
-		sprintf(fileio_command, "F%s,%" PRIx32 "/%" PRIx32 ",%" PRIx32, target->fileio_info->identifier,
+		sprintf(fileio_command, "F%s,%" PRIx64 "/%" PRIx64 ",%" PRIx64, target->fileio_info->identifier,
 				target->fileio_info->param_1,
 				target->fileio_info->param_2,
 				target->fileio_info->param_3);
 	else if (strcmp(target->fileio_info->identifier, "fstat") == 0)
-		sprintf(fileio_command, "F%s,%" PRIx32 ",%" PRIx32, target->fileio_info->identifier,
+		sprintf(fileio_command, "F%s,%" PRIx64 ",%" PRIx64, target->fileio_info->identifier,
 				target->fileio_info->param_1,
 				target->fileio_info->param_2);
 	else if (strcmp(target->fileio_info->identifier, "gettimeofday") == 0)
-		sprintf(fileio_command, "F%s,%" PRIx32 ",%" PRIx32, target->fileio_info->identifier,
+		sprintf(fileio_command, "F%s,%" PRIx64 ",%" PRIx64, target->fileio_info->identifier,
 				target->fileio_info->param_1,
 				target->fileio_info->param_2);
 	else if (strcmp(target->fileio_info->identifier, "isatty") == 0)
-		sprintf(fileio_command, "F%s,%" PRIx32, target->fileio_info->identifier,
+		sprintf(fileio_command, "F%s,%" PRIx64, target->fileio_info->identifier,
 				target->fileio_info->param_1);
 	else if (strcmp(target->fileio_info->identifier, "system") == 0)
-		sprintf(fileio_command, "F%s,%" PRIx32 "/%" PRIx32, target->fileio_info->identifier,
+		sprintf(fileio_command, "F%s,%" PRIx64 "/%" PRIx64, target->fileio_info->identifier,
 				target->fileio_info->param_1,
 				target->fileio_info->param_2);
 	else if (strcmp(target->fileio_info->identifier, "exit") == 0) {
 		/* If target hits exit syscall, report to GDB the program is terminated.
 		 * In addition, let target run its own exit syscall handler. */
 		program_exited = true;
-		sprintf(fileio_command, "W%02" PRIx32, target->fileio_info->param_1);
+		sprintf(fileio_command, "W%02" PRIx64, target->fileio_info->param_1);
 	} else {
 		LOG_DEBUG("Unknown syscall: %s", target->fileio_info->identifier);
 
diff --git a/src/target/Makefile.am b/src/target/Makefile.am
index 206b281..fcc23ad 100644
--- a/src/target/Makefile.am
+++ b/src/target/Makefile.am
@@ -39,6 +39,7 @@ TARGET_CORE_SRC = \
 	%D%/target.c \
 	%D%/target_request.c \
 	%D%/testee.c \
+	%D%/semihosting_common.c \
 	%D%/smp.c
 
 ARMV4_5_SRC = \
@@ -210,6 +211,7 @@ INTEL_IA32_SRC = \
 	%D%/nds32_v3.h \
 	%D%/nds32_v3m.h \
 	%D%/nds32_aice.h \
+	%D%/semihosting_common.h \
 	%D%/stm8.h \
 	%D%/lakemont.h \
 	%D%/x86_32_common.h \
diff --git a/src/target/arm.h b/src/target/arm.h
index dd25d53..316ff9a 100644
--- a/src/target/arm.h
+++ b/src/target/arm.h
@@ -8,6 +8,9 @@
  * Copyright (C) 2009 by Øyvind Harboe
  * oyvind.harboe@zylin.com
  *
+ * Copyright (C) 2018 by Liviu Ionescu
+ *   <ilg@livius.net>
+ *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
  * the Free Software Foundation; either version 2 of the License, or
@@ -28,7 +31,6 @@
 #include <helper/command.h>
 #include "target.h"
 
-
 /**
  * @file
  * Holds the interface to ARM cores.
@@ -181,32 +183,11 @@ struct arm {
 	/** Flag reporting armv6m based core. */
 	bool is_armv6m;
 
-	/** Flag reporting whether semihosting is active. */
-	bool is_semihosting;
-
-	/** Flag reporting whether semihosting fileio is active. */
-	bool is_semihosting_fileio;
-
-	/** Flag reporting whether semihosting fileio operation is active. */
-	bool semihosting_hit_fileio;
-
 	/** Floating point or VFP version, 0 if disabled. */
 	int arm_vfp_version;
 
-	/** Current semihosting operation. */
-	int semihosting_op;
-
-	/** Current semihosting result. */
-	int semihosting_result;
-
-	/** Value to be returned by semihosting SYS_ERRNO request. */
-	int semihosting_errno;
-
 	int (*setup_semihosting)(struct target *target, int enable);
 
-	/** Semihosting command line. */
-	char *semihosting_cmdline;
-
 	/** Backpointer to the target. */
 	struct target *target;
 
diff --git a/src/target/arm_semihosting.c b/src/target/arm_semihosting.c
index f31f901..57f3139 100644
--- a/src/target/arm_semihosting.c
+++ b/src/target/arm_semihosting.c
@@ -8,6 +8,9 @@
  *   Copyright (C) 2016 by Square, Inc.                                    *
  *   Steven Stallion <stallion@squareup.com>                               *
  *                                                                         *
+ *   Copyright (C) 2018 by Liviu Ionescu                                   *
+ *   <ilg@livius.net>                                                      *
+ *                                                                         *
  *   This program is free software; you can redistribute it and/or modify  *
  *   it under the terms of the GNU General Public License as published by  *
  *   the Free Software Foundation; either version 2 of the License, or     *
@@ -52,21 +55,6 @@
 #include <helper/log.h>
 #include <sys/stat.h>
 
-static const int open_modeflags[12] = {
-	O_RDONLY,
-	O_RDONLY | O_BINARY,
-	O_RDWR,
-	O_RDWR | O_BINARY,
-	O_WRONLY | O_CREAT | O_TRUNC,
-	O_WRONLY | O_CREAT | O_TRUNC | O_BINARY,
-	O_RDWR | O_CREAT | O_TRUNC,
-	O_RDWR | O_CREAT | O_TRUNC | O_BINARY,
-	O_WRONLY | O_CREAT | O_APPEND,
-	O_WRONLY | O_CREAT | O_APPEND | O_BINARY,
-	O_RDWR | O_CREAT | O_APPEND,
-	O_RDWR | O_CREAT | O_APPEND | O_BINARY
-};
-
 static int post_result(struct target *target)
 {
 	struct arm *arm = target_to_arm(target);
@@ -79,7 +67,7 @@ static int post_result(struct target *target)
 		uint32_t spsr;
 
 		/* return value in R0 */
-		buf_set_u32(arm->core_cache->reg_list[0].value, 0, 32, arm->semihosting_result);
+		buf_set_u32(arm->core_cache->reg_list[0].value, 0, 32, target->semihosting->result);
 		arm->core_cache->reg_list[0].dirty = 1;
 
 		/* LR --> PC */
@@ -105,523 +93,13 @@ static int post_result(struct target *target)
 		 * bkpt instruction */
 
 		/* return result in R0 */
-		buf_set_u32(arm->core_cache->reg_list[0].value, 0, 32, arm->semihosting_result);
+		buf_set_u32(arm->core_cache->reg_list[0].value, 0, 32, target->semihosting->result);
 		arm->core_cache->reg_list[0].dirty = 1;
 	}
 
 	return ERROR_OK;
 }
 
-static int do_semihosting(struct target *target)
-{
-	struct arm *arm = target_to_arm(target);
-	struct gdb_fileio_info *fileio_info = target->fileio_info;
-	uint32_t r0 = buf_get_u32(arm->core_cache->reg_list[0].value, 0, 32);
-	uint32_t r1 = buf_get_u32(arm->core_cache->reg_list[1].value, 0, 32);
-	uint8_t params[16];
-	int retval;
-
-	/*
-	 * TODO: lots of security issues are not considered yet, such as:
-	 * - no validation on target provided file descriptors
-	 * - no safety checks on opened/deleted/renamed file paths
-	 * Beware the target app you use this support with.
-	 *
-	 * TODO: unsupported semihosting fileio operations could be
-	 * implemented if we had a small working area at our disposal.
-	 */
-	switch ((arm->semihosting_op = r0)) {
-	case 0x01:	/* SYS_OPEN */
-		retval = target_read_memory(target, r1, 4, 3, params);
-		if (retval != ERROR_OK)
-			return retval;
-		else {
-			uint32_t a = target_buffer_get_u32(target, params+0);
-			uint32_t m = target_buffer_get_u32(target, params+4);
-			uint32_t l = target_buffer_get_u32(target, params+8);
-			uint8_t fn[256];
-			retval = target_read_memory(target, a, 1, l, fn);
-			if (retval != ERROR_OK)
-				return retval;
-			fn[l] = 0;
-			if (arm->is_semihosting_fileio) {
-				if (strcmp((char *)fn, ":tt") == 0)
-					arm->semihosting_result = 0;
-				else {
-					arm->semihosting_hit_fileio = true;
-					fileio_info->identifier = "open";
-					fileio_info->param_1 = a;
-					fileio_info->param_2 = l;
-					fileio_info->param_3 = open_modeflags[m];
-					fileio_info->param_4 = 0644;
-				}
-			} else {
-				if (l <= 255 && m <= 11) {
-					if (strcmp((char *)fn, ":tt") == 0) {
-						if (m < 4)
-							arm->semihosting_result = dup(STDIN_FILENO);
-						else
-							arm->semihosting_result = dup(STDOUT_FILENO);
-					} else {
-						/* cygwin requires the permission setting
-						 * otherwise it will fail to reopen a previously
-						 * written file */
-						arm->semihosting_result = open((char *)fn, open_modeflags[m], 0644);
-					}
-					arm->semihosting_errno =  errno;
-				} else {
-					arm->semihosting_result = -1;
-					arm->semihosting_errno = EINVAL;
-				}
-			}
-		}
-		break;
-
-	case 0x02:	/* SYS_CLOSE */
-		retval = target_read_memory(target, r1, 4, 1, params);
-		if (retval != ERROR_OK)
-			return retval;
-		else {
-			int fd = target_buffer_get_u32(target, params+0);
-			if (arm->is_semihosting_fileio) {
-				arm->semihosting_hit_fileio = true;
-				fileio_info->identifier = "close";
-				fileio_info->param_1 = fd;
-			} else {
-				arm->semihosting_result = close(fd);
-				arm->semihosting_errno = errno;
-			}
-		}
-		break;
-
-	case 0x03:	/* SYS_WRITEC */
-		if (arm->is_semihosting_fileio) {
-			arm->semihosting_hit_fileio = true;
-			fileio_info->identifier = "write";
-			fileio_info->param_1 = 1;
-			fileio_info->param_2 = r1;
-			fileio_info->param_3 = 1;
-		} else {
-			unsigned char c;
-			retval = target_read_memory(target, r1, 1, 1, &c);
-			if (retval != ERROR_OK)
-				return retval;
-			putchar(c);
-			arm->semihosting_result = 0;
-		}
-		break;
-
-	case 0x04:	/* SYS_WRITE0 */
-		if (arm->is_semihosting_fileio) {
-			size_t count = 0;
-			for (uint32_t a = r1;; a++) {
-				unsigned char c;
-				retval = target_read_memory(target, a, 1, 1, &c);
-				if (retval != ERROR_OK)
-					return retval;
-				if (c == '\0')
-					break;
-				count++;
-			}
-			arm->semihosting_hit_fileio = true;
-			fileio_info->identifier = "write";
-			fileio_info->param_1 = 1;
-			fileio_info->param_2 = r1;
-			fileio_info->param_3 = count;
-		} else {
-			do {
-				unsigned char c;
-				retval = target_read_memory(target, r1++, 1, 1, &c);
-				if (retval != ERROR_OK)
-					return retval;
-				if (!c)
-					break;
-				putchar(c);
-			} while (1);
-			arm->semihosting_result = 0;
-		}
-		break;
-
-	case 0x05:	/* SYS_WRITE */
-		retval = target_read_memory(target, r1, 4, 3, params);
-		if (retval != ERROR_OK)
-			return retval;
-		else {
-			int fd = target_buffer_get_u32(target, params+0);
-			uint32_t a = target_buffer_get_u32(target, params+4);
-			size_t l = target_buffer_get_u32(target, params+8);
-			if (arm->is_semihosting_fileio) {
-				arm->semihosting_hit_fileio = true;
-				fileio_info->identifier = "write";
-				fileio_info->param_1 = fd;
-				fileio_info->param_2 = a;
-				fileio_info->param_3 = l;
-			} else {
-				uint8_t *buf = malloc(l);
-				if (!buf) {
-					arm->semihosting_result = -1;
-					arm->semihosting_errno = ENOMEM;
-				} else {
-					retval = target_read_buffer(target, a, l, buf);
-					if (retval != ERROR_OK) {
-						free(buf);
-						return retval;
-					}
-					arm->semihosting_result = write(fd, buf, l);
-					arm->semihosting_errno = errno;
-					if (arm->semihosting_result >= 0)
-						arm->semihosting_result = l - arm->semihosting_result;
-					free(buf);
-				}
-			}
-		}
-		break;
-
-	case 0x06:	/* SYS_READ */
-		retval = target_read_memory(target, r1, 4, 3, params);
-		if (retval != ERROR_OK)
-			return retval;
-		else {
-			int fd = target_buffer_get_u32(target, params+0);
-			uint32_t a = target_buffer_get_u32(target, params+4);
-			ssize_t l = target_buffer_get_u32(target, params+8);
-			if (arm->is_semihosting_fileio) {
-				arm->semihosting_hit_fileio = true;
-				fileio_info->identifier = "read";
-				fileio_info->param_1 = fd;
-				fileio_info->param_2 = a;
-				fileio_info->param_3 = l;
-			} else {
-				uint8_t *buf = malloc(l);
-				if (!buf) {
-					arm->semihosting_result = -1;
-					arm->semihosting_errno = ENOMEM;
-				} else {
-					arm->semihosting_result = read(fd, buf, l);
-					arm->semihosting_errno = errno;
-					if (arm->semihosting_result >= 0) {
-						retval = target_write_buffer(target, a, arm->semihosting_result, buf);
-						if (retval != ERROR_OK) {
-							free(buf);
-							return retval;
-						}
-						arm->semihosting_result = l - arm->semihosting_result;
-					}
-					free(buf);
-				}
-			}
-		}
-		break;
-
-	case 0x07:	/* SYS_READC */
-		if (arm->is_semihosting_fileio) {
-			LOG_ERROR("SYS_READC not supported by semihosting fileio");
-			return ERROR_FAIL;
-		}
-		arm->semihosting_result = getchar();
-		break;
-
-	case 0x08:	/* SYS_ISERROR */
-		retval = target_read_memory(target, r1, 4, 1, params);
-		if (retval != ERROR_OK)
-			return retval;
-		arm->semihosting_result = (target_buffer_get_u32(target, params+0) != 0);
-		break;
-
-	case 0x09:	/* SYS_ISTTY */
-		if (arm->is_semihosting_fileio) {
-			arm->semihosting_hit_fileio = true;
-			fileio_info->identifier = "isatty";
-			fileio_info->param_1 = r1;
-		} else {
-			retval = target_read_memory(target, r1, 4, 1, params);
-			if (retval != ERROR_OK)
-				return retval;
-			arm->semihosting_result = isatty(target_buffer_get_u32(target, params+0));
-		}
-		break;
-
-	case 0x0a:	/* SYS_SEEK */
-		retval = target_read_memory(target, r1, 4, 2, params);
-		if (retval != ERROR_OK)
-			return retval;
-		else {
-			int fd = target_buffer_get_u32(target, params+0);
-			off_t pos = target_buffer_get_u32(target, params+4);
-			if (arm->is_semihosting_fileio) {
-				arm->semihosting_hit_fileio = true;
-				fileio_info->identifier = "lseek";
-				fileio_info->param_1 = fd;
-				fileio_info->param_2 = pos;
-				fileio_info->param_3 = SEEK_SET;
-			} else {
-				arm->semihosting_result = lseek(fd, pos, SEEK_SET);
-				arm->semihosting_errno = errno;
-				if (arm->semihosting_result == pos)
-					arm->semihosting_result = 0;
-			}
-		}
-		break;
-
-	case 0x0c:	/* SYS_FLEN */
-		if (arm->is_semihosting_fileio) {
-			LOG_ERROR("SYS_FLEN not supported by semihosting fileio");
-			return ERROR_FAIL;
-		}
-		retval = target_read_memory(target, r1, 4, 1, params);
-		if (retval != ERROR_OK)
-			return retval;
-		else {
-			int fd = target_buffer_get_u32(target, params+0);
-			struct stat buf;
-			arm->semihosting_result = fstat(fd, &buf);
-			if (arm->semihosting_result == -1) {
-				arm->semihosting_errno = errno;
-				arm->semihosting_result = -1;
-				break;
-			}
-			arm->semihosting_result = buf.st_size;
-		}
-		break;
-
-	case 0x0e:	/* SYS_REMOVE */
-		retval = target_read_memory(target, r1, 4, 2, params);
-		if (retval != ERROR_OK)
-			return retval;
-		else {
-			uint32_t a = target_buffer_get_u32(target, params+0);
-			uint32_t l = target_buffer_get_u32(target, params+4);
-			if (arm->is_semihosting_fileio) {
-				arm->semihosting_hit_fileio = true;
-				fileio_info->identifier = "unlink";
-				fileio_info->param_1 = a;
-				fileio_info->param_2 = l;
-			} else {
-				if (l <= 255) {
-					uint8_t fn[256];
-					retval = target_read_memory(target, a, 1, l, fn);
-					if (retval != ERROR_OK)
-						return retval;
-					fn[l] = 0;
-					arm->semihosting_result = remove((char *)fn);
-					arm->semihosting_errno =  errno;
-				} else {
-					arm->semihosting_result = -1;
-					arm->semihosting_errno = EINVAL;
-				}
-			}
-		}
-		break;
-
-	case 0x0f:	/* SYS_RENAME */
-		retval = target_read_memory(target, r1, 4, 4, params);
-		if (retval != ERROR_OK)
-			return retval;
-		else {
-			uint32_t a1 = target_buffer_get_u32(target, params+0);
-			uint32_t l1 = target_buffer_get_u32(target, params+4);
-			uint32_t a2 = target_buffer_get_u32(target, params+8);
-			uint32_t l2 = target_buffer_get_u32(target, params+12);
-			if (arm->is_semihosting_fileio) {
-				arm->semihosting_hit_fileio = true;
-				fileio_info->identifier = "rename";
-				fileio_info->param_1 = a1;
-				fileio_info->param_2 = l1;
-				fileio_info->param_3 = a2;
-				fileio_info->param_4 = l2;
-			} else {
-				if (l1 <= 255 && l2 <= 255) {
-					uint8_t fn1[256], fn2[256];
-					retval = target_read_memory(target, a1, 1, l1, fn1);
-					if (retval != ERROR_OK)
-						return retval;
-					retval = target_read_memory(target, a2, 1, l2, fn2);
-					if (retval != ERROR_OK)
-						return retval;
-					fn1[l1] = 0;
-					fn2[l2] = 0;
-					arm->semihosting_result = rename((char *)fn1, (char *)fn2);
-					arm->semihosting_errno =  errno;
-				} else {
-					arm->semihosting_result = -1;
-					arm->semihosting_errno = EINVAL;
-				}
-			}
-		}
-		break;
-
-	case 0x11:	/* SYS_TIME */
-		arm->semihosting_result = time(NULL);
-		break;
-
-	case 0x13:	/* SYS_ERRNO */
-		arm->semihosting_result = arm->semihosting_errno;
-		break;
-
-	case 0x15:	/* SYS_GET_CMDLINE */
-		retval = target_read_memory(target, r1, 4, 2, params);
-		if (retval != ERROR_OK)
-			return retval;
-		else {
-			uint32_t a = target_buffer_get_u32(target, params+0);
-			uint32_t l = target_buffer_get_u32(target, params+4);
-			char *arg = arm->semihosting_cmdline != NULL ? arm->semihosting_cmdline : "";
-			uint32_t s = strlen(arg) + 1;
-			if (l < s)
-				arm->semihosting_result = -1;
-			else {
-				retval = target_write_buffer(target, a, s, (uint8_t *)arg);
-				if (retval != ERROR_OK)
-					return retval;
-				arm->semihosting_result = 0;
-			}
-		}
-		break;
-
-	case 0x16:	/* SYS_HEAPINFO */
-		retval = target_read_memory(target, r1, 4, 1, params);
-		if (retval != ERROR_OK)
-			return retval;
-		else {
-			uint32_t a = target_buffer_get_u32(target, params+0);
-			/* tell the remote we have no idea */
-			memset(params, 0, 4*4);
-			retval = target_write_memory(target, a, 4, 4, params);
-			if (retval != ERROR_OK)
-				return retval;
-			arm->semihosting_result = 0;
-		}
-		break;
-
-	case 0x18:	/* angel_SWIreason_ReportException */
-		switch (r1) {
-		case 0x20026:	/* ADP_Stopped_ApplicationExit */
-			fprintf(stderr, "semihosting: *** application exited ***\n");
-			break;
-		case 0x20000:	/* ADP_Stopped_BranchThroughZero */
-		case 0x20001:	/* ADP_Stopped_UndefinedInstr */
-		case 0x20002:	/* ADP_Stopped_SoftwareInterrupt */
-		case 0x20003:	/* ADP_Stopped_PrefetchAbort */
-		case 0x20004:	/* ADP_Stopped_DataAbort */
-		case 0x20005:	/* ADP_Stopped_AddressException */
-		case 0x20006:	/* ADP_Stopped_IRQ */
-		case 0x20007:	/* ADP_Stopped_FIQ */
-		case 0x20020:	/* ADP_Stopped_BreakPoint */
-		case 0x20021:	/* ADP_Stopped_WatchPoint */
-		case 0x20022:	/* ADP_Stopped_StepComplete */
-		case 0x20023:	/* ADP_Stopped_RunTimeErrorUnknown */
-		case 0x20024:	/* ADP_Stopped_InternalError */
-		case 0x20025:	/* ADP_Stopped_UserInterruption */
-		case 0x20027:	/* ADP_Stopped_StackOverflow */
-		case 0x20028:	/* ADP_Stopped_DivisionByZero */
-		case 0x20029:	/* ADP_Stopped_OSSpecific */
-		default:
-			fprintf(stderr, "semihosting: exception %#x\n",
-					(unsigned) r1);
-		}
-		return target_call_event_callbacks(target, TARGET_EVENT_HALTED);
-
-	case 0x12:	/* SYS_SYSTEM */
-		/* Provide SYS_SYSTEM functionality.  Uses the
-		 * libc system command, there may be a reason *NOT*
-		 * to use this, but as I can't think of one, I
-		 * implemented it this way.
-		 */
-		retval = target_read_memory(target, r1, 4, 2, params);
-		if (retval != ERROR_OK)
-			return retval;
-		else {
-			uint32_t len = target_buffer_get_u32(target, params+4);
-			uint32_t c_ptr = target_buffer_get_u32(target, params);
-			if (arm->is_semihosting_fileio) {
-				arm->semihosting_hit_fileio = true;
-				fileio_info->identifier = "system";
-				fileio_info->param_1 = c_ptr;
-				fileio_info->param_2 = len;
-			} else {
-				uint8_t cmd[256];
-				if (len > 255) {
-					arm->semihosting_result = -1;
-					arm->semihosting_errno = EINVAL;
-				} else {
-					memset(cmd, 0x0, 256);
-					retval = target_read_memory(target, c_ptr, 1, len, cmd);
-					if (retval != ERROR_OK)
-						return retval;
-					else
-						arm->semihosting_result = system((const char *)cmd);
-				}
-			}
-		}
-		break;
-	case 0x0d:	/* SYS_TMPNAM */
-	case 0x10:	/* SYS_CLOCK */
-	case 0x17:	/* angel_SWIreason_EnterSVC */
-	case 0x30:	/* SYS_ELAPSED */
-	case 0x31:	/* SYS_TICKFREQ */
-	default:
-		fprintf(stderr, "semihosting: unsupported call %#x\n",
-				(unsigned) r0);
-		arm->semihosting_result = -1;
-		arm->semihosting_errno = ENOTSUP;
-	}
-
-	return ERROR_OK;
-}
-
-static int get_gdb_fileio_info(struct target *target, struct gdb_fileio_info *fileio_info)
-{
-	struct arm *arm = target_to_arm(target);
-
-	/* To avoid uneccessary duplication, semihosting prepares the
-	 * fileio_info structure out-of-band when the target halts. See
-	 * do_semihosting for more detail.
-	 */
-	if (!arm->is_semihosting_fileio || !arm->semihosting_hit_fileio)
-		return ERROR_FAIL;
-
-	return ERROR_OK;
-}
-
-static int gdb_fileio_end(struct target *target, int result, int fileio_errno, bool ctrl_c)
-{
-	struct arm *arm = target_to_arm(target);
-	struct gdb_fileio_info *fileio_info = target->fileio_info;
-
-	/* clear pending status */
-	arm->semihosting_hit_fileio = false;
-
-	arm->semihosting_result = result;
-	arm->semihosting_errno = fileio_errno;
-
-	/* Some fileio results do not match up with what the semihosting
-	 * operation expects; for these operations, we munge the results
-	 * below:
-	 */
-	switch (arm->semihosting_op) {
-	case 0x05:	/* SYS_WRITE */
-		if (result < 0)
-			arm->semihosting_result = fileio_info->param_3;
-		else
-			arm->semihosting_result = 0;
-		break;
-
-	case 0x06:	/* SYS_READ */
-		if (result == (int)fileio_info->param_3)
-			arm->semihosting_result = 0;
-		if (result <= 0)
-			arm->semihosting_result = fileio_info->param_3;
-		break;
-
-	case 0x0a:	/* SYS_SEEK */
-		if (result > 0)
-			arm->semihosting_result = 0;
-		break;
-	}
-
-	return post_result(target);
-}
-
 /**
  * Initialize ARM semihosting support.
  *
@@ -630,14 +108,9 @@ static int gdb_fileio_end(struct target *target, int result, int fileio_errno, b
  */
 int arm_semihosting_init(struct target *target)
 {
-	target->fileio_info = malloc(sizeof(*target->fileio_info));
-	if (target->fileio_info == NULL) {
-		LOG_ERROR("out of memory");
-		return ERROR_FAIL;
-	}
-
-	target->type->get_gdb_fileio_info = get_gdb_fileio_info;
-	target->type->gdb_fileio_end = gdb_fileio_end;
+	struct arm *arm = target_to_arm(target);
+	assert(arm->setup_semihosting);
+	semihosting_common_init(target, arm->setup_semihosting, post_result);
 
 	return ERROR_OK;
 }
@@ -662,7 +135,11 @@ int arm_semihosting(struct target *target, int *retval)
 	uint32_t pc, lr, spsr;
 	struct reg *r;
 
-	if (!arm->is_semihosting)
+	struct semihosting *semihosting = target->semihosting;
+	if (!semihosting)
+		return 0;
+
+	if (!semihosting->is_active)
 		return 0;
 
 	if (is_arm7_9(target_to_arm7_9(target)) ||
@@ -766,10 +243,24 @@ int arm_semihosting(struct target *target, int *retval)
 	/* Perform semihosting if we are not waiting on a fileio
 	 * operation to complete.
 	 */
-	if (!arm->semihosting_hit_fileio) {
-		*retval = do_semihosting(target);
-		if (*retval != ERROR_OK) {
-			LOG_ERROR("Failed semihosting operation");
+	if (!semihosting->hit_fileio) {
+		/* TODO: update for 64-bits */
+		uint32_t r0 = buf_get_u32(arm->core_cache->reg_list[0].value, 0, 32);
+		uint32_t r1 = buf_get_u32(arm->core_cache->reg_list[1].value, 0, 32);
+
+		semihosting->op = r0;
+		semihosting->param = r1;
+		semihosting->word_size_bytes = 4;
+
+		/* Check for ARM operation numbers. */
+		if (0 <= semihosting->op && semihosting->op <= 0x31) {
+			*retval = semihosting_common(target);
+			if (*retval != ERROR_OK) {
+				LOG_ERROR("Failed semihosting operation");
+				return 0;
+			}
+		} else {
+			/* Unknown operation number, not a semihosting call. */
 			return 0;
 		}
 	}
@@ -777,13 +268,8 @@ int arm_semihosting(struct target *target, int *retval)
 	/* Post result to target if we are not waiting on a fileio
 	 * operation to complete:
 	 */
-	if (!arm->semihosting_hit_fileio) {
-		*retval = post_result(target);
-		if (*retval != ERROR_OK) {
-			LOG_ERROR("Failed to post semihosting result");
-			return 0;
-		}
-
+	if (semihosting->is_resumable && !semihosting->hit_fileio) {
+		/* Resume right after the BRK instruction. */
 		*retval = target_resume(target, 1, 0, 0, 0);
 		if (*retval != ERROR_OK) {
 			LOG_ERROR("Failed to resume target");
diff --git a/src/target/arm_semihosting.h b/src/target/arm_semihosting.h
index 011f19f..cf1f8de 100644
--- a/src/target/arm_semihosting.h
+++ b/src/target/arm_semihosting.h
@@ -19,6 +19,8 @@
 #ifndef OPENOCD_TARGET_ARM_SEMIHOSTING_H
 #define OPENOCD_TARGET_ARM_SEMIHOSTING_H
 
+#include "semihosting_common.h"
+
 int arm_semihosting_init(struct target *target);
 int arm_semihosting(struct target *target, int *retval);
 
diff --git a/src/target/armv4_5.c b/src/target/armv4_5.c
index 06994ca..5ee8ead 100644
--- a/src/target/armv4_5.c
+++ b/src/target/armv4_5.c
@@ -8,6 +8,9 @@
  *   Copyright (C) 2008 by Oyvind Harboe                                   *
  *   oyvind.harboe@zylin.com                                               *
  *                                                                         *
+ *   Copyright (C) 2018 by Liviu Ionescu                                   *
+ *   <ilg@livius.net>                                                      *
+ *                                                                         *
  *   This program is free software; you can redistribute it and/or modify  *
  *   it under the terms of the GNU General Public License as published by  *
  *   the Free Software Foundation; either version 2 of the License, or     *
@@ -34,6 +37,7 @@
 #include <helper/binarybuffer.h>
 #include "algorithm.h"
 #include "register.h"
+#include "semihosting_common.h"
 
 /* offsets into armv4_5 core register cache */
 enum {
@@ -748,7 +752,7 @@ int arm_arch_state(struct target *target)
 	}
 
 	/* avoid filling log waiting for fileio reply */
-	if (arm->semihosting_hit_fileio)
+	if (target->semihosting->hit_fileio)
 		return ERROR_OK;
 
 	LOG_USER("target halted in %s state due to %s, current mode: %s\n"
@@ -758,8 +762,8 @@ int arm_arch_state(struct target *target)
 		arm_mode_name(arm->core_mode),
 		buf_get_u32(arm->cpsr->value, 0, 32),
 		buf_get_u32(arm->pc->value, 0, 32),
-		arm->is_semihosting ? ", semihosting" : "",
-		arm->is_semihosting_fileio ? " fileio" : "");
+		target->semihosting->is_active ? ", semihosting" : "",
+		target->semihosting->is_fileio ? " fileio" : "");
 
 	return ERROR_OK;
 }
@@ -1094,119 +1098,10 @@ static int jim_mcrmrc(Jim_Interp *interp, int argc, Jim_Obj * const *argv)
 	return JIM_OK;
 }
 
-COMMAND_HANDLER(handle_arm_semihosting_command)
-{
-	struct target *target = get_current_target(CMD_CTX);
-
-	if (target == NULL) {
-		LOG_ERROR("No target selected");
-		return ERROR_FAIL;
-	}
-
-	struct arm *arm = target_to_arm(target);
-
-	if (!is_arm(arm)) {
-		command_print(CMD_CTX, "current target isn't an ARM");
-		return ERROR_FAIL;
-	}
-
-	if (!arm->setup_semihosting) {
-		command_print(CMD_CTX, "semihosting not supported for current target");
-		return ERROR_FAIL;
-	}
-
-	if (CMD_ARGC > 0) {
-		int semihosting;
-
-		COMMAND_PARSE_ENABLE(CMD_ARGV[0], semihosting);
-
-		if (!target_was_examined(target)) {
-			LOG_ERROR("Target not examined yet");
-			return ERROR_FAIL;
-		}
-
-		if (arm->setup_semihosting(target, semihosting) != ERROR_OK) {
-			LOG_ERROR("Failed to Configure semihosting");
-			return ERROR_FAIL;
-		}
-
-		/* FIXME never let that "catch" be dropped! */
-		arm->is_semihosting = semihosting;
-	}
-
-	command_print(CMD_CTX, "semihosting is %s",
-		arm->is_semihosting
-		? "enabled" : "disabled");
-
-	return ERROR_OK;
-}
-
-COMMAND_HANDLER(handle_arm_semihosting_fileio_command)
-{
-	struct target *target = get_current_target(CMD_CTX);
-
-	if (target == NULL) {
-		LOG_ERROR("No target selected");
-		return ERROR_FAIL;
-	}
-
-	struct arm *arm = target_to_arm(target);
-
-	if (!is_arm(arm)) {
-		command_print(CMD_CTX, "current target isn't an ARM");
-		return ERROR_FAIL;
-	}
-
-	if (!arm->is_semihosting) {
-		command_print(CMD_CTX, "semihosting is not enabled");
-		return ERROR_FAIL;
-	}
-
-	if (CMD_ARGC > 0)
-		COMMAND_PARSE_ENABLE(CMD_ARGV[0], arm->is_semihosting_fileio);
-
-	command_print(CMD_CTX, "semihosting fileio is %s",
-		arm->is_semihosting_fileio
-		? "enabled" : "disabled");
-
-	return ERROR_OK;
-}
-
-COMMAND_HANDLER(handle_arm_semihosting_cmdline)
-{
-	struct target *target = get_current_target(CMD_CTX);
-	unsigned int i;
-
-	if (target == NULL) {
-		LOG_ERROR("No target selected");
-		return ERROR_FAIL;
-	}
-
-	struct arm *arm = target_to_arm(target);
-
-	if (!is_arm(arm)) {
-		command_print(CMD_CTX, "current target isn't an ARM");
-		return ERROR_FAIL;
-	}
-
-	if (!arm->setup_semihosting) {
-		command_print(CMD_CTX, "semihosting not supported for current target");
-		return ERROR_FAIL;
-	}
-
-	free(arm->semihosting_cmdline);
-	arm->semihosting_cmdline = CMD_ARGC > 0 ? strdup(CMD_ARGV[0]) : NULL;
-
-	for (i = 1; i < CMD_ARGC; i++) {
-		char *cmdline = alloc_printf("%s %s", arm->semihosting_cmdline, CMD_ARGV[i]);
-		if (cmdline == NULL)
-			break;
-		free(arm->semihosting_cmdline);
-		arm->semihosting_cmdline = cmdline;
-	}
-
-	return ERROR_OK;
-}
+extern __COMMAND_HANDLER(handle_common_semihosting_command);
+extern __COMMAND_HANDLER(handle_common_semihosting_fileio_command);
+extern __COMMAND_HANDLER(handle_common_semihosting_resumable_exit_command);
+extern __COMMAND_HANDLER(handle_common_semihosting_cmdline);
 
 static const struct command_registration arm_exec_command_handlers[] = {
 	{
@@ -1245,26 +1140,32 @@ static const struct command_registration arm_exec_command_handlers[] = {
 	},
 	{
 		"semihosting",
-		.handler = handle_arm_semihosting_command,
+		.handler = handle_common_semihosting_command,
 		.mode = COMMAND_EXEC,
 		.usage = "['enable'|'disable']",
 		.help = "activate support for semihosting operations",
 	},
 	{
 		"semihosting_cmdline",
-		.handler = handle_arm_semihosting_cmdline,
+		.handler = handle_common_semihosting_cmdline,
 		.mode = COMMAND_EXEC,
 		.usage = "arguments",
 		.help = "command line arguments to be passed to program",
 	},
 	{
 		"semihosting_fileio",
-		.handler = handle_arm_semihosting_fileio_command,
+		.handler = handle_common_semihosting_fileio_command,
 		.mode = COMMAND_EXEC,
 		.usage = "['enable'|'disable']",
 		.help = "activate support for semihosting fileio operations",
 	},
-
+	{
+		"semihosting_resexit",
+		.handler = handle_common_semihosting_resumable_exit_command,
+		.mode = COMMAND_EXEC,
+		.usage = "['enable'|'disable']",
+		.help = "activate support for semihosting resumable exit",
+	},
 	COMMAND_REGISTRATION_DONE
 };
 const struct command_registration arm_command_handlers[] = {
diff --git a/src/target/armv7m.c b/src/target/armv7m.c
index 7b7893f..1b4e5b1 100644
--- a/src/target/armv7m.c
+++ b/src/target/armv7m.c
@@ -11,6 +11,9 @@
  *   Copyright (C) 2007,2008 Øyvind Harboe                                 *
  *   oyvind.harboe@zylin.com                                               *
  *                                                                         *
+ *   Copyright (C) 2018 by Liviu Ionescu                                   *
+ *   <ilg@livius.net>                                                      *
+ *                                                                         *
  *   This program is free software; you can redistribute it and/or modify  *
  *   it under the terms of the GNU General Public License as published by  *
  *   the Free Software Foundation; either version 2 of the License, or     *
@@ -37,6 +40,7 @@
 #include "armv7m.h"
 #include "algorithm.h"
 #include "register.h"
+#include "semihosting_common.h"
 
 #if 0
 #define _DEBUG_INSTRUCTION_EXECUTION_
@@ -537,7 +541,7 @@ int armv7m_arch_state(struct target *target)
 	uint32_t ctrl, sp;
 
 	/* avoid filling log waiting for fileio reply */
-	if (arm->semihosting_hit_fileio)
+	if (target->semihosting->hit_fileio)
 		return ERROR_OK;
 
 	ctrl = buf_get_u32(arm->core_cache->reg_list[ARMV7M_CONTROL].value, 0, 32);
@@ -552,8 +556,8 @@ int armv7m_arch_state(struct target *target)
 		buf_get_u32(arm->pc->value, 0, 32),
 		(ctrl & 0x02) ? 'p' : 'm',
 		sp,
-		arm->is_semihosting ? ", semihosting" : "",
-		arm->is_semihosting_fileio ? " fileio" : "");
+		target->semihosting->is_active ? ", semihosting" : "",
+		target->semihosting->is_fileio ? " fileio" : "");
 
 	return ERROR_OK;
 }
diff --git a/src/target/armv8.c b/src/target/armv8.c
index 82b2b24..20f2b67 100644
--- a/src/target/armv8.c
+++ b/src/target/armv8.c
@@ -1,6 +1,9 @@
 /***************************************************************************
  *   Copyright (C) 2015 by David Ung                                       *
  *                                                                         *
+ *   Copyright (C) 2018 by Liviu Ionescu                                   *
+ *   <ilg@livius.net>                                                      *
+ *                                                                         *
  *   This program is free software; you can redistribute it and/or modify  *
  *   it under the terms of the GNU General Public License as published by  *
  *   the Free Software Foundation; either version 2 of the License, or     *
@@ -36,6 +39,7 @@
 #include "armv8_opcodes.h"
 #include "target.h"
 #include "target_type.h"
+#include "semihosting_common.h"
 
 static const char * const armv8_state_strings[] = {
 	"AArch32", "Thumb", "Jazelle", "ThumbEE", "AArch64",
@@ -1046,7 +1050,7 @@ int armv8_aarch64_state(struct target *target)
 		armv8_mode_name(arm->core_mode),
 		buf_get_u32(arm->cpsr->value, 0, 32),
 		buf_get_u64(arm->pc->value, 0, 64),
-		arm->is_semihosting ? ", semihosting" : "");
+		target->semihosting->is_active ? ", semihosting" : "");
 
 	return ERROR_OK;
 }
diff --git a/src/target/nds32.c b/src/target/nds32.c
index e4bb17f..4115ea4 100644
--- a/src/target/nds32.c
+++ b/src/target/nds32.c
@@ -2339,63 +2339,66 @@ int nds32_get_gdb_fileio_info(struct target *target, struct gdb_fileio_info *fil
 		fileio_info->identifier = NULL;
 	}
 
+	uint32_t reg_r0, reg_r1, reg_r2;
+	nds32_get_mapped_reg(nds32, R0, &reg_r0);
+	nds32_get_mapped_reg(nds32, R1, &reg_r1);
+	nds32_get_mapped_reg(nds32, R2, &reg_r2);
+
 	switch (syscall_id) {
 		case NDS32_SYSCALL_EXIT:
 			fileio_info->identifier = malloc(5);
 			sprintf(fileio_info->identifier, "exit");
-			nds32_get_mapped_reg(nds32, R0, &(fileio_info->param_1));
+			fileio_info->param_1 = reg_r0;
 			break;
 		case NDS32_SYSCALL_OPEN:
 			{
 				uint8_t filename[256];
 				fileio_info->identifier = malloc(5);
 				sprintf(fileio_info->identifier, "open");
-				nds32_get_mapped_reg(nds32, R0, &(fileio_info->param_1));
+				fileio_info->param_1 = reg_r0;
 				/* reserve fileio_info->param_2 for length of path */
-				nds32_get_mapped_reg(nds32, R1, &(fileio_info->param_3));
-				nds32_get_mapped_reg(nds32, R2, &(fileio_info->param_4));
+				fileio_info->param_3 = reg_r1;
+				fileio_info->param_4 = reg_r2;
 
-				target->type->read_buffer(target, fileio_info->param_1,
-						256, filename);
+				target->type->read_buffer(target, reg_r0, 256, filename);
 				fileio_info->param_2 = strlen((char *)filename) + 1;
 			}
 			break;
 		case NDS32_SYSCALL_CLOSE:
 			fileio_info->identifier = malloc(6);
 			sprintf(fileio_info->identifier, "close");
-			nds32_get_mapped_reg(nds32, R0, &(fileio_info->param_1));
+			fileio_info->param_1 = reg_r0;
 			break;
 		case NDS32_SYSCALL_READ:
 			fileio_info->identifier = malloc(5);
 			sprintf(fileio_info->identifier, "read");
-			nds32_get_mapped_reg(nds32, R0, &(fileio_info->param_1));
-			nds32_get_mapped_reg(nds32, R1, &(fileio_info->param_2));
-			nds32_get_mapped_reg(nds32, R2, &(fileio_info->param_3));
+			fileio_info->param_1 = reg_r0;
+			fileio_info->param_2 = reg_r1;
+			fileio_info->param_3 = reg_r2;
 			break;
 		case NDS32_SYSCALL_WRITE:
 			fileio_info->identifier = malloc(6);
 			sprintf(fileio_info->identifier, "write");
-			nds32_get_mapped_reg(nds32, R0, &(fileio_info->param_1));
-			nds32_get_mapped_reg(nds32, R1, &(fileio_info->param_2));
-			nds32_get_mapped_reg(nds32, R2, &(fileio_info->param_3));
+			fileio_info->param_1 = reg_r0;
+			fileio_info->param_2 = reg_r1;
+			fileio_info->param_3 = reg_r2;
 			break;
 		case NDS32_SYSCALL_LSEEK:
 			fileio_info->identifier = malloc(6);
 			sprintf(fileio_info->identifier, "lseek");
-			nds32_get_mapped_reg(nds32, R0, &(fileio_info->param_1));
-			nds32_get_mapped_reg(nds32, R1, &(fileio_info->param_2));
-			nds32_get_mapped_reg(nds32, R2, &(fileio_info->param_3));
+			fileio_info->param_1 = reg_r0;
+			fileio_info->param_2 = reg_r1;
+			fileio_info->param_3 = reg_r2;
 			break;
 		case NDS32_SYSCALL_UNLINK:
 			{
 				uint8_t filename[256];
 				fileio_info->identifier = malloc(7);
 				sprintf(fileio_info->identifier, "unlink");
-				nds32_get_mapped_reg(nds32, R0, &(fileio_info->param_1));
+				fileio_info->param_1 = reg_r0;
 				/* reserve fileio_info->param_2 for length of path */
 
-				target->type->read_buffer(target, fileio_info->param_1,
-						256, filename);
+				target->type->read_buffer(target, reg_r0, 256, filename);
 				fileio_info->param_2 = strlen((char *)filename) + 1;
 			}
 			break;
@@ -2404,61 +2407,57 @@ int nds32_get_gdb_fileio_info(struct target *target, struct gdb_fileio_info *fil
 				uint8_t filename[256];
 				fileio_info->identifier = malloc(7);
 				sprintf(fileio_info->identifier, "rename");
-				nds32_get_mapped_reg(nds32, R0, &(fileio_info->param_1));
+				fileio_info->param_1 = reg_r0;
 				/* reserve fileio_info->param_2 for length of old path */
-				nds32_get_mapped_reg(nds32, R1, &(fileio_info->param_3));
+				fileio_info->param_3 = reg_r1;
 				/* reserve fileio_info->param_4 for length of new path */
 
-				target->type->read_buffer(target, fileio_info->param_1,
-						256, filename);
+				target->type->read_buffer(target, reg_r0, 256, filename);
 				fileio_info->param_2 = strlen((char *)filename) + 1;
 
-				target->type->read_buffer(target, fileio_info->param_3,
-						256, filename);
+				target->type->read_buffer(target, reg_r1, 256, filename);
 				fileio_info->param_4 = strlen((char *)filename) + 1;
 			}
 			break;
 		case NDS32_SYSCALL_FSTAT:
 			fileio_info->identifier = malloc(6);
 			sprintf(fileio_info->identifier, "fstat");
-			nds32_get_mapped_reg(nds32, R0, &(fileio_info->param_1));
-			nds32_get_mapped_reg(nds32, R1, &(fileio_info->param_2));
+			fileio_info->param_1 = reg_r0;
+			fileio_info->param_2 = reg_r1;
 			break;
 		case NDS32_SYSCALL_STAT:
 			{
 				uint8_t filename[256];
 				fileio_info->identifier = malloc(5);
 				sprintf(fileio_info->identifier, "stat");
-				nds32_get_mapped_reg(nds32, R0, &(fileio_info->param_1));
+				fileio_info->param_1 = reg_r0;
 				/* reserve fileio_info->param_2 for length of old path */
-				nds32_get_mapped_reg(nds32, R1, &(fileio_info->param_3));
+				fileio_info->param_3 = reg_r1;
 
-				target->type->read_buffer(target, fileio_info->param_1,
-						256, filename);
+				target->type->read_buffer(target, reg_r0, 256, filename);
 				fileio_info->param_2 = strlen((char *)filename) + 1;
 			}
 			break;
 		case NDS32_SYSCALL_GETTIMEOFDAY:
 			fileio_info->identifier = malloc(13);
 			sprintf(fileio_info->identifier, "gettimeofday");
-			nds32_get_mapped_reg(nds32, R0, &(fileio_info->param_1));
-			nds32_get_mapped_reg(nds32, R1, &(fileio_info->param_2));
+			fileio_info->param_1 = reg_r0;
+			fileio_info->param_2 = reg_r1;
 			break;
 		case NDS32_SYSCALL_ISATTY:
 			fileio_info->identifier = malloc(7);
 			sprintf(fileio_info->identifier, "isatty");
-			nds32_get_mapped_reg(nds32, R0, &(fileio_info->param_1));
+			fileio_info->param_1 = reg_r0;
 			break;
 		case NDS32_SYSCALL_SYSTEM:
 			{
 				uint8_t command[256];
 				fileio_info->identifier = malloc(7);
 				sprintf(fileio_info->identifier, "system");
-				nds32_get_mapped_reg(nds32, R0, &(fileio_info->param_1));
+				fileio_info->param_1 = reg_r0;
 				/* reserve fileio_info->param_2 for length of old path */
 
-				target->type->read_buffer(target, fileio_info->param_1,
-						256, command);
+				target->type->read_buffer(target, reg_r0, 256, command);
 				fileio_info->param_2 = strlen((char *)command) + 1;
 			}
 			break;
diff --git a/src/target/semihosting_common.c b/src/target/semihosting_common.c
new file mode 100644
index 0000000..beeb474
--- /dev/null
+++ b/src/target/semihosting_common.c
@@ -0,0 +1,1579 @@
+/***************************************************************************
+ *   Copyright (C) 2018 by Liviu Ionescu                                   *
+ *   <ilg@livius.net>                                                      *
+ *                                                                         *
+ *   Copyright (C) 2018 by Marvell Technology Group Ltd.                   *
+ *   Written by Nicolas Pitre <nico@marvell.com>                           *
+ *                                                                         *
+ *   Copyright (C) 2010 by Spencer Oliver                                  *
+ *   spen@spen-soft.co.uk                                                  *
+ *                                                                         *
+ *   Copyright (C) 2016 by Square, Inc.                                    *
+ *   Steven Stallion <stallion@squareup.com>                               *
+ *                                                                         *
+ *   This program is free software; you can redistribute it and/or modify  *
+ *   it under the terms of the GNU General Public License as published by  *
+ *   the Free Software Foundation; either version 2 of the License, or     *
+ *   (at your option) any later version.                                   *
+ *                                                                         *
+ *   This program is distributed in the hope that it will be useful,       *
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
+ *   GNU General Public License for more details.                          *
+ *                                                                         *
+ *   You should have received a copy of the GNU General Public License     *
+ *   along with this program.  If not, see <http://www.gnu.org/licenses/>. *
+ ***************************************************************************/
+
+/**
+ * @file
+ * Common ARM semihosting support.
+ *
+ * Semihosting enables code running on a target to use some of the I/O
+ * facilities on the host computer. The target application must be linked
+ * against a library that forwards operation requests by using  an
+ * instruction trapped by the debugger.
+ *
+ * Details can be found in
+ * "Semihosting for AArch32 and AArch64, Release 2.0"
+ * https://static.docs.arm.com/100863/0200/semihosting.pdf
+ * from ARM Ltd.
+ */
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include "target.h"
+#include "target_type.h"
+#include "semihosting_common.h"
+
+#include <helper/binarybuffer.h>
+#include <helper/log.h>
+#include <sys/stat.h>
+
+static const int open_modeflags[12] = {
+	O_RDONLY,
+	O_RDONLY | O_BINARY,
+	O_RDWR,
+	O_RDWR | O_BINARY,
+	O_WRONLY | O_CREAT | O_TRUNC,
+	O_WRONLY | O_CREAT | O_TRUNC | O_BINARY,
+	O_RDWR | O_CREAT | O_TRUNC,
+	O_RDWR | O_CREAT | O_TRUNC | O_BINARY,
+	O_WRONLY | O_CREAT | O_APPEND,
+	O_WRONLY | O_CREAT | O_APPEND | O_BINARY,
+	O_RDWR | O_CREAT | O_APPEND,
+	O_RDWR | O_CREAT | O_APPEND | O_BINARY
+};
+
+static int semihosting_common_fileio_info(struct target *target,
+	struct gdb_fileio_info *fileio_info);
+static int semihosting_common_fileio_end(struct target *target, int result,
+	int fileio_errno, bool ctrl_c);
+
+static int semihosting_read_fields(struct target *target, size_t number,
+	uint8_t *fields);
+static int semihosting_write_fields(struct target *target, size_t number,
+	uint8_t *fields);
+static uint64_t semihosting_get_field(struct target *target, size_t index,
+	uint8_t *fields);
+static void semihosting_set_field(struct target *target, uint64_t value,
+	size_t index,
+	uint8_t *fields);
+
+/* Attempts to include gdb_server.h failed. */
+extern int gdb_actual_connections;
+
+/**
+ * Initialize common semihosting support.
+ *
+ * @param target Pointer to the target to initialize.
+ * @return An error status if there is a problem during initialization.
+ */
+int semihosting_common_init(struct target *target, void *setup,
+	void *post_result)
+{
+	LOG_DEBUG(" ");
+
+	target->fileio_info = malloc(sizeof(*target->fileio_info));
+	if (target->fileio_info == NULL) {
+		LOG_ERROR("out of memory");
+		return ERROR_FAIL;
+	}
+	memset(target->fileio_info, 0, sizeof(*target->fileio_info));
+
+	struct semihosting *semihosting;
+	semihosting = malloc(sizeof(*target->semihosting));
+	if (semihosting == NULL) {
+		LOG_ERROR("out of memory");
+		return ERROR_FAIL;
+	}
+
+	semihosting->is_active = false;
+	semihosting->is_fileio = false;
+	semihosting->hit_fileio = false;
+	semihosting->is_resumable = false;
+	semihosting->has_resumable_exit = false;
+	semihosting->word_size_bytes = 0;
+	semihosting->op = -1;
+	semihosting->param = 0;
+	semihosting->result = -1;
+	semihosting->sys_errno = -1;
+	semihosting->cmdline = NULL;
+
+	/* If possible, update it in setup(). */
+	semihosting->setup_time = clock();
+
+	semihosting->setup = setup;
+	semihosting->post_result = post_result;
+
+	target->semihosting = semihosting;
+
+	target->type->get_gdb_fileio_info = semihosting_common_fileio_info;
+	target->type->gdb_fileio_end = semihosting_common_fileio_end;
+
+	return ERROR_OK;
+}
+
+/**
+ * Portable implementation of ARM semihosting calls.
+ * Performs the currently pending semihosting operation
+ * encoded in target->semihosting.
+ */
+int semihosting_common(struct target *target)
+{
+	struct semihosting *semihosting = target->semihosting;
+	if (!semihosting) {
+		/* Silently ignore if the semhosting field was not set. */
+		return ERROR_OK;
+	}
+
+	struct gdb_fileio_info *fileio_info = target->fileio_info;
+
+	/*
+	 * By default return an error.
+	 * The actual result must be set by each function
+	 */
+	semihosting->result = -1;
+
+	/* Most operations are resumable, except the two exit calls. */
+	semihosting->is_resumable = true;
+
+	int retval;
+
+	/* Enough space to hold 4 long words. */
+	uint8_t fields[4*8];
+
+	LOG_DEBUG("op=0x%x, param=0x%" PRIx64, (int)semihosting->op,
+		semihosting->param);
+
+	switch (semihosting->op) {
+
+		case SEMIHOSTING_SYS_CLOCK:	/* 0x10 */
+			/*
+			 * Returns the number of centiseconds (hundredths of a second)
+			 * since the execution started.
+			 *
+			 * Values returned can be of limited use for some benchmarking
+			 * purposes because of communication overhead or other
+			 * agent-specific factors. For example, with a debug hardware
+			 * unit the request is passed back to the host for execution.
+			 * This can lead to unpredictable delays in transmission and
+			 * process scheduling.
+			 *
+			 * Use this function to calculate time intervals, by calculating
+			 * differences between intervals with and without the code
+			 * sequence to be timed.
+			 *
+			 * Entry
+			 * The PARAMETER REGISTER must contain 0. There are no other
+			 * parameters.
+			 *
+			 * Return
+			 * On exit, the RETURN REGISTER contains:
+			 * - The number of centiseconds since some arbitrary start
+			 * point, if the call is successful.
+			 * - –1 if the call is not successful. For example, because
+			 * of a communications error.
+			 */
+		{
+			clock_t delta = clock() - semihosting->setup_time;
+
+			semihosting->result = delta / (CLOCKS_PER_SEC / 100);
+		}
+		break;
+
+		case SEMIHOSTING_SYS_CLOSE:	/* 0x02 */
+			/*
+			 * Closes a file on the host system. The handle must reference
+			 * a file that was opened with SYS_OPEN.
+			 *
+			 * Entry
+			 * On entry, the PARAMETER REGISTER contains a pointer to a
+			 * one-field argument block:
+			 * - field 1 Contains a handle for an open file.
+			 *
+			 * Return
+			 * On exit, the RETURN REGISTER contains:
+			 * - 0 if the call is successful
+			 * - –1 if the call is not successful.
+			 */
+			retval = semihosting_read_fields(target, 1, fields);
+			if (retval != ERROR_OK)
+				return retval;
+			else {
+				int fd = semihosting_get_field(target, 0, fields);
+				if (semihosting->is_fileio) {
+					semihosting->hit_fileio = true;
+					fileio_info->identifier = "close";
+					fileio_info->param_1 = fd;
+				} else {
+					semihosting->result = close(fd);
+					semihosting->sys_errno = errno;
+
+					LOG_DEBUG("close(%d)=%d", fd, (int)semihosting->result);
+				}
+			}
+			break;
+
+		case SEMIHOSTING_SYS_ERRNO:	/* 0x13 */
+			/*
+			 * Returns the value of the C library errno variable that is
+			 * associated with the semihosting implementation. The errno
+			 * variable can be set by a number of C library semihosted
+			 * functions, including:
+			 * - SYS_REMOVE
+			 * - SYS_OPEN
+			 * - SYS_CLOSE
+			 * - SYS_READ
+			 * - SYS_WRITE
+			 * - SYS_SEEK.
+			 *
+			 * Whether errno is set or not, and to what value, is entirely
+			 * host-specific, except where the ISO C standard defines the
+			 * behavior.
+			 *
+			 * Entry
+			 * There are no parameters. The PARAMETER REGISTER must be 0.
+			 *
+			 * Return
+			 * On exit, the RETURN REGISTER contains the value of the C
+			 * library errno variable.
+			 */
+			semihosting->result = semihosting->sys_errno;
+			break;
+
+		case SEMIHOSTING_SYS_EXIT:	/* 0x18 */
+			/*
+			 * Note: SYS_EXIT was called angel_SWIreason_ReportException in
+			 * previous versions of the documentation.
+			 *
+			 * An application calls this operation to report an exception
+			 * to the debugger directly. The most common use is to report
+			 * that execution has completed, using ADP_Stopped_ApplicationExit.
+			 *
+			 * Note: This semihosting operation provides no means for 32-bit
+			 * callers to indicate an application exit with a specified exit
+			 * code. Semihosting callers may prefer to check for the presence
+			 * of the SH_EXT_EXTENDED_REPORT_EXCEPTION extension and use
+			 * the SYS_REPORT_EXCEPTION_EXTENDED operation instead, if it
+			 * is available.
+			 *
+			 * Entry (32-bit)
+			 * On entry, the PARAMETER register is set to a reason code
+			 * describing the cause of the trap. Not all semihosting client
+			 * implementations will necessarily trap every corresponding
+			 * event. Important reason codes are:
+			 *
+			 * - ADP_Stopped_ApplicationExit 0x20026
+			 * - ADP_Stopped_RunTimeErrorUnknown 0x20023
+			 *
+			 * Entry (64-bit)
+			 * On entry, the PARAMETER REGISTER contains a pointer to a
+			 * two-field argument block:
+			 * - field 1 The exception type, which is one of the set of
+			 * reason codes in the above tables.
+			 * - field 2 A subcode, whose meaning depends on the reason
+			 * code in field 1.
+			 * In particular, if field 1 is ADP_Stopped_ApplicationExit
+			 * then field 2 is an exit status code, as passed to the C
+			 * standard library exit() function. A simulator receiving
+			 * this request must notify a connected debugger, if present,
+			 * and then exit with the specified status.
+			 *
+			 * Return
+			 * No return is expected from these calls. However, it is
+			 * possible for the debugger to request that the application
+			 * continues by performing an RDI_Execute request or equivalent.
+			 * In this case, execution continues with the registers as they
+			 * were on entry to the operation, or as subsequently modified
+			 * by the debugger.
+			 */
+			if (semihosting->word_size_bytes == 8) {
+				retval = semihosting_read_fields(target, 2, fields);
+				if (retval != ERROR_OK)
+					return retval;
+				else {
+					int type = semihosting_get_field(target, 0, fields);
+					int code = semihosting_get_field(target, 1, fields);
+
+					if (type == ADP_STOPPED_APPLICATION_EXIT) {
+						if (!gdb_actual_connections)
+							exit(code);
+						else {
+							fprintf(stderr,
+								"semihosting: *** application exited with %d ***\n",
+								code);
+						}
+					} else {
+						fprintf(stderr,
+							"semihosting: application exception %#x\n",
+							type);
+					}
+				}
+			} else {
+				if (semihosting->param == ADP_STOPPED_APPLICATION_EXIT) {
+					if (!gdb_actual_connections)
+						exit(0);
+					else {
+						fprintf(stderr,
+							"semihosting: *** application exited normally ***\n");
+					}
+				} else if (semihosting->param == ADP_STOPPED_RUN_TIME_ERROR) {
+					/* Chosen more or less arbitrarly to have a nicer message,
+					 * otherwise all other return the same exit code 1. */
+					if (!gdb_actual_connections)
+						exit(1);
+					else {
+						fprintf(stderr,
+							"semihosting: *** application exited with error ***\n");
+					}
+				} else {
+					if (!gdb_actual_connections)
+						exit(1);
+					else {
+						fprintf(stderr,
+							"semihosting: application exception %#x\n",
+							(unsigned) semihosting->param);
+					}
+				}
+			}
+			if (!semihosting->has_resumable_exit) {
+				semihosting->is_resumable = false;
+				return target_call_event_callbacks(target, TARGET_EVENT_HALTED);
+			}
+			break;
+
+		case SEMIHOSTING_SYS_EXIT_EXTENDED:	/* 0x20 */
+			/*
+			 * This operation is only supported if the semihosting extension
+			 * SH_EXT_EXIT_EXTENDED is implemented. SH_EXT_EXIT_EXTENDED is
+			 * reported using feature byte 0, bit 0. If this extension is
+			 * supported, then the implementation provides a means to
+			 * report a normal exit with a nonzero exit status in both 32-bit
+			 * and 64-bit semihosting APIs.
+			 *
+			 * The implementation must provide the semihosting call
+			 * SYS_EXIT_EXTENDED for both A64 and A32/T32 semihosting APIs.
+			 *
+			 * SYS_EXIT_EXTENDED is used by an application to report an
+			 * exception or exit to the debugger directly. The most common
+			 * use is to report that execution has completed, using
+			 * ADP_Stopped_ApplicationExit.
+			 *
+			 * Entry
+			 * On entry, the PARAMETER REGISTER contains a pointer to a
+			 * two-field argument block:
+			 * - field 1 The exception type, which should be one of the set
+			 * of reason codes that are documented for the SYS_EXIT
+			 * (0x18) call. For example, ADP_Stopped_ApplicationExit.
+			 * - field 2 A subcode, whose meaning depends on the reason
+			 * code in field 1. In particular, if field 1 is
+			 * ADP_Stopped_ApplicationExit then field 2 is an exit status
+			 * code, as passed to the C standard library exit() function.
+			 * A simulator receiving this request must notify a connected
+			 * debugger, if present, and then exit with the specified status.
+			 *
+			 * Return
+			 * No return is expected from these calls.
+			 *
+			 * For the A64 API, this call is identical to the behavior of
+			 * the mandatory SYS_EXIT (0x18) call. If this extension is
+			 * supported, then both calls must be implemented.
+			 */
+			retval = semihosting_read_fields(target, 2, fields);
+			if (retval != ERROR_OK)
+				return retval;
+			else {
+				int type = semihosting_get_field(target, 0, fields);
+				int code = semihosting_get_field(target, 1, fields);
+
+				if (type == ADP_STOPPED_APPLICATION_EXIT) {
+					if (!gdb_actual_connections)
+						exit(code);
+					else {
+						fprintf(stderr,
+							"semihosting: *** application exited with %d ***\n",
+							code);
+					}
+				} else {
+					fprintf(stderr, "semihosting: exception %#x\n",
+						type);
+				}
+			}
+			if (!semihosting->has_resumable_exit) {
+				semihosting->is_resumable = false;
+				return target_call_event_callbacks(target, TARGET_EVENT_HALTED);
+			}
+			break;
+
+		case SEMIHOSTING_SYS_FLEN:	/* 0x0C */
+			/*
+			 * Returns the length of a specified file.
+			 *
+			 * Entry
+			 * On entry, the PARAMETER REGISTER contains a pointer to a
+			 * one-field argument block:
+			 * - field 1 A handle for a previously opened, seekable file
+			 * object.
+			 *
+			 * Return
+			 * On exit, the RETURN REGISTER contains:
+			 * - The current length of the file object, if the call is
+			 * successful.
+			 * - –1 if an error occurs.
+			 */
+			if (semihosting->is_fileio) {
+				LOG_ERROR("SYS_FLEN not supported by semihosting fileio");
+				return ERROR_FAIL;
+			}
+			retval = semihosting_read_fields(target, 1, fields);
+			if (retval != ERROR_OK)
+				return retval;
+			else {
+				int fd = semihosting_get_field(target, 0, fields);
+				struct stat buf;
+				semihosting->result = fstat(fd, &buf);
+				if (semihosting->result == -1) {
+					semihosting->sys_errno = errno;
+					LOG_DEBUG("fstat(%d)=%d", fd, (int)semihosting->result);
+					break;
+				}
+				LOG_DEBUG("fstat(%d)=%d", fd, (int)semihosting->result);
+				semihosting->result = buf.st_size;
+			}
+			break;
+
+		case SEMIHOSTING_SYS_GET_CMDLINE:	/* 0x15 */
+			/*
+			 * Returns the command line that is used for the call to the
+			 * executable, that is, argc and argv.
+			 *
+			 * Entry
+			 * On entry, the PARAMETER REGISTER points to a two-field data
+			 * block to be used for returning the command string and its length:
+			 * - field 1 A pointer to a buffer of at least the size that is
+			 * specified in field 2.
+			 * - field 2 The length of the buffer in bytes.
+			 *
+			 * Return
+			 * On exit:
+			 * If the call is successful, then the RETURN REGISTER contains 0,
+			 * the PARAMETER REGISTER is unchanged, and the data block is
+			 * updated as follows:
+			 * - field 1 A pointer to a null-terminated string of the command
+			 * line.
+			 * - field 2 The length of the string in bytes.
+			 * If the call is not successful, then the RETURN REGISTER
+			 * contains -1.
+			 *
+			 * Note: The semihosting implementation might impose limits on
+			 * the maximum length of the string that can be transferred.
+			 * However, the implementation must be able to support a
+			 * command-line length of at least 80 bytes.
+			 */
+			retval = semihosting_read_fields(target, 2, fields);
+			if (retval != ERROR_OK)
+				return retval;
+			else {
+				uint64_t addr = semihosting_get_field(target, 0, fields);
+				size_t size = semihosting_get_field(target, 1, fields);
+
+				char *arg = semihosting->cmdline != NULL ?
+					semihosting->cmdline : "";
+				uint32_t len = strlen(arg) + 1;
+				if (len > size)
+					semihosting->result = -1;
+				else {
+					semihosting_set_field(target, len, 1, fields);
+					retval = target_write_buffer(target, addr, len,
+							(uint8_t *)arg);
+					if (retval != ERROR_OK)
+						return retval;
+					semihosting->result = 0;
+
+					retval = semihosting_write_fields(target, 2, fields);
+					if (retval != ERROR_OK)
+						return retval;
+				}
+				LOG_DEBUG("SYS_GET_CMDLINE=[%s],%d", arg,
+					(int)semihosting->result);
+			}
+			break;
+
+		case SEMIHOSTING_SYS_HEAPINFO:	/* 0x16 */
+			/*
+			 * Returns the system stack and heap parameters.
+			 *
+			 * Entry
+			 * On entry, the PARAMETER REGISTER contains the address of a
+			 * pointer to a four-field data block. The contents of the data
+			 * block are filled by the function. The following C-like
+			 * pseudocode describes the layout of the block:
+			 * struct block {
+			 *   void* heap_base;
+			 *   void* heap_limit;
+			 *   void* stack_base;
+			 *   void* stack_limit;
+			 * };
+			 *
+			 * Return
+			 * On exit, the PARAMETER REGISTER is unchanged and the data
+			 * block has been updated.
+			 */
+			retval = semihosting_read_fields(target, 1, fields);
+			if (retval != ERROR_OK)
+				return retval;
+			else {
+				uint64_t addr = semihosting_get_field(target, 0, fields);
+				/* tell the remote we have no idea */
+				memset(fields, 0, 4 * semihosting->word_size_bytes);
+				retval = target_write_memory(target, addr, 4,
+						semihosting->word_size_bytes,
+						fields);
+				if (retval != ERROR_OK)
+					return retval;
+				semihosting->result = 0;
+			}
+			break;
+
+		case SEMIHOSTING_SYS_ISERROR:	/* 0x08 */
+			/*
+			 * Determines whether the return code from another semihosting
+			 * call is an error status or not.
+			 *
+			 * This call is passed a parameter block containing the error
+			 * code to examine.
+			 *
+			 * Entry
+			 * On entry, the PARAMETER REGISTER contains a pointer to a
+			 * one-field data block:
+			 * - field 1 The required status word to check.
+			 *
+			 * Return
+			 * On exit, the RETURN REGISTER contains:
+			 * - 0 if the status field is not an error indication
+			 * - A nonzero value if the status field is an error indication.
+			 */
+			retval = semihosting_read_fields(target, 1, fields);
+			if (retval != ERROR_OK)
+				return retval;
+
+			uint64_t code = semihosting_get_field(target, 0, fields);
+			semihosting->result = (code != 0);
+			break;
+
+		case SEMIHOSTING_SYS_ISTTY:	/* 0x09 */
+			/*
+			 * Checks whether a file is connected to an interactive device.
+			 *
+			 * Entry
+			 * On entry, the PARAMETER REGISTER contains a pointer to a
+			 * one-field argument block:
+			 * field 1 A handle for a previously opened file object.
+			 *
+			 * Return
+			 * On exit, the RETURN REGISTER contains:
+			 * - 1 if the handle identifies an interactive device.
+			 * - 0 if the handle identifies a file.
+			 * - A value other than 1 or 0 if an error occurs.
+			 */
+			if (semihosting->is_fileio) {
+				semihosting->hit_fileio = true;
+				fileio_info->identifier = "isatty";
+				fileio_info->param_1 = semihosting->param;
+			} else {
+				retval = semihosting_read_fields(target, 1, fields);
+				if (retval != ERROR_OK)
+					return retval;
+				int fd = semihosting_get_field(target, 0, fields);
+				semihosting->result = isatty(fd);
+				LOG_DEBUG("isatty(%d)=%d", fd, (int)semihosting->result);
+			}
+			break;
+
+		case SEMIHOSTING_SYS_OPEN:	/* 0x01 */
+			/*
+			 * Opens a file on the host system.
+			 *
+			 * The file path is specified either as relative to the current
+			 * directory of the host process, or absolute, using the path
+			 * conventions of the host operating system.
+			 *
+			 * Semihosting implementations must support opening the special
+			 * path name :semihosting-features as part of the semihosting
+			 * extensions reporting mechanism.
+			 *
+			 * ARM targets interpret the special path name :tt as meaning
+			 * the console input stream, for an open-read or the console
+			 * output stream, for an open-write. Opening these streams is
+			 * performed as part of the standard startup code for those
+			 * applications that reference the C stdio streams. The
+			 * semihosting extension SH_EXT_STDOUT_STDERR allows the
+			 * semihosting caller to open separate output streams
+			 * corresponding to stdout and stderr. This extension is
+			 * reported using feature byte 0, bit 1. Use SYS_OPEN with
+			 * the special path name :semihosting-features to access the
+			 * feature bits.
+			 *
+			 * If this extension is supported, the implementation must
+			 * support the following additional semantics to SYS_OPEN:
+			 * - If the special path name :tt is opened with an fopen
+			 * mode requesting write access (w, wb, w+, or w+b), then
+			 * this is a request to open stdout.
+			 * - If the special path name :tt is opened with a mode
+			 * requesting append access (a, ab, a+, or a+b), then this is
+			 * a request to open stderr.
+			 *
+			 * Entry
+			 * On entry, the PARAMETER REGISTER contains a pointer to a
+			 * three-field argument block:
+			 * - field 1 A pointer to a null-terminated string containing
+			 * a file or device name.
+			 * - field 2 An integer that specifies the file opening mode.
+			 * - field 3 An integer that gives the length of the string
+			 * pointed to by field 1.
+			 *
+			 * The length does not include the terminating null character
+			 * that must be present.
+			 *
+			 * Return
+			 * On exit, the RETURN REGISTER contains:
+			 * - A nonzero handle if the call is successful.
+			 * - –1 if the call is not successful.
+			 */
+			retval = semihosting_read_fields(target, 3, fields);
+			if (retval != ERROR_OK)
+				return retval;
+			else {
+				uint64_t addr = semihosting_get_field(target, 0, fields);
+				uint32_t mode = semihosting_get_field(target, 1, fields);
+				size_t len = semihosting_get_field(target, 2, fields);
+
+				if (mode > 11) {
+					semihosting->result = -1;
+					semihosting->sys_errno = EINVAL;
+					break;
+				}
+				uint8_t *fn = malloc(len+1);
+				if (!fn) {
+					semihosting->result = -1;
+					semihosting->sys_errno = ENOMEM;
+				} else {
+					retval = target_read_memory(target, addr, 1, len, fn);
+					if (retval != ERROR_OK) {
+						free(fn);
+						return retval;
+					}
+					fn[len] = 0;
+					/* TODO: implement the :semihosting-features special file.
+					 * */
+					if (semihosting->is_fileio) {
+						if (strcmp((char *)fn, ":tt") == 0)
+							semihosting->result = 0;
+						else {
+							semihosting->hit_fileio = true;
+							fileio_info->identifier = "open";
+							fileio_info->param_1 = addr;
+							fileio_info->param_2 = len;
+							fileio_info->param_3 = open_modeflags[mode];
+							fileio_info->param_4 = 0644;
+						}
+					} else {
+						if (strcmp((char *)fn, ":tt") == 0) {
+							/* Mode is:
+							 * - 0-3 ("r") for stdin,
+							 * - 4-7 ("w") for stdout,
+							 * - 8-11 ("a") for stderr */
+							if (mode < 4) {
+								semihosting->result = dup(
+										STDIN_FILENO);
+								semihosting->sys_errno = errno;
+								LOG_DEBUG("dup(STDIN)=%d",
+									(int)semihosting->result);
+							} else if (mode < 8) {
+								semihosting->result = dup(
+										STDOUT_FILENO);
+								semihosting->sys_errno = errno;
+								LOG_DEBUG("dup(STDOUT)=%d",
+									(int)semihosting->result);
+							} else {
+								semihosting->result = dup(
+										STDERR_FILENO);
+								semihosting->sys_errno = errno;
+								LOG_DEBUG("dup(STDERR)=%d",
+									(int)semihosting->result);
+							}
+						} else {
+							/* cygwin requires the permission setting
+							 * otherwise it will fail to reopen a previously
+							 * written file */
+							semihosting->result = open((char *)fn,
+									open_modeflags[mode],
+									0644);
+							semihosting->sys_errno = errno;
+							LOG_DEBUG("open('%s')=%d", fn,
+								(int)semihosting->result);
+						}
+					}
+					free(fn);
+				}
+			}
+			break;
+
+		case SEMIHOSTING_SYS_READ:	/* 0x06 */
+			/*
+			 * Reads the contents of a file into a buffer. The file position
+			 * is specified either:
+			 * - Explicitly by a SYS_SEEK.
+			 * - Implicitly one byte beyond the previous SYS_READ or
+			 * SYS_WRITE request.
+			 *
+			 * The file position is at the start of the file when it is
+			 * opened, and is lost when the file is closed. Perform the
+			 * file operation as a single action whenever possible. For
+			 * example, do not split a read of 16KB into four 4KB chunks
+			 * unless there is no alternative.
+			 *
+			 * Entry
+			 * On entry, the PARAMETER REGISTER contains a pointer to a
+			 * three-field data block:
+			 * - field 1 Contains a handle for a file previously opened
+			 * with SYS_OPEN.
+			 * - field 2 Points to a buffer.
+			 * - field 3 Contains the number of bytes to read to the buffer
+			 * from the file.
+			 *
+			 * Return
+			 * On exit, the RETURN REGISTER contains the number of bytes not
+			 * filled in the buffer (buffer_length - bytes_read) as follows:
+			 * - If the RETURN REGISTER is 0, the entire buffer was
+			 * successfully filled.
+			 * - If the RETURN REGISTER is the same as field 3, no bytes
+			 * were read (EOF can be assumed).
+			 * - If the RETURN REGISTER contains a value smaller than
+			 * field 3, the read succeeded but the buffer was only partly
+			 * filled. For interactive devices, this is the most common
+			 * return value.
+			 */
+			retval = semihosting_read_fields(target, 3, fields);
+			if (retval != ERROR_OK)
+				return retval;
+			else {
+				int fd = semihosting_get_field(target, 0, fields);
+				uint64_t addr = semihosting_get_field(target, 1, fields);
+				size_t len = semihosting_get_field(target, 2, fields);
+				if (semihosting->is_fileio) {
+					semihosting->hit_fileio = true;
+					fileio_info->identifier = "read";
+					fileio_info->param_1 = fd;
+					fileio_info->param_2 = addr;
+					fileio_info->param_3 = len;
+				} else {
+					uint8_t *buf = malloc(len);
+					if (!buf) {
+						semihosting->result = -1;
+						semihosting->sys_errno = ENOMEM;
+					} else {
+						semihosting->result = read(fd, buf, len);
+						semihosting->sys_errno = errno;
+						LOG_DEBUG("read(%d, 0x%" PRIx64 ", %zu)=%d",
+							fd,
+							addr,
+							len,
+							(int)semihosting->result);
+						if (semihosting->result >= 0) {
+							retval = target_write_buffer(target, addr,
+									semihosting->result,
+									buf);
+							if (retval != ERROR_OK) {
+								free(buf);
+								return retval;
+							}
+							/* the number of bytes NOT filled in */
+							semihosting->result = len -
+								semihosting->result;
+						}
+						free(buf);
+					}
+				}
+			}
+			break;
+
+		case SEMIHOSTING_SYS_READC:	/* 0x07 */
+			/*
+			 * Reads a byte from the console.
+			 *
+			 * Entry
+			 * The PARAMETER REGISTER must contain 0. There are no other
+			 * parameters or values possible.
+			 *
+			 * Return
+			 * On exit, the RETURN REGISTER contains the byte read from
+			 * the console.
+			 */
+			if (semihosting->is_fileio) {
+				LOG_ERROR("SYS_READC not supported by semihosting fileio");
+				return ERROR_FAIL;
+			}
+			semihosting->result = getchar();
+			LOG_DEBUG("getchar()=%d", (int)semihosting->result);
+			break;
+
+		case SEMIHOSTING_SYS_REMOVE:	/* 0x0E */
+			/*
+			 * Deletes a specified file on the host filing system.
+			 *
+			 * Entry
+			 * On entry, the PARAMETER REGISTER contains a pointer to a
+			 * two-field argument block:
+			 * - field 1 Points to a null-terminated string that gives the
+			 * path name of the file to be deleted.
+			 * - field 2 The length of the string.
+			 *
+			 * Return
+			 * On exit, the RETURN REGISTER contains:
+			 * - 0 if the delete is successful
+			 * - A nonzero, host-specific error code if the delete fails.
+			 */
+			retval = semihosting_read_fields(target, 2, fields);
+			if (retval != ERROR_OK)
+				return retval;
+			else {
+				uint64_t addr = semihosting_get_field(target, 0, fields);
+				size_t len = semihosting_get_field(target, 1, fields);
+				if (semihosting->is_fileio) {
+					semihosting->hit_fileio = true;
+					fileio_info->identifier = "unlink";
+					fileio_info->param_1 = addr;
+					fileio_info->param_2 = len;
+				} else {
+					uint8_t *fn = malloc(len+1);
+					if (!fn) {
+						semihosting->result = -1;
+						semihosting->sys_errno = ENOMEM;
+					} else {
+						retval =
+							target_read_memory(target, addr, 1, len,
+								fn);
+						if (retval != ERROR_OK) {
+							free(fn);
+							return retval;
+						}
+						fn[len] = 0;
+						semihosting->result = remove((char *)fn);
+						semihosting->sys_errno = errno;
+						LOG_DEBUG("remove('%s')=%d", fn,
+							(int)semihosting->result);
+
+						free(fn);
+					}
+				}
+			}
+			break;
+
+		case SEMIHOSTING_SYS_RENAME:	/* 0x0F */
+			/*
+			 * Renames a specified file.
+			 *
+			 * Entry
+			 * On entry, the PARAMETER REGISTER contains a pointer to a
+			 * four-field data block:
+			 * - field 1 A pointer to the name of the old file.
+			 * - field 2 The length of the old filename.
+			 * - field 3 A pointer to the new filename.
+			 * - field 4 The length of the new filename. Both strings are
+			 * null-terminated.
+			 *
+			 * Return
+			 * On exit, the RETURN REGISTER contains:
+			 * - 0 if the rename is successful.
+			 * - A nonzero, host-specific error code if the rename fails.
+			 */
+			retval = semihosting_read_fields(target, 4, fields);
+			if (retval != ERROR_OK)
+				return retval;
+			else {
+				uint64_t addr1 = semihosting_get_field(target, 0, fields);
+				size_t len1 = semihosting_get_field(target, 1, fields);
+				uint64_t addr2 = semihosting_get_field(target, 2, fields);
+				size_t len2 = semihosting_get_field(target, 3, fields);
+				if (semihosting->is_fileio) {
+					semihosting->hit_fileio = true;
+					fileio_info->identifier = "rename";
+					fileio_info->param_1 = addr1;
+					fileio_info->param_2 = len1;
+					fileio_info->param_3 = addr2;
+					fileio_info->param_4 = len2;
+				} else {
+					uint8_t *fn1 = malloc(len1+1);
+					uint8_t *fn2 = malloc(len2+1);
+					if (!fn1 || !fn2) {
+						semihosting->result = -1;
+						semihosting->sys_errno = ENOMEM;
+					} else {
+						retval = target_read_memory(target, addr1, 1, len1,
+								fn1);
+						if (retval != ERROR_OK) {
+							free(fn1);
+							free(fn2);
+							return retval;
+						}
+						retval = target_read_memory(target, addr2, 1, len2,
+								fn2);
+						if (retval != ERROR_OK) {
+							free(fn1);
+							free(fn2);
+							return retval;
+						}
+						fn1[len1] = 0;
+						fn2[len2] = 0;
+						semihosting->result = rename((char *)fn1,
+								(char *)fn2);
+						semihosting->sys_errno = errno;
+						LOG_DEBUG("rename('%s', '%s')=%d", fn1, fn2,
+							(int)semihosting->result);
+
+						free(fn1);
+						free(fn2);
+					}
+				}
+			}
+			break;
+
+		case SEMIHOSTING_SYS_SEEK:	/* 0x0A */
+			/*
+			 * Seeks to a specified position in a file using an offset
+			 * specified from the start of the file. The file is assumed
+			 * to be a byte array and the offset is given in bytes.
+			 *
+			 * Entry
+			 * On entry, the PARAMETER REGISTER contains a pointer to a
+			 * two-field data block:
+			 * - field 1 A handle for a seekable file object.
+			 * - field 2 The absolute byte position to seek to.
+			 *
+			 * Return
+			 * On exit, the RETURN REGISTER contains:
+			 * - 0 if the request is successful.
+			 * - A negative value if the request is not successful.
+			 * Use SYS_ERRNO to read the value of the host errno variable
+			 * describing the error.
+			 *
+			 * Note: The effect of seeking outside the current extent of
+			 * the file object is undefined.
+			 */
+			retval = semihosting_read_fields(target, 2, fields);
+			if (retval != ERROR_OK)
+				return retval;
+			else {
+				int fd = semihosting_get_field(target, 0, fields);
+				off_t pos = semihosting_get_field(target, 1, fields);
+				if (semihosting->is_fileio) {
+					semihosting->hit_fileio = true;
+					fileio_info->identifier = "lseek";
+					fileio_info->param_1 = fd;
+					fileio_info->param_2 = pos;
+					fileio_info->param_3 = SEEK_SET;
+				} else {
+					semihosting->result = lseek(fd, pos, SEEK_SET);
+					semihosting->sys_errno = errno;
+					LOG_DEBUG("lseek(%d, %d)=%d", fd, (int)pos,
+						(int)semihosting->result);
+					if (semihosting->result == pos)
+						semihosting->result = 0;
+				}
+			}
+			break;
+
+		case SEMIHOSTING_SYS_SYSTEM:	/* 0x12 */
+			/*
+			 * Passes a command to the host command-line interpreter.
+			 * This enables you to execute a system command such as dir,
+			 * ls, or pwd. The terminal I/O is on the host, and is not
+			 * visible to the target.
+			 *
+			 * Entry
+			 * On entry, the PARAMETER REGISTER contains a pointer to a
+			 * two-field argument block:
+			 * - field 1 Points to a string to be passed to the host
+			 * command-line interpreter.
+			 * - field 2 The length of the string.
+			 *
+			 * Return
+			 * On exit, the RETURN REGISTER contains the return status.
+			 */
+
+			/* Provide SYS_SYSTEM functionality.  Uses the
+			 * libc system command, there may be a reason *NOT*
+			 * to use this, but as I can't think of one, I
+			 * implemented it this way.
+			 */
+			retval = semihosting_read_fields(target, 2, fields);
+			if (retval != ERROR_OK)
+				return retval;
+			else {
+				uint64_t addr = semihosting_get_field(target, 0, fields);
+				size_t len = semihosting_get_field(target, 1, fields);
+				if (semihosting->is_fileio) {
+					semihosting->hit_fileio = true;
+					fileio_info->identifier = "system";
+					fileio_info->param_1 = addr;
+					fileio_info->param_2 = len;
+				} else {
+					uint8_t *cmd = malloc(len+1);
+					if (!cmd) {
+						semihosting->result = -1;
+						semihosting->sys_errno = ENOMEM;
+					} else {
+						retval = target_read_memory(target,
+								addr,
+								1,
+								len,
+								cmd);
+						if (retval != ERROR_OK) {
+							free(cmd);
+							return retval;
+						} else {
+							cmd[len] = 0;
+							semihosting->result = system(
+									(const char *)cmd);
+							LOG_DEBUG("system('%s')=%d",
+								cmd,
+								(int)semihosting->result);
+						}
+
+						free(cmd);
+					}
+				}
+			}
+			break;
+
+		case SEMIHOSTING_SYS_TIME:	/* 0x11 */
+			/*
+			 * Returns the number of seconds since 00:00 January 1, 1970.
+			 * This value is real-world time, regardless of any debug agent
+			 * configuration.
+			 *
+			 * Entry
+			 * There are no parameters.
+			 *
+			 * Return
+			 * On exit, the RETURN REGISTER contains the number of seconds.
+			 */
+			semihosting->result = time(NULL);
+			break;
+
+		case SEMIHOSTING_SYS_WRITE:	/* 0x05 */
+			/*
+			 * Writes the contents of a buffer to a specified file at the
+			 * current file position. The file position is specified either:
+			 * - Explicitly, by a SYS_SEEK.
+			 * - Implicitly as one byte beyond the previous SYS_READ or
+			 * SYS_WRITE request.
+			 *
+			 * The file position is at the start of the file when the file
+			 * is opened, and is lost when the file is closed.
+			 *
+			 * Perform the file operation as a single action whenever
+			 * possible. For example, do not split a write of 16KB into
+			 * four 4KB chunks unless there is no alternative.
+			 *
+			 * Entry
+			 * On entry, the PARAMETER REGISTER contains a pointer to a
+			 * three-field data block:
+			 * - field 1 Contains a handle for a file previously opened
+			 * with SYS_OPEN.
+			 * - field 2 Points to the memory containing the data to be written.
+			 * - field 3 Contains the number of bytes to be written from
+			 * the buffer to the file.
+			 *
+			 * Return
+			 * On exit, the RETURN REGISTER contains:
+			 * - 0 if the call is successful.
+			 * - The number of bytes that are not written, if there is an error.
+			 */
+			retval = semihosting_read_fields(target, 3, fields);
+			if (retval != ERROR_OK)
+				return retval;
+			else {
+				int fd = semihosting_get_field(target, 0, fields);
+				uint64_t addr = semihosting_get_field(target, 1, fields);
+				size_t len = semihosting_get_field(target, 2, fields);
+				if (semihosting->is_fileio) {
+					semihosting->hit_fileio = true;
+					fileio_info->identifier = "write";
+					fileio_info->param_1 = fd;
+					fileio_info->param_2 = addr;
+					fileio_info->param_3 = len;
+				} else {
+					uint8_t *buf = malloc(len);
+					if (!buf) {
+						semihosting->result = -1;
+						semihosting->sys_errno = ENOMEM;
+					} else {
+						retval = target_read_buffer(target, addr, len, buf);
+						if (retval != ERROR_OK) {
+							free(buf);
+							return retval;
+						}
+						semihosting->result = write(fd, buf, len);
+						semihosting->sys_errno = errno;
+						LOG_DEBUG("write(%d, 0x%" PRIx64 ", %zu)=%d",
+							fd,
+							addr,
+							len,
+							(int)semihosting->result);
+						if (semihosting->result >= 0) {
+							/* The number of bytes that are NOT written.
+							 * */
+							semihosting->result = len -
+								semihosting->result;
+						}
+
+						free(buf);
+					}
+				}
+			}
+			break;
+
+		case SEMIHOSTING_SYS_WRITEC:	/* 0x03 */
+			/*
+			 * Writes a character byte, pointed to by the PARAMETER REGISTER,
+			 * to the debug channel. When executed under a semihosting
+			 * debugger, the character appears on the host debugger console.
+			 *
+			 * Entry
+			 * On entry, the PARAMETER REGISTER contains a pointer to the
+			 * character.
+			 *
+			 * Return
+			 * None. The RETURN REGISTER is corrupted.
+			 */
+			if (semihosting->is_fileio) {
+				semihosting->hit_fileio = true;
+				fileio_info->identifier = "write";
+				fileio_info->param_1 = 1;
+				fileio_info->param_2 = semihosting->param;
+				fileio_info->param_3 = 1;
+			} else {
+				uint64_t addr = semihosting->param;
+				unsigned char c;
+				retval = target_read_memory(target, addr, 1, 1, &c);
+				if (retval != ERROR_OK)
+					return retval;
+				putchar(c);
+				semihosting->result = 0;
+			}
+			break;
+
+		case SEMIHOSTING_SYS_WRITE0:	/* 0x04 */
+			/*
+			 * Writes a null-terminated string to the debug channel.
+			 * When executed under a semihosting debugger, the characters
+			 * appear on the host debugger console.
+			 *
+			 * Entry
+			 * On entry, the PARAMETER REGISTER contains a pointer to the
+			 * first byte of the string.
+			 *
+			 * Return
+			 * None. The RETURN REGISTER is corrupted.
+			 */
+			if (semihosting->is_fileio) {
+				size_t count = 0;
+				uint64_t addr = semihosting->param;
+				for (;; addr++) {
+					unsigned char c;
+					retval = target_read_memory(target, addr, 1, 1, &c);
+					if (retval != ERROR_OK)
+						return retval;
+					if (c == '\0')
+						break;
+					count++;
+				}
+				semihosting->hit_fileio = true;
+				fileio_info->identifier = "write";
+				fileio_info->param_1 = 1;
+				fileio_info->param_2 = semihosting->param;
+				fileio_info->param_3 = count;
+			} else {
+				uint64_t addr = semihosting->param;
+				do {
+					unsigned char c;
+					retval = target_read_memory(target, addr++, 1, 1, &c);
+					if (retval != ERROR_OK)
+						return retval;
+					if (!c)
+						break;
+					putchar(c);
+				} while (1);
+				semihosting->result = 0;
+			}
+			break;
+
+		case SEMIHOSTING_SYS_ELAPSED:	/* 0x30 */
+		/*
+		 * Returns the number of elapsed target ticks since execution
+		 * started.
+		 * Use SYS_TICKFREQ to determine the tick frequency.
+		 *
+		 * Entry (32-bit)
+		 * On entry, the PARAMETER REGISTER points to a two-field data
+		 * block to be used for returning the number of elapsed ticks:
+		 * - field 1 The least significant field and is at the low address.
+		 * - field 2 The most significant field and is at the high address.
+		 *
+		 * Entry (64-bit)
+		 * On entry the PARAMETER REGISTER points to a one-field data
+		 * block to be used for returning the number of elapsed ticks:
+		 * - field 1 The number of elapsed ticks as a 64-bit value.
+		 *
+		 * Return
+		 * On exit:
+		 * - On success, the RETURN REGISTER contains 0, the PARAMETER
+		 * REGISTER is unchanged, and the data block pointed to by the
+		 * PARAMETER REGISTER is filled in with the number of elapsed
+		 * ticks.
+		 * - On failure, the RETURN REGISTER contains -1, and the
+		 * PARAMETER REGISTER contains -1.
+		 *
+		 * Note: Some semihosting implementations might not support this
+		 * semihosting operation, and they always return -1 in the
+		 * RETURN REGISTER.
+		 */
+
+		case SEMIHOSTING_SYS_TICKFREQ:	/* 0x31 */
+		/*
+		 * Returns the tick frequency.
+		 *
+		 * Entry
+		 * The PARAMETER REGISTER must contain 0 on entry to this routine.
+		 *
+		 * Return
+		 * On exit, the RETURN REGISTER contains either:
+		 * - The number of ticks per second.
+		 * - –1 if the target does not know the value of one tick.
+		 *
+		 * Note: Some semihosting implementations might not support
+		 * this semihosting operation, and they always return -1 in the
+		 * RETURN REGISTER.
+		 */
+
+		case SEMIHOSTING_SYS_TMPNAM:	/* 0x0D */
+		/*
+		 * Returns a temporary name for a file identified by a system
+		 * file identifier.
+		 *
+		 * Entry
+		 * On entry, the PARAMETER REGISTER contains a pointer to a
+		 * three-word argument block:
+		 * - field 1 A pointer to a buffer.
+		 * - field 2 A target identifier for this filename. Its value
+		 * must be an integer in the range 0-255.
+		 * - field 3 Contains the length of the buffer. The length must
+		 * be at least the value of L_tmpnam on the host system.
+		 *
+		 * Return
+		 * On exit, the RETURN REGISTER contains:
+		 * - 0 if the call is successful.
+		 * - –1 if an error occurs.
+		 *
+		 * The buffer pointed to by the PARAMETER REGISTER contains
+		 * the filename, prefixed with a suitable directory name.
+		 * If you use the same target identifier again, the same
+		 * filename is returned.
+		 *
+		 * Note: The returned string must be null-terminated.
+		 */
+
+		default:
+			fprintf(stderr, "semihosting: unsupported call %#x\n",
+				(unsigned) semihosting->op);
+			semihosting->result = -1;
+			semihosting->sys_errno = ENOTSUP;
+	}
+
+	if (!semihosting->hit_fileio) {
+		retval = semihosting->post_result(target);
+		if (retval != ERROR_OK) {
+			LOG_ERROR("Failed to post semihosting result");
+			return retval;
+		}
+	}
+
+	return ERROR_OK;
+}
+
+/* -------------------------------------------------------------------------
+ * Local functions. */
+
+static int semihosting_common_fileio_info(struct target *target,
+	struct gdb_fileio_info *fileio_info)
+{
+	struct semihosting *semihosting = target->semihosting;
+	if (!semihosting)
+		return ERROR_FAIL;
+
+	/*
+	 * To avoid unnecessary duplication, semihosting prepares the
+	 * fileio_info structure out-of-band when the target halts. See
+	 * do_semihosting for more detail.
+	 */
+	if (!semihosting->is_fileio || !semihosting->hit_fileio)
+		return ERROR_FAIL;
+
+	return ERROR_OK;
+}
+
+static int semihosting_common_fileio_end(struct target *target, int result,
+	int fileio_errno, bool ctrl_c)
+{
+	struct gdb_fileio_info *fileio_info = target->fileio_info;
+	struct semihosting *semihosting = target->semihosting;
+	if (!semihosting)
+		return ERROR_FAIL;
+
+	/* clear pending status */
+	semihosting->hit_fileio = false;
+
+	semihosting->result = result;
+	semihosting->sys_errno = fileio_errno;
+
+	/*
+	 * Some fileio results do not match up with what the semihosting
+	 * operation expects; for these operations, we munge the results
+	 * below:
+	 */
+	switch (semihosting->op) {
+		case SEMIHOSTING_SYS_WRITE:	/* 0x05 */
+			if (result < 0)
+				semihosting->result = fileio_info->param_3;
+			else
+				semihosting->result = 0;
+			break;
+
+		case SEMIHOSTING_SYS_READ:	/* 0x06 */
+			if (result == (int)fileio_info->param_3)
+				semihosting->result = 0;
+			if (result <= 0)
+				semihosting->result = fileio_info->param_3;
+			break;
+
+		case SEMIHOSTING_SYS_SEEK:	/* 0x0a */
+			if (result > 0)
+				semihosting->result = 0;
+			break;
+	}
+
+	return semihosting->post_result(target);
+}
+
+/**
+ * Read all fields of a command from target to buffer.
+ */
+static int semihosting_read_fields(struct target *target, size_t number,
+	uint8_t *fields)
+{
+	struct semihosting *semihosting = target->semihosting;
+	return target_read_memory(target, semihosting->param,
+			semihosting->word_size_bytes, number, fields);
+}
+
+/**
+ * Write all fields of a command from buffer to target.
+ */
+static int semihosting_write_fields(struct target *target, size_t number,
+	uint8_t *fields)
+{
+	struct semihosting *semihosting = target->semihosting;
+	return target_write_memory(target, semihosting->param,
+			semihosting->word_size_bytes, number, fields);
+}
+
+/**
+ * Extract a field from the buffer, considering register size and endianness.
+ */
+static uint64_t semihosting_get_field(struct target *target, size_t index,
+	uint8_t *fields)
+{
+	struct semihosting *semihosting = target->semihosting;
+	if (semihosting->word_size_bytes == 8)
+		return target_buffer_get_u64(target, fields + (index * 8));
+	else
+		return target_buffer_get_u32(target, fields + (index * 4));
+}
+
+/**
+ * Store a field in the buffer, considering register size and endianness.
+ */
+static void semihosting_set_field(struct target *target, uint64_t value,
+	size_t index,
+	uint8_t *fields)
+{
+	struct semihosting *semihosting = target->semihosting;
+	if (semihosting->word_size_bytes == 8)
+		target_buffer_set_u64(target, fields + (index * 8), value);
+	else
+		target_buffer_set_u32(target, fields + (index * 4), value);
+}
+
+
+/* -------------------------------------------------------------------------
+ * Common semihosting commands handlers. */
+
+__COMMAND_HANDLER(handle_common_semihosting_command)
+{
+	struct target *target = get_current_target(CMD_CTX);
+
+	if (target == NULL) {
+		LOG_ERROR("No target selected");
+		return ERROR_FAIL;
+	}
+
+	struct semihosting *semihosting = target->semihosting;
+	if (!semihosting) {
+		command_print(CMD_CTX, "semihosting not supported for current target");
+		return ERROR_FAIL;
+	}
+
+	if (CMD_ARGC > 0) {
+		int is_active;
+
+		COMMAND_PARSE_ENABLE(CMD_ARGV[0], is_active);
+
+		if (!target_was_examined(target)) {
+			LOG_ERROR("Target not examined yet");
+			return ERROR_FAIL;
+		}
+
+		if (semihosting && semihosting->setup(target, is_active) != ERROR_OK) {
+			LOG_ERROR("Failed to Configure semihosting");
+			return ERROR_FAIL;
+		}
+
+		/* FIXME never let that "catch" be dropped! (???) */
+		semihosting->is_active = is_active;
+	}
+
+	command_print(CMD_CTX, "semihosting is %s",
+		semihosting->is_active
+		? "enabled" : "disabled");
+
+	return ERROR_OK;
+}
+
+
+__COMMAND_HANDLER(handle_common_semihosting_fileio_command)
+{
+	struct target *target = get_current_target(CMD_CTX);
+
+	if (target == NULL) {
+		LOG_ERROR("No target selected");
+		return ERROR_FAIL;
+	}
+
+	struct semihosting *semihosting = target->semihosting;
+	if (!semihosting) {
+		command_print(CMD_CTX, "semihosting not supported for current target");
+		return ERROR_FAIL;
+	}
+
+	if (!semihosting->is_active) {
+		command_print(CMD_CTX, "semihosting not yet enabled for current target");
+		return ERROR_FAIL;
+	}
+
+	if (CMD_ARGC > 0)
+		COMMAND_PARSE_ENABLE(CMD_ARGV[0], semihosting->is_fileio);
+
+	command_print(CMD_CTX, "semihosting fileio is %s",
+		semihosting->is_fileio
+		? "enabled" : "disabled");
+
+	return ERROR_OK;
+}
+
+__COMMAND_HANDLER(handle_common_semihosting_cmdline)
+{
+	struct target *target = get_current_target(CMD_CTX);
+	unsigned int i;
+
+	if (target == NULL) {
+		LOG_ERROR("No target selected");
+		return ERROR_FAIL;
+	}
+
+	struct semihosting *semihosting = target->semihosting;
+	if (!semihosting) {
+		command_print(CMD_CTX, "semihosting not supported for current target");
+		return ERROR_FAIL;
+	}
+
+	free(semihosting->cmdline);
+	semihosting->cmdline = CMD_ARGC > 0 ? strdup(CMD_ARGV[0]) : NULL;
+
+	for (i = 1; i < CMD_ARGC; i++) {
+		char *cmdline = alloc_printf("%s %s", semihosting->cmdline, CMD_ARGV[i]);
+		if (cmdline == NULL)
+			break;
+		free(semihosting->cmdline);
+		semihosting->cmdline = cmdline;
+	}
+
+	command_print(CMD_CTX, "semihosting command line is [%s]",
+		semihosting->cmdline);
+
+	return ERROR_OK;
+}
+
+__COMMAND_HANDLER(handle_common_semihosting_resumable_exit_command)
+{
+	struct target *target = get_current_target(CMD_CTX);
+
+	if (target == NULL) {
+		LOG_ERROR("No target selected");
+		return ERROR_FAIL;
+	}
+
+	struct semihosting *semihosting = target->semihosting;
+	if (!semihosting) {
+		command_print(CMD_CTX, "semihosting not supported for current target");
+		return ERROR_FAIL;
+	}
+
+	if (!semihosting->is_active) {
+		command_print(CMD_CTX, "semihosting not yet enabled for current target");
+		return ERROR_FAIL;
+	}
+
+	if (CMD_ARGC > 0)
+		COMMAND_PARSE_ENABLE(CMD_ARGV[0], semihosting->has_resumable_exit);
+
+	command_print(CMD_CTX, "semihosting resumable exit is %s",
+		semihosting->has_resumable_exit
+		? "enabled" : "disabled");
+
+	return ERROR_OK;
+}
diff --git a/src/target/semihosting_common.h b/src/target/semihosting_common.h
new file mode 100644
index 0000000..8fb5e0c
--- /dev/null
+++ b/src/target/semihosting_common.h
@@ -0,0 +1,163 @@
+/***************************************************************************
+ *   Copyright (C) 2018 by Liviu Ionescu                                   *
+ *   <ilg@livius.net>                                                      *
+ *                                                                         *
+ *   Copyright (C) 2009 by Marvell Technology Group Ltd.                   *
+ *   Written by Nicolas Pitre <nico@marvell.com>                           *
+ *                                                                         *
+ *   This program is free software; you can redistribute it and/or modify  *
+ *   it under the terms of the GNU General Public License as published by  *
+ *   the Free Software Foundation; either version 2 of the License, or     *
+ *   (at your option) any later version.                                   *
+ *                                                                         *
+ *   This program is distributed in the hope that it will be useful,       *
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
+ *   GNU General Public License for more details.                          *
+ *                                                                         *
+ *   You should have received a copy of the GNU General Public License     *
+ *   along with this program.  If not, see <http://www.gnu.org/licenses/>. *
+ ***************************************************************************/
+
+#ifndef OPENOCD_TARGET_SEMIHOSTING_COMMON_H
+#define OPENOCD_TARGET_SEMIHOSTING_COMMON_H
+
+#include <stdint.h>
+#include <stdbool.h>
+#include <time.h>
+
+/*
+ * According to:
+ * "Semihosting for AArch32 and AArch64, Release 2.0"
+ * https://static.docs.arm.com/100863/0200/semihosting.pdf
+ * from ARM Ltd.
+ *
+ * The available semihosting operation numbers passed in R0 are allocated
+ * as follows:
+ * - 0x00-0x31 Used by ARM.
+ * - 0x32-0xFF Reserved for future use by ARM.
+ * - 0x100-0x1FF Reserved for user applications. These are not used by ARM.
+ *   However, if you are writing your own SVC operations, you are advised
+ *   to use a different SVC number rather than using the semihosted
+ *   SVC number and these operation type numbers.
+ * - 0x200-0xFFFFFFFF Undefined and currently unused. It is recommended
+ *   that you do not use these.
+ */
+
+enum semihosting_operation_numbers {
+	/*
+	 * ARM semihosting operations, in lexicographic order.
+	 */
+	SEMIHOSTING_ENTER_SVC = 0x17,	/* DEPRECATED */
+
+	SEMIHOSTING_SYS_CLOSE = 0x02,
+	SEMIHOSTING_SYS_CLOCK = 0x10,
+	SEMIHOSTING_SYS_ELAPSED = 0x30,
+	SEMIHOSTING_SYS_ERRNO = 0x13,
+	SEMIHOSTING_SYS_EXIT = 0x18,
+	SEMIHOSTING_SYS_EXIT_EXTENDED = 0x20,
+	SEMIHOSTING_SYS_FLEN = 0x0C,
+	SEMIHOSTING_SYS_GET_CMDLINE = 0x15,
+	SEMIHOSTING_SYS_HEAPINFO = 0x16,
+	SEMIHOSTING_SYS_ISERROR = 0x08,
+	SEMIHOSTING_SYS_ISTTY = 0x09,
+	SEMIHOSTING_SYS_OPEN = 0x01,
+	SEMIHOSTING_SYS_READ = 0x06,
+	SEMIHOSTING_SYS_READC = 0x07,
+	SEMIHOSTING_SYS_REMOVE = 0x0E,
+	SEMIHOSTING_SYS_RENAME = 0x0F,
+	SEMIHOSTING_SYS_SEEK = 0x0A,
+	SEMIHOSTING_SYS_SYSTEM = 0x12,
+	SEMIHOSTING_SYS_TICKFREQ = 0x31,
+	SEMIHOSTING_SYS_TIME = 0x11,
+	SEMIHOSTING_SYS_TMPNAM = 0x0D,
+	SEMIHOSTING_SYS_WRITE = 0x05,
+	SEMIHOSTING_SYS_WRITEC = 0x03,
+	SEMIHOSTING_SYS_WRITE0 = 0x04,
+};
+
+/*
+ * Codes used by SEMIHOSTING_SYS_EXIT (formerly
+ * SEMIHOSTING_REPORT_EXCEPTION).
+ * On 64-bits, the exit code is passed explicitly.
+ */
+enum semihosting_reported_exceptions {
+	/* On 32 bits, use it for exit(0) */
+	ADP_STOPPED_APPLICATION_EXIT = ((2 << 16) + 38),
+	/* On 32 bits, use it for exit(1) */
+	ADP_STOPPED_RUN_TIME_ERROR = ((2 << 16) + 35),
+};
+
+struct target;
+
+/*
+ * A pointer to this structure was added to the target structure.
+ */
+struct semihosting {
+
+	/** A flag reporting whether semihosting is active. */
+	bool is_active;
+
+	/** A flag reporting whether semihosting fileio is active. */
+	bool is_fileio;
+
+	/** A flag reporting whether semihosting fileio operation is active. */
+	bool hit_fileio;
+
+	/** Most are resumable, except the two exit calls. */
+	bool is_resumable;
+
+	/**
+	 * When SEMIHOSTING_SYS_EXIT is called outside a debug session,
+	 * things are simple, the openocd process calls exit() and passes
+	 * the value returned by the target.
+	 * When SEMIHOSTING_SYS_EXIT is called during a debug session,
+	 * by default execution returns to the debugger, leaving the
+	 * debugger in a HALT state, similar to the state entered when
+	 * encountering a break.
+	 * In some use cases, it is useful to have SEMIHOSTING_SYS_EXIT
+	 * return normally, as any semihosting call, and do not break
+	 * to the debugger.
+	 * The standard allows this to happen, but the condition
+	 * to trigger it is a bit obscure ("by performing an RDI_Execute
+	 * request or equivalent").
+	 *
+	 * To make the SEMIHOSTING_SYS_EXIT call return normally, enable
+	 * this variable via the dedicated command (default: disabled).
+	 */
+	bool has_resumable_exit;
+
+	/** The Target (hart) word size; 8 for 64-bits targets. */
+	size_t word_size_bytes;
+
+	/** The current semihosting operation (R0 on ARM). */
+	int op;
+
+	/** The current semihosting parameter (R1 or ARM). */
+	uint64_t param;
+
+	/**
+	 * The current semihosting result to be returned to the application.
+	 * Usually 0 for success, -1 for error,
+	 * but sometimes a useful value, even a pointer.
+	 */
+	int64_t result;
+
+	/** The value to be returned by semihosting SYS_ERRNO request. */
+	int sys_errno;
+
+	/** The semihosting command line to be passed to the target. */
+	char *cmdline;
+
+	/** The current time when 'execution starts' */
+	clock_t setup_time;
+
+	int (*setup)(struct target *target, int enable);
+	int (*post_result)(struct target *target);
+};
+
+int semihosting_common_init(struct target *target, void *setup,
+	void *post_result);
+int semihosting_common(struct target *target);
+
+#endif	/* OPENOCD_TARGET_SEMIHOSTING_COMMON_H */
diff --git a/src/target/target.h b/src/target/target.h
index c5fb55b..51a5b69 100644
--- a/src/target/target.h
+++ b/src/target/target.h
@@ -205,6 +205,9 @@ struct target {
 
 	/* file-I/O information for host to do syscall */
 	struct gdb_fileio_info *fileio_info;
+
+	/* The semihosting information, extracted from the target. */
+	struct semihosting *semihosting;
 };
 
 struct target_list {
@@ -214,10 +217,10 @@ struct target_list {
 
 struct gdb_fileio_info {
 	char *identifier;
-	uint32_t param_1;
-	uint32_t param_2;
-	uint32_t param_3;
-	uint32_t param_4;
+	uint64_t param_1;
+	uint64_t param_2;
+	uint64_t param_3;
+	uint64_t param_4;
 };
 
 /** Returns the instance-specific name of the specified target. */