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// SPDX-License-Identifier: GPL-2.0-or-later
/***************************************************************************
* Copyright (C) 2018 by Liviu Ionescu *
* ilg@livius.net *
* *
* Copyright (C) 2009 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> *
***************************************************************************/
/**
* @file
* Hold RISC-V semihosting support.
*
* The RISC-V code is inspired from ARM semihosting.
*
* Details can be found in chapter 8 of DUI0203I_rvct_developer_guide.pdf
* from ARM Ltd.
*/
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include <helper/log.h>
#include "target/target.h"
#include "riscv.h"
#include "riscv_reg.h"
static int riscv_semihosting_setup(struct target *target, int enable);
static int riscv_semihosting_post_result(struct target *target);
/**
* Initialize RISC-V semihosting. Use common ARM code.
*/
void riscv_semihosting_init(struct target *target)
{
semihosting_common_init(target, riscv_semihosting_setup,
riscv_semihosting_post_result);
}
/**
* Check for and process a semihosting request using the ARM protocol). This
* is meant to be called when the target is stopped due to a debug mode entry.
*
* @param target Pointer to the target to process.
* @param retval Pointer to a location where the return code will be stored
* @return non-zero value if a request was processed or an error encountered
*/
enum semihosting_result riscv_semihosting(struct target *target, int *retval)
{
struct semihosting *semihosting = target->semihosting;
if (!semihosting) {
LOG_TARGET_DEBUG(target, " -> NONE (!semihosting)");
return SEMIHOSTING_NONE;
}
if (!semihosting->is_active) {
LOG_TARGET_DEBUG(target, " -> NONE (!semihosting->is_active)");
return SEMIHOSTING_NONE;
}
riscv_reg_t pc;
int result = riscv_reg_get(target, &pc, GDB_REGNO_PC);
if (result != ERROR_OK)
return SEMIHOSTING_ERROR;
/*
* The instructions that trigger a semihosting call,
* always uncompressed, should look like:
*/
uint32_t magic[] = {
0x01f01013, /* slli zero,zero,0x1f */
0x00100073, /* ebreak */
0x40705013 /* srai zero,zero,0x7 */
};
/* Read three uncompressed instructions: The previous, the current one (pointed to by PC) and the next one */
for (int i = 0; i < 3; i++) {
uint8_t buf[4];
/* Instruction memories may not support arbitrary read size. Use any size that will work. */
target_addr_t address = (pc - 4) + 4 * i;
*retval = riscv_read_by_any_size(target, address, 4, buf);
if (*retval != ERROR_OK)
return SEMIHOSTING_ERROR;
uint32_t value = target_buffer_get_u32(target, buf);
LOG_TARGET_DEBUG(target, "compare 0x%08x from 0x%" PRIx64 " against 0x%08x",
value, address, magic[i]);
if (value != magic[i]) {
LOG_TARGET_DEBUG(target, " -> NONE (no magic)");
return SEMIHOSTING_NONE;
}
}
/*
* Perform semihosting call if we are not waiting on a fileio
* operation to complete.
*/
if (!semihosting->hit_fileio) {
/* RISC-V uses A0 and A1 to pass function arguments */
riscv_reg_t r0;
riscv_reg_t r1;
result = riscv_reg_get(target, &r0, GDB_REGNO_A0);
if (result != ERROR_OK) {
LOG_TARGET_ERROR(target, "Could not read semihosting operation code (register a0)");
return SEMIHOSTING_ERROR;
}
result = riscv_reg_get(target, &r1, GDB_REGNO_A1);
if (result != ERROR_OK) {
LOG_TARGET_ERROR(target, "Could not read semihosting operation code (register a1)");
return SEMIHOSTING_ERROR;
}
semihosting->op = r0;
semihosting->param = r1;
semihosting->word_size_bytes = riscv_xlen(target) / 8;
/* Check for ARM operation numbers. */
if ((semihosting->op >= 0 && semihosting->op <= 0x31) ||
(semihosting->op >= 0x100 && semihosting->op <= 0x107)) {
*retval = semihosting_common(target);
if (*retval != ERROR_OK) {
LOG_TARGET_ERROR(target, "Failed semihosting operation (0x%02X)", semihosting->op);
return SEMIHOSTING_ERROR;
}
} else {
/* Unknown operation number, not a semihosting call. */
LOG_TARGET_ERROR(target, "Unknown semihosting operation requested (op = 0x%x)", semihosting->op);
return SEMIHOSTING_NONE;
}
}
/* Resume right after the EBREAK 4 bytes instruction. */
*retval = riscv_reg_set(target, GDB_REGNO_PC, pc + 4);
if (*retval != ERROR_OK)
return SEMIHOSTING_ERROR;
/*
* Resume target if we are not waiting on a fileio
* operation to complete.
*/
if (semihosting->is_resumable && !semihosting->hit_fileio) {
LOG_TARGET_DEBUG(target, " -> HANDLED");
return SEMIHOSTING_HANDLED;
}
LOG_TARGET_DEBUG(target, " -> WAITING");
return SEMIHOSTING_WAITING;
}
/* -------------------------------------------------------------------------
* Local functions. */
/**
* Called via semihosting->setup() later, after the target is known,
* usually on the first semihosting command.
*/
static int riscv_semihosting_setup(struct target *target, int enable)
{
LOG_TARGET_DEBUG(target, "enable=%d", enable);
struct semihosting *semihosting = target->semihosting;
if (semihosting)
semihosting->setup_time = clock();
return ERROR_OK;
}
static int riscv_semihosting_post_result(struct target *target)
{
struct semihosting *semihosting = target->semihosting;
if (!semihosting) {
/* If not enabled, silently ignored. */
return 0;
}
LOG_TARGET_DEBUG(target, "Result: 0x%" PRIx64, semihosting->result);
riscv_reg_set(target, GDB_REGNO_A0, semihosting->result);
return 0;
}
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