semihosting: Split out guestfd.c

In arm-compat-semi.c, we have more advanced treatment of
guest file descriptors than we do in other implementations.
Split out GuestFD and related functions to a new file so
that they can be shared.

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

3 files changed, 144 insertions, 142 deletions

diff --git a/semihosting/arm-compat-semi.c b/semihosting/arm-compat-semi.c
index 1033e75..2fa7f23 100644
--- a/semihosting/arm-compat-semi.c
+++ b/semihosting/arm-compat-semi.c
@@ -32,12 +32,13 @@
  */
 
 #include "qemu/osdep.h"
-
 #include "semihosting/semihost.h"
 #include "semihosting/console.h"
 #include "semihosting/common-semi.h"
+#include "semihosting/guestfd.h"
 #include "qemu/timer.h"
 #include "exec/gdbstub.h"
+
 #ifdef CONFIG_USER_ONLY
 #include "qemu.h"
 
@@ -123,27 +124,6 @@ static int open_modeflags[12] = {
     O_RDWR | O_CREAT | O_APPEND | O_BINARY
 };
 
-typedef enum GuestFDType {
-    GuestFDUnused = 0,
-    GuestFDHost = 1,
-    GuestFDGDB = 2,
-    GuestFDFeatureFile = 3,
-} GuestFDType;
-
-/*
- * Guest file descriptors are integer indexes into an array of
- * these structures (we will dynamically resize as necessary).
- */
-typedef struct GuestFD {
-    GuestFDType type;
-    union {
-        int hostfd;
-        target_ulong featurefile_offset;
-    };
-} GuestFD;
-
-static GArray *guestfd_array;
-
 #ifndef CONFIG_USER_ONLY
 
 /**
@@ -269,98 +249,6 @@ common_semi_sys_exit_extended(CPUState *cs, int nr)
 #endif
 
 /*
- * Allocate a new guest file descriptor and return it; if we
- * couldn't allocate a new fd then return -1.
- * This is a fairly simplistic implementation because we don't
- * expect that most semihosting guest programs will make very
- * heavy use of opening and closing fds.
- */
-static int alloc_guestfd(void)
-{
-    guint i;
-
-    if (!guestfd_array) {
-        /* New entries zero-initialized, i.e. type GuestFDUnused */
-        guestfd_array = g_array_new(FALSE, TRUE, sizeof(GuestFD));
-    }
-
-    /* SYS_OPEN should return nonzero handle on success. Start guestfd from 1 */
-    for (i = 1; i < guestfd_array->len; i++) {
-        GuestFD *gf = &g_array_index(guestfd_array, GuestFD, i);
-
-        if (gf->type == GuestFDUnused) {
-            return i;
-        }
-    }
-
-    /* All elements already in use: expand the array */
-    g_array_set_size(guestfd_array, i + 1);
-    return i;
-}
-
-/*
- * Look up the guestfd in the data structure; return NULL
- * for out of bounds, but don't check whether the slot is unused.
- * This is used internally by the other guestfd functions.
- */
-static GuestFD *do_get_guestfd(int guestfd)
-{
-    if (!guestfd_array) {
-        return NULL;
-    }
-
-    if (guestfd <= 0 || guestfd >= guestfd_array->len) {
-        return NULL;
-    }
-
-    return &g_array_index(guestfd_array, GuestFD, guestfd);
-}
-
-/*
- * Associate the specified guest fd (which must have been
- * allocated via alloc_fd() and not previously used) with
- * the specified host/gdb fd.
- */
-static void associate_guestfd(int guestfd, int hostfd)
-{
-    GuestFD *gf = do_get_guestfd(guestfd);
-
-    assert(gf);
-    gf->type = use_gdb_syscalls() ? GuestFDGDB : GuestFDHost;
-    gf->hostfd = hostfd;
-}
-
-/*
- * Deallocate the specified guest file descriptor. This doesn't
- * close the host fd, it merely undoes the work of alloc_fd().
- */
-static void dealloc_guestfd(int guestfd)
-{
-    GuestFD *gf = do_get_guestfd(guestfd);
-
-    assert(gf);
-    gf->type = GuestFDUnused;
-}
-
-/*
- * Given a guest file descriptor, get the associated struct.
- * If the fd is not valid, return NULL. This is the function
- * used by the various semihosting calls to validate a handle
- * from the guest.
- * Note: calling alloc_guestfd() or dealloc_guestfd() will
- * invalidate any GuestFD* obtained by calling this function.
- */
-static GuestFD *get_guestfd(int guestfd)
-{
-    GuestFD *gf = do_get_guestfd(guestfd);
-
-    if (!gf || gf->type == GuestFDUnused) {
-        return NULL;
-    }
-    return gf;
-}
-
-/*
  * The semihosting API has no concept of its errno being thread-safe,
  * as the API design predates SMP CPUs and was intended as a simple
  * real-hardware set of debug functionality. For QEMU, we make the
@@ -665,22 +553,13 @@ static const uint8_t featurefile_data[] = {
     SH_EXT_EXIT_EXTENDED | SH_EXT_STDOUT_STDERR, /* Feature byte 0 */
 };
 
-static void init_featurefile_guestfd(int guestfd)
-{
-    GuestFD *gf = do_get_guestfd(guestfd);
-
-    assert(gf);
-    gf->type = GuestFDFeatureFile;
-    gf->featurefile_offset = 0;
-}
-
-static uint32_t featurefile_closefn(CPUState *cs, GuestFD *gf)
+static uint32_t staticfile_closefn(CPUState *cs, GuestFD *gf)
 {
     /* Nothing to do */
     return 0;
 }
 
-static uint32_t featurefile_writefn(CPUState *cs, GuestFD *gf,
+static uint32_t staticfile_writefn(CPUState *cs, GuestFD *gf,
                                     target_ulong buf, uint32_t len)
 {
     /* This fd can never be open for writing */
@@ -689,7 +568,7 @@ static uint32_t featurefile_writefn(CPUState *cs, GuestFD *gf,
     return set_swi_errno(cs, -1);
 }
 
-static uint32_t featurefile_readfn(CPUState *cs, GuestFD *gf,
+static uint32_t staticfile_readfn(CPUState *cs, GuestFD *gf,
                                    target_ulong buf, uint32_t len)
 {
     CPUArchState *env = cs->env_ptr;
@@ -703,11 +582,11 @@ static uint32_t featurefile_readfn(CPUState *cs, GuestFD *gf,
     }
 
     for (i = 0; i < len; i++) {
-        if (gf->featurefile_offset >= sizeof(featurefile_data)) {
+        if (gf->staticfile.off >= gf->staticfile.len) {
             break;
         }
-        s[i] = featurefile_data[gf->featurefile_offset];
-        gf->featurefile_offset++;
+        s[i] = gf->staticfile.data[gf->staticfile.off];
+        gf->staticfile.off++;
     }
 
     unlock_user(s, buf, len);
@@ -716,21 +595,21 @@ static uint32_t featurefile_readfn(CPUState *cs, GuestFD *gf,
     return len - i;
 }
 
-static uint32_t featurefile_isattyfn(CPUState *cs, GuestFD *gf)
+static uint32_t staticfile_isattyfn(CPUState *cs, GuestFD *gf)
 {
     return 0;
 }
 
-static uint32_t featurefile_seekfn(CPUState *cs, GuestFD *gf,
+static uint32_t staticfile_seekfn(CPUState *cs, GuestFD *gf,
                                    target_ulong offset)
 {
-    gf->featurefile_offset = offset;
+    gf->staticfile.off = offset;
     return 0;
 }
 
-static uint32_t featurefile_flenfn(CPUState *cs, GuestFD *gf)
+static uint32_t staticfile_flenfn(CPUState *cs, GuestFD *gf)
 {
-    return sizeof(featurefile_data);
+    return gf->staticfile.len;
 }
 
 typedef struct GuestFDFunctions {
@@ -759,13 +638,13 @@ static const GuestFDFunctions guestfd_fns[] = {
         .seekfn = gdb_seekfn,
         .flenfn = gdb_flenfn,
     },
-    [GuestFDFeatureFile] = {
-        .closefn = featurefile_closefn,
-        .writefn = featurefile_writefn,
-        .readfn = featurefile_readfn,
-        .isattyfn = featurefile_isattyfn,
-        .seekfn = featurefile_seekfn,
-        .flenfn = featurefile_flenfn,
+    [GuestFDStatic] = {
+        .closefn = staticfile_closefn,
+        .writefn = staticfile_writefn,
+        .readfn = staticfile_readfn,
+        .isattyfn = staticfile_isattyfn,
+        .seekfn = staticfile_seekfn,
+        .flenfn = staticfile_flenfn,
     },
 };
 
@@ -886,7 +765,8 @@ target_ulong do_common_semihosting(CPUState *cs)
                 errno = EACCES;
                 return set_swi_errno(cs, -1);
             }
-            init_featurefile_guestfd(guestfd);
+            staticfile_guestfd(guestfd, featurefile_data,
+                               sizeof(featurefile_data));
             return guestfd;
         }
 
diff --git a/semihosting/guestfd.c b/semihosting/guestfd.c
new file mode 100644
index 0000000..b6405f5
--- /dev/null
+++ b/semihosting/guestfd.c
@@ -0,0 +1,118 @@
+/*
+ * Hosted file support for semihosting syscalls.
+ *
+ * Copyright (c) 2005, 2007 CodeSourcery.
+ * Copyright (c) 2019 Linaro
+ * Copyright © 2020 by Keith Packard <keithp@keithp.com>
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#include "qemu/osdep.h"
+#include "exec/gdbstub.h"
+#include "semihosting/guestfd.h"
+
+static GArray *guestfd_array;
+
+/*
+ * Allocate a new guest file descriptor and return it; if we
+ * couldn't allocate a new fd then return -1.
+ * This is a fairly simplistic implementation because we don't
+ * expect that most semihosting guest programs will make very
+ * heavy use of opening and closing fds.
+ */
+int alloc_guestfd(void)
+{
+    guint i;
+
+    if (!guestfd_array) {
+        /* New entries zero-initialized, i.e. type GuestFDUnused */
+        guestfd_array = g_array_new(FALSE, TRUE, sizeof(GuestFD));
+    }
+
+    /* SYS_OPEN should return nonzero handle on success. Start guestfd from 1 */
+    for (i = 1; i < guestfd_array->len; i++) {
+        GuestFD *gf = &g_array_index(guestfd_array, GuestFD, i);
+
+        if (gf->type == GuestFDUnused) {
+            return i;
+        }
+    }
+
+    /* All elements already in use: expand the array */
+    g_array_set_size(guestfd_array, i + 1);
+    return i;
+}
+
+/*
+ * Look up the guestfd in the data structure; return NULL
+ * for out of bounds, but don't check whether the slot is unused.
+ * This is used internally by the other guestfd functions.
+ */
+static GuestFD *do_get_guestfd(int guestfd)
+{
+    if (!guestfd_array) {
+        return NULL;
+    }
+
+    if (guestfd <= 0 || guestfd >= guestfd_array->len) {
+        return NULL;
+    }
+
+    return &g_array_index(guestfd_array, GuestFD, guestfd);
+}
+
+/*
+ * Given a guest file descriptor, get the associated struct.
+ * If the fd is not valid, return NULL. This is the function
+ * used by the various semihosting calls to validate a handle
+ * from the guest.
+ * Note: calling alloc_guestfd() or dealloc_guestfd() will
+ * invalidate any GuestFD* obtained by calling this function.
+ */
+GuestFD *get_guestfd(int guestfd)
+{
+    GuestFD *gf = do_get_guestfd(guestfd);
+
+    if (!gf || gf->type == GuestFDUnused) {
+        return NULL;
+    }
+    return gf;
+}
+
+/*
+ * Associate the specified guest fd (which must have been
+ * allocated via alloc_fd() and not previously used) with
+ * the specified host/gdb fd.
+ */
+void associate_guestfd(int guestfd, int hostfd)
+{
+    GuestFD *gf = do_get_guestfd(guestfd);
+
+    assert(gf);
+    gf->type = use_gdb_syscalls() ? GuestFDGDB : GuestFDHost;
+    gf->hostfd = hostfd;
+}
+
+void staticfile_guestfd(int guestfd, const uint8_t *data, size_t len)
+{
+    GuestFD *gf = do_get_guestfd(guestfd);
+
+    assert(gf);
+    gf->type = GuestFDStatic;
+    gf->staticfile.data = data;
+    gf->staticfile.len = len;
+    gf->staticfile.off = 0;
+}
+
+/*
+ * Deallocate the specified guest file descriptor. This doesn't
+ * close the host fd, it merely undoes the work of alloc_fd().
+ */
+void dealloc_guestfd(int guestfd)
+{
+    GuestFD *gf = do_get_guestfd(guestfd);
+
+    assert(gf);
+    gf->type = GuestFDUnused;
+}
diff --git a/semihosting/meson.build b/semihosting/meson.build
index 10b3b99..d2c1c37 100644
--- a/semihosting/meson.build
+++ b/semihosting/meson.build
@@ -1,3 +1,7 @@
+specific_ss.add(when: 'CONFIG_SEMIHOSTING', if_true: files(
+  'guestfd.c',
+))
+
 specific_ss.add(when: ['CONFIG_SEMIHOSTING', 'CONFIG_SOFTMMU'], if_true: files(
   'config.c',
   'console.c',