[Qemu-devel] [PATCH v4 2/2] semihosting: add --semihosting-config arg sub-argument

[Leon Alrae]

Add new "arg" sub-argument to the --semihosting-config allowing the user
to pass multiple input arguments separately. It is required for example
by UHI semihosting to construct argc and argv.

Also, update ARM semihosting to support new option (at the moment it is
the only target which cares about arguments).

If the semihosting is enabled and no semihosting args have been specified,
then fall back to -kernel/-append. The -append string is split on whitespace
before initializing semihosting.argv[1..n]; this is different from what
QEMU MIPS machines' pseudo-bootloaders do (i.e. argv[1] contains the whole
-append), but is more intuitive from UHI user's point of view and Linux
kernel just does not care as it concatenates argv[1..n] into single cmdline
string anyway.

Signed-off-by: Leon Alrae <address@hidden>
---
 include/exec/semihost.h | 18 ++++++++++++++
 qemu-options.hx         | 21 ++++++++++++----
 target-arm/arm-semi.c   | 10 +++-----
 vl.c                    | 64 +++++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 101 insertions(+), 12 deletions(-)

diff --git a/include/exec/semihost.h b/include/exec/semihost.h
index c2f0bcb..5980939 100644
--- a/include/exec/semihost.h
+++ b/include/exec/semihost.h
@@ -36,9 +36,27 @@ static inline SemihostingTarget semihosting_get_target(void)
 {
     return SEMIHOSTING_TARGET_AUTO;
 }
+
+static inline const char *semihosting_get_arg(int i)
+{
+    return NULL;
+}
+
+static inline int semihosting_get_argc(void)
+{
+    return 0;
+}
+
+static inline const char *semihosting_get_cmdline(void)
+{
+    return NULL;
+}
 #else
 bool semihosting_enabled(void);
 SemihostingTarget semihosting_get_target(void);
+const char *semihosting_get_arg(int i);
+int semihosting_get_argc(void);
+const char *semihosting_get_cmdline(void);
 #endif
 
 #endif
diff --git a/qemu-options.hx b/qemu-options.hx
index ec356f6..90500ad 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -3296,14 +3296,25 @@ STEXI
 Enable semihosting mode (ARM, M68K, Xtensa only).
 ETEXI
 DEF("semihosting-config", HAS_ARG, QEMU_OPTION_semihosting_config,
-    "-semihosting-config [enable=on|off,]target=native|gdb|auto   semihosting 
configuration\n",
+    "-semihosting-config 
[enable=on|off][,target=native|gdb|auto][,arg=str[,...]]\n" \
+    "                semihosting configuration\n",
 QEMU_ARCH_ARM | QEMU_ARCH_M68K | QEMU_ARCH_XTENSA | QEMU_ARCH_LM32)
 STEXI
address@hidden -semihosting-config [enable=on|off,]target=native|gdb|auto
address@hidden -semihosting-config 
[enable=on|off][,target=native|gdb|auto][,arg=str[,...]]
 @findex -semihosting-config
-Enable semihosting and define where the semihosting calls will be addressed,
-to QEMU (@code{native}) or to GDB (@code{gdb}). The default is @code{auto}, 
which means
address@hidden during debug sessions and @code{native} otherwise (ARM, M68K, 
Xtensa only).
+Enable and configure semihosting (ARM, M68K, Xtensa only).
address@hidden @option
address@hidden address@hidden|gdb|auto}
+Defines where the semihosting calls will be addressed, to QEMU (@code{native})
+or to GDB (@code{gdb}). The default is @code{auto}, which means @code{gdb}
+during debug sessions and @code{native} otherwise.
address@hidden address@hidden,address@hidden,...
+Allows the user to pass input arguments, and can be used multiple times to 
build
+up a list. The old-style @code{-kernel}/@code{-append} method of passing a
+command line is still supported for backward compatibility. If both the
address@hidden arg} and the @code{-kernel}/@code{-append} are
+specified, the former is passed to semihosting as it always takes precedence.
address@hidden table
 ETEXI
 DEF("old-param", 0, QEMU_OPTION_old_param,
     "-old-param      old param mode\n", QEMU_ARCH_ARM)
diff --git a/target-arm/arm-semi.c b/target-arm/arm-semi.c
index a8b83e6..74a67e9 100644
--- a/target-arm/arm-semi.c
+++ b/target-arm/arm-semi.c
@@ -27,6 +27,7 @@
 #include <time.h>
 
 #include "cpu.h"
+#include "exec/semihost.h"
 #ifdef CONFIG_USER_ONLY
 #include "qemu.h"
 
@@ -440,10 +441,7 @@ uint32_t do_arm_semihosting(CPUARMState *env)
             input_size = arg1;
             /* Compute the size of the output string.  */
 #if !defined(CONFIG_USER_ONLY)
-            output_size = strlen(ts->boot_info->kernel_filename)
-                        + 1  /* Separating space.  */
-                        + strlen(ts->boot_info->kernel_cmdline)
-                        + 1; /* Terminating null byte.  */
+            output_size = strlen(semihosting_get_cmdline()) + 1;
 #else
             unsigned int i;
 
@@ -474,9 +472,7 @@ uint32_t do_arm_semihosting(CPUARMState *env)
 
             /* Copy the command-line arguments.  */
 #if !defined(CONFIG_USER_ONLY)
-            pstrcpy(output_buffer, output_size, 
ts->boot_info->kernel_filename);
-            pstrcat(output_buffer, output_size, " ");
-            pstrcat(output_buffer, output_size, ts->boot_info->kernel_cmdline);
+            pstrcpy(output_buffer, output_size, semihosting_get_cmdline());
 #else
             if (output_size == 1) {
                 /* Empty command-line.  */
diff --git a/vl.c b/vl.c
index f3319a9..d599411 100644
--- a/vl.c
+++ b/vl.c
@@ -486,6 +486,9 @@ static QemuOptsList qemu_semihosting_config_opts = {
         }, {
             .name = "target",
             .type = QEMU_OPT_STRING,
+        }, {
+            .name = "arg",
+            .type = QEMU_OPT_STRING,
         },
         { /* end of list */ }
     },
@@ -1230,6 +1233,9 @@ static void configure_msg(QemuOpts *opts)
 typedef struct SemihostingConfig {
     bool enabled;
     SemihostingTarget target;
+    const char **argv;
+    int argc;
+    const char *cmdline; /* concatenated argv */
 } SemihostingConfig;
 
 static SemihostingConfig semihosting;
@@ -1244,6 +1250,56 @@ SemihostingTarget semihosting_get_target(void)
     return semihosting.target;
 }
 
+const char *semihosting_get_arg(int i)
+{
+    if (i >= semihosting.argc) {
+        return NULL;
+    }
+    return semihosting.argv[i];
+}
+
+int semihosting_get_argc(void)
+{
+    return semihosting.argc;
+}
+
+const char *semihosting_get_cmdline(void)
+{
+    if (semihosting.cmdline == NULL && semihosting.argc > 0) {
+        semihosting.cmdline = g_strjoinv(" ", (gchar **)semihosting.argv);
+    }
+    return semihosting.cmdline;
+}
+
+static int add_semihosting_arg(const char *name, const char *val, void *opaque)
+{
+    SemihostingConfig *s = opaque;
+    if (strcmp(name, "arg") == 0) {
+        s->argc++;
+        /* one extra element as g_strjoinv() expects NULL-terminated array */
+        s->argv = g_realloc(s->argv, (s->argc + 1) * sizeof(void *));
+        s->argv[s->argc - 1] = val;
+        s->argv[s->argc] = NULL;
+    }
+    return 0;
+}
+
+/* Use strings passed via -kernel/-append to initialize semihosting.argv[] */
+static inline void semihosting_arg_fallback(const char *file, const char *cmd)
+{
+    char *cmd_token;
+
+    /* argv[0] */
+    add_semihosting_arg("arg", file, &semihosting);
+
+    /* split -append and initialize argv[1..n] */
+    cmd_token = strtok(g_strdup(cmd), " ");
+    while (cmd_token) {
+        add_semihosting_arg("arg", cmd_token, &semihosting);
+        cmd_token = strtok(NULL, " ");
+    }
+}
+
 /***********************************************************/
 /* USB devices */
 
@@ -3592,6 +3648,9 @@ int main(int argc, char **argv, char **envp)
                     } else {
                         semihosting.target = SEMIHOSTING_TARGET_AUTO;
                     }
+                    /* Set semihosting argument count and vector */
+                    qemu_opt_foreach(opts, add_semihosting_arg,
+                                     &semihosting, 0);
                 } else {
                     fprintf(stderr, "Unsupported semihosting-config %s\n",
                             optarg);
@@ -4150,6 +4209,11 @@ int main(int argc, char **argv, char **envp)
         exit(1);
     }
 
+    if (semihosting_enabled() && !semihosting_get_argc() && kernel_filename) {
+        /* fall back to the -kernel/-append */
+        semihosting_arg_fallback(kernel_filename, kernel_cmdline);
+    }
+
     os_set_line_buffering();
 
 #ifdef CONFIG_SPICE