Support 'help' as a synonym for '?' in command line options

For command line options which permit '?' meaning 'please list the
permitted values', add support for 'help' as a synonym, by abstracting
the check out into a helper function.

This change means that in some cases where we were being lazy in
our string parsing, "?junk" will now be rejected as an invalid option
rather than being (undocumentedly) treated the same way as "?".

Update the documentation to use 'help' rather than '?', since '?'
is a shell metacharacter and thus prone to fail confusingly if there
is a single character filename in the current working directory and
the '?' has not been escaped. It's therefore better to steer users
towards 'help', though '?' is retained for backwards compatibility.

We do not, however, update the output of the system emulator's -help
(or any documentation autogenerated from the qemu-options.hx which
is the source of the -help text) because libvirt parses our -help
output and will break. At a later date when QEMU provides a better
interface so libvirt can avoid having to do this, we can update the
-help text too.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

17 files changed, 70 insertions, 23 deletions

diff --git a/arch_init.c b/arch_init.c
index 26f30ef987..60823baabd 100644
--- a/arch_init.c
+++ b/arch_init.c
@@ -680,7 +680,7 @@ void select_soundhw(const char *optarg)
 {
     struct soundhw *c;
 
-    if (*optarg == '?') {
+    if (is_help_option(optarg)) {
     show_valid_cards:
 
         printf("Valid sound card names (comma separated):\n");
@@ -688,7 +688,7 @@ void select_soundhw(const char *optarg)
             printf ("%-11s %s\n", c->name, c->descr);
         }
         printf("\n-soundhw all will enable all of the above\n");
-        exit(*optarg != '?');
+        exit(!is_help_option(optarg));
     }
     else {
         size_t l;
diff --git a/blockdev.c b/blockdev.c
index 3d7501565d..8669142704 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -398,11 +398,11 @@ DriveInfo *drive_init(QemuOpts *opts, int default_to_scsi)
 #endif
 
     if ((buf = qemu_opt_get(opts, "format")) != NULL) {
-       if (strcmp(buf, "?") == 0) {
-           error_printf("Supported formats:");
-           bdrv_iterate_format(bdrv_format_print, NULL);
-           error_printf("\n");
-           return NULL;
+        if (is_help_option(buf)) {
+            error_printf("Supported formats:");
+            bdrv_iterate_format(bdrv_format_print, NULL);
+            error_printf("\n");
+            return NULL;
         }
         drv = bdrv_find_whitelisted_format(buf);
         if (!drv) {
diff --git a/bsd-user/main.c b/bsd-user/main.c
index cd33d655f5..095ae8eaaa 100644
--- a/bsd-user/main.c
+++ b/bsd-user/main.c
@@ -681,7 +681,7 @@ static void usage(void)
            "-g port           wait gdb connection to port\n"
            "-L path           set the elf interpreter prefix (default=%s)\n"
            "-s size           set the stack size in bytes (default=%ld)\n"
-           "-cpu model        select CPU (-cpu ? for list)\n"
+           "-cpu model        select CPU (-cpu help for list)\n"
            "-drop-ld-preload  drop LD_PRELOAD for target process\n"
            "-E var=value      sets/modifies targets environment variable(s)\n"
            "-U var            unsets targets environment variable(s)\n"
@@ -825,7 +825,7 @@ int main(int argc, char **argv)
             qemu_uname_release = argv[optind++];
         } else if (!strcmp(r, "cpu")) {
             cpu_model = argv[optind++];
-            if (strcmp(cpu_model, "?") == 0) {
+            if (is_help_option(cpu_model)) {
 /* XXX: implement xxx_cpu_list for targets that still miss it */
 #if defined(cpu_list)
                     cpu_list(stdout, &fprintf);
diff --git a/hw/mips_jazz.c b/hw/mips_jazz.c
index bf1b799c4d..db927f14d0 100644
--- a/hw/mips_jazz.c
+++ b/hw/mips_jazz.c
@@ -239,7 +239,7 @@ static void mips_jazz_init(MemoryRegion *address_space,
             dp83932_init(nd, 0x80001000, 2, get_system_memory(), rc4030[4],
                          rc4030_opaque, rc4030_dma_memory_rw);
             break;
-        } else if (strcmp(nd->model, "?") == 0) {
+        } else if (is_help_option(nd->model)) {
             fprintf(stderr, "qemu: Supported NICs: dp83932\n");
             exit(1);
         } else {
diff --git a/hw/qdev-monitor.c b/hw/qdev-monitor.c
index 7915b4500d..b22a37a00c 100644
--- a/hw/qdev-monitor.c
+++ b/hw/qdev-monitor.c
@@ -138,13 +138,13 @@ int qdev_device_help(QemuOpts *opts)
     ObjectClass *klass;
 
     driver = qemu_opt_get(opts, "driver");
-    if (driver && !strcmp(driver, "?")) {
+    if (driver && is_help_option(driver)) {
         bool show_no_user = false;
         object_class_foreach(qdev_print_devinfo, TYPE_DEVICE, false, &show_no_user);
         return 1;
     }
 
-    if (!driver || !qemu_opt_get(opts, "?")) {
+    if (!driver || !qemu_opt_has_help_opt(opts)) {
         return 0;
     }
 
diff --git a/hw/watchdog.c b/hw/watchdog.c
index a42124d520..b52acedd98 100644
--- a/hw/watchdog.c
+++ b/hw/watchdog.c
@@ -55,7 +55,7 @@ int select_watchdog(const char *p)
     QemuOpts *opts;
 
     /* -watchdog ? lists available devices and exits cleanly. */
-    if (strcmp(p, "?") == 0) {
+    if (is_help_option(p)) {
         QLIST_FOREACH(model, &watchdog_list, entry) {
             fprintf(stderr, "\t%s\t%s\n",
                      model->wdt_name, model->wdt_description);
diff --git a/linux-user/main.c b/linux-user/main.c
index a0ab8e839c..25eaa11a1f 100644
--- a/linux-user/main.c
+++ b/linux-user/main.c
@@ -3140,7 +3140,7 @@ static void handle_arg_uname(const char *arg)
 static void handle_arg_cpu(const char *arg)
 {
     cpu_model = strdup(arg);
-    if (cpu_model == NULL || strcmp(cpu_model, "?") == 0) {
+    if (cpu_model == NULL || is_help_option(cpu_model)) {
         /* XXX: implement xxx_cpu_list for targets that still miss it */
 #if defined(cpu_list_id)
         cpu_list_id(stdout, &fprintf, "");
@@ -3231,7 +3231,7 @@ struct qemu_argument arg_table[] = {
     {"s",          "QEMU_STACK_SIZE",  true,  handle_arg_stack_size,
      "size",       "set the stack size to 'size' bytes"},
     {"cpu",        "QEMU_CPU",         true,  handle_arg_cpu,
-     "model",      "select CPU (-cpu ? for list)"},
+     "model",      "select CPU (-cpu help for list)"},
     {"E",          "QEMU_SET_ENV",     true,  handle_arg_set_env,
      "var=value",  "sets targets environment variable (see below)"},
     {"U",          "QEMU_UNSET_ENV",   true,  handle_arg_unset_env,
diff --git a/net.c b/net.c
index dbca77bad1..32ca50eaf0 100644
--- a/net.c
+++ b/net.c
@@ -691,8 +691,9 @@ int qemu_show_nic_models(const char *arg, const char *const *models)
 {
     int i;
 
-    if (!arg || strcmp(arg, "?"))
+    if (!arg || !is_help_option(arg)) {
         return 0;
+    }
 
     fprintf(stderr, "qemu: Supported NIC models: ");
     for (i = 0 ; models[i]; i++)
diff --git a/qemu-common.h b/qemu-common.h
index d26ff39e87..dd91912024 100644
--- a/qemu-common.h
+++ b/qemu-common.h
@@ -136,6 +136,24 @@ int qemu_main(int argc, char **argv, char **envp);
 void qemu_get_timedate(struct tm *tm, int offset);
 int qemu_timedate_diff(struct tm *tm);
 
+/**
+ * is_help_option:
+ * @s: string to test
+ *
+ * Check whether @s is one of the standard strings which indicate
+ * that the user is asking for a list of the valid values for a
+ * command option like -cpu or -M. The current accepted strings
+ * are 'help' and '?'. '?' is deprecated (it is a shell wildcard
+ * which makes it annoying to use in a reliable way) but provided
+ * for backwards compatibility.
+ *
+ * Returns: true if @s is a request for a list.
+ */
+static inline bool is_help_option(const char *s)
+{
+    return !strcmp(s, "?") || !strcmp(s, "help");
+}
+
 /* cutils.c */
 void pstrcpy(char *buf, int buf_size, const char *str);
 void strpadcpy(char *buf, int buf_size, const char *str, char pad);
diff --git a/qemu-doc.texi b/qemu-doc.texi
index 84dad19579..a41448a7a7 100644
--- a/qemu-doc.texi
+++ b/qemu-doc.texi
@@ -2390,7 +2390,7 @@ Set the x86 elf interpreter prefix (default=/usr/local/qemu-i386)
 @item -s size
 Set the x86 stack size in bytes (default=524288)
 @item -cpu model
-Select CPU model (-cpu ? for list and additional feature selection)
+Select CPU model (-cpu help for list and additional feature selection)
 @item -ignore-environment
 Start with an empty environment. Without this option,
 the initial environment is a copy of the caller's environment.
diff --git a/qemu-ga.c b/qemu-ga.c
index 8199da789c..f1a39ec3a6 100644
--- a/qemu-ga.c
+++ b/qemu-ga.c
@@ -736,7 +736,7 @@ int main(int argc, char **argv)
             break;
         case 'b': {
             char **list_head, **list;
-            if (*optarg == '?') {
+            if (is_help_option(optarg)) {
                 list_head = list = qmp_get_command_list();
                 while (*list != NULL) {
                     printf("%s\n", *list);
diff --git a/qemu-img.c b/qemu-img.c
index 80cfb9b167..b866f8081e 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -350,7 +350,7 @@ static int img_create(int argc, char **argv)
         img_size = (uint64_t)sval;
     }
 
-    if (options && !strcmp(options, "?")) {
+    if (options && is_help_option(options)) {
         ret = print_block_option_help(filename, fmt);
         goto out;
     }
@@ -744,7 +744,7 @@ static int img_convert(int argc, char **argv)
     /* Initialize before goto out */
     qemu_progress_init(progress, 2.0);
 
-    if (options && !strcmp(options, "?")) {
+    if (options && is_help_option(options)) {
         ret = print_block_option_help(out_filename, out_fmt);
         goto out;
     }
diff --git a/qemu-option.c b/qemu-option.c
index 8334190c53..27891e74e7 100644
--- a/qemu-option.c
+++ b/qemu-option.c
@@ -529,6 +529,18 @@ const char *qemu_opt_get(QemuOpts *opts, const char *name)
     return opt ? opt->str : NULL;
 }
 
+bool qemu_opt_has_help_opt(QemuOpts *opts)
+{
+    QemuOpt *opt;
+
+    QTAILQ_FOREACH_REVERSE(opt, &opts->head, QemuOptHead, next) {
+        if (is_help_option(opt->name)) {
+            return true;
+        }
+    }
+    return false;
+}
+
 bool qemu_opt_get_bool(QemuOpts *opts, const char *name, bool defval)
 {
     QemuOpt *opt = qemu_opt_find(opts, name);
diff --git a/qemu-option.h b/qemu-option.h
index 951dec3cc4..ca729862d5 100644
--- a/qemu-option.h
+++ b/qemu-option.h
@@ -107,6 +107,18 @@ struct QemuOptsList {
 };
 
 const char *qemu_opt_get(QemuOpts *opts, const char *name);
+/**
+ * qemu_opt_has_help_opt:
+ * @opts: options to search for a help request
+ *
+ * Check whether the options specified by @opts include one of the
+ * standard strings which indicate that the user is asking for a
+ * list of the valid values for a command line option (as defined
+ * by is_help_option()).
+ *
+ * Returns: true if @opts includes 'help' or equivalent.
+ */
+bool qemu_opt_has_help_opt(QemuOpts *opts);
 bool qemu_opt_get_bool(QemuOpts *opts, const char *name, bool defval);
 uint64_t qemu_opt_get_number(QemuOpts *opts, const char *name, uint64_t defval);
 uint64_t qemu_opt_get_size(QemuOpts *opts, const char *name, uint64_t defval);
diff --git a/qemu-options.hx b/qemu-options.hx
index dc68e15033..9277414782 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -6,6 +6,10 @@ HXCOMM construct option structures, enums and help message for specified
 HXCOMM architectures.
 HXCOMM HXCOMM can be used for comments, discarded from both texi and C
 
+HXCOMM TODO : when we are able to change -help output without breaking
+HXCOMM libvirt we should update the help options which refer to -cpu ?,
+HXCOMM -driver ?, etc to use the preferred -cpu help etc instead.
+
 DEFHEADING(Standard options:)
 STEXI
 @table @option
diff --git a/qemu-timer.c b/qemu-timer.c
index de9897788d..062fdf2cb9 100644
--- a/qemu-timer.c
+++ b/qemu-timer.c
@@ -183,7 +183,7 @@ void configure_alarms(char const *opt)
     char *name;
     struct qemu_alarm_timer tmp;
 
-    if (!strcmp(opt, "?")) {
+    if (is_help_option(opt)) {
         show_available_alarms();
         exit(0);
     }
diff --git a/vl.c b/vl.c
index 9fea320bb2..1fd11148e7 100644
--- a/vl.c
+++ b/vl.c
@@ -2086,7 +2086,7 @@ static QEMUMachine *machine_parse(const char *name)
         printf("%-20s %s%s\n", m->name, m->desc,
                m->is_default ? " (default)" : "");
     }
-    exit(!name || *name != '?');
+    exit(!name || !is_help_option(name));
 }
 
 static int tcg_init(void)
@@ -3216,7 +3216,7 @@ int main(int argc, char **argv, char **envp)
      */
     cpudef_init();
 
-    if (cpu_model && *cpu_model == '?') {
+    if (cpu_model && is_help_option(cpu_model)) {
         list_cpus(stdout, &fprintf, cpu_model);
         exit(0);
     }