[Qemu-devel] [PATCH 5/6] trace-state: [simple] add "-trace events" argument to control initial state

[Lluís <xscript@gmx.net>]

When using the "simple" tracing backend, all events are in disabled state by
default.

The "-trace events" argument can be used to provide a file with a list of trace
event names that will be enabled prior to starting execution. This saves the
user from manually toggling event states through the monitor interface, as well
as enables early tracing for the selected points, much like other
more-sophisticated backends like "ust" or "dtrace".

Signed-off-by: Lluís Vilanova <vilanova@ac.upc.edu>
---
 docs/tracing.txt |    5 +++
 qemu-config.c    |    5 ++-
 qemu-options.hx  |   18 ++++++++--
 vl.c             |   94 +++++++++++++++++++++++++++++++++++-------------------
 4 files changed, 84 insertions(+), 38 deletions(-)

diff --git a/docs/tracing.txt b/docs/tracing.txt
index 49e030e..5f86f1a 100644
--- a/docs/tracing.txt
+++ b/docs/tracing.txt
@@ -144,6 +144,11 @@ source tree.  It may not be as powerful as platform-specific or third-party
 trace backends but it is portable.  This is the recommended trace backend
 unless you have specific needs for more advanced backends.
 
+==== Enabling trace events from the command line ====
+
+The "-trace events=<file>" command line argument can be used to enable the
+events listed in <file> from the very beginning of the program.
+
 ==== Monitor commands ====
 
 * info trace
diff --git a/qemu-config.c b/qemu-config.c
index 323d3c2..0a00081 100644
--- a/qemu-config.c
+++ b/qemu-config.c
@@ -300,12 +300,15 @@ static QemuOptsList qemu_mon_opts = {
 #ifdef CONFIG_SIMPLE_TRACE
 static QemuOptsList qemu_trace_opts = {
     .name = "trace",
-    .implied_opt_name = "trace",
+    .implied_opt_name = "file",
     .head = QTAILQ_HEAD_INITIALIZER(qemu_trace_opts.head),
     .desc = {
         {
             .name = "file",
             .type = QEMU_OPT_STRING,
+        },{
+            .name = "events",
+            .type = QEMU_OPT_STRING,
         },
         { /* end if list */ }
     },
diff --git a/qemu-options.hx b/qemu-options.hx
index ef60730..e7b93b5 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -2358,13 +2358,23 @@ option will prevent QEMU from loading these configuration files at startup.
 ETEXI
 #ifdef CONFIG_SIMPLE_TRACE
 DEF("trace", HAS_ARG, QEMU_OPTION_trace,
-    "-trace\n"
-    "                Specify a trace file to log traces to\n",
+    "-trace [file=]<file>[,events=<file>]\n"
+    "                specify tracing options\n",
     QEMU_ARCH_ALL)
 STEXI
-@item -trace
+@item -trace [file=]@var{file}[,events=@var{file}]
 @findex -trace
-Specify a trace file to log output traces to.
+
+Specify tracing options.
+
+@table @option
+@item file=@var{file}
+Log output traces to @var{file}.
+@item events=@var{file}
+Immediately enable events listed in @var{file}.
+The file must contain one event name (as listed in the @var{trace-events} file)
+per line.
+@end table
 ETEXI
 #endif
 
diff --git a/vl.c b/vl.c
index c387f2b..5d6b03b 100644
--- a/vl.c
+++ b/vl.c
@@ -1931,7 +1931,7 @@ static int virtcon_parse(const char *devname)
 }
 
 static int debugcon_parse(const char *devname)
-{   
+{
     QemuOpts *opts;
 
     if (!qemu_chr_open("debugcon", devname, NULL)) {
@@ -2039,6 +2039,7 @@ int main(int argc, char **argv, char **envp)
 #endif
     int defconfig = 1;
     const char *trace_file = NULL;
+    const char *trace_events_file = NULL;
 
     atexit(qemu_run_exit_notifiers);
     error_set_progname(argv[0]);
@@ -2112,7 +2113,7 @@ int main(int argc, char **argv, char **envp)
         if (optind >= argc)
             break;
         if (argv[optind][0] != '-') {
-	    hda_opts = drive_add(IF_DEFAULT, 0, argv[optind++], HD_OPTS);
+            hda_opts = drive_add(IF_DEFAULT, 0, argv[optind++], HD_OPTS);
         } else {
             const QEMUOption *popt;
 
@@ -2174,15 +2175,15 @@ int main(int argc, char **argv, char **envp)
                 break;
             case QEMU_OPTION_drive:
                 drive_def(optarg);
-	        break;
+                break;
             case QEMU_OPTION_set:
                 if (qemu_set_option(optarg) != 0)
                     exit(1);
-	        break;
+                break;
             case QEMU_OPTION_global:
                 if (qemu_global_option(optarg) != 0)
                     exit(1);
-	        break;
+                break;
             case QEMU_OPTION_mtdblock:
                 drive_add(IF_MTD, -1, optarg, MTD_OPTS);
                 break;
@@ -2229,7 +2230,7 @@ int main(int argc, char **argv, char **envp)
                         fprintf(stderr, "qemu: invalid physical CHS format\n");
                         exit(1);
                     }
-		    if (hda_opts != NULL) {
+                    if (hda_opts != NULL) {
                         char num[16];
                         snprintf(num, sizeof(num), "%d", cyls);
                         qemu_opt_set(hda_opts, "cyls", num);
@@ -2431,9 +2432,9 @@ int main(int argc, char **argv, char **envp)
             case QEMU_OPTION_S:
                 autostart = 0;
                 break;
-	    case QEMU_OPTION_k:
-		keyboard_layout = optarg;
-		break;
+            case QEMU_OPTION_k:
+                keyboard_layout = optarg;
+                break;
             case QEMU_OPTION_localtime:
                 rtc_utc = 0;
                 break;
@@ -2616,9 +2617,9 @@ int main(int argc, char **argv, char **envp)
             case QEMU_OPTION_debugcon:
                 add_device_config(DEV_DEBUGCON, optarg);
                 break;
-	    case QEMU_OPTION_loadvm:
-		loadvm = optarg;
-		break;
+            case QEMU_OPTION_loadvm:
+                loadvm = optarg;
+                break;
             case QEMU_OPTION_full_screen:
                 full_screen = 1;
                 break;
@@ -2693,7 +2694,7 @@ int main(int argc, char **argv, char **envp)
                     exit(1);
                 }
                 break;
-	    case QEMU_OPTION_vnc:
+            case QEMU_OPTION_vnc:
 #ifdef CONFIG_VNC
                 display_remote++;
                 vnc_display = optarg;
@@ -2730,11 +2731,11 @@ int main(int argc, char **argv, char **envp)
                     exit(1);
                 }
                 break;
-	    case QEMU_OPTION_option_rom:
-		if (nb_option_roms >= MAX_OPTION_ROMS) {
-		    fprintf(stderr, "Too many option ROMs\n");
-		    exit(1);
-		}
+            case QEMU_OPTION_option_rom:
+                if (nb_option_roms >= MAX_OPTION_ROMS) {
+                    fprintf(stderr, "Too many option ROMs\n");
+                    exit(1);
+                }
                 opts = qemu_opts_parse(qemu_find_opts("option-rom"), optarg, 1);
                 option_rom[nb_option_roms].name = qemu_opt_get(opts, "romfile");
                 option_rom[nb_option_roms].bootindex =
@@ -2743,25 +2744,25 @@ int main(int argc, char **argv, char **envp)
                     fprintf(stderr, "Option ROM file is not specified\n");
                     exit(1);
                 }
-		nb_option_roms++;
-		break;
+                nb_option_roms++;
+                break;
             case QEMU_OPTION_semihosting:
                 semihosting_enabled = 1;
                 break;
             case QEMU_OPTION_name:
                 qemu_name = qemu_strdup(optarg);
-		 {
-		     char *p = strchr(qemu_name, ',');
-		     if (p != NULL) {
-		        *p++ = 0;
-			if (strncmp(p, "process=", 8)) {
-			    fprintf(stderr, "Unknown subargument %s to -name\n", p);
-			    exit(1);
-			}
-			p += 8;
-			os_set_proc_name(p);
-		     }	
-		 }	
+                 {
+                     char *p = strchr(qemu_name, ',');
+                     if (p != NULL) {
+                        *p++ = 0;
+                        if (strncmp(p, "process=", 8)) {
+                            fprintf(stderr, "Unknown subargument %s to -name\n", p);
+                            exit(1);
+                        }
+                        p += 8;
+                        os_set_proc_name(p);
+                     }
+                 }
                 break;
             case QEMU_OPTION_prom_env:
                 if (nb_prom_envs >= MAX_PROM_ENVS) {
@@ -2833,9 +2834,10 @@ int main(int argc, char **argv, char **envp)
                 break;
 #ifdef CONFIG_SIMPLE_TRACE
             case QEMU_OPTION_trace:
-                opts = qemu_opts_parse(qemu_find_opts("trace"), optarg, 0);
+                opts = qemu_opts_parse(qemu_find_opts("trace"), optarg, 1);
                 if (opts) {
                     trace_file = qemu_opt_get(opts, "file");
+                    trace_events_file = qemu_opt_get(opts, "events");
                 }
                 break;
 #endif
@@ -2887,6 +2889,32 @@ int main(int argc, char **argv, char **envp)
     if (!st_init(trace_file)) {
         fprintf(stderr, "warning: unable to initialize simple trace backend\n");
     }
+    if (trace_events_file) {
+        FILE *trace_events_fp = fopen(trace_events_file, "r");
+        if (!trace_events_fp) {
+            fprintf(stderr, "could not open trace events file '%s': %s\n",
+                    trace_events_file, strerror(errno));
+            exit(1);
+        }
+        char line_buf[1024];
+        char *line;
+        for (line = fgets(line_buf, 1024, trace_events_fp); line != NULL;
+             line = fgets(line_buf, 1024, trace_events_fp)) {
+            int len = strlen(line);
+            if (len > 1) {              /* skip empty lines */
+                line[len - 1] = '\0';
+                if (!st_change_trace_event_state(line, true)) {
+                    fprintf(stderr, "trace event '%s' does not exist\n", line);
+                    exit(1);
+                }
+            }
+        }
+        if (fclose(trace_events_fp) != 0) {
+            fprintf(stderr, "error closing file '%s': %s\n",
+                    trace_events_file, strerror(errno));
+            exit(1);
+        }
+    }
 
     /* If no data_dir is specified then try to find it relative to the
        executable path.  */