trace: [bsd-user] Commandline arguments to control tracing

[Changed const char *trace_file to char *trace_file since it's a
heap-allocated string that needs to be freed.  This type is also
returned by trace_opt_parse() and used in vl.c.

Also fixed coding style on for(;;) and else statement as suggested by
Eric Blake <eblake@redhat.com> since the patch modifies these lines or
close enough.
--Stefan]

Signed-off-by: Lluís Vilanova <vilanova@ac.upc.edu>
Message-id: 146860252322.30668.18276041739086338328.stgit@fimbulvetr.bsc.es
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

bsd-user/main.c

@@ -21,6 +21,7 @@
 
 #include "qapi/error.h"
 #include "qemu.h"
+#include "qemu/config-file.h"
 #include "qemu/path.h"
 #include "qemu/help_option.h"
 /* For tb_lock */
@@ -30,6 +31,8 @@
 #include "qemu/timer.h"
 #include "qemu/envlist.h"
 #include "exec/log.h"
+#include "trace/control.h"
+#include "glib-compat.h"
 
 int singlestep;
 unsigned long mmap_min_addr;
@@ -687,6 +690,8 @@ static void usage(void)
            "-p pagesize       set the host page size to 'pagesize'\n"
            "-singlestep       always run in singlestep mode\n"
            "-strace           log system calls\n"
+           "-trace            [[enable=]<pattern>][,events=<file>][,file=<file>]\n"
+           "                  specify tracing options\n"
            "\n"
            "Environment variables:\n"
            "QEMU_STRACE       Print system calls and arguments similar to the\n"
@@ -735,6 +740,7 @@ int main(int argc, char **argv)
     int gdbstub_port = 0;
     char **target_environ, **wrk;
     envlist_t *envlist = NULL;
+    char *trace_file = NULL;
     bsd_type = target_openbsd;
 
     if (argc <= 1)
@@ -754,8 +760,10 @@ int main(int argc, char **argv)
 
     cpu_model = NULL;
 
+    qemu_add_opts(&qemu_trace_opts);
+
     optind = 1;
-    for(;;) {
+    for (;;) {
         if (optind >= argc)
             break;
         r = argv[optind];
@@ -840,8 +848,10 @@ int main(int argc, char **argv)
             singlestep = 1;
         } else if (!strcmp(r, "strace")) {
             do_strace = 1;
-        } else
-        {
+        } else if (!strcmp(r, "trace")) {
+            g_free(trace_file);
+            trace_file = trace_opt_parse(optarg);
+        } else {
             usage();
         }
     }
@@ -865,6 +875,11 @@ int main(int argc, char **argv)
     }
     filename = argv[optind];
 
+    if (!trace_init_backends()) {
+        exit(1);
+    }
+    trace_init_file(trace_file);
+
     /* Zero out regs */
     memset(regs, 0, sizeof(struct target_pt_regs));