Re: [Qemu-devel] [questions] about qemu log

[William Dauchy]

On Wed, Aug 6, 2014 at 12:43 PM, William Dauchy <address@hidden> wrote:
> this make it incompatible with -daemonize option.
> there should be a possibility to detach the process and also redirect
> stderr somewhere.

I have done a quick and dirty patch for my own qemu binary so I can
use daemonize and also redirect stderr to syslog.

diff --git a/include/sysemu/os-posix.h b/include/sysemu/os-posix.h
index f131521..bf92ec1 100644
--- a/include/sysemu/os-posix.h
+++ b/include/sysemu/os-posix.h
@@ -34,6 +34,7 @@ void os_setup_signal_handling(void);
 void os_daemonize(void);
 void os_setup_post(void);
 int os_mlock(void);
+void tolog(FILE **pfp);

 typedef struct timeval qemu_timeval;
 #define qemu_gettimeofday(tp) gettimeofday(tp, NULL)
diff --git a/os-posix.c b/os-posix.c
index cb2a7f7..8d8d425 100644
--- a/os-posix.c
+++ b/os-posix.c
@@ -33,6 +33,8 @@
 #include <pwd.h>
 #include <grp.h>
 #include <libgen.h>
+#include <stdio.h>
+#include <syslog.h>

 /* Needed early for CONFIG_BSD etc. */
 #include "config-host.h"
@@ -250,6 +252,28 @@ void os_daemonize(void)
     }
 }

+static size_t writer(void *cookie, char const *data, size_t len)
+{
+    while(*data == ' ') {
+        ++data;
+ --len;
+    }
+
+    syslog(LOG_DEBUG, "%.*s", len, data);
+    return len;
+}
+
+static int noop(void) {return 0;}
+static cookie_io_functions_t log_fn = {
+    (void*) noop, (void*) writer, (void*) noop, (void*) noop
+};
+
+void tolog(FILE **pfp)
+{
+    *pfp = fopencookie(NULL, "w", log_fn);
+    setvbuf(*pfp, NULL, _IOLBF, 0);
+}
+
 void os_setup_post(void)
 {
     int fd = 0;
@@ -280,8 +304,8 @@ void os_setup_post(void)

     if (daemonize) {
         dup2(fd, 0);
-        dup2(fd, 1);
-        dup2(fd, 2);
+ tolog(&stdout);
+ tolog(&stderr);

         close(fd);
     }
diff --git a/vl.c b/vl.c
index fe451aa..6b6b62c 100644
--- a/vl.c
+++ b/vl.c
@@ -3969,6 +3970,10 @@ int main(int argc, char **argv, char **envp)
     loc_set_none();

     os_daemonize();
+    if (is_daemonized()) {
+ tolog(&stdout);
+ tolog(&stderr);
+    }

     if (qemu_init_main_loop()) {
         fprintf(stderr, "qemu_init_main_loop failed\n");

-- 
William