log: Redirect stderr to logfile if deamonized

In case of daemonize, use the logfile passed with the -D option in
order to redirect stderr to it instead of /dev/null.

Also remove some unused code in log.h.

Signed-off-by: Dimitris Aragiorgis <dimara@arrikto.com>
Message-Id: <1455795518-19205-1-git-send-email-dimara@arrikto.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

include/qemu/log.h

@@ -94,12 +94,6 @@ static inline void qemu_log_close(void)
     }
 }
 
-/* Set up a new log file */
-static inline void qemu_log_set_file(FILE *f)
-{
-    qemu_logfile = f;
-}
-
 /* define log items */
 typedef struct QEMULogItem {
     int mask;

os-posix.c

@@ -37,6 +37,7 @@
 #include "qemu-options.h"
 #include "qemu/rcu.h"
 #include "qemu/error-report.h"
+#include "qemu/log.h"
 
 #ifdef CONFIG_LINUX
 #include <sys/prctl.h>
@@ -275,7 +276,10 @@ void os_setup_post(void)
 
         dup2(fd, 0);
         dup2(fd, 1);
-        dup2(fd, 2);
+        /* In case -D is given do not redirect stderr to /dev/null */
+        if (!qemu_logfile) {
+            dup2(fd, 2);
+        }
 
         close(fd);
 

util/log.c

@@ -56,13 +56,20 @@ void do_qemu_set_log(int log_flags, bool use_own_buffers)
 #ifdef CONFIG_TRACE_LOG
     qemu_loglevel |= LOG_TRACE;
 #endif
-    if (qemu_loglevel && !qemu_logfile) {
+    if ((qemu_loglevel || is_daemonized()) && !qemu_logfile) {
         if (logfilename) {
             qemu_logfile = fopen(logfilename, log_append ? "a" : "w");
             if (!qemu_logfile) {
                 perror(logfilename);
                 _exit(1);
             }
+            /* In case we are a daemon redirect stderr to logfile */
+            if (is_daemonized()) {
+                dup2(fileno(qemu_logfile), STDERR_FILENO);
+                fclose(qemu_logfile);
+                /* This will skip closing logfile in qemu_log_close() */
+                qemu_logfile = stderr;
+            }
         } else {
             /* Default to stderr if no log file specified */
             qemu_logfile = stderr;
@@ -82,7 +89,7 @@ void do_qemu_set_log(int log_flags, bool use_own_buffers)
             log_append = 1;
         }
     }
-    if (!qemu_loglevel && qemu_logfile) {
+    if (!qemu_loglevel && !is_daemonized() && qemu_logfile) {
         qemu_log_close();
     }
 }