1 files changed, 19 insertions, 2 deletions
diff --git a/util/log.c b/util/log.c
index 671b6174e4..b219081e91 100644
--- a/util/log.c
+++ b/util/log.c
@@ -89,11 +89,28 @@ void do_qemu_set_log(int log_flags, bool use_own_buffers)
         qemu_log_close();
     }
 }
-
+/*
+ * Allow the user to include %d in their logfile which will be
+ * substituted with the current PID. This is useful for debugging many
+ * nested linux-user tasks but will result in lots of logs.
+ */
 void qemu_set_log_filename(const char *filename)
 {
+    char *pidstr;
     g_free(logfilename);
-    logfilename = g_strdup(filename);
+
+    pidstr = strstr(filename, "%");
+    if (pidstr) {
+        /* We only accept one %d, no other format strings */
+        if (pidstr[1] != 'd' || strchr(pidstr + 2, '%')) {
+            error_report("Bad logfile format: %s", filename);
+            logfilename = NULL;
+        } else {
+            logfilename = g_strdup_printf(filename, getpid());
+        }
+    } else {
+        logfilename = g_strdup(filename);
+    }
     qemu_log_close();
     qemu_set_log(qemu_loglevel);
 }