log: Fix qemu_set_log_filename() error handling

When qemu_set_log_filename() detects an invalid file name, it reports
an error, closes the log file (if any), and starts logging to stderr
(unless daemonized or nothing is being logged).

This is wrong.  Asking for an invalid log file on the command line
should be fatal.  Asking for one in the monitor should fail without
messing up an existing logfile.

Fix by converting qemu_set_log_filename() to Error.  Pass it
&error_fatal, except for hmp_logfile report errors.

This also permits testing without a subprocess, so do that.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <1466011636-6112-4-git-send-email-armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>

8 files changed, 25 insertions, 42 deletions

diff --git a/bsd-user/main.c b/bsd-user/main.c
index abe9a26..4819b9e 100644
--- a/bsd-user/main.c
+++ b/bsd-user/main.c
@@ -19,6 +19,7 @@
 #include "qemu/osdep.h"
 #include <machine/trap.h>
 
+#include "qapi/error.h"
 #include "qemu.h"
 #include "qemu/path.h"
 #include "qemu/help_option.h"
@@ -847,7 +848,7 @@ int main(int argc, char **argv)
 
     /* init debug */
     qemu_log_needs_buffers();
-    qemu_set_log_filename(log_file);
+    qemu_set_log_filename(log_file, &error_fatal);
     if (log_mask) {
         int mask;
 
diff --git a/include/qemu/log.h b/include/qemu/log.h
index df8d041..8bec6b4 100644
--- a/include/qemu/log.h
+++ b/include/qemu/log.h
@@ -106,7 +106,7 @@ extern const QEMULogItem qemu_log_items[];
 
 void qemu_set_log(int log_flags);
 void qemu_log_needs_buffers(void);
-void qemu_set_log_filename(const char *filename);
+void qemu_set_log_filename(const char *filename, Error **errp);
 void qemu_set_dfilter_ranges(const char *ranges, Error **errp);
 bool qemu_log_in_addr_range(uint64_t addr);
 int qemu_str_to_log_mask(const char *str);
diff --git a/linux-user/main.c b/linux-user/main.c
index b9a4e0e..358ed01 100644
--- a/linux-user/main.c
+++ b/linux-user/main.c
@@ -21,6 +21,7 @@
 #include <sys/syscall.h>
 #include <sys/resource.h>
 
+#include "qapi/error.h"
 #include "qemu.h"
 #include "qemu/path.h"
 #include "qemu/cutils.h"
@@ -3845,7 +3846,7 @@ static void handle_arg_log(const char *arg)
 
 static void handle_arg_log_filename(const char *arg)
 {
-    qemu_set_log_filename(arg);
+    qemu_set_log_filename(arg, &error_fatal);
 }
 
 static void handle_arg_set_env(const char *arg)
diff --git a/monitor.c b/monitor.c
index a5d054b..6f960f1 100644
--- a/monitor.c
+++ b/monitor.c
@@ -1111,7 +1111,12 @@ void qmp_client_migrate_info(const char *protocol, const char *hostname,
 
 static void hmp_logfile(Monitor *mon, const QDict *qdict)
 {
-    qemu_set_log_filename(qdict_get_str(qdict, "filename"));
+    Error *err = NULL;
+
+    qemu_set_log_filename(qdict_get_str(qdict, "filename"), &err);
+    if (err) {
+        error_report_err(err);
+    }
 }
 
 static void hmp_log(Monitor *mon, const QDict *qdict)
diff --git a/tests/test-logging.c b/tests/test-logging.c
index e043adc..440e75f 100644
--- a/tests/test-logging.c
+++ b/tests/test-logging.c
@@ -75,49 +75,24 @@ static void test_parse_range(void)
     error_free_or_abort(&err);
 }
 
-#ifdef CONFIG_HAS_GLIB_SUBPROCESS_TESTS
-/* As the only real failure from a bad log filename path spec is
- * reporting to the user we have to use the g_test_trap_subprocess
- * mechanism and check no errors reported on stderr.
- */
-static void test_parse_path_subprocess(void)
-{
-    /* All these should work without issue */
-    qemu_set_log_filename("/tmp/qemu.log");
-    qemu_set_log_filename("/tmp/qemu-%d.log");
-    qemu_set_log_filename("/tmp/qemu.log.%d");
-}
 static void test_parse_path(void)
 {
-    g_test_trap_subprocess ("/logging/parse_path/subprocess", 0, 0);
-    g_test_trap_assert_passed();
-    g_test_trap_assert_stdout("");
-    g_test_trap_assert_stderr("");
-}
-static void test_parse_invalid_path_subprocess(void)
-{
-    qemu_set_log_filename("/tmp/qemu-%d%d.log");
-}
-static void test_parse_invalid_path(void)
-{
-    g_test_trap_subprocess ("/logging/parse_invalid_path/subprocess", 0, 0);
-    g_test_trap_assert_passed();
-    g_test_trap_assert_stdout("");
-    g_test_trap_assert_stderr("Bad logfile format: /tmp/qemu-%d%d.log\n");
+    Error *err = NULL;
+
+    qemu_set_log_filename("/tmp/qemu.log", &error_abort);
+    qemu_set_log_filename("/tmp/qemu-%d.log", &error_abort);
+    qemu_set_log_filename("/tmp/qemu.log.%d", &error_abort);
+
+    qemu_set_log_filename("/tmp/qemu-%d%d.log", &err);
+    error_free_or_abort(&err);
 }
-#endif /* CONFIG_HAS_GLIB_SUBPROCESS_TESTS */
 
 int main(int argc, char **argv)
 {
     g_test_init(&argc, &argv, NULL);
 
     g_test_add_func("/logging/parse_range", test_parse_range);
-#ifdef CONFIG_HAS_GLIB_SUBPROCESS_TESTS
     g_test_add_func("/logging/parse_path", test_parse_path);
-    g_test_add_func("/logging/parse_path/subprocess", test_parse_path_subprocess);
-    g_test_add_func("/logging/parse_invalid_path", test_parse_invalid_path);
-    g_test_add_func("/logging/parse_invalid_path/subprocess", test_parse_invalid_path_subprocess);
-#endif
 
     return g_test_run();
 }
diff --git a/trace/control.c b/trace/control.c
index d099f73..e1556a3 100644
--- a/trace/control.c
+++ b/trace/control.c
@@ -19,6 +19,7 @@
 #ifdef CONFIG_TRACE_LOG
 #include "qemu/log.h"
 #endif
+#include "qapi/error.h"
 #include "qemu/error-report.h"
 #include "monitor/monitor.h"
 
@@ -187,7 +188,7 @@ void trace_init_file(const char *file)
      * only applies to the simple backend; use "-D" for the log backend.
      */
     if (file) {
-        qemu_set_log_filename(file);
+        qemu_set_log_filename(file, &error_fatal);
     }
 #else
     if (file) {
diff --git a/util/log.c b/util/log.c
index fcf85c6..32e4160 100644
--- a/util/log.c
+++ b/util/log.c
@@ -103,7 +103,7 @@ void qemu_log_needs_buffers(void)
  * 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)
+void qemu_set_log_filename(const char *filename, Error **errp)
 {
     char *pidstr;
     g_free(logfilename);
@@ -112,8 +112,8 @@ void qemu_set_log_filename(const char *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;
+            error_setg(errp, "Bad logfile format: %s", filename);
+            return;
         } else {
             logfilename = g_strdup_printf(filename, getpid());
         }
diff --git a/vl.c b/vl.c
index 749c421..c85833a 100644
--- a/vl.c
+++ b/vl.c
@@ -4054,7 +4054,7 @@ int main(int argc, char **argv, char **envp)
     /* Open the logfile at this point and set the log mask if necessary.
      */
     if (log_file) {
-        qemu_set_log_filename(log_file);
+        qemu_set_log_filename(log_file, &error_fatal);
     }
 
     if (log_mask) {