path: root/trace/ftrace.c
diff options
authorDaniel P. Berrange <berrange@redhat.com>2016-10-04 14:35:51 +0100
committerStefan Hajnoczi <stefanha@redhat.com>2016-10-12 09:35:54 +0200
commit8ed5372874377af4a84a330eeaff1d9d663ca930 (patch)
tree56df50260e123fea831136b9f3a4b9066cb34430 /trace/ftrace.c
parent7f1b588f20d027730676e627713ae3bbf6baab04 (diff)
trace: don't abort qemu if ftrace can't be initialized
If the ftrace backend is compiled into QEMU, any attempt to start QEMU while non-root will fail due to the inability to open /sys/kernel/debug/tracing/tracing_on. Add a fallback into the code so that it connects up the trace_marker_fd variable to /dev/null when getting EACCES on the 'trace_on' file. This allows QEMU to run, with ftrace turned into a no-op. [Fixed s/setting/getting/ and s/EACCESS/EACCES/ errors pointed out by Eric Blake <eblake@redhat.com>. --Stefan] Signed-off-by: Daniel P. Berrange <berrange@redhat.com> Message-id: 1475588159-30598-13-git-send-email-berrange@redhat.com Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Diffstat (limited to 'trace/ftrace.c')
1 files changed, 6 insertions, 0 deletions
diff --git a/trace/ftrace.c b/trace/ftrace.c
index e953922f5b..3588bb0eb4 100644
--- a/trace/ftrace.c
+++ b/trace/ftrace.c
@@ -51,6 +51,12 @@ bool ftrace_init(void)
snprintf(path, PATH_MAX, "%s/tracing/tracing_on", debugfs);
trace_fd = open(path, O_WRONLY);
if (trace_fd < 0) {
+ if (errno == EACCES) {
+ trace_marker_fd = open("/dev/null", O_WRONLY);
+ if (trace_marker_fd != -1) {
+ return true;
+ }
+ }
perror("Could not open ftrace 'tracing_on' file");
return false;
} else {