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[Qemu-devel] [PATCH v6 12/20] trace: don't abort qemu if ftrace can't be
From: |
Daniel P. Berrange |
Subject: |
[Qemu-devel] [PATCH v6 12/20] trace: don't abort qemu if ftrace can't be initialized |
Date: |
Tue, 4 Oct 2016 14:35:51 +0100 |
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 setting
EACCESS on the 'trace_on' file. This allows QEMU to
run, with ftrace turned into a no-op.
Signed-off-by: Daniel P. Berrange <address@hidden>
---
trace/ftrace.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/trace/ftrace.c b/trace/ftrace.c
index e953922..3588bb0 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 {
--
2.7.4
- Re: [Qemu-devel] [PATCH v6 04/20] trace: convert code to use event iterators, (continued)
- [Qemu-devel] [PATCH v6 02/20] trace: remove double-underscore in event name, Daniel P. Berrange, 2016/10/04
- [Qemu-devel] [PATCH v6 01/20] trace: move colo trace events to net/ sub-directory, Daniel P. Berrange, 2016/10/04
- [Qemu-devel] [PATCH v6 03/20] trace: add trace event iterator APIs, Daniel P. Berrange, 2016/10/04
- [Qemu-devel] [PATCH v6 05/20] trace: remove some now unused functions, Daniel P. Berrange, 2016/10/04
- [Qemu-devel] [PATCH v6 06/20] trace: remove global 'uint16 dstate[]' array, Daniel P. Berrange, 2016/10/04
- [Qemu-devel] [PATCH v6 07/20] trace: remove duplicate control.h includes in generated-tracers.h, Daniel P. Berrange, 2016/10/04
- [Qemu-devel] [PATCH v6 08/20] trace: break circular dependency in event-internal.h, Daniel P. Berrange, 2016/10/04
- [Qemu-devel] [PATCH v6 09/20] trace: give each trace event a named TraceEvent struct, Daniel P. Berrange, 2016/10/04
- [Qemu-devel] [PATCH v6 10/20] trace: remove the TraceEventID and TraceEventVCPUID enums, Daniel P. Berrange, 2016/10/04
- [Qemu-devel] [PATCH v6 12/20] trace: don't abort qemu if ftrace can't be initialized,
Daniel P. Berrange <=
- [Qemu-devel] [PATCH v6 13/20] trace: provide mechanism for registering trace events, Daniel P. Berrange, 2016/10/04
- [Qemu-devel] [PATCH v6 11/20] trace: emit name <-> ID mapping in simpletrace header, Daniel P. Berrange, 2016/10/04
- [Qemu-devel] [PATCH v6 14/20] trace: dynamically allocate trace_dstate in CPUState, Daniel P. Berrange, 2016/10/04
- [Qemu-devel] [PATCH v6 15/20] trace: dynamically allocate event IDs at runtime, Daniel P. Berrange, 2016/10/04
- [Qemu-devel] [PATCH v6 16/20] trace: get rid of generated-events.h/generated-events.c, Daniel P. Berrange, 2016/10/04
- [Qemu-devel] [PATCH v6 17/20] trace: rename _read_events to read_events, Daniel P. Berrange, 2016/10/04
- [Qemu-devel] [PATCH v6 19/20] trace: pass trace-events to tracetool as a positional param, Daniel P. Berrange, 2016/10/04