[tip:perf/core] perf trace: Improve messages related to /proc/sys/kernel/perf_event_paranoid
From: tip-bot for Arnaldo Carvalho de Melo
Date: Wed Oct 23 2013 - 03:59:27 EST
Commit-ID: a8f23d8f8af43d49cd3331681913b76e4951e1a4
Gitweb: http://git.kernel.org/tip/a8f23d8f8af43d49cd3331681913b76e4951e1a4
Author: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
AuthorDate: Thu, 17 Oct 2013 17:38:29 -0300
Committer: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
CommitDate: Thu, 17 Oct 2013 17:38:29 -0300
perf trace: Improve messages related to /proc/sys/kernel/perf_event_paranoid
kernel/events/core.c has:
/*
* perf event paranoia level:
* -1 - not paranoid at all
* 0 - disallow raw tracepoint access for unpriv
* 1 - disallow cpu events for unpriv
* 2 - disallow kernel profiling for unpriv
*/
int sysctl_perf_event_paranoid __read_mostly = 1;
So, with the default being 1, a non-root user can trace his stuff:
[acme@zoo ~]$ cat /proc/sys/kernel/perf_event_paranoid
1
[acme@zoo ~]$ yes > /dev/null &
[1] 15338
[acme@zoo ~]$ trace -p 15338 | head -5
0.005 ( 0.005 ms): write(fd: 1</dev/null>, buf: 0x7fe6db765000, count: 4096 ) = 4096
0.045 ( 0.001 ms): write(fd: 1</dev/null>, buf: 0x7fe6db765000, count: 4096 ) = 4096
0.085 ( 0.001 ms): write(fd: 1</dev/null>, buf: 0x7fe6db765000, count: 4096 ) = 4096
0.125 ( 0.001 ms): write(fd: 1</dev/null>, buf: 0x7fe6db765000, count: 4096 ) = 4096
0.165 ( 0.001 ms): write(fd: 1</dev/null>, buf: 0x7fe6db765000, count: 4096 ) = 4096
[acme@zoo ~]$
[acme@zoo ~]$ trace --duration 1 sleep 1
1002.148 (1001.218 ms): nanosleep(rqtp: 0x7fff46c79250 ) = 0
[acme@zoo ~]$
[acme@zoo ~]$ trace -- usleep 1 | tail -5
0.905 ( 0.002 ms): brk( ) = 0x1c82000
0.910 ( 0.003 ms): brk(brk: 0x1ca3000 ) = 0x1ca3000
0.913 ( 0.001 ms): brk( ) = 0x1ca3000
0.990 ( 0.059 ms): nanosleep(rqtp: 0x7fffe31a3280 ) = 0
0.995 ( 0.000 ms): exit_group(
[acme@zoo ~]$
But can't do system wide tracing:
[acme@zoo ~]$ trace
Error: Operation not permitted.
Hint: Check /proc/sys/kernel/perf_event_paranoid setting.
Hint: For system wide tracing it needs to be set to -1.
Hint: The current value is 1.
[acme@zoo ~]$
[acme@zoo ~]$ trace --cpu 0
Error: Operation not permitted.
Hint: Check /proc/sys/kernel/perf_event_paranoid setting.
Hint: For system wide tracing it needs to be set to -1.
Hint: The current value is 1.
[acme@zoo ~]$
If the paranoid level is >= 2, i.e. turn this perf stuff off for !root users:
[acme@zoo ~]$ sudo sh -c 'echo 2 > /proc/sys/kernel/perf_event_paranoid'
[acme@zoo ~]$ cat /proc/sys/kernel/perf_event_paranoid
2
[acme@zoo ~]$
[acme@zoo ~]$ trace usleep 1
Error: Permission denied.
Hint: Check /proc/sys/kernel/perf_event_paranoid setting.
Hint: For your workloads it needs to be <= 1
Hint: For system wide tracing it needs to be set to -1.
Hint: The current value is 2.
[acme@zoo ~]$
[acme@zoo ~]$ trace
Error: Permission denied.
Hint: Check /proc/sys/kernel/perf_event_paranoid setting.
Hint: For your workloads it needs to be <= 1
Hint: For system wide tracing it needs to be set to -1.
Hint: The current value is 2.
[acme@zoo ~]$
[acme@zoo ~]$ trace --cpu 1
Error: Permission denied.
Hint: Check /proc/sys/kernel/perf_event_paranoid setting.
Hint: For your workloads it needs to be <= 1
Hint: For system wide tracing it needs to be set to -1.
Hint: The current value is 2.
[acme@zoo ~]$
If the user manages to get what he/she wants, convincing root not
to be paranoid at all...
[root@zoo ~]# echo -1 > /proc/sys/kernel/perf_event_paranoid
[root@zoo ~]# cat /proc/sys/kernel/perf_event_paranoid
-1
[root@zoo ~]#
[acme@zoo ~]$ ps -eo user,pid,comm | grep Xorg
root 729 Xorg
[acme@zoo ~]$
[acme@zoo ~]$ trace -a --duration 0.001 -e \!select,ioctl,writev | grep Xorg | head -5
23.143 ( 0.003 ms): Xorg/729 setitimer(which: REAL, value: 0x7fffaadf16e0 ) = 0
23.152 ( 0.004 ms): Xorg/729 read(fd: 31, buf: 0x2544af0, count: 4096 ) = 8
23.161 ( 0.002 ms): Xorg/729 read(fd: 31, buf: 0x2544af0, count: 4096 ) = -1 EAGAIN Resource temporarily unavailable
23.175 ( 0.002 ms): Xorg/729 setitimer(which: REAL, value: 0x7fffaadf16e0 ) = 0
23.235 ( 0.002 ms): Xorg/729 setitimer(which: REAL, value: 0x7fffaadf16e0 ) = 0
[acme@zoo ~]$
Cc: Adrian Hunter <adrian.hunter@xxxxxxxxx>
Cc: David Ahern <dsahern@xxxxxxxxx>
Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Mike Galbraith <efault@xxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Stephane Eranian <eranian@xxxxxxxxxx>
Link: http://lkml.kernel.org/n/tip-di28olfwd28rvkox7v3hqhu1@xxxxxxxxxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
---
tools/perf/builtin-trace.c | 17 +++++++++++------
tools/perf/util/evlist.c | 36 ++++++++++++++++++++++++++++++++++++
tools/perf/util/evlist.h | 1 +
3 files changed, 48 insertions(+), 6 deletions(-)
diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
index 78b0d6a..db959ac 100644
--- a/tools/perf/builtin-trace.c
+++ b/tools/perf/builtin-trace.c
@@ -1713,10 +1713,8 @@ static int trace__run(struct trace *trace, int argc, const char **argv)
}
err = perf_evlist__open(evlist);
- if (err < 0) {
- fprintf(trace->output, "Couldn't create the events: %s\n", strerror(errno));
- goto out_delete_maps;
- }
+ if (err < 0)
+ goto out_error_open;
err = perf_evlist__mmap(evlist, UINT_MAX, false);
if (err < 0) {
@@ -1813,14 +1811,21 @@ out_delete_evlist:
out:
trace->live = false;
return err;
-out_error_tp:
{
char errbuf[BUFSIZ];
+
+out_error_tp:
perf_evlist__strerror_tp(evlist, errno, errbuf, sizeof(errbuf));
+ goto out_error;
+
+out_error_open:
+ perf_evlist__strerror_open(evlist, errno, errbuf, sizeof(errbuf));
+
+out_error:
fprintf(trace->output, "%s\n", errbuf);
-}
goto out_delete_evlist;
}
+}
static int trace__replay(struct trace *trace)
{
diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index 6737420..0b5425b 100644
--- a/tools/perf/util/evlist.c
+++ b/tools/perf/util/evlist.c
@@ -1153,3 +1153,39 @@ int perf_evlist__strerror_tp(struct perf_evlist *evlist __maybe_unused,
return 0;
}
+
+int perf_evlist__strerror_open(struct perf_evlist *evlist __maybe_unused,
+ int err, char *buf, size_t size)
+{
+ int printed, value;
+ char sbuf[128], *emsg = strerror_r(err, sbuf, sizeof(sbuf));
+
+ switch (err) {
+ case EACCES:
+ case EPERM:
+ printed = scnprintf(buf, size,
+ "Error:\t%s.\n"
+ "Hint:\tCheck /proc/sys/kernel/perf_event_paranoid setting.", emsg);
+
+ if (filename__read_int("/proc/sys/kernel/perf_event_paranoid", &value))
+ break;
+
+ printed += scnprintf(buf + printed, size - printed, "\nHint:\t");
+
+ if (value >= 2) {
+ printed += scnprintf(buf + printed, size - printed,
+ "For your workloads it needs to be <= 1\nHint:\t");
+ }
+ printed += scnprintf(buf + printed, size - printed,
+ "For system wide tracing it needs to be set to -1");
+
+ printed += scnprintf(buf + printed, size - printed,
+ ".\nHint:\tThe current value is %d.", value);
+ break;
+ default:
+ scnprintf(buf, size, "%s", emsg);
+ break;
+ }
+
+ return 0;
+}
diff --git a/tools/perf/util/evlist.h b/tools/perf/util/evlist.h
index 386de10..7f8f1ae 100644
--- a/tools/perf/util/evlist.h
+++ b/tools/perf/util/evlist.h
@@ -169,6 +169,7 @@ static inline struct perf_evsel *perf_evlist__last(struct perf_evlist *evlist)
size_t perf_evlist__fprintf(struct perf_evlist *evlist, FILE *fp);
int perf_evlist__strerror_tp(struct perf_evlist *evlist, int err, char *buf, size_t size);
+int perf_evlist__strerror_open(struct perf_evlist *evlist, int err, char *buf, size_t size);
static inline unsigned int perf_mmap__read_head(struct perf_mmap *mm)
{
--
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