From a8f23d8f8af43d49cd3331681913b76e4951e1a4 Mon Sep 17 00:00:00 2001 From: Arnaldo Carvalho de Melo Date: Thu, 17 Oct 2013 17:38:29 -0300 Subject: [PATCH] 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, buf: 0x7fe6db765000, count: 4096 ) = 4096 0.045 ( 0.001 ms): write(fd: 1, buf: 0x7fe6db765000, count: 4096 ) = 4096 0.085 ( 0.001 ms): write(fd: 1, buf: 0x7fe6db765000, count: 4096 ) = 4096 0.125 ( 0.001 ms): write(fd: 1, buf: 0x7fe6db765000, count: 4096 ) = 4096 0.165 ( 0.001 ms): write(fd: 1, 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 Cc: David Ahern Cc: Frederic Weisbecker Cc: Jiri Olsa Cc: Mike Galbraith Cc: Paul Mackerras Cc: Peter Zijlstra Cc: Stephane Eranian Link: http://lkml.kernel.org/n/tip-di28olfwd28rvkox7v3hqhu1@git.kernel.org Signed-off-by: Arnaldo Carvalho de Melo --- 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 78b0d6a5fdff..db959ac3d46e 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 6737420891cd..0b5425b4d8d6 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 386de1036442..7f8f1aeb9cfe 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) { -- 2.20.1