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authorArnaldo Carvalho de Melo <acme@redhat.com>2016-05-12 16:07:47 -0300
committerArnaldo Carvalho de Melo <acme@redhat.com>2016-05-12 16:13:16 -0300
commit08094828b711dd32de57e9e3314935e19db71b3d (patch)
tree0300f537c751abff6e0def9f773729e8e6981e80
parent7d173913a6420f2818afeca70b268f064441f69b (diff)
downloadlinux-08094828b711dd32de57e9e3314935e19db71b3d.tar.gz
perf evsel: Handle EACCESS + perf_event_paranoid=2 in fallback()
Now with the default for the kernel.perf_event_paranoid sysctl being 2 [1] we need to fall back to :u, i.e. to set perf_event_attr.exclude_kernel to 1. Before: [acme@jouet linux]$ perf record usleep 1 Error: You may not have permission to collect stats. Consider tweaking /proc/sys/kernel/perf_event_paranoid, which controls use of the performance events system by unprivileged users (without CAP_SYS_ADMIN). The current value is 2: -1: Allow use of (almost) all events by all users >= 0: Disallow raw tracepoint access by users without CAP_IOC_LOCK >= 1: Disallow CPU event access by users without CAP_SYS_ADMIN >= 2: Disallow kernel profiling by users without CAP_SYS_ADMIN [acme@jouet linux]$ After: [acme@jouet linux]$ perf record usleep 1 [ perf record: Woken up 1 times to write data ] [ perf record: Captured and wrote 0.016 MB perf.data (7 samples) ] [acme@jouet linux]$ perf evlist cycles:u [acme@jouet linux]$ perf evlist -v cycles:u: size: 112, { sample_period, sample_freq }: 4000, sample_type: IP|TID|TIME|PERIOD, disabled: 1, inherit: 1, exclude_kernel: 1, mmap: 1, comm: 1, freq: 1, enable_on_exec: 1, task: 1, sample_id_all: 1, exclude_guest: 1, mmap2: 1, comm_exec: 1 [acme@jouet linux]$ And if the user turns on verbose mode, an explanation will appear: [acme@jouet linux]$ perf record -v usleep 1 Warning: kernel.perf_event_paranoid=2, trying to fall back to excluding kernel samples mmap size 528384B [ perf record: Woken up 1 times to write data ] Looking at the vmlinux_path (8 entries long) Using /lib/modules/4.6.0-rc7+/build/vmlinux for symbols [ perf record: Captured and wrote 0.016 MB perf.data (7 samples) ] [acme@jouet linux]$ [1] 0161028b7c8a ("perf/core: Change the default paranoia level to 2") Reported-by: Ingo Molnar <mingo@kernel.org> Cc: Adrian Hunter <adrian.hunter@intel.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: David Ahern <dsahern@gmail.com> Cc: Jiri Olsa <jolsa@kernel.org> Cc: Kees Cook <keescook@chromium.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Wang Nan <wangnan0@huawei.com> Link: http://lkml.kernel.org/n/tip-b20jmx4dxt5hpaa9t2rroi0o@git.kernel.org Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
-rw-r--r--tools/perf/util/evsel.c18
1 files changed, 18 insertions, 0 deletions
diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index a5f339d447cc..645dc1828836 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -2345,6 +2345,8 @@ out:
bool perf_evsel__fallback(struct perf_evsel *evsel, int err,
char *msg, size_t msgsize)
{
+ int paranoid;
+
if ((err == ENOENT || err == ENXIO || err == ENODEV) &&
evsel->attr.type == PERF_TYPE_HARDWARE &&
evsel->attr.config == PERF_COUNT_HW_CPU_CYCLES) {
@@ -2364,6 +2366,22 @@ bool perf_evsel__fallback(struct perf_evsel *evsel, int err,
zfree(&evsel->name);
return true;
+ } else if (err == EACCES && !evsel->attr.exclude_kernel &&
+ (paranoid = perf_event_paranoid()) > 1) {
+ const char *name = perf_evsel__name(evsel);
+ char *new_name;
+
+ if (asprintf(&new_name, "%s%su", name, strchr(name, ':') ? "" : ":") < 0)
+ return false;
+
+ if (evsel->name)
+ free(evsel->name);
+ evsel->name = new_name;
+ scnprintf(msg, msgsize,
+"kernel.perf_event_paranoid=%d, trying to fall back to excluding kernel samples", paranoid);
+ evsel->attr.exclude_kernel = 1;
+
+ return true;
}
return false;