From: Arnaldo Carvalho de Melo <[email protected]>
If we're not sampling the kernel, we shouldn't care about kptr_restrict
neither synthesize anything for assisting in resolving kernel samples,
like the reference relocation symbol or kernel modules information.
Before:
$ cat /proc/sys/kernel/kptr_restrict /proc/sys/kernel/perf_event_paranoid
2
2
$ perf record sleep 1
WARNING: Kernel address maps (/proc/{kallsyms,modules}) are restricted,
check /proc/sys/kernel/kptr_restrict.
Samples in kernel functions may not be resolved if a suitable vmlinux
file is not found in the buildid cache or in the vmlinux path.
Samples in kernel modules won't be resolved at all.
If some relocation was applied (e.g. kexec) symbols may be misresolved
even with a suitable vmlinux or kallsyms file.
Couldn't record kernel reference relocation symbol
Symbol resolution may be skewed if relocation was used (e.g. kexec).
Check /proc/kallsyms permission or run as root.
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.001 MB perf.data (8 samples) ]
$ perf evlist -v
cycles:uppp: 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, precise_ip: 3, sample_id_all: 1,
exclude_guest: 1, mmap2: 1, comm_exec: 1
$
After:
$ perf record sleep 1
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.001 MB perf.data (10 samples) ]
$
Cc: Adrian Hunter <[email protected]>
Cc: David Ahern <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Wang Nan <[email protected]>
Link: http://lkml.kernel.org/n/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>
---
tools/perf/builtin-record.c | 26 ++++++++++++++------------
1 file changed, 14 insertions(+), 12 deletions(-)
diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index 5f78ce943407..003255910c05 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -765,17 +765,19 @@ static int record__synthesize(struct record *rec, bool
tail)
goto out;
}
- err = perf_event__synthesize_kernel_mmap(tool,
process_synthesized_event,
- machine);
- WARN_ONCE(err < 0, "Couldn't record kernel reference relocation
symbol\n"
- "Symbol resolution may be skewed if relocation was
used (e.g. kexec).\n"
- "Check /proc/kallsyms permission or run as root.\n");
-
- err = perf_event__synthesize_modules(tool, process_synthesized_event,
- machine);
- WARN_ONCE(err < 0, "Couldn't record kernel module information.\n"
- "Symbol resolution may be skewed if relocation was
used (e.g. kexec).\n"
- "Check /proc/modules permission or run as root.\n");
+ if (!perf_evlist__exclude_kernel(rec->evlist)) {
+ err = perf_event__synthesize_kernel_mmap(tool,
process_synthesized_event,
+ machine);
+ WARN_ONCE(err < 0, "Couldn't record kernel reference relocation
symbol\n"
+ "Symbol resolution may be skewed if
relocation was used (e.g. kexec).\n"
+ "Check /proc/kallsyms permission or run as
root.\n");
+
+ err = perf_event__synthesize_modules(tool,
process_synthesized_event,
+ machine);
+ WARN_ONCE(err < 0, "Couldn't record kernel module
information.\n"
+ "Symbol resolution may be skewed if
relocation was used (e.g. kexec).\n"
+ "Check /proc/modules permission or run as
root.\n");
+ }
if (perf_guest) {
machines__process_guests(&session->machines,
@@ -1709,7 +1711,7 @@ int cmd_record(int argc, const char **argv)
err = -ENOMEM;
- if (symbol_conf.kptr_restrict)
+ if (symbol_conf.kptr_restrict &&
!perf_evlist__exclude_kernel(rec->evlist))
pr_warning(
"WARNING: Kernel address maps (/proc/{kallsyms,modules}) are restricted,\n"
"check /proc/sys/kernel/kptr_restrict.\n\n"
--
2.13.6
