summaryrefslogtreecommitdiff
diff options
context:
space:
mode:
authorWang Nan <wangnan0@huawei.com>2015-04-25 07:25:03 +0000
committerArnaldo Carvalho de Melo <acme@redhat.com>2015-04-27 13:24:32 -0300
commitc671835021798c1c40ca0b55b49feff76ed5e0e1 (patch)
tree6479c2cb7432d9105ef05f76f18c99549cdbcebd
parent410ceb8f2f1d4edeb02d229ef192e76602005b8b (diff)
downloadlinux-c671835021798c1c40ca0b55b49feff76ed5e0e1.tar.gz
perf top: Fix a segfault when kernel map is restricted.
Perf top raise a warning if a kernel sample is collected but kernel map is restricted. The warning message needs to dereference al.map->dso... However, previous perf_event__preprocess_sample() doesn't always guarantee al.map != NULL, for example, when kernel map is restricted. This patch validates al.map before dereferencing, avoid the segfault. Before this patch: $ cat /proc/sys/kernel/kptr_restrict 1 $ perf top -p 120183 perf: Segmentation fault -------- backtrace -------- /path/to/perf[0x509868] /lib64/libc.so.6(+0x3545f)[0x7f9a1540045f] /path/to/perf[0x448820] /path/to/perf(cmd_top+0xe3c)[0x44a5dc] /path/to/perf[0x4766a2] /path/to/perf(main+0x5f5)[0x42e545] /lib64/libc.so.6(__libc_start_main+0xf4)[0x7f9a153ecbd4] /path/to/perf[0x42e674] And gdb call trace: Program received signal SIGSEGV, Segmentation fault. perf_event__process_sample (machine=0xa44030, sample=0x7fffffffa4c0, evsel=0xa43b00, event=0x7ffff41c3000, tool=0x7fffffffa8a0) at builtin-top.c:736 736 !RB_EMPTY_ROOT(&al.map->dso->symbols[MAP__FUNCTION]) ? (gdb) bt #0 perf_event__process_sample (machine=0xa44030, sample=0x7fffffffa4c0, evsel=0xa43b00, event=0x7ffff41c3000, tool=0x7fffffffa8a0) at builtin-top.c:736 #1 perf_top__mmap_read_idx (top=top@entry=0x7fffffffa8a0, idx=idx@entry=0) at builtin-top.c:855 #2 0x000000000044a5dd in perf_top__mmap_read (top=0x7fffffffa8a0) at builtin-top.c:872 #3 __cmd_top (top=0x7fffffffa8a0) at builtin-top.c:997 #4 cmd_top (argc=<optimized out>, argv=<optimized out>, prefix=<optimized out>) at builtin-top.c:1267 #5 0x00000000004766a3 in run_builtin (p=p@entry=0x8a6ce8 <commands+264>, argc=argc@entry=3, argv=argv@entry=0x7fffffffdf70) at perf.c:371 #6 0x000000000042e546 in handle_internal_command (argv=0x7fffffffdf70, argc=3) at perf.c:430 #7 run_argv (argv=0x7fffffffdcf0, argcp=0x7fffffffdcfc) at perf.c:474 #8 main (argc=3, argv=0x7fffffffdf70) at perf.c:589 (gdb) Signed-off-by: Wang Nan <wangnan0@huawei.com> Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: David Ahern <dsahern@gmail.com> Cc: Jiri Olsa <jolsa@kernel.org> Cc: Paul Mackerras <paulus@samba.org> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Zefan Li <lizefan@huawei.com> Link: http://lkml.kernel.org/r/1429946703-80807-1-git-send-email-wangnan0@huawei.com Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
-rw-r--r--tools/perf/builtin-top.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
index 1cb3436276d1..6a4d5d41c671 100644
--- a/tools/perf/builtin-top.c
+++ b/tools/perf/builtin-top.c
@@ -733,7 +733,7 @@ static void perf_event__process_sample(struct perf_tool *tool,
"Kernel address maps (/proc/{kallsyms,modules}) are restricted.\n\n"
"Check /proc/sys/kernel/kptr_restrict.\n\n"
"Kernel%s samples will not be resolved.\n",
- !RB_EMPTY_ROOT(&al.map->dso->symbols[MAP__FUNCTION]) ?
+ al.map && !RB_EMPTY_ROOT(&al.map->dso->symbols[MAP__FUNCTION]) ?
" modules" : "");
if (use_browser <= 0)
sleep(5);