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SubjectRe: [PATCH/RFC 2/2] perf tools: Check callchain is corrupted
Em Thu, May 31, 2012 at 02:43:27PM +0900, Namhyung Kim escreveu:
> We faced segmentation fault on perf top -G at very high sampling
> rate due to a corrupted callchain. While the root cause was not
> revealed (I failed to figure it out), this patch tries to protect
> us from the segfault on such cases.

Capping the callchain lenght may even be a feature, not a consistency
check, but I don't know how long, for consistency checking, we should
consider too much, as there are cases of loooong callchains.

Ingo? Peter?

- Arnaldo

> Reported-by: Arnaldo Carvalho de Melo <acme@redhat.com>
> Signed-off-by: Namhyung Kim <namhyung.kim@lge.com>
> ---
> include/linux/perf_event.h | 4 ++--
> tools/perf/util/session.c | 14 +++++++++++++-
> 2 files changed, 15 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
> index 8adf70e9e3cc..0430ea6054ef 100644
> --- a/include/linux/perf_event.h
> +++ b/include/linux/perf_event.h
> @@ -555,6 +555,8 @@ enum perf_event_type {
> PERF_RECORD_MAX, /* non-ABI */
> };
>
> +#define PERF_MAX_STACK_DEPTH 255
> +
> enum perf_callchain_context {
> PERF_CONTEXT_HV = (__u64)-32,
> PERF_CONTEXT_KERNEL = (__u64)-128,
> @@ -609,8 +611,6 @@ struct perf_guest_info_callbacks {
> #include <linux/sysfs.h>
> #include <asm/local.h>
>
> -#define PERF_MAX_STACK_DEPTH 255
> -
> struct perf_callchain_entry {
> __u64 nr;
> __u64 ip[PERF_MAX_STACK_DEPTH];
> diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
> index a7de2acac460..fa14e60ed459 100644
> --- a/tools/perf/util/session.c
> +++ b/tools/perf/util/session.c
> @@ -300,6 +300,11 @@ int machine__resolve_callchain(struct machine *self,
>
> callchain_cursor_reset(&callchain_cursor);
>
> + if (chain->nr > PERF_MAX_STACK_DEPTH) {
> + pr_warning("corrupted callchain. skipping...\n");
> + return 0;
> + }
> +
> for (i = 0; i < chain->nr; i++) {
> u64 ip;
> struct addr_location al;
> @@ -318,7 +323,14 @@ int machine__resolve_callchain(struct machine *self,
> case PERF_CONTEXT_USER:
> cpumode = PERF_RECORD_MISC_USER; break;
> default:
> - break;
> + pr_debug("invalid callchain context: "
> + "%"PRId64"\n", (s64) ip);
> + /*
> + * It seems the callchain is corrupted.
> + * Discard all.
> + */
> + callchain_cursor_reset(&callchain_cursor);
> + return 0;
> }
> continue;
> }
> --
> 1.7.10.1


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