lkml.org 
[lkml]   [2019]   [Sep]   [30]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [PATCH 1/3] perf script brstackinsn: Fix recovery from LBR/binary mismatch
Em Fri, Sep 27, 2019 at 04:35:44PM -0700, Andi Kleen escreveu:
> From: Andi Kleen <ak@linux.intel.com>
>
> When the LBR data and the instructions in a binary do not match the
> loop printing instructions could get confused and print a long
> stream of bogus <bad> instructions.
>
> The problem was that if the instruction decoder cannot decode an
> instruction it ilen wasn't initialized, so the loop going through
> the basic block would continue with the previous value.
>
> Harden the code to avoid such problems:
> - Make sure ilen is always freshly initialized and is 0 for bad
> instructions.
> - Do not overrun the code buffer while printing instructions
> - Print a warning message if the final jump is not on an
> instruction boundary.

Thanks, applied.

- Arnaldo

> Signed-off-by: Andi Kleen <ak@linux.intel.com>
> ---
> tools/perf/builtin-script.c | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/tools/perf/builtin-script.c b/tools/perf/builtin-script.c
> index e079b34201f2..32b17d51c982 100644
> --- a/tools/perf/builtin-script.c
> +++ b/tools/perf/builtin-script.c
> @@ -1061,7 +1061,7 @@ static int perf_sample__fprintf_brstackinsn(struct perf_sample *sample,
> continue;
>
> insn = 0;
> - for (off = 0;; off += ilen) {
> + for (off = 0; off < (unsigned)len; off += ilen) {
> uint64_t ip = start + off;
>
> printed += ip__fprintf_sym(ip, thread, x.cpumode, x.cpu, &lastsym, attr, fp);
> @@ -1072,6 +1072,7 @@ static int perf_sample__fprintf_brstackinsn(struct perf_sample *sample,
> printed += print_srccode(thread, x.cpumode, ip);
> break;
> } else {
> + ilen = 0;
> printed += fprintf(fp, "\t%016" PRIx64 "\t%s\n", ip,
> dump_insn(&x, ip, buffer + off, len - off, &ilen));
> if (ilen == 0)
> @@ -1081,6 +1082,8 @@ static int perf_sample__fprintf_brstackinsn(struct perf_sample *sample,
> insn++;
> }
> }
> + if (off != (unsigned)len)
> + printed += fprintf(fp, "\tmismatch of LBR data and executable\n");
> }
>
> /*
> @@ -1121,6 +1124,7 @@ static int perf_sample__fprintf_brstackinsn(struct perf_sample *sample,
> goto out;
> }
> for (off = 0; off <= end - start; off += ilen) {
> + ilen = 0;
> printed += fprintf(fp, "\t%016" PRIx64 "\t%s\n", start + off,
> dump_insn(&x, start + off, buffer + off, len - off, &ilen));
> if (ilen == 0)
> --
> 2.21.0

--

- Arnaldo

\
 
 \ /
  Last update: 2019-09-30 12:51    [W:0.072 / U:0.184 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site