Em Fri, Sep 27, 2019 at 04:35:44PM -0700, Andi Kleen escreveu:
> From: Andi Kleen <a...@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 <a...@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

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