linux-kernel - Re: [PATCH 2/2] perf script: Fix invalid LBR/binary mismatch error

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Message-ID: <20191127151852.GH22719@kernel.org>
Date:   Wed, 27 Nov 2019 12:18:52 -0300
From:   Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>
To:     Adrian Hunter <adrian.hunter@...el.com>
Cc:     Jiri Olsa <jolsa@...hat.com>, linux-kernel@...r.kernel.org,
        Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH 2/2] perf script: Fix invalid LBR/binary mismatch error

Em Wed, Nov 27, 2019 at 11:56:31AM +0200, Adrian Hunter escreveu:
> The 'len' returned by grab_bb() includes an extra MAXINSN bytes to allow
> for the last instruction, so the the final 'offs' will not be 'len'.
> Fix the error condition logic accordingly.
> 
> Before:
> 
>   $ perf record -e '{intel_pt//,cpu/mem_inst_retired.all_loads,aux-sample-size=8192/pp}:u' grep -rqs jhgjhg /boot
>   [ perf record: Woken up 19 times to write data ]
>   [ perf record: Captured and wrote 2.274 MB perf.data ]
>   $ perf script -F +brstackinsn --xed --itrace=i1usl100 | head
>             grep 13759 [002]  8091.310257:       1862                                        instructions:uH:      5641d58069eb bmexec+0x86b (/bin/grep)
>         bmexec+2485:
>         00005641d5806b35                        jnz 0x5641d5806bd0              # MISPRED
>         00005641d5806bd0                        movzxb  (%r13,%rdx,1), %eax
>         00005641d5806bd6                        add %rdi, %rax
>         00005641d5806bd9                        movzxb  -0x1(%rax), %edx
>         00005641d5806bdd                        cmp %rax, %r14
>         00005641d5806be0                        jnb 0x5641d58069c0              # MISPRED
>         mismatch of LBR data and executable
>         00005641d58069c0                        movzxb  (%r13,%rdx,1), %edi
> 
> After:
> 
>   $ perf script -F +brstackinsn --xed --itrace=i1usl100 | head
>             grep 13759 [002]  8091.310257:       1862                                        instructions:uH:      5641d58069eb bmexec+0x86b (/bin/grep)
>         bmexec+2485:
>         00005641d5806b35                        jnz 0x5641d5806bd0              # MISPRED
>         00005641d5806bd0                        movzxb  (%r13,%rdx,1), %eax
>         00005641d5806bd6                        add %rdi, %rax
>         00005641d5806bd9                        movzxb  -0x1(%rax), %edx
>         00005641d5806bdd                        cmp %rax, %r14
>         00005641d5806be0                        jnb 0x5641d58069c0              # MISPRED
>         00005641d58069c0                        movzxb  (%r13,%rdx,1), %edi
>         00005641d58069c6                        add %rax, %rdi

Thanks, applied,

- Arnaldo
 
> Reported-by: Andi Kleen <ak@...ux.intel.com>
> Fixes: e98df280bc2a ("perf script brstackinsn: Fix recovery from LBR/binary mismatch")
> Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>
> ---
>  tools/perf/builtin-script.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/perf/builtin-script.c b/tools/perf/builtin-script.c
> index e8db26b9b29e..e2406b291c1c 100644
> --- a/tools/perf/builtin-script.c
> +++ b/tools/perf/builtin-script.c
> @@ -1126,7 +1126,7 @@ static int perf_sample__fprintf_brstackinsn(struct perf_sample *sample,
>  				insn++;
>  			}
>  		}
> -		if (off != (unsigned)len)
> +		if (off != end - start)
>  			printed += fprintf(fp, "\tmismatch of LBR data and executable\n");
>  	}
>  
> -- 
> 2.17.1

-- 

- Arnaldo