linux-kernel - Re: [PATCH] perf: perf can not parser the backtrace of app in the 32bit system and 64bit kernel.

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Date:   Thu, 7 May 2020 09:10:03 +0800
From:   Jiping Ma <Jiping.Ma2@...driver.com>
To:     will.deacon@....com, mark.rutland@....com, catalin.marinas@....com
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] perf: perf can not parser the backtrace of app in the
 32bit system and 64bit kernel.

Hi, Will

Please help to review the patch.

Thanks,
Jiping

On 04/29/2020 12:51 PM, Jiping Ma wrote:
> We test it as the following steps.
> # gcc -g -mthumb -gdwarf -o test test.c
> # export CALLGRAPH=dwarf
> #(./perftest ./test profiling 1; cd ./profiling/; perf script)
>
> Thanks,
> Jiping
>
> On 04/29/2020 12:01 PM, Jiping Ma wrote:
>> Record PC value from regs[15], it should be regs[32], which cause perf
>> parser the backtrace failed.
>>
>> Signed-off-by: Jiping Ma <jiping.ma2@...driver.com>
>> ---
>>   arch/arm64/kernel/perf_regs.c | 4 ++++
>>   1 file changed, 4 insertions(+)
>>
>> diff --git a/arch/arm64/kernel/perf_regs.c 
>> b/arch/arm64/kernel/perf_regs.c
>> index 0bbac61..04088e6 100644
>> --- a/arch/arm64/kernel/perf_regs.c
>> +++ b/arch/arm64/kernel/perf_regs.c
>> @@ -32,6 +32,10 @@ u64 perf_reg_value(struct pt_regs *regs, int idx)
>>       if ((u32)idx == PERF_REG_ARM64_PC)
>>           return regs->pc;
>>   +    if (perf_reg_abi(current) == PERF_SAMPLE_REGS_ABI_32
>> +        && idx == 15)
>> +        return regs->regs[PERF_REG_ARM64_PC];
>> +
>>       return regs->regs[idx];
>>   }
>