linux-kernel - Re: [PATCH][V3] arm64: perf: Get the wrong PC value in REGS_ABI

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Date:   Tue, 26 May 2020 10:46:20 +0800
From:   Jiping Ma <Jiping.Ma2@...driver.com>
To:     will.deacon@....com, paul.gortmaker@...driver.com,
        mark.rutland@....com, catalin.marinas@....com,
        bruce.ashfield@...il.com, yue.tao@...driver.com
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        zhe.he@...driver.com
Subject: Re: [PATCH][V3] arm64: perf: Get the wrong PC value in REGS_ABI_32
 mode

Hi, Will

Please help to review the change.

Thanks,
Jiping

On 05/11/2020 10:52 AM, Jiping Ma wrote:
> Modified the patch subject and the change description.
>
> PC value is get from regs[15] in REGS_ABI_32 mode, but correct PC
> is regs->pc(regs[PERF_REG_ARM64_PC]) in arm64 kernel, which caused
> that perf can not parser the backtrace of app with dwarf mode in the
> 32bit system and 64bit kernel.
>
> 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..0ef2880 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->pc;
> +
>   	return regs->regs[idx];
>   }
>