Re: [PATCH][V3] arm64: perf: Get the wrong PC value in REGS_ABI_32 mode

[Jiping Ma]

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@xxxxxxxxxxxxx>
> ---
>   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];
>   }
>