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

[Jiping Ma <Jiping.Ma2@windriver.com>]

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@windriver.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];
>   }
>