Re: [PATCH] arm64: kprobe: fix an error in single stepping support

[Yeoreum Yun]

Hi Yiren,

> From: "Yiren.Xie" <1534428646@xxxxxx>
>
> It is obvious a conflict between the code and the comment.
> And verified that with this modification it can read the DAIF status.
>
> Signed-off-by: Yiren.Xie <1534428646@xxxxxx>
> ---
>  arch/arm64/kernel/probes/decode-insn.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/arm64/kernel/probes/decode-insn.c b/arch/arm64/kernel/probes/decode-insn.c
> index 6438bf62e753..22383eb1c22c 100644
> --- a/arch/arm64/kernel/probes/decode-insn.c
> +++ b/arch/arm64/kernel/probes/decode-insn.c
> @@ -40,7 +40,7 @@ static bool __kprobes aarch64_insn_is_steppable(u32 insn)
>  		 */
>  		if (aarch64_insn_is_mrs(insn))
>  			return aarch64_insn_extract_system_reg(insn)
> -			     != AARCH64_INSN_SPCLREG_DAIF;
> +			     == AARCH64_INSN_SPCLREG_DAIF;
>
>  		/*
>  		 * The HINT instruction is steppable only if it is in whitelist

Nit:
When single-stepped, the DAIF bits are set, in setup_singlesteup(),
Reading a DAIF via mrs instruction isn't correct value as comments
describe.

What is conflict?

Thanks.