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

1534428646@qq.com posted 1 patch 1 year ago
There is a newer version of this series
arch/arm64/kernel/probes/decode-insn.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
[PATCH] arm64: kprobe: fix an error in single stepping support
Posted by 1534428646@qq.com 1 year ago
From: "Yiren.Xie" <1534428646@qq.com>

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@qq.com>
---
 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
-- 
2.34.1
Re: [PATCH] arm64: kprobe: fix an error in single stepping support
Posted by Yeoreum Yun 1 year ago
Hi Yiren,

> From: "Yiren.Xie" <1534428646@qq.com>
>
> 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@qq.com>
> ---
>  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.