linux-kernel - Re: [PATCH v2] ARC: bpf: Correct conditional check in 'check_jmp

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Message-ID: <920e71ab-2375-4722-bcf3-d6aaf8e68b3a@vahedi.org>
Date: Wed, 13 Nov 2024 21:00:12 +0100 (GMT+01:00)
From: Shahab Vahedi <list+bpf@...edi.org>
To: Hardevsinh Palaniya <hardevsinh.palaniya@...iconsignals.io>
Cc: ast@...nel.org, vadim.fedorenko@...ux.dev,
	tarang.raval@...iconsignals.io,
	Daniel Borkmann <daniel@...earbox.net>,
	Andrii Nakryiko <andrii@...nel.org>,
	Martin KaFai Lau <martin.lau@...ux.dev>,
	Eduard Zingerman <eddyz87@...il.com>, Song Liu <song@...nel.org>,
	Yonghong Song <yonghong.song@...ux.dev>,
	John Fastabend <john.fastabend@...il.com>,
	KP Singh <kpsingh@...nel.org>, Stanislav Fomichev <sdf@...ichev.me>,
	Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
	Vineet Gupta <vgupta@...nel.org>, bpf@...r.kernel.org,
	linux-snps-arc@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] ARC: bpf: Correct conditional check in
 'check_jmp_32'

> The original code checks 'if (ARC_CC_AL)', which is always true since
> ARC_CC_AL is a constant. This makes the check redundant and likely
> obscures the intention of verifying whether the jump is conditional.
>
> Updates the code to check cond == ARC_CC_AL instead, reflecting the intent
> to differentiate conditional from unconditional jumps.
>
> Suggested-by: Vadim Fedorenko <vadim.fedorenko@...ux.dev>
> Signed-off-by: Hardevsinh Palaniya <hardevsinh.palaniya@...iconsignals.io>
> ---
>
> Changelog in V2:
>
> - Changed subject line
> - Updated condition check to 'if (cond == ARC_CC_AL)' instead of removing it
>
> Link for v1: https://lore.kernel.org/bpf/e6d27adb-151c-46c1-9668-1cd2b492321b@linux.dev/T/#t
> ---
> arch/arc/net/bpf_jit_arcv2.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/arc/net/bpf_jit_arcv2.c b/arch/arc/net/bpf_jit_arcv2.c
> index 4458e409ca0a..6d989b6d88c6 100644
> --- a/arch/arc/net/bpf_jit_arcv2.c
> +++ b/arch/arc/net/bpf_jit_arcv2.c
> @@ -2916,7 +2916,7 @@ bool check_jmp_32(u32 curr_off, u32 targ_off, u8 cond)
>     addendum = (cond == ARC_CC_AL) ? 0 : INSN_len_normal;
>     disp = get_displacement(curr_off + addendum, targ_off);
>
> -   if (ARC_CC_AL)
> +   if (cond == ARC_CC_AL)
>         return is_valid_far_disp(disp);
>     else
>         return is_valid_near_disp(disp);
> --
> 2.43.0

Thank you for your contribution!

Acked-by: Shahab Vahedi <list+bpf@...edi.org>