Re: [PATCH bpf-next v3 3/6] bpf: fix the usage of BPF_TRAMP_F_SKIP_FRAME

From: Andreas Schwab <schwab@linux-m68k.org>
To: Menglong Dong <menglong8.dong@gmail.com>
Cc: Menglong Dong <menglong.dong@linux.dev>,
	 ast@kernel.org, rostedt@goodmis.org,  daniel@iogearbox.net,
	 john.fastabend@gmail.com, andrii@kernel.org,
	 martin.lau@linux.dev,  eddyz87@gmail.com, song@kernel.org,
	 yonghong.song@linux.dev,  kpsingh@kernel.org, sdf@fomichev.me,
	 haoluo@google.com,  jolsa@kernel.org, mhiramat@kernel.org,
	 mark.rutland@arm.com, mathieu.desnoyers@efficios.com,
	 jiang.biao@linux.dev, bpf@vger.kernel.org,
	 linux-kernel@vger.kernel.org,
	linux-trace-kernel@vger.kernel.org,
	 linux-riscv@lists.infradead.org
Subject: Re: [PATCH bpf-next v3 3/6] bpf: fix the usage of BPF_TRAMP_F_SKIP_FRAME
Date: Fri, 19 Dec 2025 15:50:15 +0100	[thread overview]
Message-ID: <878qeyedaw.fsf@igel.home> (raw)
In-Reply-To: <CADxym3Y098836fHHRSjeryxCp=CPB8sDU19TBBVs07VZOERJXw@mail.gmail.com> (Menglong Dong's message of "Fri, 19 Dec 2025 22:04:32 +0800")

On Dez 19 2025, Menglong Dong wrote:

> @@ -1171,6 +1167,8 @@ static int __arch_prepare_bpf_trampoline(struct
> bpf_tramp_image *im,
>         }
>
>         if (flags & BPF_TRAMP_F_CALL_ORIG) {
> +               /* skip to actual body of traced function */
> +               orig_call += RV_FENTRY_NINSNS * 4;

Before this line, orig_call still contains the same value as func_addr,
with the latter being dead, so there is not much point in using a copy.

-- 
Andreas Schwab, schwab@linux-m68k.org
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