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

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Message-ID: <CADxym3ZSHtqAn+_6pKEO+95tRp13eRCUuPqCfcM=xqMbhcf3PA@mail.gmail.com>
Date: Fri, 19 Dec 2025 22:54:28 +0800
From: Menglong Dong <menglong8.dong@...il.com>
To: Andreas Schwab <schwab@...ux-m68k.org>
Cc: Menglong Dong <menglong.dong@...ux.dev>, ast@...nel.org, rostedt@...dmis.org, 
	daniel@...earbox.net, john.fastabend@...il.com, andrii@...nel.org, 
	martin.lau@...ux.dev, eddyz87@...il.com, song@...nel.org, 
	yonghong.song@...ux.dev, kpsingh@...nel.org, sdf@...ichev.me, 
	haoluo@...gle.com, jolsa@...nel.org, mhiramat@...nel.org, 
	mark.rutland@....com, mathieu.desnoyers@...icios.com, jiang.biao@...ux.dev, 
	bpf@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-trace-kernel@...r.kernel.org, linux-riscv@...ts.infradead.org
Subject: Re: [PATCH bpf-next v3 3/6] bpf: fix the usage of BPF_TRAMP_F_SKIP_FRAME

On Fri, Dec 19, 2025 at 10:50 PM Andreas Schwab <schwab@...ux-m68k.org> wrote:
>
> 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.

Yeah, we can use "func_addr + RV_FENTRY_NINSNS * 4" here directly.

>
> --
> Andreas Schwab, schwab@...ux-m68k.org
> GPG Key fingerprint = 7578 EB47 D4E5 4D69 2510  2552 DF73 E780 A9DA AEC1
> "And now for something completely different."