linux-kernel - Re: [PATCH bpf-next v2 06/18] bpf: tracing: add support to record and check the accessed args

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Message-ID: <CAEf4BzYpfYJyFKj0Uvtj+h2mBe1AXDwa2pfFCF7E377JufSU3g@mail.gmail.com>
Date: Mon, 14 Jul 2025 15:07:18 -0700
From: Andrii Nakryiko <andrii.nakryiko@...il.com>
To: Menglong Dong <menglong8.dong@...il.com>
Cc: alexei.starovoitov@...il.com, rostedt@...dmis.org, jolsa@...nel.org, 
	bpf@...r.kernel.org, Menglong Dong <dongml2@...natelecom.cn>, 
	John Fastabend <john.fastabend@...il.com>, Martin KaFai Lau <martin.lau@...ux.dev>, 
	Eduard Zingerman <eddyz87@...il.com>, Song Liu <song@...nel.org>, 
	Yonghong Song <yonghong.song@...ux.dev>, KP Singh <kpsingh@...nel.org>, 
	Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>, Simon Horman <horms@...nel.org>, 
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH bpf-next v2 06/18] bpf: tracing: add support to record and
 check the accessed args

On Thu, Jul 3, 2025 at 5:20 AM Menglong Dong <menglong8.dong@...il.com> wrote:
>
> In this commit, we add the 'accessed_args' field to struct bpf_prog_aux,
> which is used to record the accessed index of the function args in
> btf_ctx_access().

Do we need to bother giving access to arguments through direct ctx[i]
access for these multi-fentry/fexit programs? We have
bpf_get_func_arg_cnt() and bpf_get_func_arg() which can be used to get
any given argument at runtime.


>
> Meanwhile, we add the function btf_check_func_part_match() to compare the
> accessed function args of two function prototype. This function will be
> used in the following commit.
>
> Signed-off-by: Menglong Dong <dongml2@...natelecom.cn>
> ---
>  include/linux/bpf.h   |   4 ++
>  include/linux/btf.h   |   3 +-
>  kernel/bpf/btf.c      | 108 +++++++++++++++++++++++++++++++++++++++++-
>  net/sched/bpf_qdisc.c |   2 +-
>  4 files changed, 113 insertions(+), 4 deletions(-)
>

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