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Sat, 12 Sep 2026 09:42:09 -0700 (PDT) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 Date: Sat, 12 Sep 2026 09:42:07 -0700 Message-Id: From: "Alexei Starovoitov" To: "Florent Revest (Anthropic)" , , "Alexei Starovoitov" , "Daniel Borkmann" , "Andrii Nakryiko" Cc: "Martin KaFai Lau" , "Eduard Zingerman" , "Kumar Kartikeya Dwivedi" , "Song Liu" , "Yonghong Song" , "Jiri Olsa" , "KP Singh" , "John Fastabend" , "Leon Hwang" , "Junseo Lim" , "Sechang Lim" , "Puranjay Mohan" , "Xu Kuohai" , "Ilya Leoshkevich" , "Hari Bathini" , "Christophe Leroy" , "Naveen N Rao" , =?utf-8?q?Bj=C3=B6rn_T=C3=B6pel?= , "Pu Lehui" , "Tiezhu Yang" , "Hengqi Chen" , Subject: Re: [PATCH bpf v2 1/2] bpf: Skip detached progs in trampoline images that are still in use X-Mailer: aerc References: <20260912095924.866254-1-florent.revest@linux.dev> <20260912095924.866254-2-florent.revest@linux.dev> In-Reply-To: <20260912095924.866254-2-florent.revest@linux.dev> On Sat Sep 12, 2026 at 2:59 AM PDT, Florent Revest (Anthropic) wrote: > +/* > + * Each prog call in a trampoline image is preceded by a nop. When the p= rog is > + * detached, the nop is patched to a jump to target, right after the cal= l, so > + * that tasks still running in the image skip the prog. > + */ > +struct bpf_tramp_skip { > + struct bpf_prog *prog; prog pointer shouldn't be necessary. > + void *nop; > + void *target; > +}; > + > struct bpf_tramp_image { > void *image; > int size; > @@ -1374,8 +1389,27 @@ struct bpf_tramp_image { > struct rcu_head rcu; > struct work_struct work; > }; > + /* entry in tr->images, the image holds a reference on tr */ > + struct bpf_trampoline *tr; > + struct list_head list; > + struct bpf_tramp_skip *skips; > + int nr_skips; I don't follow why you need link list and 'tr' pointer here. Also why keep ip_after_call ? Replace ip_after_call with array of bpf_tramp_skip { void *nop, *target; } and then in bpf_tramp_image_put() instead of ip_after_call do: for (i =3D 0; i < im->nr_skips; i++) { struct bpf_tramp_skip *skip =3D &im->skips[i]; err =3D bpf_arch_text_poke(skip->nop, BPF_MOD_NOP, BPF_MOD_JUMP, NULL, skip->target); } what am I missing?