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Tue, 18 Nov 2025 04:37:26 -0800 (PST) From: Menglong Dong X-Google-Original-From: Menglong Dong To: ast@kernel.org, rostedt@goodmis.org Cc: 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 Subject: [PATCH bpf-next v3 6/6] bpf: implement "jmp" mode for trampoline Date: Tue, 18 Nov 2025 20:36:34 +0800 Message-ID: <20251118123639.688444-7-dongml2@chinatelecom.cn> X-Mailer: git-send-email 2.51.2 In-Reply-To: <20251118123639.688444-1-dongml2@chinatelecom.cn> References: <20251118123639.688444-1-dongml2@chinatelecom.cn> 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" Implement the "jmp" mode for the bpf trampoline. For the ftrace_managed case, we need only to set the FTRACE_OPS_FL_JMP on the tr->fops if "jmp" is needed. For the bpf poke case, we will check the origin poke type with the "origin_flags", and current poke type with "tr->flags". The function bpf_trampoline_update_fentry() is introduced to do the job. The "jmp" mode will only be enabled with CONFIG_DYNAMIC_FTRACE_WITH_JMP enabled and BPF_TRAMP_F_SHARE_IPMODIFY is not set. With BPF_TRAMP_F_SHARE_IPMODIFY, we need to get the origin call ip from the stack, so we can't use the "jmp" mode. Signed-off-by: Menglong Dong Acked-by: Steven Rostedt (Google) --- v3: - wrap the write to tr->fops->flags with CONFIG_DYNAMIC_FTRACE_WITH_JMP - reset BPF_TRAMP_F_SKIP_FRAME when the second try of modify_fentry in bpf_trampoline_update() v2: - rename bpf_text_poke to bpf_trampoline_update_fentry - remove the BPF_TRAMP_F_JMPED and check the current mode with the origin flags instead. --- kernel/bpf/trampoline.c | 75 +++++++++++++++++++++++++++++++---------- 1 file changed, 58 insertions(+), 17 deletions(-) diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c index 0230ad19533e..976d89011b15 100644 --- a/kernel/bpf/trampoline.c +++ b/kernel/bpf/trampoline.c @@ -175,24 +175,42 @@ static struct bpf_trampoline *bpf_trampoline_lookup(u= 64 key) return tr; } =20 -static int unregister_fentry(struct bpf_trampoline *tr, void *old_addr) +static int bpf_trampoline_update_fentry(struct bpf_trampoline *tr, u32 ori= g_flags, + void *old_addr, void *new_addr) { + enum bpf_text_poke_type new_t =3D BPF_MOD_CALL, old_t =3D BPF_MOD_CALL; void *ip =3D tr->func.addr; + + if (!new_addr) + new_t =3D BPF_MOD_NOP; + else if (bpf_trampoline_use_jmp(tr->flags)) + new_t =3D BPF_MOD_JUMP; + + if (!old_addr) + old_t =3D BPF_MOD_NOP; + else if (bpf_trampoline_use_jmp(orig_flags)) + old_t =3D BPF_MOD_JUMP; + + return bpf_arch_text_poke(ip, old_t, new_t, old_addr, new_addr); +} + +static int unregister_fentry(struct bpf_trampoline *tr, u32 orig_flags, + void *old_addr) +{ int ret; =20 if (tr->func.ftrace_managed) ret =3D unregister_ftrace_direct(tr->fops, (long)old_addr, false); else - ret =3D bpf_arch_text_poke(ip, BPF_MOD_CALL, BPF_MOD_NOP, - old_addr, NULL); + ret =3D bpf_trampoline_update_fentry(tr, orig_flags, old_addr, NULL); =20 return ret; } =20 -static int modify_fentry(struct bpf_trampoline *tr, void *old_addr, void *= new_addr, +static int modify_fentry(struct bpf_trampoline *tr, u32 orig_flags, + void *old_addr, void *new_addr, bool lock_direct_mutex) { - void *ip =3D tr->func.addr; int ret; =20 if (tr->func.ftrace_managed) { @@ -201,10 +219,8 @@ static int modify_fentry(struct bpf_trampoline *tr, vo= id *old_addr, void *new_ad else ret =3D modify_ftrace_direct_nolock(tr->fops, (long)new_addr); } else { - ret =3D bpf_arch_text_poke(ip, - old_addr ? BPF_MOD_CALL : BPF_MOD_NOP, - new_addr ? BPF_MOD_CALL : BPF_MOD_NOP, - old_addr, new_addr); + ret =3D bpf_trampoline_update_fentry(tr, orig_flags, old_addr, + new_addr); } return ret; } @@ -229,8 +245,7 @@ static int register_fentry(struct bpf_trampoline *tr, v= oid *new_addr) return ret; ret =3D register_ftrace_direct(tr->fops, (long)new_addr); } else { - ret =3D bpf_arch_text_poke(ip, BPF_MOD_NOP, BPF_MOD_CALL, - NULL, new_addr); + ret =3D bpf_trampoline_update_fentry(tr, 0, NULL, new_addr); } =20 return ret; @@ -416,7 +431,7 @@ static int bpf_trampoline_update(struct bpf_trampoline = *tr, bool lock_direct_mut return PTR_ERR(tlinks); =20 if (total =3D=3D 0) { - err =3D unregister_fentry(tr, tr->cur_image->image); + err =3D unregister_fentry(tr, orig_flags, tr->cur_image->image); bpf_tramp_image_put(tr->cur_image); tr->cur_image =3D NULL; goto out; @@ -440,9 +455,20 @@ static int bpf_trampoline_update(struct bpf_trampoline= *tr, bool lock_direct_mut =20 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS again: - if ((tr->flags & BPF_TRAMP_F_SHARE_IPMODIFY) && - (tr->flags & BPF_TRAMP_F_CALL_ORIG)) - tr->flags |=3D BPF_TRAMP_F_ORIG_STACK; + if (tr->flags & BPF_TRAMP_F_CALL_ORIG) { + if (tr->flags & BPF_TRAMP_F_SHARE_IPMODIFY) { + /* The BPF_TRAMP_F_SKIP_FRAME can be cleared in the + * first try, reset it in the second try. + */ + tr->flags |=3D BPF_TRAMP_F_ORIG_STACK | BPF_TRAMP_F_SKIP_FRAME; + } else if (IS_ENABLED(CONFIG_DYNAMIC_FTRACE_WITH_JMP)) { + /* Use "jmp" instead of "call" for the trampoline + * in the origin call case, and we don't need to + * skip the frame. + */ + tr->flags &=3D ~BPF_TRAMP_F_SKIP_FRAME; + } + } #endif =20 size =3D arch_bpf_trampoline_size(&tr->func.model, tr->flags, @@ -473,10 +499,18 @@ static int bpf_trampoline_update(struct bpf_trampolin= e *tr, bool lock_direct_mut if (err) goto out_free; =20 +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_JMP + if (bpf_trampoline_use_jmp(tr->flags)) + tr->fops->flags |=3D FTRACE_OPS_FL_JMP; + else + tr->fops->flags &=3D ~FTRACE_OPS_FL_JMP; +#endif + WARN_ON(tr->cur_image && total =3D=3D 0); if (tr->cur_image) /* progs already running at this address */ - err =3D modify_fentry(tr, tr->cur_image->image, im->image, lock_direct_m= utex); + err =3D modify_fentry(tr, orig_flags, tr->cur_image->image, + im->image, lock_direct_mutex); else /* first time registering */ err =3D register_fentry(tr, im->image); @@ -499,8 +533,15 @@ static int bpf_trampoline_update(struct bpf_trampoline= *tr, bool lock_direct_mut tr->cur_image =3D im; out: /* If any error happens, restore previous flags */ - if (err) + if (err) { tr->flags =3D orig_flags; +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_JMP + if (bpf_trampoline_use_jmp(tr->flags)) + tr->fops->flags |=3D FTRACE_OPS_FL_JMP; + else + tr->fops->flags &=3D ~FTRACE_OPS_FL_JMP; +#endif + } kfree(tlinks); return err; =20 --=20 2.51.2