From patchwork Fri May 31 14:22:30 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Vasiliy Kovalev X-Patchwork-Id: 13681747 X-Patchwork-Delegate: bpf@iogearbox.net Received: from air.basealt.ru (air.basealt.ru [194.107.17.39]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id AB92A20B34; Fri, 31 May 2024 14:22:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=194.107.17.39 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1717165358; cv=none; b=jxLu+ruLG00bjiSu+hDeJf79GhOzKk6QKt5ywhNFJsr6BFCwKOIrrpHbODW47/NJzu8RKcoqRsypsnbwr/3bk8V1IEdQoUjvJV5ZGYPsvAXvThyJyD74vWVroyNOStoZDxnHNGRB+tfjzZwtObt378BFhORpY5r9Q8G6bxM/OMU= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1717165358; c=relaxed/simple; bh=DrH+77i5wmV2sWNd9DVAO5Ms5FxE6ZoVWh5X6bEtYFE=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version:Content-Type; b=YRV8imFrnm3Z/THnyvtWJKcIPUgl0OglnJsgno36X/FRnHrH4SN+xZSZLSM+Xx23Vv1m9nVXXf+i9oFDTRTHOWhrHyeBMrf3vAMrPXksoccrbY5zaJXgaRnC0Ub0Am3KxBGv0QN3hIHIKDg0LT/HJMQWta9pYwPh797/atj2Yz8= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=altlinux.org; spf=pass smtp.mailfrom=altlinux.org; arc=none smtp.client-ip=194.107.17.39 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=altlinux.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=altlinux.org Received: by air.basealt.ru (Postfix, from userid 490) id C76FF2F20245; Fri, 31 May 2024 14:22:34 +0000 (UTC) X-Spam-Level: Received: from altlinux.malta.altlinux.ru (obninsk.basealt.ru [217.15.195.17]) by air.basealt.ru (Postfix) with ESMTPSA id 54FAC2F20242; Fri, 31 May 2024 14:22:34 +0000 (UTC) From: kovalev@altlinux.org To: stable@vger.kernel.org Cc: bpf@vger.kernel.org, lvc-project@linuxtesting.org, kovalev@altlinux.org, dutyrok@altlinux.org, oficerovas@altlinux.org Subject: [PATCH v2 5.10.y 1/2] bpf: Convert BPF_DISPATCHER to use static_call() (not ftrace) Date: Fri, 31 May 2024 17:22:30 +0300 Message-Id: <20240531142231.51068-2-kovalev@altlinux.org> X-Mailer: git-send-email 2.33.8 In-Reply-To: <20240531142231.51068-1-kovalev@altlinux.org> References: <20240531142231.51068-1-kovalev@altlinux.org> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Patchwork-Delegate: bpf@iogearbox.net From: Peter Zijlstra [ Upstream commit c86df29d11dfba27c0a1f5039cd6fe387fbf4239 ] The dispatcher function is currently abusing the ftrace __fentry__ call location for its own purposes -- this obviously gives trouble when the dispatcher and ftrace are both in use. A previous solution tried using __attribute__((patchable_function_entry())) which works, except it is GCC-8+ only, breaking the build on the earlier still supported compilers. Instead use static_call() -- which has its own annotations and does not conflict with ftrace -- to rewrite the dispatch function. By using: return static_call()(ctx, insni, bpf_func) you get a perfect forwarding tail call as function body (iow a single jmp instruction). By having the default static_call() target be bpf_dispatcher_nop_func() it retains the default behaviour (an indirect call to the argument function). Only once a dispatcher program is attached is the target rewritten to directly call the JIT'ed image. Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Daniel Borkmann Tested-by: Björn Töpel Tested-by: Jiri Olsa Acked-by: Björn Töpel Acked-by: Jiri Olsa Link: https://lkml.kernel.org/r/Y1/oBlK0yFk5c/Im@hirez.programming.kicks-ass.net Link: https://lore.kernel.org/bpf/20221103120647.796772565@infradead.org Signed-off-by: Vasiliy Kovalev --- include/linux/bpf.h | 39 ++++++++++++++++++++++++++++++++++++++- kernel/bpf/dispatcher.c | 22 ++++++++-------------- 2 files changed, 46 insertions(+), 15 deletions(-) diff --git a/include/linux/bpf.h b/include/linux/bpf.h index a75faf437e750..2c4a08699de21 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -21,6 +21,7 @@ #include #include #include +#include struct bpf_verifier_env; struct bpf_verifier_log; @@ -659,6 +660,10 @@ struct bpf_dispatcher { void *image; u32 image_off; struct bpf_ksym ksym; +#ifdef CONFIG_HAVE_STATIC_CALL + struct static_call_key *sc_key; + void *sc_tramp; +#endif }; static __always_inline unsigned int bpf_dispatcher_nop_func( @@ -676,6 +681,34 @@ struct bpf_trampoline *bpf_trampoline_get(u64 key, struct bpf_attach_target_info *tgt_info); void bpf_trampoline_put(struct bpf_trampoline *tr); int arch_prepare_bpf_dispatcher(void *image, s64 *funcs, int num_funcs); + +/* + * When the architecture supports STATIC_CALL replace the bpf_dispatcher_fn + * indirection with a direct call to the bpf program. If the architecture does + * not have STATIC_CALL, avoid a double-indirection. + */ +#ifdef CONFIG_HAVE_STATIC_CALL + +#define __BPF_DISPATCHER_SC_INIT(_name) \ + .sc_key = &STATIC_CALL_KEY(_name), \ + .sc_tramp = STATIC_CALL_TRAMP_ADDR(_name), + +#define __BPF_DISPATCHER_SC(name) \ + DEFINE_STATIC_CALL(bpf_dispatcher_##name##_call, bpf_dispatcher_nop_func) + +#define __BPF_DISPATCHER_CALL(name) \ + static_call(bpf_dispatcher_##name##_call)(ctx, insnsi, bpf_func) + +#define __BPF_DISPATCHER_UPDATE(_d, _new) \ + __static_call_update((_d)->sc_key, (_d)->sc_tramp, (_new)) + +#else +#define __BPF_DISPATCHER_SC_INIT(name) +#define __BPF_DISPATCHER_SC(name) +#define __BPF_DISPATCHER_CALL(name) bpf_func(ctx, insnsi) +#define __BPF_DISPATCHER_UPDATE(_d, _new) +#endif + #define BPF_DISPATCHER_INIT(_name) { \ .mutex = __MUTEX_INITIALIZER(_name.mutex), \ .func = &_name##_func, \ @@ -687,20 +720,23 @@ int arch_prepare_bpf_dispatcher(void *image, s64 *funcs, int num_funcs); .name = #_name, \ .lnode = LIST_HEAD_INIT(_name.ksym.lnode), \ }, \ + __BPF_DISPATCHER_SC_INIT(_name##_call) \ } #define DEFINE_BPF_DISPATCHER(name) \ + __BPF_DISPATCHER_SC(name); \ noinline unsigned int bpf_dispatcher_##name##_func( \ const void *ctx, \ const struct bpf_insn *insnsi, \ unsigned int (*bpf_func)(const void *, \ const struct bpf_insn *)) \ { \ - return bpf_func(ctx, insnsi); \ + return __BPF_DISPATCHER_CALL(name); \ } \ EXPORT_SYMBOL(bpf_dispatcher_##name##_func); \ struct bpf_dispatcher bpf_dispatcher_##name = \ BPF_DISPATCHER_INIT(bpf_dispatcher_##name); + #define DECLARE_BPF_DISPATCHER(name) \ unsigned int bpf_dispatcher_##name##_func( \ const void *ctx, \ @@ -708,6 +744,7 @@ int arch_prepare_bpf_dispatcher(void *image, s64 *funcs, int num_funcs); unsigned int (*bpf_func)(const void *, \ const struct bpf_insn *)); \ extern struct bpf_dispatcher bpf_dispatcher_##name; + #define BPF_DISPATCHER_FUNC(name) bpf_dispatcher_##name##_func #define BPF_DISPATCHER_PTR(name) (&bpf_dispatcher_##name) void bpf_dispatcher_change_prog(struct bpf_dispatcher *d, struct bpf_prog *from, diff --git a/kernel/bpf/dispatcher.c b/kernel/bpf/dispatcher.c index 2444bd15cc2d0..23042cfb5e809 100644 --- a/kernel/bpf/dispatcher.c +++ b/kernel/bpf/dispatcher.c @@ -4,6 +4,7 @@ #include #include #include +#include /* The BPF dispatcher is a multiway branch code generator. The * dispatcher is a mechanism to avoid the performance penalty of an @@ -104,17 +105,11 @@ static int bpf_dispatcher_prepare(struct bpf_dispatcher *d, void *image) static void bpf_dispatcher_update(struct bpf_dispatcher *d, int prev_num_progs) { - void *old, *new; - u32 noff; - int err; - - if (!prev_num_progs) { - old = NULL; - noff = 0; - } else { - old = d->image + d->image_off; + void *new; + u32 noff = 0; + + if (prev_num_progs) noff = d->image_off ^ (PAGE_SIZE / 2); - } new = d->num_progs ? d->image + noff : NULL; if (new) { @@ -122,11 +117,10 @@ static void bpf_dispatcher_update(struct bpf_dispatcher *d, int prev_num_progs) return; } - err = bpf_arch_text_poke(d->func, BPF_MOD_JUMP, old, new); - if (err || !new) - return; + __BPF_DISPATCHER_UPDATE(d, new ?: &bpf_dispatcher_nop_func); - d->image_off = noff; + if (new) + d->image_off = noff; } void bpf_dispatcher_change_prog(struct bpf_dispatcher *d, struct bpf_prog *from,