From patchwork Wed Feb 21 16:25:22 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Benjamin Tissoires X-Patchwork-Id: 774697 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 E3E3C823DF; Wed, 21 Feb 2024 16:25:50 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708532751; cv=none; b=DnYMNey9BtyIPLggB1IvJ0Xsw6I5QTW+NFfLc5cFXeWolxGrtSsavYc07By90J9GnVUkHa3XPPr8xHdjfmPZfG5fhrvDtDRQSA8V3qOwB3xsVpxBUjMfzdI6spJE/jTQ9ETNO8d7FqiQc3h+LLMQ4WEByi4DkAZzJswJ2cdFz2E= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708532751; c=relaxed/simple; bh=mPB13lwDyMmrcL43OZduPdt7XlyPzMPfxJk3wSQi6i0=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=Oftbbu/8ox7DEXFoBloQm8ubXDIOE9aq63qNTHGQcwz3KUlVMJZFnjxtiJJm2rmwBDx7dZu8NeSV8xJTtYsH+7AP0jET/C/bKLkMSdt2nBfX9NkJWAtVSPH3RdQdUZmGy/z0i7UsHS1NGlFxUsuA9Z2FxFTlvwEk+SOOlgr1Onc= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=lK9/4QRA; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="lK9/4QRA" Received: by smtp.kernel.org (Postfix) with ESMTPSA id BC97FC43394; Wed, 21 Feb 2024 16:25:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1708532750; bh=mPB13lwDyMmrcL43OZduPdt7XlyPzMPfxJk3wSQi6i0=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=lK9/4QRANbD1ikbby/u0uvG3pn30oMZMO7T/xeFCDV9WRQwCRm6rEZJuhX4fJ0UNb ew6N0AztOnXVz38LOtF+7SfdmVhNNND6BTPvevlw4CBuPrpcDYcloh0u7v/Fa1CpPS 89yR3b5t2PUloP30P851IFD3Yq5L2mO9Ovw/ez1wz3i/4hVoYarm1rsjkXeAMEvnNQ UVv6Y2CH1JNETFNXrS9n/3lvDvS2Bjep51D9D7OJwCJDPUXHW3UeTUflHY5Axm2YDG UZSjDEeLJFR8S5IEwCs7d72NRVWHPFJS+x0lB94Wvr1Ium5WbO/Yir0RZS9edBV57Q PQ2ETCkOqFDlw== From: Benjamin Tissoires Date: Wed, 21 Feb 2024 17:25:22 +0100 Subject: [PATCH RFC bpf-next v3 06/16] bpf/helpers: introduce bpf_timer_set_sleepable_cb() kfunc Precedence: bulk X-Mailing-List: linux-input@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-Id: <20240221-hid-bpf-sleepable-v3-6-1fb378ca6301@kernel.org> References: <20240221-hid-bpf-sleepable-v3-0-1fb378ca6301@kernel.org> In-Reply-To: <20240221-hid-bpf-sleepable-v3-0-1fb378ca6301@kernel.org> To: Alexei Starovoitov , Daniel Borkmann , John Fastabend , Andrii Nakryiko , Martin KaFai Lau , Eduard Zingerman , Song Liu , Yonghong Song , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa , Jiri Kosina , Benjamin Tissoires , Jonathan Corbet , Shuah Khan Cc: bpf@vger.kernel.org, linux-kernel@vger.kernel.org, linux-input@vger.kernel.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, Benjamin Tissoires X-Mailer: b4 0.12.4 X-Developer-Signature: v=1; a=ed25519-sha256; t=1708532719; l=7632; i=bentiss@kernel.org; s=20230215; h=from:subject:message-id; bh=mPB13lwDyMmrcL43OZduPdt7XlyPzMPfxJk3wSQi6i0=; b=B+nS9++S8JmQb74JEXeGhA+6cIAUKNJ+sqzNSBI47ZNlqXnNUN21KpkprCmTmKXWhLg9LpMLu 1MZFXPpPuMTDvZlZhGhDZb2jV20Ba+XsRdmHsoNJRxySklYsp7IIIbC X-Developer-Key: i=bentiss@kernel.org; a=ed25519; pk=7D1DyAVh6ajCkuUTudt/chMuXWIJHlv2qCsRkIizvFw= In this patch, bpf_timer_set_sleepable_cb() is functionally equivalent to bpf_timer_set_callback(), to the exception that it enforces the timer to be started with BPF_F_TIMER_SLEEPABLE. But given that bpf_timer_set_callback() is a helper when bpf_timer_set_sleepable_cb() is a kfunc, we need to teach the verifier about its attached callback. Marking that callback as sleepable will be done in a separate patch Signed-off-by: Benjamin Tissoires --- new in v3 (split from v2 02/10) --- kernel/bpf/helpers.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++-- kernel/bpf/verifier.c | 31 +++++++++++++++++++++++++++++-- 2 files changed, 75 insertions(+), 4 deletions(-) diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c index f9add0abe40a..2c6dc3d0ffff 100644 --- a/kernel/bpf/helpers.c +++ b/kernel/bpf/helpers.c @@ -1108,6 +1108,7 @@ struct bpf_hrtimer { void __rcu *callback_fn; void *value; struct semaphore sleepable_lock; + bool is_sleepable; }; /* the actual struct hidden inside uapi struct bpf_timer */ @@ -1270,8 +1271,8 @@ static const struct bpf_func_proto bpf_timer_init_proto = { .arg3_type = ARG_ANYTHING, }; -BPF_CALL_3(bpf_timer_set_callback, struct bpf_timer_kern *, timer, void *, callback_fn, - struct bpf_prog_aux *, aux) +static int __bpf_timer_set_callback(struct bpf_timer_kern *timer, void *callback_fn, + struct bpf_prog_aux *aux, bool is_sleepable) { struct bpf_prog *prev, *prog = aux->prog; struct bpf_hrtimer *t; @@ -1311,12 +1312,19 @@ BPF_CALL_3(bpf_timer_set_callback, struct bpf_timer_kern *, timer, void *, callb t->prog = prog; } rcu_assign_pointer(t->callback_fn, callback_fn); + t->is_sleepable = is_sleepable; up(&t->sleepable_lock); out: __bpf_spin_unlock_irqrestore(&timer->lock); return ret; } +BPF_CALL_3(bpf_timer_set_callback, struct bpf_timer_kern *, timer, void *, callback_fn, + struct bpf_prog_aux *, aux) +{ + return __bpf_timer_set_callback(timer, callback_fn, aux, false); +} + static const struct bpf_func_proto bpf_timer_set_callback_proto = { .func = bpf_timer_set_callback, .gpl_only = true, @@ -1342,6 +1350,11 @@ BPF_CALL_3(bpf_timer_start, struct bpf_timer_kern *, timer, u64, nsecs, u64, fla goto out; } + if (t->is_sleepable && !(flags & BPF_F_TIMER_SLEEPABLE)) { + ret = -EINVAL; + goto out; + } + if (flags & BPF_F_TIMER_ABS) mode = HRTIMER_MODE_ABS_SOFT; else @@ -2606,6 +2619,36 @@ __bpf_kfunc void bpf_throw(u64 cookie) WARN(1, "A call to BPF exception callback should never return\n"); } +/** + * bpf_timer_set_sleepable_cb() - Configure the timer to call %callback_fn + * static function in a sleepable context. + * @timer: The bpf_timer that needs to be configured + * @callback_fn: a static bpf function + * + * @returns %0 on success. %-EINVAL if %timer was not initialized with + * bpf_timer_init() earlier. %-EPERM if %timer is in a map that doesn't + * have any user references. + * The user space should either hold a file descriptor to a map with timers + * or pin such map in bpffs. When map is unpinned or file descriptor is + * closed all timers in the map will be cancelled and freed. + * + * This kfunc is equivalent to %bpf_timer_set_callback except that it tells + * the verifier that the target callback is run in a sleepable context. + */ +__bpf_kfunc int bpf_timer_set_sleepable_cb(struct bpf_timer_kern *timer, + int (callback_fn)(void *map, int *key, struct bpf_timer *timer)) +{ + struct bpf_throw_ctx ctx = {}; + + arch_bpf_stack_walk(bpf_stack_walker, &ctx); + WARN_ON_ONCE(!ctx.aux); + + if (!ctx.aux) + return -EINVAL; + + return __bpf_timer_set_callback(timer, (void *)callback_fn, ctx.aux, true); +} + __bpf_kfunc_end_defs(); BTF_KFUNCS_START(generic_btf_ids) @@ -2682,6 +2725,7 @@ BTF_ID_FLAGS(func, bpf_dynptr_is_null) BTF_ID_FLAGS(func, bpf_dynptr_is_rdonly) BTF_ID_FLAGS(func, bpf_dynptr_size) BTF_ID_FLAGS(func, bpf_dynptr_clone) +BTF_ID_FLAGS(func, bpf_timer_set_sleepable_cb) BTF_KFUNCS_END(common_btf_ids) static const struct btf_kfunc_id_set common_kfunc_set = { diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 2b11687063ff..91e583c6feba 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -501,6 +501,8 @@ static bool is_dynptr_ref_function(enum bpf_func_id func_id) } static bool is_sync_callback_calling_kfunc(u32 btf_id); +static bool is_async_callback_calling_kfunc(u32 btf_id); +static bool is_callback_calling_kfunc(u32 btf_id); static bool is_bpf_throw_kfunc(struct bpf_insn *insn); static bool is_sync_callback_calling_function(enum bpf_func_id func_id) @@ -530,7 +532,8 @@ static bool is_sync_callback_calling_insn(struct bpf_insn *insn) static bool is_async_callback_calling_insn(struct bpf_insn *insn) { - return (bpf_helper_call(insn) && is_async_callback_calling_function(insn->imm)); + return (bpf_helper_call(insn) && is_async_callback_calling_function(insn->imm)) || + (bpf_pseudo_kfunc_call(insn) && is_async_callback_calling_kfunc(insn->imm)); } static bool is_storage_get_function(enum bpf_func_id func_id) @@ -9459,7 +9462,7 @@ static int push_callback_call(struct bpf_verifier_env *env, struct bpf_insn *ins */ env->subprog_info[subprog].is_cb = true; if (bpf_pseudo_kfunc_call(insn) && - !is_sync_callback_calling_kfunc(insn->imm)) { + !is_callback_calling_kfunc(insn->imm)) { verbose(env, "verifier bug: kfunc %s#%d not marked as callback-calling\n", func_id_name(insn->imm), insn->imm); return -EFAULT; @@ -10963,6 +10966,7 @@ enum special_kfunc_type { KF_bpf_percpu_obj_drop_impl, KF_bpf_throw, KF_bpf_iter_css_task_new, + KF_bpf_timer_set_sleepable_cb, }; BTF_SET_START(special_kfunc_set) @@ -10989,6 +10993,7 @@ BTF_ID(func, bpf_throw) #ifdef CONFIG_CGROUPS BTF_ID(func, bpf_iter_css_task_new) #endif +BTF_ID(func, bpf_timer_set_sleepable_cb) BTF_SET_END(special_kfunc_set) BTF_ID_LIST(special_kfunc_list) @@ -11019,6 +11024,7 @@ BTF_ID(func, bpf_iter_css_task_new) #else BTF_ID_UNUSED #endif +BTF_ID(func, bpf_timer_set_sleepable_cb) static bool is_kfunc_ret_null(struct bpf_kfunc_call_arg_meta *meta) { @@ -11344,12 +11350,23 @@ static bool is_sync_callback_calling_kfunc(u32 btf_id) return btf_id == special_kfunc_list[KF_bpf_rbtree_add_impl]; } +static bool is_async_callback_calling_kfunc(u32 btf_id) +{ + return btf_id == special_kfunc_list[KF_bpf_timer_set_sleepable_cb]; +} + static bool is_bpf_throw_kfunc(struct bpf_insn *insn) { return bpf_pseudo_kfunc_call(insn) && insn->off == 0 && insn->imm == special_kfunc_list[KF_bpf_throw]; } +static bool is_callback_calling_kfunc(u32 btf_id) +{ + return is_sync_callback_calling_kfunc(btf_id) || + is_async_callback_calling_kfunc(btf_id); +} + static bool is_rbtree_lock_required_kfunc(u32 btf_id) { return is_bpf_rbtree_api_kfunc(btf_id); @@ -12120,6 +12137,16 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn, } } + if (is_async_callback_calling_kfunc(meta.func_id)) { + err = push_callback_call(env, insn, insn_idx, meta.subprogno, + set_timer_callback_state); + if (err) { + verbose(env, "kfunc %s#%d failed callback verification\n", + func_name, meta.func_id); + return err; + } + } + rcu_lock = is_kfunc_bpf_rcu_read_lock(&meta); rcu_unlock = is_kfunc_bpf_rcu_read_unlock(&meta);