From patchwork Thu Apr 18 19:09:08 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrii Nakryiko X-Patchwork-Id: 13635247 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 7A46917A93E; Thu, 18 Apr 2024 19:09:14 +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=1713467354; cv=none; b=FAhQtRrEHx7pCIRPASoCUmTyWYDSiniq/S10dX7QPundmiwwKS7vbADxtI2YgdNLbziIorYGaOGNuKcUHllcUs+U3URirfxhEaDHWccr3vKrgIknAVg9JKguKkynjkJY58t6NUl2oImUJJXW5P9F/skyC4zAtgxTvgXfb38Sd1A= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1713467354; c=relaxed/simple; bh=o+p+igQ4FBx5KCCF7nvkKmVDm0IeVUjotiEU4ySmHYw=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=Xtcp05GxZwCk8hEHQIMcwVbJ6PxtT34fC63JvzubOVGxMdV617RQhfSQoVhNm8fZ/MCG3g0mRgddFNNLbbYo726eQuRkMkqQuKR57Z0i5G24izu5YQ/M6BtrNCcPLwJq9paR/qWyuLDbNuBExmlbad6rzOfvwQ43+wuudSGCSOs= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=QTTVatkm; 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="QTTVatkm" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D7ACEC113CC; Thu, 18 Apr 2024 19:09:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1713467354; bh=o+p+igQ4FBx5KCCF7nvkKmVDm0IeVUjotiEU4ySmHYw=; h=From:To:Cc:Subject:Date:From; b=QTTVatkmL5i3GCPN0BJ1MR+6XPFv7f7hE5mKDU0Gk9O16IXDL8/QZ1vHtQtvmG2Kf jYIZcRpv8P9Nv5ELcIsdfnAPU+IVs/Ti4g7WsjWA5Qr3K7C6mrMuZMQTtozecRBqZI jIQQbZNp2dJe/hezZJ2eeuK2e9Xh5dca5zVeJ3JSf54FeRVFfLLmns7v1LqYupRS4U PtGAtZthaaJ17fdPKhrblEmSG5eP3y2B/6GOVGSuaWqE/NgQmJjRAznTS/Gf8GxjRu +24y0eLIYHV77CextfNzqg9dX7BAYDljHO4AM6+4eUSV4w2gMg7du7tZ8rmdUdqtIh DmLfazQANKukA== From: Andrii Nakryiko To: linux-trace-kernel@vger.kernel.org, rostedt@goodmis.org, mhiramat@kernel.org Cc: bpf@vger.kernel.org, jolsa@kernel.org, Andrii Nakryiko , "Paul E . McKenney" Subject: [PATCH v4 1/2] ftrace: make extra rcu_is_watching() validation check optional Date: Thu, 18 Apr 2024 12:09:08 -0700 Message-ID: <20240418190909.704286-1-andrii@kernel.org> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Introduce CONFIG_FTRACE_VALIDATE_RCU_IS_WATCHING config option to control whether ftrace low-level code performs additional rcu_is_watching()-based validation logic in an attempt to catch noinstr violations. This check is expected to never be true and is mostly useful for low-level validation of ftrace subsystem invariants. For most users it should probably be kept disabled to eliminate unnecessary runtime overhead. This improves BPF multi-kretprobe (relying on ftrace and rethook infrastructure) runtime throughput by 2%, according to BPF benchmarks ([0]). [0] https://lore.kernel.org/bpf/CAEf4BzauQ2WKMjZdc9s0rBWa01BYbgwHN6aNDXQSHYia47pQ-w@mail.gmail.com/ Cc: Steven Rostedt Cc: Masami Hiramatsu Cc: Paul E. McKenney Acked-by: Masami Hiramatsu (Google) Signed-off-by: Andrii Nakryiko --- include/linux/trace_recursion.h | 2 +- kernel/trace/Kconfig | 13 +++++++++++++ 2 files changed, 14 insertions(+), 1 deletion(-) diff --git a/include/linux/trace_recursion.h b/include/linux/trace_recursion.h index d48cd92d2364..24ea8ac049b4 100644 --- a/include/linux/trace_recursion.h +++ b/include/linux/trace_recursion.h @@ -135,7 +135,7 @@ extern void ftrace_record_recursion(unsigned long ip, unsigned long parent_ip); # define do_ftrace_record_recursion(ip, pip) do { } while (0) #endif -#ifdef CONFIG_ARCH_WANTS_NO_INSTR +#ifdef CONFIG_FTRACE_VALIDATE_RCU_IS_WATCHING # define trace_warn_on_no_rcu(ip) \ ({ \ bool __ret = !rcu_is_watching(); \ diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig index 61c541c36596..7aebd1b8f93e 100644 --- a/kernel/trace/Kconfig +++ b/kernel/trace/Kconfig @@ -974,6 +974,19 @@ config FTRACE_RECORD_RECURSION_SIZE This file can be reset, but the limit can not change in size at runtime. +config FTRACE_VALIDATE_RCU_IS_WATCHING + bool "Validate RCU is on during ftrace execution" + depends on FUNCTION_TRACER + depends on ARCH_WANTS_NO_INSTR + help + All callbacks that attach to the function tracing have some sort of + protection against recursion. This option is only to verify that + ftrace (and other users of ftrace_test_recursion_trylock()) are not + called outside of RCU, as if they are, it can cause a race. But it + also has a noticeable overhead when enabled. + + If unsure, say N + config RING_BUFFER_RECORD_RECURSION bool "Record functions that recurse in the ring buffer" depends on FTRACE_RECORD_RECURSION