From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 952A4CF8861 for ; Thu, 20 Nov 2025 15:13:44 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id EDA186B00D0; Thu, 20 Nov 2025 10:13:43 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id E8AC36B00D2; Thu, 20 Nov 2025 10:13:43 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id D79AA6B00D3; Thu, 20 Nov 2025 10:13:43 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id C21D56B00D0 for ; Thu, 20 Nov 2025 10:13:43 -0500 (EST) Received: from smtpin30.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay05.hostedemail.com (Postfix) with ESMTP id 89A6B566E1 for ; Thu, 20 Nov 2025 15:13:43 +0000 (UTC) X-FDA: 84131329926.30.E0D7905 Received: from mail-wr1-f74.google.com (mail-wr1-f74.google.com [209.85.221.74]) by imf12.hostedemail.com (Postfix) with ESMTP id B517C4001E for ; Thu, 20 Nov 2025 15:13:41 +0000 (UTC) Authentication-Results: imf12.hostedemail.com; dkim=pass header.d=google.com header.s=20230601 header.b=ALP8XJec; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf12.hostedemail.com: domain of 3IzAfaQUKCFAw3Dw9y66y3w.u64305CF-442Dsu2.69y@flex--elver.bounces.google.com designates 209.85.221.74 as permitted sender) smtp.mailfrom=3IzAfaQUKCFAw3Dw9y66y3w.u64305CF-442Dsu2.69y@flex--elver.bounces.google.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1763651621; a=rsa-sha256; cv=none; b=SP6MZkJgvDFcZCYTudBu2p/s/SFaCqtljjOvOmxpFAXPgUXVigEHqCHo87yx7Sje+J7LCG PxKN7ECTI31EX5E9mdWB5Sy9HbT7gnkMM6GrUvQwntEWxfS3hiIj46itl4comajtHsnAiC OMsSpGiBoVwGNoqErgFbpoKv6ndCi4A= ARC-Authentication-Results: i=1; imf12.hostedemail.com; dkim=pass header.d=google.com header.s=20230601 header.b=ALP8XJec; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf12.hostedemail.com: domain of 3IzAfaQUKCFAw3Dw9y66y3w.u64305CF-442Dsu2.69y@flex--elver.bounces.google.com designates 209.85.221.74 as permitted sender) smtp.mailfrom=3IzAfaQUKCFAw3Dw9y66y3w.u64305CF-442Dsu2.69y@flex--elver.bounces.google.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1763651621; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=pcD6uieBoqcsyDkA1zkurf5hLc/pXwP1OAaVy3DV1GQ=; b=VniCaLmG1yx6euzu/OHld9S124yAq99nKYPfJabEklZ6XKEKOn3GCO+3kPj3OaGUgR6ovq kHTX/ce4z/6WjkNSNPFwMbryW73oad5efCGxsDgcopybQDXKgPPrfptGZ9qClcA6SwVm03 yqSFLp4nj2m/WYP3kjO7RWKJSmgp49I= Received: by mail-wr1-f74.google.com with SMTP id ffacd0b85a97d-42b3c965ce5so789099f8f.2 for ; Thu, 20 Nov 2025 07:13:41 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1763651620; x=1764256420; darn=kvack.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=pcD6uieBoqcsyDkA1zkurf5hLc/pXwP1OAaVy3DV1GQ=; b=ALP8XJecoDvwJ17tulVOFlFwnalKztm3Skr4KfqJVp/1YbNPxyOzh+PhEY1QzI86iz 700YT3GOJpf45N9YiJjULO9FglMtb+TP6tjaaTJwC7NdYyYu+d7uo1sbNRCvuiloWfth hgsKeInHkgOcxGcHHPDHrye6zuzZgqq+0ygpArv6OYpb+yz6XYzTmQQGwrQSBfxU4MS6 dTJFPogRJLRfH/zhGJgjteyCpOeGZ3qmVhAq6WIteL6hUomRPINKDi5VKdZhLV1nWUBU sz5QqyI95OTEzQBeGSj77Z4UOgk5qCmZnOqoe+vDve3f3/b9joQP8tSjO/2WE2J1soAT DUuw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1763651620; x=1764256420; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=pcD6uieBoqcsyDkA1zkurf5hLc/pXwP1OAaVy3DV1GQ=; b=XlFvRaKr5eZEgkxm8g+l0+6Kym7VVXuTimv1KK4SoUjg1K9p/33LZfPo9FZC4dnVJB iVhwZyfDPtEOc/m0ypqsIecBRlMlfdH2ElXZ4fsRCEnRirS3lAB28Hntae+kSPkj/cRo HZVG0DJ6NII1FQ4vA8AHOcP6VCrOO/cGIU8bEh93RtCn/sIme1HGhiwMZULyE+Aqdvzq 09gO1n7kFM7dgKiACy4dHLBzhWvpPnYkIg11qO8E+T2T/3nL81GyB1m495c7yoTtsGoy 1DFoY8KV0JLK16Ji3Ny/+3Q+SWkLJB+Rw21jSjTr8qw7TBCAxw/VCFXLEJBBtzfvDi5m G1mQ== X-Forwarded-Encrypted: i=1; AJvYcCXDVL7d+9PlIbMEOPcgtGx/Yh84K8I2XOH2K5hcht0jsS6TWG+bGDmUYpQOl+BnUTBtSPqtRhDrHA==@kvack.org X-Gm-Message-State: AOJu0YxmetIVwQ/yuw6QLc5yhPDlPjhP7lRCttOYLgeMWqfRLB7VocAp tLvu9yPMiuGpqGFPcINVEGUVixruqBM6jIzqUnF42cCF+kQ2pj2QzeGI9lkF1zIZi2FSqoUs/Pn 6QA== X-Google-Smtp-Source: AGHT+IH2phiGswjRxahv1kYcFFnsn5EpFBG5GTvKLIn0Gw3adW5QmNBoQt0gQRrs7c/SRmL4IrpsGmOf6A== X-Received: from wrwn2.prod.google.com ([2002:a5d:67c2:0:b0:42b:349a:10f6]) (user=elver job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6000:2002:b0:42b:3746:3b84 with SMTP id ffacd0b85a97d-42cb9a6acd7mr3408354f8f.55.1763651619825; Thu, 20 Nov 2025 07:13:39 -0800 (PST) Date: Thu, 20 Nov 2025 16:09:53 +0100 In-Reply-To: <20251120151033.3840508-7-elver@google.com> Mime-Version: 1.0 References: <20251120145835.3833031-2-elver@google.com> <20251120151033.3840508-7-elver@google.com> X-Mailer: git-send-email 2.52.0.rc1.455.g30608eb744-goog Message-ID: <20251120151033.3840508-29-elver@google.com> Subject: [PATCH v4 28/35] kcov: Enable context analysis From: Marco Elver To: elver@google.com, Peter Zijlstra , Boqun Feng , Ingo Molnar , Will Deacon Cc: "David S. Miller" , Luc Van Oostenryck , Chris Li , "Paul E. McKenney" , Alexander Potapenko , Arnd Bergmann , Bart Van Assche , Christoph Hellwig , Dmitry Vyukov , Eric Dumazet , Frederic Weisbecker , Greg Kroah-Hartman , Herbert Xu , Ian Rogers , Jann Horn , Joel Fernandes , Johannes Berg , Jonathan Corbet , Josh Triplett , Justin Stitt , Kees Cook , Kentaro Takeda , Lukas Bulwahn , Mark Rutland , Mathieu Desnoyers , Miguel Ojeda , Nathan Chancellor , Neeraj Upadhyay , Nick Desaulniers , Steven Rostedt , Tetsuo Handa , Thomas Gleixner , Thomas Graf , Uladzislau Rezki , Waiman Long , kasan-dev@googlegroups.com, linux-crypto@vger.kernel.org, linux-doc@vger.kernel.org, linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-security-module@vger.kernel.org, linux-sparse@vger.kernel.org, linux-wireless@vger.kernel.org, llvm@lists.linux.dev, rcu@vger.kernel.org Content-Type: text/plain; charset="UTF-8" X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: B517C4001E X-Stat-Signature: twtakp7715xyof7xyc5uezbg9w5masy8 X-Rspam-User: X-HE-Tag: 1763651621-853846 X-HE-Meta: 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 rZ1Y7gKT 6mPKpjaI8cjnrb3ZzSTAqHtKUTjOuw/jBqGU/sOU/o14Hw0eDtsDPhLkLo55JOrPxs8k/FWrtQbIieA6OvKXyGRKiT4Ljje+HJJKz189Xxh+brv6dBwFSCzTPb1GST+0nHShGMOsh9AhfwnXomgiJF6aDgdJdsc6/mDvr1cBGejB74G9xKwVGF8NdHkkM9gv6TVyA3Xp0MCIrJfb6pe2nVLSfi69rl0Fu0wHw+FPFnYjn6dvfhtN0K+D9WR1cM1JMVKHq2anqvb75A1AQPcwGl3FWPVh2XitQ7qRNBAOvYn7MuCG62XrhWkZBzjdTBEq2fBSuVW867lqVZZqXcXbP1uHv/zJZJiRfvTookc1JCSxofeJwWYL4WAe85pjXAatJDHDjRuULyH7mHLFrinozeKOzcVyKY4Yk0cMW X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Enable context analysis for the KCOV subsystem. Signed-off-by: Marco Elver --- v4: * Fix new temporary variable type. * Rename capability -> context analysis. v2: * Remove disable/enable_context_analysis() around headers. --- kernel/Makefile | 2 ++ kernel/kcov.c | 36 +++++++++++++++++++++++++----------- 2 files changed, 27 insertions(+), 11 deletions(-) diff --git a/kernel/Makefile b/kernel/Makefile index 9fe722305c9b..82d49723904d 100644 --- a/kernel/Makefile +++ b/kernel/Makefile @@ -43,6 +43,8 @@ KASAN_SANITIZE_kcov.o := n KCSAN_SANITIZE_kcov.o := n UBSAN_SANITIZE_kcov.o := n KMSAN_SANITIZE_kcov.o := n + +CONTEXT_ANALYSIS_kcov.o := y CFLAGS_kcov.o := $(call cc-option, -fno-conserve-stack) -fno-stack-protector obj-y += sched/ diff --git a/kernel/kcov.c b/kernel/kcov.c index 6563141f5de9..6cbc6e2d8aee 100644 --- a/kernel/kcov.c +++ b/kernel/kcov.c @@ -55,13 +55,13 @@ struct kcov { refcount_t refcount; /* The lock protects mode, size, area and t. */ spinlock_t lock; - enum kcov_mode mode; + enum kcov_mode mode __guarded_by(&lock); /* Size of arena (in long's). */ - unsigned int size; + unsigned int size __guarded_by(&lock); /* Coverage buffer shared with user space. */ - void *area; + void *area __guarded_by(&lock); /* Task for which we collect coverage, or NULL. */ - struct task_struct *t; + struct task_struct *t __guarded_by(&lock); /* Collecting coverage from remote (background) threads. */ bool remote; /* Size of remote area (in long's). */ @@ -391,6 +391,7 @@ void kcov_task_init(struct task_struct *t) } static void kcov_reset(struct kcov *kcov) + __must_hold(&kcov->lock) { kcov->t = NULL; kcov->mode = KCOV_MODE_INIT; @@ -400,6 +401,7 @@ static void kcov_reset(struct kcov *kcov) } static void kcov_remote_reset(struct kcov *kcov) + __must_hold(&kcov->lock) { int bkt; struct kcov_remote *remote; @@ -419,6 +421,7 @@ static void kcov_remote_reset(struct kcov *kcov) } static void kcov_disable(struct task_struct *t, struct kcov *kcov) + __must_hold(&kcov->lock) { kcov_task_reset(t); if (kcov->remote) @@ -435,8 +438,11 @@ static void kcov_get(struct kcov *kcov) static void kcov_put(struct kcov *kcov) { if (refcount_dec_and_test(&kcov->refcount)) { - kcov_remote_reset(kcov); - vfree(kcov->area); + /* Context-safety: no references left, object being destroyed. */ + context_unsafe( + kcov_remote_reset(kcov); + vfree(kcov->area); + ); kfree(kcov); } } @@ -491,6 +497,7 @@ static int kcov_mmap(struct file *filep, struct vm_area_struct *vma) unsigned long size, off; struct page *page; unsigned long flags; + void *area; spin_lock_irqsave(&kcov->lock, flags); size = kcov->size * sizeof(unsigned long); @@ -499,10 +506,11 @@ static int kcov_mmap(struct file *filep, struct vm_area_struct *vma) res = -EINVAL; goto exit; } + area = kcov->area; spin_unlock_irqrestore(&kcov->lock, flags); vm_flags_set(vma, VM_DONTEXPAND); for (off = 0; off < size; off += PAGE_SIZE) { - page = vmalloc_to_page(kcov->area + off); + page = vmalloc_to_page(area + off); res = vm_insert_page(vma, vma->vm_start + off, page); if (res) { pr_warn_once("kcov: vm_insert_page() failed\n"); @@ -522,10 +530,10 @@ static int kcov_open(struct inode *inode, struct file *filep) kcov = kzalloc(sizeof(*kcov), GFP_KERNEL); if (!kcov) return -ENOMEM; + spin_lock_init(&kcov->lock); kcov->mode = KCOV_MODE_DISABLED; kcov->sequence = 1; refcount_set(&kcov->refcount, 1); - spin_lock_init(&kcov->lock); filep->private_data = kcov; return nonseekable_open(inode, filep); } @@ -556,6 +564,7 @@ static int kcov_get_mode(unsigned long arg) * vmalloc fault handling path is instrumented. */ static void kcov_fault_in_area(struct kcov *kcov) + __must_hold(&kcov->lock) { unsigned long stride = PAGE_SIZE / sizeof(unsigned long); unsigned long *area = kcov->area; @@ -584,6 +593,7 @@ static inline bool kcov_check_handle(u64 handle, bool common_valid, static int kcov_ioctl_locked(struct kcov *kcov, unsigned int cmd, unsigned long arg) + __must_hold(&kcov->lock) { struct task_struct *t; unsigned long flags, unused; @@ -814,6 +824,7 @@ static inline bool kcov_mode_enabled(unsigned int mode) } static void kcov_remote_softirq_start(struct task_struct *t) + __must_hold(&kcov_percpu_data.lock) { struct kcov_percpu_data *data = this_cpu_ptr(&kcov_percpu_data); unsigned int mode; @@ -831,6 +842,7 @@ static void kcov_remote_softirq_start(struct task_struct *t) } static void kcov_remote_softirq_stop(struct task_struct *t) + __must_hold(&kcov_percpu_data.lock) { struct kcov_percpu_data *data = this_cpu_ptr(&kcov_percpu_data); @@ -896,10 +908,12 @@ void kcov_remote_start(u64 handle) /* Put in kcov_remote_stop(). */ kcov_get(kcov); /* - * Read kcov fields before unlock to prevent races with - * KCOV_DISABLE / kcov_remote_reset(). + * Read kcov fields before unlocking kcov_remote_lock to prevent races + * with KCOV_DISABLE and kcov_remote_reset(); cannot acquire kcov->lock + * here, because it might lead to deadlock given kcov_remote_lock is + * acquired _after_ kcov->lock elsewhere. */ - mode = kcov->mode; + mode = context_unsafe(kcov->mode); sequence = kcov->sequence; if (in_task()) { size = kcov->remote_size; -- 2.52.0.rc1.455.g30608eb744-goog