From patchwork Wed Aug 14 18:54:12 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrii Nakryiko X-Patchwork-Id: 13763818 X-Patchwork-Delegate: bpf@iogearbox.net 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 A8E411BDAB9; Wed, 14 Aug 2024 18:54:37 +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=1723661677; cv=none; b=ctviX31q1O73UAavIaeUvknFaaagumkVdU9FuxxrZZlF9Y/0u4zqyB5dVsDwMCnD6nD5i5ae6wfY1fgjGHz3XsJjt++RptvmPcWz4O/U+YqzggxE8kqwkT3s2DWw5pIoMBh8diUgDqTWia5SxOpuWv9za3LsCK4CqjCEYxOie3A= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723661677; c=relaxed/simple; bh=meM8TTb69/Y4fY3OabSKLiXw5VaLsiU5NV41UXNHZhM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=CR7SHSEbBIfaKnhj/DbGDoEAXYYM4KJnaDldk+M+MELdllKQ+xze2q0Wil9yzubMMRi6qSKxptwkGVUuk/RHZQM3rSHu+XWVhG2Q7wkM4O5ouGCKYb7IYBTHJx8m4dAdNwJKo3uxqoo1Fr0I69NSQ6Mf49Lz67o9lXhnHilaeXU= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=KLgO4BwC; 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="KLgO4BwC" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 65C9DC4AF0D; Wed, 14 Aug 2024 18:54:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1723661677; bh=meM8TTb69/Y4fY3OabSKLiXw5VaLsiU5NV41UXNHZhM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=KLgO4BwCbpY9tJo23F10bWnNCJdFyks5asNxMjP6XgzxUpK313FOpp8FQsY4D+d7c spKvluMklIOOhLqmatYCHA9kR2hE4MhJ5JPaCEaYqFvFhJEAUmMkJnSsU70nR1j857 JAICAzLHKH4CmYLOs3KydHdzjXEgToxVOpAT9Lek8R0X3OvB4ggKqr/+Fl98oh21wJ WJZExoaaEbLDrKbQk52GS/OLrnFJWScCQzrMp+LVTXoLFRji3FbI3fnXHT9t3bpNxv ZiodpCvszXvgzjzDI/eay4+Gl8EyTPmEY262Fn/faA7DsdOTSdYkURj48ro+scNw5m PR3Skup654FWg== From: Andrii Nakryiko To: bpf@vger.kernel.org Cc: linux-mm@kvack.org, akpm@linux-foundation.org, adobriyan@gmail.com, shakeel.butt@linux.dev, hannes@cmpxchg.org, ak@linux.intel.com, osandov@osandov.com, song@kernel.org, jannh@google.com, linux-fsdevel@vger.kernel.org, willy@infradead.org, Andrii Nakryiko Subject: [PATCH v6 bpf-next 05/10] lib/buildid: rename build_id_parse() into build_id_parse_nofault() Date: Wed, 14 Aug 2024 11:54:12 -0700 Message-ID: <20240814185417.1171430-6-andrii@kernel.org> X-Mailer: git-send-email 2.43.5 In-Reply-To: <20240814185417.1171430-1-andrii@kernel.org> References: <20240814185417.1171430-1-andrii@kernel.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 Make it clear that build_id_parse() assumes that it can take no page fault by renaming it and current few users to build_id_parse_nofault(). Also add build_id_parse() stub which for now falls back to non-sleepable implementation, but will be changed in subsequent patches to take advantage of sleepable context. PROCMAP_QUERY ioctl() on /proc//maps file is using build_id_parse() and will automatically take advantage of more reliable sleepable context implementation. Signed-off-by: Andrii Nakryiko --- include/linux/buildid.h | 4 ++-- kernel/bpf/stackmap.c | 2 +- kernel/events/core.c | 2 +- lib/buildid.c | 25 ++++++++++++++++++++++--- 4 files changed, 26 insertions(+), 7 deletions(-) diff --git a/include/linux/buildid.h b/include/linux/buildid.h index 20aa3c2d89f7..014a88c41073 100644 --- a/include/linux/buildid.h +++ b/include/linux/buildid.h @@ -7,8 +7,8 @@ #define BUILD_ID_SIZE_MAX 20 struct vm_area_struct; -int build_id_parse(struct vm_area_struct *vma, unsigned char *build_id, - __u32 *size); +int build_id_parse(struct vm_area_struct *vma, unsigned char *build_id, __u32 *size); +int build_id_parse_nofault(struct vm_area_struct *vma, unsigned char *build_id, __u32 *size); int build_id_parse_buf(const void *buf, unsigned char *build_id, u32 buf_size); #if IS_ENABLED(CONFIG_STACKTRACE_BUILD_ID) || IS_ENABLED(CONFIG_VMCORE_INFO) diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c index c99f8e5234ac..770ae8e88016 100644 --- a/kernel/bpf/stackmap.c +++ b/kernel/bpf/stackmap.c @@ -156,7 +156,7 @@ static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs, goto build_id_valid; } vma = find_vma(current->mm, ips[i]); - if (!vma || build_id_parse(vma, id_offs[i].build_id, NULL)) { + if (!vma || build_id_parse_nofault(vma, id_offs[i].build_id, NULL)) { /* per entry fall back to ips */ id_offs[i].status = BPF_STACK_BUILD_ID_IP; id_offs[i].ip = ips[i]; diff --git a/kernel/events/core.c b/kernel/events/core.c index aa3450bdc227..c263a8b0ce54 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -8851,7 +8851,7 @@ static void perf_event_mmap_event(struct perf_mmap_event *mmap_event) mmap_event->event_id.header.size = sizeof(mmap_event->event_id) + size; if (atomic_read(&nr_build_id_events)) - build_id_parse(vma, mmap_event->build_id, &mmap_event->build_id_size); + build_id_parse_nofault(vma, mmap_event->build_id, &mmap_event->build_id_size); perf_iterate_sb(perf_event_mmap_output, mmap_event, diff --git a/lib/buildid.c b/lib/buildid.c index e8fc4aeb01f2..c1cbd34f3685 100644 --- a/lib/buildid.c +++ b/lib/buildid.c @@ -293,10 +293,12 @@ static int get_build_id_64(struct freader *r, unsigned char *build_id, __u32 *si * @build_id: buffer to store build id, at least BUILD_ID_SIZE long * @size: returns actual build id size in case of success * - * Return: 0 on success, -EINVAL otherwise + * Assumes no page fault can be taken, so if relevant portions of ELF file are + * not already paged in, fetching of build ID fails. + * + * Return: 0 on success; negative error, otherwise */ -int build_id_parse(struct vm_area_struct *vma, unsigned char *build_id, - __u32 *size) +int build_id_parse_nofault(struct vm_area_struct *vma, unsigned char *build_id, __u32 *size) { const Elf32_Ehdr *ehdr; struct freader r; @@ -335,6 +337,23 @@ int build_id_parse(struct vm_area_struct *vma, unsigned char *build_id, return ret; } +/* + * Parse build ID of ELF file mapped to VMA + * @vma: vma object + * @build_id: buffer to store build id, at least BUILD_ID_SIZE long + * @size: returns actual build id size in case of success + * + * Assumes faultable context and can cause page faults to bring in file data + * into page cache. + * + * Return: 0 on success; negative error, otherwise + */ +int build_id_parse(struct vm_area_struct *vma, unsigned char *build_id, __u32 *size) +{ + /* fallback to non-faultable version for now */ + return build_id_parse_nofault(vma, build_id, size); +} + /** * build_id_parse_buf - Get build ID from a buffer * @buf: ELF note section(s) to parse