From nobody Sun Feb 8 12:19:51 2026 Received: from mail-wm1-f73.google.com (mail-wm1-f73.google.com [209.85.128.73]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 16843405FB for ; Tue, 23 Apr 2024 23:27:43 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.73 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1713914865; cv=none; b=f0CheKgoeUJDSJRpBooaSWzoegqwy7vGXCyMYNDU3021PPP/x7tm7dHUvr921Ar4eKBwaD+ZS6WfDoYaPno44080jxvPner+eyTIKhT4KYlh8S90Gt6TwXLFaBhaPKGc88wmiNJykJneR0n6qBgWH7vm9qNzULuTNppajUQ1wko= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1713914865; c=relaxed/simple; bh=l6oDZivJcyQTCOy+gknzagGu6pD9fjWdRZ/T8AH6uxk=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=I3XW5ZKoFqVwzrmWLVZJ5o6pAL4qfKdW9K5U12GQgYnw12DVrN5iVyrSluQaOeEjpyqUMT3f8BW9qxidAMpEh6VaIe/+2yaS5EvXbDG1iMn27qLr6JQgY0EsylXSaXXeMibOYG7Nu+fFn19k9mkEil29W77F/bv8B6mf/U7z6CM= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--vdonnefort.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=KBYjzMWN; arc=none smtp.client-ip=209.85.128.73 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--vdonnefort.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="KBYjzMWN" Received: by mail-wm1-f73.google.com with SMTP id 5b1f17b1804b1-417bf71efb4so1442155e9.0 for ; Tue, 23 Apr 2024 16:27:43 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1713914862; x=1714519662; darn=vger.kernel.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=RPOnWL9RPpAUuW6zSj0DHbUYz85VJ46LckD0gpweWUA=; b=KBYjzMWN/Vb1FaJMmcGldTfjlsH1Uz11TC8lW6+1dmV/Zl9R7qbUL3ZFAuCOFbjgKY V5yJI94I4T5guHJUx8Tv7V/1RGqD0wi66Fz6MJqeEbO6zIIHMRJPMMrcByoB/LQUMxtl IAVcn2z3P59gwGPqAeDjFfGjkF5nYjuKnUfxivurUdS2O3uLfZ4t5e6/V7ISTw0N1sJH tzbbnyORVz4c2vKMOd8slpkel1RwNtTkPYbomtfOV/tf5ur+Dnl26dEemQxlwDOerQPk TCloioMR20kwRcf3hIiEPADWoBtnoYdM4QkkG2DZA7wBAfQvbGrOBj9kYMl/73owkJ2N g83w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1713914862; x=1714519662; 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=RPOnWL9RPpAUuW6zSj0DHbUYz85VJ46LckD0gpweWUA=; b=cShRS3GhBQNMFqPky781BWYsYSAjY7qKOjv6HN5Wvz792M3VohtQuvj6T0IsH3pBgj t0JKWyxM8P/m2W2sz3cSjsQrcV4C8JrvbQwIDf1SiJCNLiLSQJchBjX7cqrBl/jCWh5X o3jY+KRcQPh8RkhVAo5ITZo+QshBKE4fNhGHfbMAoU7T7LFjyjwoOCk8gQAj0HmoB1RJ 4/E/35/miZ20HacLNbxMFlzUrWtL+444fkiZkriG26vE/enbMqm3YV2NT6cVI3tztDza KPUXXkncY6wWFY8sc2DQiZvgWNLbfrmhzVc/D7gLevu5WrIzVw5xsOyAsus5/iLJM8ME p5gg== X-Forwarded-Encrypted: i=1; AJvYcCXSMX4mztRfM+qaSggquNHyEXBMhQb+DPBZi5ibEAlqmibjNQwmaSVrMl1Aqjt2tTwvfOpQQhMPJSMvg+DYRDkTLU3vZyOqfZu5ZJf1 X-Gm-Message-State: AOJu0YxEQIuCP2px/OgJ+EsZRzhbwkbc7F/cPYPKhbmTZviNEGWtx0P4 M3WtqKce/jJYeWstEBrZ6Q3rVpXS/4Sh/6H3JLjdnTsAeGEDe21OQyCbIPkJPG++0HqTesL/2Uf v0SBtENo0kf4fSuvs7Q== X-Google-Smtp-Source: AGHT+IGcdysYgUX4limEoSe99eX1kVHNgFXvvBzAevVZIP8Mf4AJfQvspS4UgnqLHo17qIW313pU+cLeRpPTxzU0 X-Received: from vdonnefort.c.googlers.com ([fda3:e722:ac3:cc00:28:9cb1:c0a8:2eea]) (user=vdonnefort job=sendgmr) by 2002:a7b:cc16:0:b0:419:e61c:f388 with SMTP id f22-20020a7bcc16000000b00419e61cf388mr17264wmh.4.1713914862375; Tue, 23 Apr 2024 16:27:42 -0700 (PDT) Date: Wed, 24 Apr 2024 00:27:24 +0100 In-Reply-To: <20240423232728.1492340-1-vdonnefort@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20240423232728.1492340-1-vdonnefort@google.com> X-Mailer: git-send-email 2.44.0.769.g3c40516874-goog Message-ID: <20240423232728.1492340-2-vdonnefort@google.com> Subject: [PATCH v21 1/5] ring-buffer: Allocate sub-buffers with __GFP_COMP From: Vincent Donnefort To: rostedt@goodmis.org, mhiramat@kernel.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org Cc: mathieu.desnoyers@efficios.com, kernel-team@android.com, rdunlap@infradead.org, rppt@kernel.org, david@redhat.com, Vincent Donnefort Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" In preparation for the ring-buffer memory mapping, allocate compound pages for the ring-buffer sub-buffers to enable us to map them to user-space with vm_insert_pages(). Signed-off-by: Vincent Donnefort diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 25476ead681b..cc9ebe593571 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -1524,7 +1524,7 @@ static int __rb_allocate_pages(struct ring_buffer_per= _cpu *cpu_buffer, list_add(&bpage->list, pages); =20 page =3D alloc_pages_node(cpu_to_node(cpu_buffer->cpu), - mflags | __GFP_ZERO, + mflags | __GFP_COMP | __GFP_ZERO, cpu_buffer->buffer->subbuf_order); if (!page) goto free_pages; @@ -1609,7 +1609,7 @@ rb_allocate_cpu_buffer(struct trace_buffer *buffer, l= ong nr_pages, int cpu) =20 cpu_buffer->reader_page =3D bpage; =20 - page =3D alloc_pages_node(cpu_to_node(cpu), GFP_KERNEL | __GFP_ZERO, + page =3D alloc_pages_node(cpu_to_node(cpu), GFP_KERNEL | __GFP_COMP | __G= FP_ZERO, cpu_buffer->buffer->subbuf_order); if (!page) goto fail_free_reader; @@ -5579,7 +5579,7 @@ ring_buffer_alloc_read_page(struct trace_buffer *buff= er, int cpu) goto out; =20 page =3D alloc_pages_node(cpu_to_node(cpu), - GFP_KERNEL | __GFP_NORETRY | __GFP_ZERO, + GFP_KERNEL | __GFP_NORETRY | __GFP_COMP | __GFP_ZERO, cpu_buffer->buffer->subbuf_order); if (!page) { kfree(bpage); --=20 2.44.0.769.g3c40516874-goog From nobody Sun Feb 8 12:19:51 2026 Received: from mail-yb1-f202.google.com (mail-yb1-f202.google.com [209.85.219.202]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E489D44384 for ; Tue, 23 Apr 2024 23:27:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.219.202 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1713914867; cv=none; b=kQnWgdc1uLI8HsQOzAun+8Y7HbX7qD8D52GqVUM7WgQe74Nxk6dOSyqYSbhNAgpppwLgE1d5/D9kNgsSg+KN6vKGtThYfWZCB2F4H1ZgQzLebNA7ummKYInyG+a54JzdMDFNwwt48t+B5sf/KNI1mV8m1BVkLIkpI88vvSthJxc= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1713914867; c=relaxed/simple; bh=4GBqTgZusgtREyzBkWMshnbF/bTDUOA5UOwno1qufr0=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=K6Cx0iJdNNgcAUTK1hP8jN2bAEGuEWe94RDQ18BAQPBYnXqG3blppe75mqAY9cMg2QgJqQ5MeyskA4oc8VBKPaMIzXODhx88oUBIVQ2rUB6Ol0srAkomMPoOSsTcSUAGSWevXms9n62JI4YZeiLVukhyCuIRo6WztIONpB8zr7M= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--vdonnefort.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=3FJXJCFs; arc=none smtp.client-ip=209.85.219.202 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--vdonnefort.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="3FJXJCFs" Received: by mail-yb1-f202.google.com with SMTP id 3f1490d57ef6-dc6b2682870so11118967276.0 for ; Tue, 23 Apr 2024 16:27:45 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1713914865; x=1714519665; darn=vger.kernel.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=KGGhlhHcrtvsLzBLVtBaJiNhKHV3FjN4Xdf9+voLC7k=; b=3FJXJCFsrOyGSqlz0oPLG5Ux/xLFk1wlMVMXc2kG3CAncua4yVAJBm0K44y+zIF3G2 rKCIEZSOcLV1/XMHfHYgFuYSXMYtMwSjALVHJIj3oOI6macDB3xL0VCIvixhBopK0PS5 uVR6n81hjcBQ2N3n73AnAxyEfW75iidRe4Q+EKxjQkE7CT/m8pS9ya4uXTQhLtrdAXai T5uuIfiumUlPwXqlT0X+YULCeq1whuhAm0XUtd1huysJUbZ2BBIVHq/UCHidlS0AC5Ol 6012WRXv1mZgk1FLzNTE4CBkhdq4opvLZ6ZxvpQM6bYRfALVXZ2D2oxEVMHUORJoYZrR lOvA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1713914865; x=1714519665; 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=KGGhlhHcrtvsLzBLVtBaJiNhKHV3FjN4Xdf9+voLC7k=; b=kFdJl8gZol2Cg91Pw7TaXerYZBCyUhgvDpsBRUWvtoUaCtWn1YEOhU53G+l4DwGOW4 K1WSXZVrc0adK9lO1dgrw+piBaK1GJ1k1k8p6/HHti2+E2DW6nuV+etvn8PL0tvrXsXm hxXVAzjxEi1jgpEOzfqFUEzuurFtmnpRfxvNCkvxKDhr+syOUms5t9nNTcNZh9hB4oRR /HtT4+95Ghe7yswJLaRtElMJpdAgfBId63zNEMhrbow98gJoseEJiFxBozDpAIsWx7Gn qYLbtLstzVSUBwdEcrE9bi/r8BGIQHnRrAVzNB7BxgSqAmGZLFTK8uh9t7+yGdwQg54+ yzcA== X-Forwarded-Encrypted: i=1; AJvYcCWKgpgHtbLNY/GozaZ9jCV9zSEv4Sv1k8HHgWF+V7u4UIBw4o3Nvh/qEVXiWDhKl0u/H/u3DDwkWd0DzVyBsTTGlttDm/vtDsjFTvNc X-Gm-Message-State: AOJu0YxZ2d533EJNBIxBFtNCug2OIw0n5QlZbJLGX4ANaGiH6I6MNGe8 PUzUu/BusO8vTFECkSn4QFR5uTUyUx7fEBWMYuc3VfzkeSnjDM7S6vt7c95lw2G3/Q11KMdXsRs m8qjXKeKpuKmyW/rEqg== X-Google-Smtp-Source: AGHT+IH/t+cNCM+isu9yMK4PkYrKvgLfuqkOcx8GrD3g/C3sx9RtvN7lXGh3h8zpmSqQFXOTqBhpJ6/YgHp2c0hk X-Received: from vdonnefort.c.googlers.com ([fda3:e722:ac3:cc00:28:9cb1:c0a8:2eea]) (user=vdonnefort job=sendgmr) by 2002:a25:d851:0:b0:de4:5ec1:57af with SMTP id p78-20020a25d851000000b00de45ec157afmr321950ybg.10.1713914864892; Tue, 23 Apr 2024 16:27:44 -0700 (PDT) Date: Wed, 24 Apr 2024 00:27:25 +0100 In-Reply-To: <20240423232728.1492340-1-vdonnefort@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20240423232728.1492340-1-vdonnefort@google.com> X-Mailer: git-send-email 2.44.0.769.g3c40516874-goog Message-ID: <20240423232728.1492340-3-vdonnefort@google.com> Subject: [PATCH v21 2/5] ring-buffer: Introducing ring-buffer mapping functions From: Vincent Donnefort To: rostedt@goodmis.org, mhiramat@kernel.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org Cc: mathieu.desnoyers@efficios.com, kernel-team@android.com, rdunlap@infradead.org, rppt@kernel.org, david@redhat.com, Vincent Donnefort , linux-mm@kvack.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" In preparation for allowing the user-space to map a ring-buffer, add a set of mapping functions: ring_buffer_{map,unmap}() And controls on the ring-buffer: ring_buffer_map_get_reader() /* swap reader and head */ Mapping the ring-buffer also involves: A unique ID for each subbuf of the ring-buffer, currently they are only identified through their in-kernel VA. A meta-page, where are stored ring-buffer statistics and a description for the current reader The linear mapping exposes the meta-page, and each subbuf of the ring-buffer, ordered following their unique ID, assigned during the first mapping. Once mapped, no subbuf can get in or out of the ring-buffer: the buffer size will remain unmodified and the splice enabling functions will in reality simply memcpy the data instead of swapping subbufs. CC: Signed-off-by: Vincent Donnefort diff --git a/include/linux/ring_buffer.h b/include/linux/ring_buffer.h index dc5ae4e96aee..96d2140b471e 100644 --- a/include/linux/ring_buffer.h +++ b/include/linux/ring_buffer.h @@ -6,6 +6,8 @@ #include #include =20 +#include + struct trace_buffer; struct ring_buffer_iter; =20 @@ -223,4 +225,8 @@ int trace_rb_cpu_prepare(unsigned int cpu, struct hlist= _node *node); #define trace_rb_cpu_prepare NULL #endif =20 +int ring_buffer_map(struct trace_buffer *buffer, int cpu, + struct vm_area_struct *vma); +int ring_buffer_unmap(struct trace_buffer *buffer, int cpu); +int ring_buffer_map_get_reader(struct trace_buffer *buffer, int cpu); #endif /* _LINUX_RING_BUFFER_H */ diff --git a/include/uapi/linux/trace_mmap.h b/include/uapi/linux/trace_mma= p.h new file mode 100644 index 000000000000..b682e9925539 --- /dev/null +++ b/include/uapi/linux/trace_mmap.h @@ -0,0 +1,46 @@ +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */ +#ifndef _TRACE_MMAP_H_ +#define _TRACE_MMAP_H_ + +#include + +/** + * struct trace_buffer_meta - Ring-buffer Meta-page description + * @meta_page_size: Size of this meta-page. + * @meta_struct_len: Size of this structure. + * @subbuf_size: Size of each sub-buffer. + * @nr_subbufs: Number of subbfs in the ring-buffer, including the reader. + * @reader.lost_events: Number of events lost at the time of the reader sw= ap. + * @reader.id: subbuf ID of the current reader. ID range [0 : @nr_subbufs= - 1] + * @reader.read: Number of bytes read on the reader subbuf. + * @flags: Placeholder for now, 0 until new features are supported. + * @entries: Number of entries in the ring-buffer. + * @overrun: Number of entries lost in the ring-buffer. + * @read: Number of entries that have been read. + * @Reserved1: Internal use only. + * @Reserved2: Internal use only. + */ +struct trace_buffer_meta { + __u32 meta_page_size; + __u32 meta_struct_len; + + __u32 subbuf_size; + __u32 nr_subbufs; + + struct { + __u64 lost_events; + __u32 id; + __u32 read; + } reader; + + __u64 flags; + + __u64 entries; + __u64 overrun; + __u64 read; + + __u64 Reserved1; + __u64 Reserved2; +}; + +#endif /* _TRACE_MMAP_H_ */ diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index cc9ebe593571..84f8744fa110 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -9,6 +9,7 @@ #include #include #include +#include #include #include #include @@ -26,6 +27,7 @@ #include #include #include +#include =20 #include #include @@ -338,6 +340,7 @@ struct buffer_page { local_t entries; /* entries on this page */ unsigned long real_end; /* real end of data */ unsigned order; /* order of the page */ + u32 id; /* ID for external mapping */ struct buffer_data_page *page; /* Actual data page */ }; =20 @@ -484,6 +487,12 @@ struct ring_buffer_per_cpu { u64 read_stamp; /* pages removed since last reset */ unsigned long pages_removed; + + unsigned int mapped; + struct mutex mapping_lock; + unsigned long *subbuf_ids; /* ID to subbuf VA */ + struct trace_buffer_meta *meta_page; + /* ring buffer pages to update, > 0 to add, < 0 to remove */ long nr_pages_to_update; struct list_head new_pages; /* new pages to add */ @@ -1599,6 +1608,7 @@ rb_allocate_cpu_buffer(struct trace_buffer *buffer, l= ong nr_pages, int cpu) init_irq_work(&cpu_buffer->irq_work.work, rb_wake_up_waiters); init_waitqueue_head(&cpu_buffer->irq_work.waiters); init_waitqueue_head(&cpu_buffer->irq_work.full_waiters); + mutex_init(&cpu_buffer->mapping_lock); =20 bpage =3D kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()), GFP_KERNEL, cpu_to_node(cpu)); @@ -1789,8 +1799,6 @@ bool ring_buffer_time_stamp_abs(struct trace_buffer *= buffer) return buffer->time_stamp_abs; } =20 -static void rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer); - static inline unsigned long rb_page_entries(struct buffer_page *bpage) { return local_read(&bpage->entries) & RB_WRITE_MASK; @@ -5211,6 +5219,22 @@ static void rb_clear_buffer_page(struct buffer_page = *page) page->read =3D 0; } =20 +static void rb_update_meta_page(struct ring_buffer_per_cpu *cpu_buffer) +{ + struct trace_buffer_meta *meta =3D cpu_buffer->meta_page; + + meta->reader.read =3D cpu_buffer->reader_page->read; + meta->reader.id =3D cpu_buffer->reader_page->id; + meta->reader.lost_events =3D cpu_buffer->lost_events; + + meta->entries =3D local_read(&cpu_buffer->entries); + meta->overrun =3D local_read(&cpu_buffer->overrun); + meta->read =3D cpu_buffer->read; + + /* Some archs do not have data cache coherency between kernel and user-sp= ace */ + flush_dcache_folio(virt_to_folio(cpu_buffer->meta_page)); +} + static void rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer) { @@ -5255,6 +5279,9 @@ rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer) cpu_buffer->lost_events =3D 0; cpu_buffer->last_overrun =3D 0; =20 + if (cpu_buffer->mapped) + rb_update_meta_page(cpu_buffer); + rb_head_page_activate(cpu_buffer); cpu_buffer->pages_removed =3D 0; } @@ -5469,6 +5496,12 @@ int ring_buffer_swap_cpu(struct trace_buffer *buffer= _a, cpu_buffer_a =3D buffer_a->buffers[cpu]; cpu_buffer_b =3D buffer_b->buffers[cpu]; =20 + /* It's up to the callers to not try to swap mapped buffers */ + if (WARN_ON_ONCE(cpu_buffer_a->mapped || cpu_buffer_b->mapped)) { + ret =3D -EBUSY; + goto out; + } + /* At least make sure the two buffers are somewhat the same */ if (cpu_buffer_a->nr_pages !=3D cpu_buffer_b->nr_pages) goto out; @@ -5733,7 +5766,8 @@ int ring_buffer_read_page(struct trace_buffer *buffer, * Otherwise, we can simply swap the page with the one passed in. */ if (read || (len < (commit - read)) || - cpu_buffer->reader_page =3D=3D cpu_buffer->commit_page) { + cpu_buffer->reader_page =3D=3D cpu_buffer->commit_page || + cpu_buffer->mapped) { struct buffer_data_page *rpage =3D cpu_buffer->reader_page->page; unsigned int rpos =3D read; unsigned int pos =3D 0; @@ -5956,6 +5990,11 @@ int ring_buffer_subbuf_order_set(struct trace_buffer= *buffer, int order) =20 cpu_buffer =3D buffer->buffers[cpu]; =20 + if (cpu_buffer->mapped) { + err =3D -EBUSY; + goto error; + } + /* Update the number of pages to match the new size */ nr_pages =3D old_size * buffer->buffers[cpu]->nr_pages; nr_pages =3D DIV_ROUND_UP(nr_pages, buffer->subbuf_size); @@ -6057,6 +6096,367 @@ int ring_buffer_subbuf_order_set(struct trace_buffe= r *buffer, int order) } EXPORT_SYMBOL_GPL(ring_buffer_subbuf_order_set); =20 +static int rb_alloc_meta_page(struct ring_buffer_per_cpu *cpu_buffer) +{ + struct page *page; + + if (cpu_buffer->meta_page) + return 0; + + page =3D alloc_page(GFP_USER | __GFP_ZERO); + if (!page) + return -ENOMEM; + + cpu_buffer->meta_page =3D page_to_virt(page); + + return 0; +} + +static void rb_free_meta_page(struct ring_buffer_per_cpu *cpu_buffer) +{ + unsigned long addr =3D (unsigned long)cpu_buffer->meta_page; + + free_page(addr); + cpu_buffer->meta_page =3D NULL; +} + +static void rb_setup_ids_meta_page(struct ring_buffer_per_cpu *cpu_buffer, + unsigned long *subbuf_ids) +{ + struct trace_buffer_meta *meta =3D cpu_buffer->meta_page; + unsigned int nr_subbufs =3D cpu_buffer->nr_pages + 1; + struct buffer_page *first_subbuf, *subbuf; + int id =3D 0; + + subbuf_ids[id] =3D (unsigned long)cpu_buffer->reader_page->page; + cpu_buffer->reader_page->id =3D id++; + + first_subbuf =3D subbuf =3D rb_set_head_page(cpu_buffer); + do { + if (WARN_ON(id >=3D nr_subbufs)) + break; + + subbuf_ids[id] =3D (unsigned long)subbuf->page; + subbuf->id =3D id; + + rb_inc_page(&subbuf); + id++; + } while (subbuf !=3D first_subbuf); + + /* install subbuf ID to kern VA translation */ + cpu_buffer->subbuf_ids =3D subbuf_ids; + + meta->meta_page_size =3D PAGE_SIZE; + meta->meta_struct_len =3D sizeof(*meta); + meta->nr_subbufs =3D nr_subbufs; + meta->subbuf_size =3D cpu_buffer->buffer->subbuf_size + BUF_PAGE_HDR_SIZE; + + rb_update_meta_page(cpu_buffer); +} + +static struct ring_buffer_per_cpu * +rb_get_mapped_buffer(struct trace_buffer *buffer, int cpu) +{ + struct ring_buffer_per_cpu *cpu_buffer; + + if (!cpumask_test_cpu(cpu, buffer->cpumask)) + return ERR_PTR(-EINVAL); + + cpu_buffer =3D buffer->buffers[cpu]; + + mutex_lock(&cpu_buffer->mapping_lock); + + if (!cpu_buffer->mapped) { + mutex_unlock(&cpu_buffer->mapping_lock); + return ERR_PTR(-ENODEV); + } + + return cpu_buffer; +} + +static void rb_put_mapped_buffer(struct ring_buffer_per_cpu *cpu_buffer) +{ + mutex_unlock(&cpu_buffer->mapping_lock); +} + +/* + * Fast-path for rb_buffer_(un)map(). Called whenever the meta-page doesn'= t need + * to be set-up or torn-down. + */ +static int __rb_inc_dec_mapped(struct ring_buffer_per_cpu *cpu_buffer, + bool inc) +{ + unsigned long flags; + + lockdep_assert_held(&cpu_buffer->mapping_lock); + + if (inc && cpu_buffer->mapped =3D=3D UINT_MAX) + return -EBUSY; + + if (WARN_ON(!inc && cpu_buffer->mapped =3D=3D 0)) + return -EINVAL; + + mutex_lock(&cpu_buffer->buffer->mutex); + raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); + + if (inc) + cpu_buffer->mapped++; + else + cpu_buffer->mapped--; + + raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); + mutex_unlock(&cpu_buffer->buffer->mutex); + + return 0; +} + +/* + * +--------------+ pgoff =3D=3D 0 + * | meta page | + * +--------------+ pgoff =3D=3D 1 + * | subbuffer 0 | + * | | + * +--------------+ pgoff =3D=3D (1 + (1 << subbuf_order)) + * | subbuffer 1 | + * | | + * ... + */ +#ifdef CONFIG_MMU +static int __rb_map_vma(struct ring_buffer_per_cpu *cpu_buffer, + struct vm_area_struct *vma) +{ + unsigned long nr_subbufs, nr_pages, vma_pages, pgoff =3D vma->vm_pgoff; + unsigned int subbuf_pages, subbuf_order; + struct page **pages; + int p =3D 0, s =3D 0; + int err; + + if (vma->vm_flags & VM_WRITE || vma->vm_flags & VM_EXEC || + !(vma->vm_flags & VM_MAYSHARE)) + return -EPERM; + + vm_flags_mod(vma, + VM_MIXEDMAP | VM_PFNMAP | + VM_DONTCOPY | VM_DONTDUMP | VM_DONTEXPAND | VM_IO, + VM_MAYWRITE); + + lockdep_assert_held(&cpu_buffer->mapping_lock); + + subbuf_order =3D cpu_buffer->buffer->subbuf_order; + subbuf_pages =3D 1 << subbuf_order; + + nr_subbufs =3D cpu_buffer->nr_pages + 1; /* + reader-subbuf */ + nr_pages =3D ((nr_subbufs) << subbuf_order) - pgoff + 1; /* + meta-page */ + + vma_pages =3D (vma->vm_end - vma->vm_start) >> PAGE_SHIFT; + if (!vma_pages || vma_pages > nr_pages) + return -EINVAL; + + nr_pages =3D vma_pages; + + pages =3D kcalloc(nr_pages, sizeof(*pages), GFP_KERNEL); + if (!pages) + return -ENOMEM; + + if (!pgoff) { + pages[p++] =3D virt_to_page(cpu_buffer->meta_page); + + /* + * TODO: Align sub-buffers on their size, once + * vm_insert_pages() supports the zero-page. + */ + } else { + /* Skip the meta-page */ + pgoff--; + + if (pgoff % subbuf_pages) { + err =3D -EINVAL; + goto out; + } + + s +=3D pgoff / subbuf_pages; + } + + while (s < nr_subbufs && p < nr_pages) { + struct page *page =3D virt_to_page(cpu_buffer->subbuf_ids[s]); + int off =3D 0; + + for (; off < (1 << (subbuf_order)); off++, page++) { + if (p >=3D nr_pages) + break; + + pages[p++] =3D page; + } + s++; + } + + err =3D vm_insert_pages(vma, vma->vm_start, pages, &nr_pages); + +out: + kfree(pages); + + return err; +} +#else +static int __rb_map_vma(struct ring_buffer_per_cpu *cpu_buffer, + struct vm_area_struct *vma) +{ + return -EOPNOTSUPP; +} +#endif + +int ring_buffer_map(struct trace_buffer *buffer, int cpu, + struct vm_area_struct *vma) +{ + struct ring_buffer_per_cpu *cpu_buffer; + unsigned long flags, *subbuf_ids; + int err =3D 0; + + if (!cpumask_test_cpu(cpu, buffer->cpumask)) + return -EINVAL; + + cpu_buffer =3D buffer->buffers[cpu]; + + mutex_lock(&cpu_buffer->mapping_lock); + + if (cpu_buffer->mapped) { + err =3D __rb_map_vma(cpu_buffer, vma); + if (!err) + err =3D __rb_inc_dec_mapped(cpu_buffer, true); + mutex_unlock(&cpu_buffer->mapping_lock); + return err; + } + + /* prevent another thread from changing buffer/sub-buffer sizes */ + mutex_lock(&buffer->mutex); + + err =3D rb_alloc_meta_page(cpu_buffer); + if (err) + goto unlock; + + /* subbuf_ids include the reader while nr_pages does not */ + subbuf_ids =3D kcalloc(cpu_buffer->nr_pages + 1, sizeof(*subbuf_ids), GFP= _KERNEL); + if (!subbuf_ids) { + rb_free_meta_page(cpu_buffer); + err =3D -ENOMEM; + goto unlock; + } + + atomic_inc(&cpu_buffer->resize_disabled); + + /* + * Lock all readers to block any subbuf swap until the subbuf IDs are + * assigned. + */ + raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); + rb_setup_ids_meta_page(cpu_buffer, subbuf_ids); + raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); + + err =3D __rb_map_vma(cpu_buffer, vma); + if (!err) { + raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); + cpu_buffer->mapped =3D 1; + raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); + } else { + kfree(cpu_buffer->subbuf_ids); + cpu_buffer->subbuf_ids =3D NULL; + rb_free_meta_page(cpu_buffer); + } + +unlock: + mutex_unlock(&buffer->mutex); + mutex_unlock(&cpu_buffer->mapping_lock); + + return err; +} + +int ring_buffer_unmap(struct trace_buffer *buffer, int cpu) +{ + struct ring_buffer_per_cpu *cpu_buffer; + unsigned long flags; + int err =3D 0; + + if (!cpumask_test_cpu(cpu, buffer->cpumask)) + return -EINVAL; + + cpu_buffer =3D buffer->buffers[cpu]; + + mutex_lock(&cpu_buffer->mapping_lock); + + if (!cpu_buffer->mapped) { + err =3D -ENODEV; + goto out; + } else if (cpu_buffer->mapped > 1) { + __rb_inc_dec_mapped(cpu_buffer, false); + goto out; + } + + mutex_lock(&buffer->mutex); + raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); + + cpu_buffer->mapped =3D 0; + + raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); + + kfree(cpu_buffer->subbuf_ids); + cpu_buffer->subbuf_ids =3D NULL; + rb_free_meta_page(cpu_buffer); + atomic_dec(&cpu_buffer->resize_disabled); + + mutex_unlock(&buffer->mutex); + +out: + mutex_unlock(&cpu_buffer->mapping_lock); + + return err; +} + +int ring_buffer_map_get_reader(struct trace_buffer *buffer, int cpu) +{ + struct ring_buffer_per_cpu *cpu_buffer; + unsigned long reader_size; + unsigned long flags; + + cpu_buffer =3D rb_get_mapped_buffer(buffer, cpu); + if (IS_ERR(cpu_buffer)) + return (int)PTR_ERR(cpu_buffer); + + raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); + +consume: + if (rb_per_cpu_empty(cpu_buffer)) + goto out; + + reader_size =3D rb_page_size(cpu_buffer->reader_page); + + /* + * There are data to be read on the current reader page, we can + * return to the caller. But before that, we assume the latter will read + * everything. Let's update the kernel reader accordingly. + */ + if (cpu_buffer->reader_page->read < reader_size) { + while (cpu_buffer->reader_page->read < reader_size) + rb_advance_reader(cpu_buffer); + goto out; + } + + if (WARN_ON(!rb_get_reader_page(cpu_buffer))) + goto out; + + goto consume; + +out: + /* Some archs do not have data cache coherency between kernel and user-sp= ace */ + flush_dcache_folio(virt_to_folio(cpu_buffer->reader_page->page)); + + rb_update_meta_page(cpu_buffer); + + raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); + rb_put_mapped_buffer(cpu_buffer); + + return 0; +} + /* * We only allocate new buffers, never free them if the CPU goes down. * If we were to free the buffer, then the user would lose any trace that = was in --=20 2.44.0.769.g3c40516874-goog From nobody Sun Feb 8 12:19:51 2026 Received: from mail-wm1-f73.google.com (mail-wm1-f73.google.com [209.85.128.73]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9676B53398 for ; Tue, 23 Apr 2024 23:27:48 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.73 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1713914870; cv=none; b=ZO9hqEByimEEqAZWmXap0h43LodgV/zOVeXSFMN+j44Gud6WyTqPDmpc+2UrZhTVN4VcqC/XED9hKeF7qWx0PPM1P48/iONvWW5dDMErRcKwuuvF1WRfOFOpe2Xs+IkWMfUwtN+lgF0Lrj6vYlhRsekqSIoKQc/tx1DrXPx40yY= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1713914870; c=relaxed/simple; bh=VhRUrMgDXvxrbFcK977T8yS4Vw+MmwCzKPPOBPrfvio=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=UwGWl2pa8HiFlGfyFywMaOtUUFs3KVqMzlMxu9bfHIt8qCcYEhwRbJICHLyuxlVyIYgK9+qpmXzmYo6fa1nLq9aNZz9E2HKvbvg7CQgCXqD9ehmJFU4h0axD+0G/eC2XwBizzBEqP9Yta+cOA2iDbVBtmT9swFU7JhH0qeF4asE= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--vdonnefort.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=gV79sV/w; arc=none smtp.client-ip=209.85.128.73 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--vdonnefort.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="gV79sV/w" Received: by mail-wm1-f73.google.com with SMTP id 5b1f17b1804b1-417fb8195d7so29796885e9.0 for ; Tue, 23 Apr 2024 16:27:48 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1713914867; x=1714519667; darn=vger.kernel.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=kaFaT9yjXtresVS5HFOg4DBcxHZeTWd1pZVR5Za+Mxc=; b=gV79sV/wpw+PwVFufPOBxghtSO+aHsjJ3kOxTNtnQakAQzPxTh6S3mF6Hi8B8bXR8y dDpK0niANFmAL+I1ERO11b1Y9dObETpYysa4sguhEi6jk6X7ujqmCMIr60FJs6Rey0ZJ py2YODRSnzk76H0xjNGUs0V76p+9xHguzuwM/jhHeJdKpy/SfT2nEJNP34k7zqxgjQNQ 5zKxPnk60vQ2IQvmzRjmHa+k87uygH+/t0GBO1kvr48UPXvpXmmKQGphd7AbQdti1J5d a9gUsSzA4+fSBH8SvvHNHcSrMD7vTuABwW2swr1E1Tr+2l5gUHDdMfIZr+PE9ZiEqEtS nnTQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1713914867; x=1714519667; 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=kaFaT9yjXtresVS5HFOg4DBcxHZeTWd1pZVR5Za+Mxc=; b=f6LGKa9lRgvhXds+5jKGIo/3iv1CJfPS5WEqNxJF/NaIU5j333j25vpzK900vOvvvu sTXFjaaZ+IevSuxsfx/au8EOzLIk71+u2l1LaRyCeuuvGAzgiR5HaSKhKKve3h6pSXm0 t1eqd9tqd5GXkRBv5g25QMx/2Pgv2Ex0BovSb+IKNz0TIfjqja5BIHDXc67k7apJOgA6 hORLsLSAFCaO/rePRnrpl5VftqiEHJvaI/ob1EwxAtwY2iqydLZGIv+QHhwistoSK9Ow dSsvQsSy8fKEwVaD0Nh2nXcbq3Jju/kaEwhHv/gX+4pdhEydWD/gOLq8OM2yhiYXbV8B B+ew== X-Forwarded-Encrypted: i=1; AJvYcCU6G8IXxb00veuarXBV0t4mo8O3Ng1xk6OsuoApUTRRCa68tLn5BeFUS/nxJGXQdi286G3aHS7/ttHUUcJbBTSuAMFbgIxk4yuTpOil X-Gm-Message-State: AOJu0Yz3eUOHjdoZzV+77k8TGQbQf9lFQrSeX2d3Cx+ZZSFwftGH5Lep aDSOOmzHCHcyNVUonIOnxV3D1GoFZHNgQwbJzQ6jrt2QyZxm7PdYoJWwt4+1hFOHf5ZvI9+PG2d PwBmlpzrTRQx+WKn45A== X-Google-Smtp-Source: AGHT+IFCDABCADdFLnD0phykkbD9Gu5AIQBZ62UxA/EhQAKHMu7J7egaT2rm+tUe6aiIMaJ0/Tc/k/iDgGFOOjAe X-Received: from vdonnefort.c.googlers.com ([fda3:e722:ac3:cc00:28:9cb1:c0a8:2eea]) (user=vdonnefort job=sendgmr) by 2002:a05:600c:5352:b0:41a:3485:19c4 with SMTP id hi18-20020a05600c535200b0041a348519c4mr3395wmb.3.1713914867196; Tue, 23 Apr 2024 16:27:47 -0700 (PDT) Date: Wed, 24 Apr 2024 00:27:26 +0100 In-Reply-To: <20240423232728.1492340-1-vdonnefort@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20240423232728.1492340-1-vdonnefort@google.com> X-Mailer: git-send-email 2.44.0.769.g3c40516874-goog Message-ID: <20240423232728.1492340-4-vdonnefort@google.com> Subject: [PATCH v21 3/5] tracing: Allow user-space mapping of the ring-buffer From: Vincent Donnefort To: rostedt@goodmis.org, mhiramat@kernel.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org Cc: mathieu.desnoyers@efficios.com, kernel-team@android.com, rdunlap@infradead.org, rppt@kernel.org, david@redhat.com, Vincent Donnefort , linux-mm@kvack.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Currently, user-space extracts data from the ring-buffer via splice, which is handy for storage or network sharing. However, due to splice limitations, it is imposible to do real-time analysis without a copy. A solution for that problem is to let the user-space map the ring-buffer directly. The mapping is exposed via the per-CPU file trace_pipe_raw. The first element of the mapping is the meta-page. It is followed by each subbuffer constituting the ring-buffer, ordered by their unique page ID: * Meta-page -- include/uapi/linux/trace_mmap.h for a description * Subbuf ID 0 * Subbuf ID 1 ... It is therefore easy to translate a subbuf ID into an offset in the mapping: reader_id =3D meta->reader->id; reader_offset =3D meta->meta_page_size + reader_id * meta->subbuf_size; When new data is available, the mapper must call a newly introduced ioctl: TRACE_MMAP_IOCTL_GET_READER. This will update the Meta-page reader ID to point to the next reader containing unread data. Mapping will prevent snapshot and buffer size modifications. CC: Signed-off-by: Vincent Donnefort diff --git a/include/uapi/linux/trace_mmap.h b/include/uapi/linux/trace_mma= p.h index b682e9925539..bd1066754220 100644 --- a/include/uapi/linux/trace_mmap.h +++ b/include/uapi/linux/trace_mmap.h @@ -43,4 +43,6 @@ struct trace_buffer_meta { __u64 Reserved2; }; =20 +#define TRACE_MMAP_IOCTL_GET_READER _IO('T', 0x1) + #endif /* _TRACE_MMAP_H_ */ diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 233d1af39fff..a35e7f598233 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -1191,6 +1191,12 @@ static void tracing_snapshot_instance_cond(struct tr= ace_array *tr, return; } =20 + if (tr->mapped) { + trace_array_puts(tr, "*** BUFFER MEMORY MAPPED ***\n"); + trace_array_puts(tr, "*** Can not use snapshot (sorry) ***\n"); + return; + } + local_irq_save(flags); update_max_tr(tr, current, smp_processor_id(), cond_data); local_irq_restore(flags); @@ -1323,7 +1329,7 @@ static int tracing_arm_snapshot_locked(struct trace_a= rray *tr) lockdep_assert_held(&trace_types_lock); =20 spin_lock(&tr->snapshot_trigger_lock); - if (tr->snapshot =3D=3D UINT_MAX) { + if (tr->snapshot =3D=3D UINT_MAX || tr->mapped) { spin_unlock(&tr->snapshot_trigger_lock); return -EBUSY; } @@ -6068,7 +6074,7 @@ static void tracing_set_nop(struct trace_array *tr) { if (tr->current_trace =3D=3D &nop_trace) return; -=09 + tr->current_trace->enabled--; =20 if (tr->current_trace->reset) @@ -8194,15 +8200,32 @@ tracing_buffers_splice_read(struct file *file, loff= _t *ppos, return ret; } =20 -/* An ioctl call with cmd 0 to the ring buffer file will wake up all waite= rs */ static long tracing_buffers_ioctl(struct file *file, unsigned int cmd, uns= igned long arg) { struct ftrace_buffer_info *info =3D file->private_data; struct trace_iterator *iter =3D &info->iter; + int err; + + if (cmd =3D=3D TRACE_MMAP_IOCTL_GET_READER) { + if (!(file->f_flags & O_NONBLOCK)) { + err =3D ring_buffer_wait(iter->array_buffer->buffer, + iter->cpu_file, + iter->tr->buffer_percent, + NULL, NULL); + if (err) + return err; + } =20 - if (cmd) - return -ENOIOCTLCMD; + return ring_buffer_map_get_reader(iter->array_buffer->buffer, + iter->cpu_file); + } else if (cmd) { + return -ENOTTY; + } =20 + /* + * An ioctl call with cmd 0 to the ring buffer file will wake up all + * waiters + */ mutex_lock(&trace_types_lock); =20 /* Make sure the waiters see the new wait_index */ @@ -8214,6 +8237,76 @@ static long tracing_buffers_ioctl(struct file *file,= unsigned int cmd, unsigned return 0; } =20 +#ifdef CONFIG_TRACER_MAX_TRACE +static int get_snapshot_map(struct trace_array *tr) +{ + int err =3D 0; + + /* + * Called with mmap_lock held. lockdep would be unhappy if we would now + * take trace_types_lock. Instead use the specific + * snapshot_trigger_lock. + */ + spin_lock(&tr->snapshot_trigger_lock); + + if (tr->snapshot || tr->mapped =3D=3D UINT_MAX) + err =3D -EBUSY; + else + tr->mapped++; + + spin_unlock(&tr->snapshot_trigger_lock); + + /* Wait for update_max_tr() to observe iter->tr->mapped */ + if (tr->mapped =3D=3D 1) + synchronize_rcu(); + + return err; + +} +static void put_snapshot_map(struct trace_array *tr) +{ + spin_lock(&tr->snapshot_trigger_lock); + if (!WARN_ON(!tr->mapped)) + tr->mapped--; + spin_unlock(&tr->snapshot_trigger_lock); +} +#else +static inline int get_snapshot_map(struct trace_array *tr) { return 0; } +static inline void put_snapshot_map(struct trace_array *tr) { } +#endif + +static void tracing_buffers_mmap_close(struct vm_area_struct *vma) +{ + struct ftrace_buffer_info *info =3D vma->vm_file->private_data; + struct trace_iterator *iter =3D &info->iter; + + WARN_ON(ring_buffer_unmap(iter->array_buffer->buffer, iter->cpu_file)); + put_snapshot_map(iter->tr); +} + +static const struct vm_operations_struct tracing_buffers_vmops =3D { + .close =3D tracing_buffers_mmap_close, +}; + +static int tracing_buffers_mmap(struct file *filp, struct vm_area_struct *= vma) +{ + struct ftrace_buffer_info *info =3D filp->private_data; + struct trace_iterator *iter =3D &info->iter; + int ret =3D 0; + + ret =3D get_snapshot_map(iter->tr); + if (ret) + return ret; + + ret =3D ring_buffer_map(iter->array_buffer->buffer, iter->cpu_file, vma); + if (ret) + put_snapshot_map(iter->tr); + + vma->vm_ops =3D &tracing_buffers_vmops; + + return ret; +} + static const struct file_operations tracing_buffers_fops =3D { .open =3D tracing_buffers_open, .read =3D tracing_buffers_read, @@ -8223,6 +8316,7 @@ static const struct file_operations tracing_buffers_f= ops =3D { .splice_read =3D tracing_buffers_splice_read, .unlocked_ioctl =3D tracing_buffers_ioctl, .llseek =3D no_llseek, + .mmap =3D tracing_buffers_mmap, }; =20 static ssize_t diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h index 64450615ca0c..749a182dab48 100644 --- a/kernel/trace/trace.h +++ b/kernel/trace/trace.h @@ -336,6 +336,7 @@ struct trace_array { bool allocated_snapshot; spinlock_t snapshot_trigger_lock; unsigned int snapshot; + unsigned int mapped; unsigned long max_latency; #ifdef CONFIG_FSNOTIFY struct dentry *d_max_latency; --=20 2.44.0.769.g3c40516874-goog From nobody Sun Feb 8 12:19:51 2026 Received: from mail-wm1-f74.google.com (mail-wm1-f74.google.com [209.85.128.74]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id EAC0853E01 for ; Tue, 23 Apr 2024 23:27:50 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.74 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1713914872; cv=none; b=neLx5J/VC4/0vX24GqeV6nyHx0bvfaBRbpqVRnbpIerxQOKTaNiucv2r1oHn1iOxkAyOVasFwYlzDtqKbWhqXXK7VSwibJcJBK0d0NLqqT7TMcwzD615bF3+a+ChRqbHC0c3q9E98Jf5qfgGXCY26SY9f9yUtX7KTT2/nda27Bo= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1713914872; c=relaxed/simple; bh=nHh/TTjK2tW0sUwPgbpncHpLmKF71Gsdpp0iLEYgt+E=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=t6XK2A465E7A+W9LgarGAqUvOzmy+yBFjsHKWUp0kfRYuV6r3Qk50lssxvButUdSd4rMCQ/5OY0206Fex/olmmAJAb0JDS0l+ttZCT2OBa0zppAV9GvyOSwwAoWFsgUgY2fbta1oeOuRe3j2xmTvvO76WUIxVEE6KKKffcWWLEw= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--vdonnefort.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=Pm2vw3HM; arc=none smtp.client-ip=209.85.128.74 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--vdonnefort.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="Pm2vw3HM" Received: by mail-wm1-f74.google.com with SMTP id 5b1f17b1804b1-41a8440a8cfso11487865e9.3 for ; Tue, 23 Apr 2024 16:27:50 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1713914869; x=1714519669; darn=vger.kernel.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=5feaOC8gyTsjpelUvOVH7lOOqHGrllvmXVDESYI+Fsc=; b=Pm2vw3HMzksnC6J9Xal9ruHZyCPx0ckLCTKir7QxJDKr36f1XYCagvqJ9NPtr0kfKx cpaS0RhW/BPq2cHHVPjz8c8UivXgXTJvpz4b0IDmZdwU626EjHEaj0QOak5hkxs5LWFx ry1vFT6appD3o+jUBc2ynhOxpp5NrymjHFOS5JJYd+k1OTXN6SGeOQp00WEhc68ZCRkX 926t7p6V95DpmwEDo+2CXagee6GRoXbdyzqFg3wicRkfbc5QMKOG1xjRN1BcOZFpItCg hsGCDwX2+4tR363zd3eMdCE7DG2l58CFhpzLgSwUulDzbXF2V0Wx8zupawkXtwWEInmg BoiQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1713914869; x=1714519669; 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=5feaOC8gyTsjpelUvOVH7lOOqHGrllvmXVDESYI+Fsc=; b=Ey3PZcKx9VRwcfqnJJEjvIT+VABQbNZPCdszA/YcBptc3jIwKEkFA7tR5JKiwZyC/9 QsCgr/L6HjUvMrrqkxk0tPGnQKIvWXp+a8clb9wzqpD/I/6hj/ewTJ5AlOSYy5mHryBT CEbDpGz27f4Ca0Oa7h/U9cjiiZpMRaqEa3hC/h0KTcxLkKiSQ7JA81VTb9vmtsc9IOWH WjwSouF5HEjE3+agcyQZq18Dsbc9gWDnBGkPbANWHXndCXFIhurCmLgTsakxsBqXwee2 dDvjv142yELZzRWLuIWRYFwrFKpOW7dc1cjh5Y1VHsDu/pEbzpFp5zpllBZH6omoNCBX uanA== X-Forwarded-Encrypted: i=1; AJvYcCVbqd+XifePYQSGqF+8OEdlfO5i4M+kyDXsXKkyBcva/touZGsPhQaTU4isomLkNbnrPGxQDY7nj4LwqNHBx1JcBccTchVvl8p2Xn5w X-Gm-Message-State: AOJu0YxaSNEaCVgu39Vxqh5y8Kok+0bzPl67KhtR9Gp7jdwJdxveB1QQ Iwup2Y/43qOMED6xPW+yK6H4bEIdNfUpxfCJeoAi4Nz3xN/vBLL3OmGeaZBlteW+shFO0AVTGGh cl33ZlETkqgLS7I1gMw== X-Google-Smtp-Source: AGHT+IGobDASNC2M4SuR4i6AGmQEVnnG7arRSCFRe+N/BkW5us/J6MMCgFgIFRATBAP/2+0EUKu472oLhyyKxnU/ X-Received: from vdonnefort.c.googlers.com ([fda3:e722:ac3:cc00:28:9cb1:c0a8:2eea]) (user=vdonnefort job=sendgmr) by 2002:a05:600c:1c85:b0:419:f572:66f8 with SMTP id k5-20020a05600c1c8500b00419f57266f8mr3676wms.3.1713914869501; Tue, 23 Apr 2024 16:27:49 -0700 (PDT) Date: Wed, 24 Apr 2024 00:27:27 +0100 In-Reply-To: <20240423232728.1492340-1-vdonnefort@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20240423232728.1492340-1-vdonnefort@google.com> X-Mailer: git-send-email 2.44.0.769.g3c40516874-goog Message-ID: <20240423232728.1492340-5-vdonnefort@google.com> Subject: [PATCH v21 4/5] Documentation: tracing: Add ring-buffer mapping From: Vincent Donnefort To: rostedt@goodmis.org, mhiramat@kernel.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org Cc: mathieu.desnoyers@efficios.com, kernel-team@android.com, rdunlap@infradead.org, rppt@kernel.org, david@redhat.com, Vincent Donnefort Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" It is now possible to mmap() a ring-buffer to stream its content. Add some documentation and a code example. Signed-off-by: Vincent Donnefort diff --git a/Documentation/trace/index.rst b/Documentation/trace/index.rst index 5092d6c13af5..0b300901fd75 100644 --- a/Documentation/trace/index.rst +++ b/Documentation/trace/index.rst @@ -29,6 +29,7 @@ Linux Tracing Technologies timerlat-tracer intel_th ring-buffer-design + ring-buffer-map stm sys-t coresight/index diff --git a/Documentation/trace/ring-buffer-map.rst b/Documentation/trace/= ring-buffer-map.rst new file mode 100644 index 000000000000..8e296bcc0d7f --- /dev/null +++ b/Documentation/trace/ring-buffer-map.rst @@ -0,0 +1,106 @@ +.. SPDX-License-Identifier: GPL-2.0 + +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D +Tracefs ring-buffer memory mapping +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D + +:Author: Vincent Donnefort + +Overview +=3D=3D=3D=3D=3D=3D=3D=3D +Tracefs ring-buffer memory map provides an efficient method to stream data +as no memory copy is necessary. The application mapping the ring-buffer be= comes +then a consumer for that ring-buffer, in a similar fashion to trace_pipe. + +Memory mapping setup +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D +The mapping works with a mmap() of the trace_pipe_raw interface. + +The first system page of the mapping contains ring-buffer statistics and +description. It is referred to as the meta-page. One of the most important +fields of the meta-page is the reader. It contains the sub-buffer ID which= can +be safely read by the mapper (see ring-buffer-design.rst). + +The meta-page is followed by all the sub-buffers, ordered by ascending ID.= It is +therefore effortless to know where the reader starts in the mapping: + +.. code-block:: c + + reader_id =3D meta->reader->id; + reader_offset =3D meta->meta_page_size + reader_id * meta->subbuf_= size; + +When the application is done with the current reader, it can get a new one= using +the trace_pipe_raw ioctl() TRACE_MMAP_IOCTL_GET_READER. This ioctl also up= dates +the meta-page fields. + +Limitations +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D +When a mapping is in place on a Tracefs ring-buffer, it is not possible to +either resize it (either by increasing the entire size of the ring-buffer = or +each subbuf). It is also not possible to use snapshot and causes splice to= copy +the ring buffer data instead of using the copyless swap from the ring buff= er. + +Concurrent readers (either another application mapping that ring-buffer or= the +kernel with trace_pipe) are allowed but not recommended. They will compete= for +the ring-buffer and the output is unpredictable, just like concurrent read= ers on +trace_pipe would be. + +Example +=3D=3D=3D=3D=3D=3D=3D + +.. code-block:: c + + #include + #include + #include + #include + + #include + + #include + #include + + #define TRACE_PIPE_RAW "/sys/kernel/tracing/per_cpu/cpu0/trace_pip= e_raw" + + int main(void) + { + int page_size =3D getpagesize(), fd, reader_id; + unsigned long meta_len, data_len; + struct trace_buffer_meta *meta; + void *map, *reader, *data; + + fd =3D open(TRACE_PIPE_RAW, O_RDONLY | O_NONBLOCK); + if (fd < 0) + exit(EXIT_FAILURE); + + map =3D mmap(NULL, page_size, PROT_READ, MAP_SHARED, fd, 0= ); + if (map =3D=3D MAP_FAILED) + exit(EXIT_FAILURE); + + meta =3D (struct trace_buffer_meta *)map; + meta_len =3D meta->meta_page_size; + + printf("entries: %llu\n", meta->entries); + printf("overrun: %llu\n", meta->overrun); + printf("read: %llu\n", meta->read); + printf("nr_subbufs: %u\n", meta->nr_subbufs); + + data_len =3D meta->subbuf_size * meta->nr_subbufs; + data =3D mmap(NULL, data_len, PROT_READ, MAP_SHARED, fd, m= eta_len); + if (data =3D=3D MAP_FAILED) + exit(EXIT_FAILURE); + + if (ioctl(fd, TRACE_MMAP_IOCTL_GET_READER) < 0) + exit(EXIT_FAILURE); + + reader_id =3D meta->reader.id; + reader =3D data + meta->subbuf_size * reader_id; + + printf("Current reader address: %p\n", reader); + + munmap(data, data_len); + munmap(meta, meta_len); + close (fd); + + return 0; + } --=20 2.44.0.769.g3c40516874-goog From nobody Sun Feb 8 12:19:51 2026 Received: from mail-yw1-f202.google.com (mail-yw1-f202.google.com [209.85.128.202]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9698E5465D for ; Tue, 23 Apr 2024 23:27:52 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.202 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1713914874; cv=none; b=oo+lP3piRVAq+PFfoNV6z7lgSxdEqq72MLR6vNgukO1q4JC9MiCZcC92ij0vfzB82JuPx11RorCzDANdhKkfk4sN8vOZWyqCJpEa/rKptzipK9Xj3Sci18SIJOECHhD8F0/YAZrSIUNdJRXFPwebDXqRSbps/EVRYwCjLcZYPAE= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1713914874; c=relaxed/simple; bh=O+d59qShzTvBafQqHxGHCWx9WOV1oznH7Tjy6QhzJ58=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=EKRFKBkxu6TK0oPMtB0roY6IMxpE1bovAwsIOQXDOUWcSHaLwW8kPcqglDa64PxvEuTF6HRvvPFsQIpLPWOi7eIOYm1d4A9WVo6ptdotZWphRAFW5Xp6vSZVxm0PtoiX36ryM/HEHwF+sY7dGXXJRUJfbB99BBtcTPwrrUecGi8= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--vdonnefort.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=kfwhtSiV; arc=none smtp.client-ip=209.85.128.202 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--vdonnefort.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="kfwhtSiV" Received: by mail-yw1-f202.google.com with SMTP id 00721157ae682-61afa79081dso105926877b3.2 for ; Tue, 23 Apr 2024 16:27:52 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1713914871; x=1714519671; darn=vger.kernel.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=jZdtNgS1ADfpekPvRs2FP/KMWugpYNDTTPI4F/Zzcws=; b=kfwhtSiVDPDR+jmNsislXCaxcargR/wzvT5IkA7KeMqiJEvHevKcPtGdZ0vsYgYI8M DPsmeJqy/N8LXp4g8fkRGl8Z3OCwqk6g3BkOiAw8T9DirW6LY5JliLb+V9+ZSGnUD3ZV mnWspgTYcIxFikUP9wQZ3nMtgaiV0WX6TctAg58EYIRsL8DC+syIu4h48RaPxFEDxqPG b5pYxPLe7Hfq0LWPQPKK3Mss7su8c0YWTCZFmWgkXj18VFSyAlkX7p70lOsZI+INfCP0 D+CxkkYrxfKWuLNdwRP6xZ/w3j0BsV6TkRoFYyzkvTleZAijJfqEdL5Hi1D5i1UMcg5u 8p+w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1713914871; x=1714519671; 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=jZdtNgS1ADfpekPvRs2FP/KMWugpYNDTTPI4F/Zzcws=; b=fGyxajwpXxlJ5IP4cFPmCxDo2xwJKYx9rgwRa4Y1obB2sjlNu4CjtZxR40tvfL6uiN 18aHY6NPgkeC/MB0CqoG4z5vzXg+3lowkoSCHrUaz3nkPQc6JVGJX38BNkBuj4lmkidR WOhVZmY1rX1MOTDh2nfnYm6ewa9uLBLDi9eyHY6+D9ifJLrDbiyNMOHRlm47omZcOnP3 +3991nOcd1YqmMaJtFcQRZveHQoVKYKbvwp2sYJj4r9CBF8Qq8jaExNPVXV+5eQ9p/c3 kq4Sqp7NszGVg3MXTcI48UAjUQHQ8fAG7r1L03kx7aWhsPd3QOABrN42Lfmd+T7iNBNM eqpQ== X-Forwarded-Encrypted: i=1; AJvYcCW8+v27tmp810hN4v4RTTalw6e44tM5x4o83cO6s7ImdlH/G+TwwVUblgmo+VkZM2bkAlJSobKjBZOn1tyWQBjJRX3J1rIUSRk7dcdi X-Gm-Message-State: AOJu0YzO4qbs+nf5ursPxwi2JWqzHZkyX0MmFMyLfyam3dmzDFpahNxR 3+d8tTX5yDgVs+isFFVFKVPw8eWNrDPxZ9GCIlytI3krU6uTjlXBs3dSeV9hqpQFhfzZYhwSlmQ LmwMwfONEQUzeNsLDOQ== X-Google-Smtp-Source: AGHT+IH4/mAx1hYl3afF7Qar39Gq1rc/svAz1+g2LLqjYvaMe23uDdtQOlrMd2cLvxAmncxfRuv3qRqHypQexyVI X-Received: from vdonnefort.c.googlers.com ([fda3:e722:ac3:cc00:28:9cb1:c0a8:2eea]) (user=vdonnefort job=sendgmr) by 2002:a0d:d6d5:0:b0:61b:1722:cbfd with SMTP id y204-20020a0dd6d5000000b0061b1722cbfdmr205760ywd.7.1713914871746; Tue, 23 Apr 2024 16:27:51 -0700 (PDT) Date: Wed, 24 Apr 2024 00:27:28 +0100 In-Reply-To: <20240423232728.1492340-1-vdonnefort@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20240423232728.1492340-1-vdonnefort@google.com> X-Mailer: git-send-email 2.44.0.769.g3c40516874-goog Message-ID: <20240423232728.1492340-6-vdonnefort@google.com> Subject: [PATCH v21 5/5] ring-buffer/selftest: Add ring-buffer mapping test From: Vincent Donnefort To: rostedt@goodmis.org, mhiramat@kernel.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org Cc: mathieu.desnoyers@efficios.com, kernel-team@android.com, rdunlap@infradead.org, rppt@kernel.org, david@redhat.com, Vincent Donnefort , Shuah Khan , Shuah Khan , linux-kselftest@vger.kernel.org, Muhammad Usama Anjum Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" This test maps a ring-buffer and validate the meta-page after reset and after emitting few events. Cc: Shuah Khan Cc: Shuah Khan Cc: linux-kselftest@vger.kernel.org Acked-by: Muhammad Usama Anjum Signed-off-by: Vincent Donnefort diff --git a/tools/testing/selftests/ring-buffer/.gitignore b/tools/testing= /selftests/ring-buffer/.gitignore new file mode 100644 index 000000000000..3aed1a2a6c67 --- /dev/null +++ b/tools/testing/selftests/ring-buffer/.gitignore @@ -0,0 +1 @@ +map_test diff --git a/tools/testing/selftests/ring-buffer/Makefile b/tools/testing/s= elftests/ring-buffer/Makefile new file mode 100644 index 000000000000..627c5fa6d1ab --- /dev/null +++ b/tools/testing/selftests/ring-buffer/Makefile @@ -0,0 +1,8 @@ +# SPDX-License-Identifier: GPL-2.0 +CFLAGS +=3D -Wl,-no-as-needed -Wall +CFLAGS +=3D $(KHDR_INCLUDES) +CFLAGS +=3D -D_GNU_SOURCE + +TEST_GEN_PROGS =3D map_test + +include ../lib.mk diff --git a/tools/testing/selftests/ring-buffer/config b/tools/testing/sel= ftests/ring-buffer/config new file mode 100644 index 000000000000..d936f8f00e78 --- /dev/null +++ b/tools/testing/selftests/ring-buffer/config @@ -0,0 +1,2 @@ +CONFIG_FTRACE=3Dy +CONFIG_TRACER_SNAPSHOT=3Dy diff --git a/tools/testing/selftests/ring-buffer/map_test.c b/tools/testing= /selftests/ring-buffer/map_test.c new file mode 100644 index 000000000000..b95eedddbb8c --- /dev/null +++ b/tools/testing/selftests/ring-buffer/map_test.c @@ -0,0 +1,288 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Ring-buffer memory mapping tests + * + * Copyright (c) 2024 Vincent Donnefort + */ +#include +#include +#include +#include +#include +#include + +#include + +#include +#include + +#include "../user_events/user_events_selftests.h" /* share tracefs setup */ +#include "../kselftest_harness.h" + +#define TRACEFS_ROOT "/sys/kernel/tracing" + +static int __tracefs_write(const char *path, const char *value) +{ + int fd, ret; + + fd =3D open(path, O_WRONLY | O_TRUNC); + if (fd < 0) + return fd; + + ret =3D write(fd, value, strlen(value)); + + close(fd); + + return ret =3D=3D -1 ? -errno : 0; +} + +static int __tracefs_write_int(const char *path, int value) +{ + char *str; + int ret; + + if (asprintf(&str, "%d", value) < 0) + return -1; + + ret =3D __tracefs_write(path, str); + + free(str); + + return ret; +} + +#define tracefs_write_int(path, value) \ + ASSERT_EQ(__tracefs_write_int((path), (value)), 0) + +#define tracefs_write(path, value) \ + ASSERT_EQ(__tracefs_write((path), (value)), 0) + +static int tracefs_reset(void) +{ + if (__tracefs_write_int(TRACEFS_ROOT"/tracing_on", 0)) + return -1; + if (__tracefs_write(TRACEFS_ROOT"/trace", "")) + return -1; + if (__tracefs_write(TRACEFS_ROOT"/set_event", "")) + return -1; + if (__tracefs_write(TRACEFS_ROOT"/current_tracer", "nop")) + return -1; + + return 0; +} + +struct tracefs_cpu_map_desc { + struct trace_buffer_meta *meta; + int cpu_fd; +}; + +int tracefs_cpu_map(struct tracefs_cpu_map_desc *desc, int cpu) +{ + int page_size =3D getpagesize(); + char *cpu_path; + void *map; + + if (asprintf(&cpu_path, + TRACEFS_ROOT"/per_cpu/cpu%d/trace_pipe_raw", + cpu) < 0) + return -ENOMEM; + + desc->cpu_fd =3D open(cpu_path, O_RDONLY | O_NONBLOCK); + free(cpu_path); + if (desc->cpu_fd < 0) + return -ENODEV; + + map =3D mmap(NULL, page_size, PROT_READ, MAP_SHARED, desc->cpu_fd, 0); + if (map =3D=3D MAP_FAILED) + return -errno; + + desc->meta =3D (struct trace_buffer_meta *)map; + + return 0; +} + +void tracefs_cpu_unmap(struct tracefs_cpu_map_desc *desc) +{ + munmap(desc->meta, desc->meta->meta_page_size); + close(desc->cpu_fd); +} + +FIXTURE(map) { + struct tracefs_cpu_map_desc map_desc; + bool umount; +}; + +FIXTURE_VARIANT(map) { + int subbuf_size; +}; + +FIXTURE_VARIANT_ADD(map, subbuf_size_4k) { + .subbuf_size =3D 4, +}; + +FIXTURE_VARIANT_ADD(map, subbuf_size_8k) { + .subbuf_size =3D 8, +}; + +FIXTURE_SETUP(map) +{ + int cpu =3D sched_getcpu(); + cpu_set_t cpu_mask; + bool fail, umount; + char *message; + + if (!tracefs_enabled(&message, &fail, &umount)) { + if (fail) { + TH_LOG("Tracefs setup failed: %s", message); + ASSERT_FALSE(fail); + } + SKIP(return, "Skipping: %s", message); + } + + self->umount =3D umount; + + ASSERT_GE(cpu, 0); + + ASSERT_EQ(tracefs_reset(), 0); + + tracefs_write_int(TRACEFS_ROOT"/buffer_subbuf_size_kb", variant->subbuf_s= ize); + + ASSERT_EQ(tracefs_cpu_map(&self->map_desc, cpu), 0); + + /* + * Ensure generated events will be found on this very same ring-buffer. + */ + CPU_ZERO(&cpu_mask); + CPU_SET(cpu, &cpu_mask); + ASSERT_EQ(sched_setaffinity(0, sizeof(cpu_mask), &cpu_mask), 0); +} + +FIXTURE_TEARDOWN(map) +{ + tracefs_reset(); + + if (self->umount) + tracefs_unmount(); + + tracefs_cpu_unmap(&self->map_desc); +} + +TEST_F(map, meta_page_check) +{ + struct tracefs_cpu_map_desc *desc =3D &self->map_desc; + int cnt =3D 0; + + ASSERT_EQ(desc->meta->entries, 0); + ASSERT_EQ(desc->meta->overrun, 0); + ASSERT_EQ(desc->meta->read, 0); + + ASSERT_EQ(desc->meta->reader.id, 0); + ASSERT_EQ(desc->meta->reader.read, 0); + + ASSERT_EQ(ioctl(desc->cpu_fd, TRACE_MMAP_IOCTL_GET_READER), 0); + ASSERT_EQ(desc->meta->reader.id, 0); + + tracefs_write_int(TRACEFS_ROOT"/tracing_on", 1); + for (int i =3D 0; i < 16; i++) + tracefs_write_int(TRACEFS_ROOT"/trace_marker", i); +again: + ASSERT_EQ(ioctl(desc->cpu_fd, TRACE_MMAP_IOCTL_GET_READER), 0); + + ASSERT_EQ(desc->meta->entries, 16); + ASSERT_EQ(desc->meta->overrun, 0); + ASSERT_EQ(desc->meta->read, 16); + + ASSERT_EQ(desc->meta->reader.id, 1); + + if (!(cnt++)) + goto again; +} + +TEST_F(map, data_mmap) +{ + struct tracefs_cpu_map_desc *desc =3D &self->map_desc; + unsigned long meta_len, data_len; + void *data; + + meta_len =3D desc->meta->meta_page_size; + data_len =3D desc->meta->subbuf_size * desc->meta->nr_subbufs; + + /* Map all the available subbufs */ + data =3D mmap(NULL, data_len, PROT_READ, MAP_SHARED, + desc->cpu_fd, meta_len); + ASSERT_NE(data, MAP_FAILED); + munmap(data, data_len); + + /* Map all the available subbufs - 1 */ + data_len -=3D desc->meta->subbuf_size; + data =3D mmap(NULL, data_len, PROT_READ, MAP_SHARED, + desc->cpu_fd, meta_len); + ASSERT_NE(data, MAP_FAILED); + munmap(data, data_len); + + /* Overflow the available subbufs by 1 */ + meta_len +=3D desc->meta->subbuf_size * 2; + data =3D mmap(NULL, data_len, PROT_READ, MAP_SHARED, + desc->cpu_fd, meta_len); + ASSERT_EQ(data, MAP_FAILED); +} + +FIXTURE(snapshot) { + bool umount; +}; + +FIXTURE_SETUP(snapshot) +{ + bool fail, umount; + struct stat sb; + char *message; + + if (stat(TRACEFS_ROOT"/snapshot", &sb)) + SKIP(return, "Skipping: %s", "snapshot not available"); + + if (!tracefs_enabled(&message, &fail, &umount)) { + if (fail) { + TH_LOG("Tracefs setup failed: %s", message); + ASSERT_FALSE(fail); + } + SKIP(return, "Skipping: %s", message); + } + + self->umount =3D umount; +} + +FIXTURE_TEARDOWN(snapshot) +{ + __tracefs_write(TRACEFS_ROOT"/events/sched/sched_switch/trigger", + "!snapshot"); + tracefs_reset(); + + if (self->umount) + tracefs_unmount(); +} + +TEST_F(snapshot, excludes_map) +{ + struct tracefs_cpu_map_desc map_desc; + int cpu =3D sched_getcpu(); + + ASSERT_GE(cpu, 0); + tracefs_write(TRACEFS_ROOT"/events/sched/sched_switch/trigger", + "snapshot"); + ASSERT_EQ(tracefs_cpu_map(&map_desc, cpu), -EBUSY); +} + +TEST_F(snapshot, excluded_by_map) +{ + struct tracefs_cpu_map_desc map_desc; + int cpu =3D sched_getcpu(); + + ASSERT_EQ(tracefs_cpu_map(&map_desc, cpu), 0); + + ASSERT_EQ(__tracefs_write(TRACEFS_ROOT"/events/sched/sched_switch/trigger= ", + "snapshot"), -EBUSY); + ASSERT_EQ(__tracefs_write(TRACEFS_ROOT"/snapshot", + "1"), -EBUSY); +} + +TEST_HARNESS_MAIN --=20 2.44.0.769.g3c40516874-goog