From nobody Fri Dec 19 01:24:53 2025 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 35237180A62 for ; Fri, 14 Jun 2024 16:30:48 +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=1718382648; cv=none; b=Un8TRkqMBEKWwNqF/EnjP1mWd05pw8SZvoc5zr1EsSHckPEevHuXoAv2qHaYx8VGG7HWMvY2Z1PHI9K5ZyD/6bRmRocZnpsjgtn65+BRa5JPlEv3Rb9cxNCSiVQfhR1tmM5GYskxFUC5XT3cNC8YOlklNiEmuG+qgLg6sY23ONQ= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1718382648; c=relaxed/simple; bh=fCPmXMT3aB4IJwdM6fzKMEvkYFFB7mz8RlBdKCUh5BY=; h=Message-ID:Date:From:To:Cc:Subject:References:MIME-Version: Content-Type; b=UuLvOlk/bFjlrnEwVwLJEvGj/x8MCm5V7TquaCZEytxG8LSRW4/+sQq9wEkeOl7AtwgXd+4wYRP4poljY28aJov0Huptpm2+d2+AUVZd+msTyWP/nMgGlon5iUm6vVWXh9wIzi2IHLtZeA240qJTVwyIAcaBdBtzuBjyyQ24Ao8= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0AB55C4AF60; Fri, 14 Jun 2024 16:30:48 +0000 (UTC) Received: from rostedt by gandalf with local (Exim 4.97) (envelope-from ) id 1sI9pX-00000001rrR-0X0Z; Fri, 14 Jun 2024 12:31:11 -0400 Message-ID: <20240614163110.988739295@goodmis.org> User-Agent: quilt/0.68 Date: Fri, 14 Jun 2024 12:30:20 -0400 From: Steven Rostedt To: linux-kernel@vger.kernel.org Cc: Masami Hiramatsu , Mark Rutland , Mathieu Desnoyers , Andrew Morton , Vincent Donnefort , Joel Fernandes , Daniel Bristot de Oliveira , Ingo Molnar , Peter Zijlstra , Thomas Gleixner , Vineeth Pillai , Youssef Esmat , Beau Belgrave , Alexander Graf , Baoquan He , Borislav Petkov , "Paul E. McKenney" , David Howells , Mike Rapoport , Dave Hansen , Tony Luck , Guenter Roeck , Ross Zwisler , Kees Cook Subject: [for-next][PATCH 05/13] ring-buffer: Add output of ring buffer meta page References: <20240614163015.456541709@goodmis.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: "Steven Rostedt (Google)" Add a buffer_meta per-cpu file for the trace instance that is mapped to boot memory. This shows the current meta-data and can be used by user space tools to record off the current mappings to help reconstruct the ring buffer after a reboot. It does not expose any virtual addresses, just indexes into the sub-buffer pages. Link: https://lkml.kernel.org/r/20240612232025.854471446@goodmis.org Cc: Masami Hiramatsu Cc: Mark Rutland Cc: Mathieu Desnoyers Cc: Andrew Morton Cc: Vincent Donnefort Cc: Joel Fernandes Cc: Daniel Bristot de Oliveira Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Vineeth Pillai Cc: Youssef Esmat Cc: Beau Belgrave Cc: Alexander Graf Cc: Baoquan He Cc: Borislav Petkov Cc: "Paul E. McKenney" Cc: David Howells Cc: Mike Rapoport Cc: Dave Hansen Cc: Tony Luck Cc: Guenter Roeck Cc: Ross Zwisler Cc: Kees Cook Signed-off-by: Steven Rostedt (Google) --- kernel/trace/ring_buffer.c | 77 ++++++++++++++++++++++++++++++++++++++ kernel/trace/trace.c | 30 ++++++++++++++- kernel/trace/trace.h | 2 + 3 files changed, 107 insertions(+), 2 deletions(-) diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 0e3ed7f1cc5d..25b0e61e8c76 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -32,6 +32,8 @@ #include #include =20 +#include "trace.h" + /* * The "absolute" timestamp in the buffer is only 59 bits. * If a clock has the 5 MSBs set, it needs to be saved and @@ -1647,6 +1649,81 @@ static void rb_range_meta_init(struct trace_buffer *= buffer, int nr_pages) } } =20 +static void *rbm_start(struct seq_file *m, loff_t *pos) +{ + struct ring_buffer_per_cpu *cpu_buffer =3D m->private; + struct ring_buffer_meta *meta =3D cpu_buffer->ring_meta; + unsigned long val; + + if (!meta) + return NULL; + + if (*pos > meta->nr_subbufs) + return NULL; + + val =3D *pos; + val++; + + return (void *)val; +} + +static void *rbm_next(struct seq_file *m, void *v, loff_t *pos) +{ + (*pos)++; + + return rbm_start(m, pos); +} + +static int rb_meta_subbuf_idx(struct ring_buffer_meta *meta, void *subbuf); + +static int rbm_show(struct seq_file *m, void *v) +{ + struct ring_buffer_per_cpu *cpu_buffer =3D m->private; + struct ring_buffer_meta *meta =3D cpu_buffer->ring_meta; + unsigned long val =3D (unsigned long)v; + + if (val =3D=3D 1) { + seq_printf(m, "head_buffer: %d\n", + rb_meta_subbuf_idx(meta, (void *)meta->head_buffer)); + seq_printf(m, "commit_buffer: %d\n", + rb_meta_subbuf_idx(meta, (void *)meta->commit_buffer)); + seq_printf(m, "subbuf_size: %d\n", meta->subbuf_size); + seq_printf(m, "nr_subbufs: %d\n", meta->nr_subbufs); + return 0; + } + + val -=3D 2; + seq_printf(m, "buffer[%ld]: %d\n", val, meta->buffers[val]); + + return 0; +} + +static void rbm_stop(struct seq_file *m, void *p) +{ +} + +static const struct seq_operations rb_meta_seq_ops =3D { + .start =3D rbm_start, + .next =3D rbm_next, + .show =3D rbm_show, + .stop =3D rbm_stop, +}; + +int ring_buffer_meta_seq_init(struct file *file, struct trace_buffer *buff= er, int cpu) +{ + struct seq_file *m; + int ret; + + ret =3D seq_open(file, &rb_meta_seq_ops); + if (ret) + return ret; + + m =3D file->private_data; + m->private =3D buffer->buffers[cpu]; + + return 0; +} + static int __rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer, long nr_pages, struct list_head *pages) { diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index ff2b504fbe00..622fe670949d 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -5018,7 +5018,7 @@ static int show_traces_open(struct inode *inode, stru= ct file *file) return 0; } =20 -static int show_traces_release(struct inode *inode, struct file *file) +static int tracing_seq_release(struct inode *inode, struct file *file) { struct trace_array *tr =3D inode->i_private; =20 @@ -5059,7 +5059,7 @@ static const struct file_operations show_traces_fops = =3D { .open =3D show_traces_open, .read =3D seq_read, .llseek =3D seq_lseek, - .release =3D show_traces_release, + .release =3D tracing_seq_release, }; =20 static ssize_t @@ -6860,6 +6860,22 @@ tracing_total_entries_read(struct file *filp, char _= _user *ubuf, return simple_read_from_buffer(ubuf, cnt, ppos, buf, r); } =20 +static int tracing_buffer_meta_open(struct inode *inode, struct file *filp) +{ + struct trace_array *tr =3D inode->i_private; + int cpu =3D tracing_get_cpu(inode); + int ret; + + ret =3D tracing_check_open_get_tr(tr); + if (ret) + return ret; + + ret =3D ring_buffer_meta_seq_init(filp, tr->array_buffer.buffer, cpu); + if (ret < 0) + __trace_array_put(tr); + return ret; +} + static ssize_t tracing_free_buffer_write(struct file *filp, const char __user *ubuf, size_t cnt, loff_t *ppos) @@ -7436,6 +7452,13 @@ static const struct file_operations tracing_entries_= fops =3D { .release =3D tracing_release_generic_tr, }; =20 +static const struct file_operations tracing_buffer_meta_fops =3D { + .open =3D tracing_buffer_meta_open, + .read =3D seq_read, + .llseek =3D seq_lseek, + .release =3D tracing_seq_release, +}; + static const struct file_operations tracing_total_entries_fops =3D { .open =3D tracing_open_generic_tr, .read =3D tracing_total_entries_read, @@ -8668,6 +8691,9 @@ tracing_init_tracefs_percpu(struct trace_array *tr, l= ong cpu) trace_create_cpu_file("buffer_size_kb", TRACE_MODE_READ, d_cpu, tr, cpu, &tracing_entries_fops); =20 + if (tr->range_addr_start) + trace_create_cpu_file("buffer_meta", TRACE_MODE_READ, d_cpu, + tr, cpu, &tracing_buffer_meta_fops); #ifdef CONFIG_TRACER_SNAPSHOT if (!tr->range_addr_start) { trace_create_cpu_file("snapshot", TRACE_MODE_WRITE, d_cpu, diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h index 5dd48932509c..3e56d3b22212 100644 --- a/kernel/trace/trace.h +++ b/kernel/trace/trace.h @@ -645,6 +645,8 @@ trace_buffer_lock_reserve(struct trace_buffer *buffer, unsigned long len, unsigned int trace_ctx); =20 +int ring_buffer_meta_seq_init(struct file *file, struct trace_buffer *buff= er, int cpu); + struct trace_entry *tracing_get_trace_entry(struct trace_array *tr, struct trace_array_cpu *data); =20 --=20 2.43.0