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Message-ID: <20240306020005.782553145@goodmis.org>
Date: Tue, 05 Mar 2024 20:59:13 -0500
From: Steven Rostedt <rostedt@...dmis.org>
To: linux-kernel@...r.kernel.org,
linux-trace-kernel@...r.kernel.org
Cc: Masami Hiramatsu <mhiramat@...nel.org>,
Mark Rutland <mark.rutland@....com>,
Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Vincent Donnefort <vdonnefort@...gle.com>,
Joel Fernandes <joel@...lfernandes.org>,
Daniel Bristot de Oliveira <bristot@...hat.com>,
Ingo Molnar <mingo@...nel.org>,
Peter Zijlstra <peterz@...radead.org>,
suleiman@...gle.com,
Thomas Gleixner <tglx@...utronix.de>,
Vineeth Pillai <vineeth@...byteword.org>,
Youssef Esmat <youssefesmat@...gle.com>,
Beau Belgrave <beaub@...ux.microsoft.com>,
Alexander Graf <graf@...zon.com>,
Baoquan He <bhe@...hat.com>,
Borislav Petkov <bp@...en8.de>,
"Paul E. McKenney" <paulmck@...nel.org>,
David Howells <dhowells@...hat.com>
Subject: [PATCH 3/8] tracing: Create "boot_mapped" instance for memory mapped buffer
From: "Steven Rostedt (Google)" <rostedt@...dmis.org>
Add two global variables trace_buffer_start and trace_buffer_size. If they
are both set, then a "boot_mapped" instance will be created using the
memory specified by these variables as its ring buffer.
The instance will exist in:
/sys/kernel/tracing/instances/boot_mapped
Note, because the ring buffer is using a defined memory ranged, it will
act just like a memory mapped ring buffer. It will not have a snapshot
buffer, as it can't swap out the buffer. The snapshot files as well as any
tracers that uses a snapshot will not be present in the boot_mapped
instance.
Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
---
include/linux/trace.h | 7 +++++
kernel/trace/trace.c | 65 ++++++++++++++++++++++++++++++++++++-------
kernel/trace/trace.h | 3 ++
3 files changed, 65 insertions(+), 10 deletions(-)
diff --git a/include/linux/trace.h b/include/linux/trace.h
index fdcd76b7be83..75dab6bb88c9 100644
--- a/include/linux/trace.h
+++ b/include/linux/trace.h
@@ -33,6 +33,13 @@ struct trace_array;
int register_ftrace_export(struct trace_export *export);
int unregister_ftrace_export(struct trace_export *export);
+/*
+ * If the below are set, then a "boot_mapped" tracing instance will
+ * be created using this memory for its ring buffer.
+ */
+extern unsigned long trace_buffer_start;
+extern unsigned long trace_buffer_size;
+
/**
* trace_array_puts - write a constant string into the trace buffer.
* @tr: The trace array to write to
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index ff0b0a999171..ff986d2a4bd0 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -4900,6 +4900,11 @@ static int tracing_open(struct inode *inode, struct file *file)
static bool
trace_ok_for_array(struct tracer *t, struct trace_array *tr)
{
+#ifdef CONFIG_TRACER_SNAPSHOT
+ /* arrays with mapped buffer range do not have snapshots */
+ if (tr->range_addr_start && t->use_max_tr)
+ return false;
+#endif
return (tr->flags & TRACE_ARRAY_FL_GLOBAL) || t->allow_instances;
}
@@ -8670,11 +8675,13 @@ tracing_init_tracefs_percpu(struct trace_array *tr, long cpu)
tr, cpu, &tracing_entries_fops);
#ifdef CONFIG_TRACER_SNAPSHOT
- trace_create_cpu_file("snapshot", TRACE_MODE_WRITE, d_cpu,
- tr, cpu, &snapshot_fops);
+ if (!tr->range_addr_start) {
+ trace_create_cpu_file("snapshot", TRACE_MODE_WRITE, d_cpu,
+ tr, cpu, &snapshot_fops);
- trace_create_cpu_file("snapshot_raw", TRACE_MODE_READ, d_cpu,
- tr, cpu, &snapshot_raw_fops);
+ trace_create_cpu_file("snapshot_raw", TRACE_MODE_READ, d_cpu,
+ tr, cpu, &snapshot_raw_fops);
+ }
#endif
}
@@ -9211,7 +9218,18 @@ allocate_trace_buffer(struct trace_array *tr, struct array_buffer *buf, int size
buf->tr = tr;
- buf->buffer = ring_buffer_alloc(size, rb_flags);
+ if (tr->range_addr_start && tr->range_addr_size) {
+ buf->buffer = ring_buffer_alloc_range(size, rb_flags, 0,
+ tr->range_addr_start,
+ tr->range_addr_size);
+ /*
+ * This is basically the same as a mapped buffer,
+ * with the same restrictions.
+ */
+ tr->mapped++;
+ } else {
+ buf->buffer = ring_buffer_alloc(size, rb_flags);
+ }
if (!buf->buffer)
return -ENOMEM;
@@ -9248,6 +9266,10 @@ static int allocate_trace_buffers(struct trace_array *tr, int size)
return ret;
#ifdef CONFIG_TRACER_MAX_TRACE
+ /* Fix mapped buffer trace arrays do not have snapshot buffers */
+ if (tr->range_addr_start)
+ return 0;
+
ret = allocate_trace_buffer(tr, &tr->max_buffer,
allocate_snapshot ? size : 1);
if (MEM_FAIL(ret, "Failed to allocate trace buffer\n")) {
@@ -9348,7 +9370,9 @@ static int trace_array_create_dir(struct trace_array *tr)
}
static struct trace_array *
-trace_array_create_systems(const char *name, const char *systems)
+trace_array_create_systems(const char *name, const char *systems,
+ unsigned long range_addr_start,
+ unsigned long range_addr_size)
{
struct trace_array *tr;
int ret;
@@ -9374,6 +9398,10 @@ trace_array_create_systems(const char *name, const char *systems)
goto out_free_tr;
}
+ /* Only for boot up memory mapped ring buffers */
+ tr->range_addr_start = range_addr_start;
+ tr->range_addr_size = range_addr_size;
+
tr->trace_flags = global_trace.trace_flags & ~ZEROED_TRACE_FLAGS;
cpumask_copy(tr->tracing_cpumask, cpu_all_mask);
@@ -9431,9 +9459,24 @@ trace_array_create_systems(const char *name, const char *systems)
static struct trace_array *trace_array_create(const char *name)
{
- return trace_array_create_systems(name, NULL);
+ return trace_array_create_systems(name, NULL, 0, 0);
+}
+
+unsigned long trace_buffer_start;
+unsigned long trace_buffer_size;
+
+static int __init trace_range_tr(void)
+{
+ if (!trace_buffer_start || !trace_buffer_size)
+ return 0;
+
+ trace_array_create_systems("boot_mapped", NULL,
+ trace_buffer_start, trace_buffer_size);
+ return 0;
}
+fs_initcall(trace_range_tr);
+
static int instance_mkdir(const char *name)
{
struct trace_array *tr;
@@ -9485,7 +9528,7 @@ struct trace_array *trace_array_get_by_name(const char *name, const char *system
goto out_unlock;
}
- tr = trace_array_create_systems(name, systems);
+ tr = trace_array_create_systems(name, systems, 0, 0);
if (IS_ERR(tr))
tr = NULL;
@@ -9678,8 +9721,10 @@ init_tracer_tracefs(struct trace_array *tr, struct dentry *d_tracer)
MEM_FAIL(1, "Could not allocate function filter files");
#ifdef CONFIG_TRACER_SNAPSHOT
- trace_create_file("snapshot", TRACE_MODE_WRITE, d_tracer,
- tr, &snapshot_fops);
+ if (!tr->range_addr_start) {
+ trace_create_file("snapshot", TRACE_MODE_WRITE, d_tracer,
+ tr, &snapshot_fops);
+ }
#endif
trace_create_file("error_log", TRACE_MODE_WRITE, d_tracer,
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 749a182dab48..d22d7c3b770a 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -338,6 +338,9 @@ struct trace_array {
unsigned int snapshot;
unsigned int mapped;
unsigned long max_latency;
+ /* The below is for memory mapped ring buffer */
+ unsigned long range_addr_start;
+ unsigned long range_addr_size;
#ifdef CONFIG_FSNOTIFY
struct dentry *d_max_latency;
struct work_struct fsnotify_work;
--
2.43.0
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