Commit 96e43537 authored by Vincent Donnefort's avatar Vincent Donnefort Committed by Steven Rostedt (Google)
Browse files

tracing: Introduce trace remotes 

A trace remote relies on ring-buffer remotes to read and control
compatible tracing buffers, written by entity such as firmware or
hypervisor.

Add a Tracefs directory remotes/ that contains all instances of trace
remotes. Each instance follows the same hierarchy as any other to ease
the support by existing user-space tools.

This currently does not provide any event support, which will come
later.

Link: https://patch.msgid.link/20260309162516.2623589-6-vdonnefort@google.com


Reviewed-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: default avatarVincent Donnefort <vdonnefort@google.com>
Signed-off-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
parent fbd1743e

include/linux/trace_remote.h

0 → 100644
+36 −0
Original line number Diff line number Diff line 
/* SPDX-License-Identifier: GPL-2.0 */



#ifndef _LINUX_TRACE_REMOTE_H

#define _LINUX_TRACE_REMOTE_H



#include <linux/ring_buffer.h>



/**

 * struct trace_remote_callbacks - Callbacks used by Tracefs to control the remote

 * @load_trace_buffer:  Called before Tracefs accesses the trace buffer for the first

 *			time. Must return a &trace_buffer_desc

 *			(most likely filled with trace_remote_alloc_buffer())

 * @unload_trace_buffer:

 *			Called once Tracefs has no use for the trace buffer

 *			(most likely call trace_remote_free_buffer())

 * @enable_tracing:	Called on Tracefs tracing_on. It is expected from the

 *			remote to allow writing.

 * @swap_reader_page:	Called when Tracefs consumes a new page from a

 *			ring-buffer. It is expected from the remote to isolate a

 *			new reader-page from the @cpu ring-buffer.

 */

struct trace_remote_callbacks {

	struct trace_buffer_desc *(*load_trace_buffer)(unsigned long size, void *priv);

	void	(*unload_trace_buffer)(struct trace_buffer_desc *desc, void *priv);

	int	(*enable_tracing)(bool enable, void *priv);

	int	(*swap_reader_page)(unsigned int cpu, void *priv);

};



int trace_remote_register(const char *name, struct trace_remote_callbacks *cbs, void *priv);



int trace_remote_alloc_buffer(struct trace_buffer_desc *desc, size_t desc_size, size_t buffer_size,

			      const struct cpumask *cpumask);



void trace_remote_free_buffer(struct trace_buffer_desc *desc);



#endif

kernel/trace/Kconfig

+3 −0
Original line number Diff line number Diff line
@@ -1281,4 +1281,7 @@ config HIST_TRIGGERS_DEBUG 


source "kernel/trace/rv/Kconfig"



config TRACE_REMOTE

	bool



endif # FTRACE

kernel/trace/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -128,4 +128,5 @@ obj-$(CONFIG_FPROBE_EVENTS) += trace_fprobe.o 
obj-$(CONFIG_TRACEPOINT_BENCHMARK) += trace_benchmark.o

obj-$(CONFIG_RV) += rv/



obj-$(CONFIG_TRACE_REMOTE) += trace_remote.o

libftrace-y := ftrace.o

kernel/trace/trace.c

+1 −1
Original line number Diff line number Diff line
@@ -8589,7 +8589,7 @@ static struct dentry *tracing_dentry_percpu(struct trace_array *tr, int cpu) 
	return tr->percpu_dir;

}



static struct dentry *

struct dentry *

trace_create_cpu_file(const char *name, umode_t mode, struct dentry *parent,

		      void *data, long cpu, const struct file_operations *fops)

{

kernel/trace/trace.h

+6 −0
Original line number Diff line number Diff line
@@ -689,6 +689,12 @@ struct dentry *trace_create_file(const char *name, 
				 struct dentry *parent,

				 void *data,

				 const struct file_operations *fops);

struct dentry *trace_create_cpu_file(const char *name,

				     umode_t mode,

				     struct dentry *parent,

				     void *data,

				     long cpu,

				     const struct file_operations *fops);





/**