Commit cb1f98c5 authored by Steven Rostedt (Google)'s avatar Steven Rostedt (Google)
Browse files

tracing: Add creation of instances at boot command line 

Add kernel command line to add tracing instances. This only creates
instances at boot but still does not enable any events to them. Later
changes will extend this command line to add enabling of events, filters,
and triggers. As well as possibly redirecting trace_printk()!

Link: https://lkml.kernel.org/r/20230207173026.186210158@goodmis.org



Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: default avatarRoss Zwisler <zwisler@google.com>
Signed-off-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
parent 9971c3f9

Documentation/admin-guide/kernel-parameters.txt

+6 −0
Original line number Diff line number Diff line
@@ -6272,6 +6272,12 @@ 
			comma-separated list of trace events to enable. See

			also Documentation/trace/events.rst



	trace_instance=[instance-info]

			[FTRACE] Create a ring buffer instance early in boot up.

			This will be listed in:



				/sys/kernel/tracing/instances



	trace_options=[option-list]

			[FTRACE] Enable or disable tracer options at boot.

			The option-list is a comma delimited list of options

kernel/trace/trace.c

+50 −0
Original line number Diff line number Diff line
@@ -49,6 +49,8 @@ 
#include <linux/irq_work.h>

#include <linux/workqueue.h>



#include <asm/setup.h> /* COMMAND_LINE_SIZE */



#include "trace.h"

#include "trace_output.h"
@@ -186,6 +188,9 @@ static char *default_bootup_tracer; 
static bool allocate_snapshot;

static bool snapshot_at_boot;



static char boot_instance_info[COMMAND_LINE_SIZE] __initdata;

static int boot_instance_index;



static int __init set_cmdline_ftrace(char *str)

{

	strlcpy(bootup_tracer_buf, str, MAX_TRACER_SIZE);
@@ -239,6 +244,23 @@ static int __init boot_snapshot(char *str) 
__setup("ftrace_boot_snapshot", boot_snapshot);





static int __init boot_instance(char *str)

{

	char *slot = boot_instance_info + boot_instance_index;

	int left = sizeof(boot_instance_info) - boot_instance_index;

	int ret;



	if (strlen(str) >= left)

		return -1;



	ret = snprintf(slot, left, "%s\t", str);

	boot_instance_index += ret;



	return 1;

}

__setup("trace_instance=", boot_instance);





static char trace_boot_options_buf[MAX_TRACER_SIZE] __initdata;



static int __init set_trace_boot_options(char *str)
@@ -10144,6 +10166,31 @@ ssize_t trace_parse_run_command(struct file *file, const char __user *buffer, 
	return ret;

}



__init static void enable_instances(void)

{

	struct trace_array *tr;

	char *curr_str;

	char *str;

	char *tok;



	/* A tab is always appended */

	boot_instance_info[boot_instance_index - 1] = '\0';

	str = boot_instance_info;



	while ((curr_str = strsep(&str, "\t"))) {



		tok = strsep(&curr_str, ",");



		tr = trace_array_get_by_name(tok);

		if (!tr) {

			pr_warn("Failed to create instance buffer %s\n", curr_str);

			continue;

		}

		/* Allow user space to delete it */

		trace_array_put(tr);

	}

}



__init static int tracer_alloc_buffers(void)

{

	int ring_buf_size;
@@ -10302,6 +10349,9 @@ void __init early_trace_init(void) 
void __init trace_init(void)

{

	trace_event_init();



	if (boot_instance_index)

		enable_instances();

}



__init static void clear_boot_tracer(void)