Commit 9c1c251d authored by Steven Rostedt (Google)'s avatar Steven Rostedt (Google)
Browse files

tracing: Allow boot instances to have snapshot buffers 

Add to ftrace_boot_snapshot, "=<instance>" name, where the instance will
get a snapshot buffer, and will take a snapshot at the end of boot (which
will save the boot traces).

Link: https://lkml.kernel.org/r/20230207173026.792774721@goodmis.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 d503b8f7

Documentation/admin-guide/kernel-parameters.txt

+9 −0
Original line number Diff line number Diff line
@@ -1532,6 +1532,15 @@ 
			boot up that is likely to be overridden by user space

			start up functionality.



			Optionally, the snapshot can also be defined for a tracing

			instance that was created by the trace_instance= command

			line parameter.



			trace_instance=foo,sched_switch ftrace_boot_snapshot=foo



			The above will cause the "foo" tracing instance to trigger

			a snapshot at the end of boot up.



	ftrace_dump_on_oops[=orig_cpu]

			[FTRACE] will dump the trace buffers on oops.

			If no parameter is passed, ftrace will dump

kernel/trace/trace.c

+72 −7
Original line number Diff line number Diff line
@@ -191,6 +191,9 @@ static bool snapshot_at_boot; 
static char boot_instance_info[COMMAND_LINE_SIZE] __initdata;

static int boot_instance_index;



static char boot_snapshot_info[COMMAND_LINE_SIZE] __initdata;

static int boot_snapshot_index;



static int __init set_cmdline_ftrace(char *str)

{

	strlcpy(bootup_tracer_buf, str, MAX_TRACER_SIZE);
@@ -227,9 +230,22 @@ __setup("traceoff_on_warning", stop_trace_on_warning); 


static int __init boot_alloc_snapshot(char *str)

{

	char *slot = boot_snapshot_info + boot_snapshot_index;

	int left = sizeof(boot_snapshot_info) - boot_snapshot_index;

	int ret;



	if (str[0] == '=') {

		str++;

		if (strlen(str) >= left)

			return -1;



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

		boot_snapshot_index += ret;

	} else {

		allocate_snapshot = true;

		/* We also need the main ring buffer expanded */

		ring_buffer_expanded = true;

	}

	return 1;

}

__setup("alloc_snapshot", boot_alloc_snapshot);
@@ -9254,10 +9270,6 @@ static int allocate_trace_buffers(struct trace_array *tr, int size) 
	}

	tr->allocated_snapshot = allocate_snapshot;



	/*

	 * Only the top level trace array gets its snapshot allocated

	 * from the kernel command line.

	 */

	allocate_snapshot = false;

#endif
@@ -10173,6 +10185,47 @@ ssize_t trace_parse_run_command(struct file *file, const char __user *buffer, 
	return ret;

}



#ifdef CONFIG_TRACER_MAX_TRACE

__init static bool tr_needs_alloc_snapshot(const char *name)

{

	char *test;

	int len = strlen(name);

	bool ret;



	if (!boot_snapshot_index)

		return false;



	if (strncmp(name, boot_snapshot_info, len) == 0 &&

	    boot_snapshot_info[len] == '\t')

		return true;



	test = kmalloc(strlen(name) + 3, GFP_KERNEL);

	if (!test)

		return false;



	sprintf(test, "\t%s\t", name);

	ret = strstr(boot_snapshot_info, test) == NULL;

	kfree(test);

	return ret;

}



__init static void do_allocate_snapshot(const char *name)

{

	if (!tr_needs_alloc_snapshot(name))

		return;



	/*

	 * When allocate_snapshot is set, the next call to

	 * allocate_trace_buffers() (called by trace_array_get_by_name())

	 * will allocate the snapshot buffer. That will alse clear

	 * this flag.

	 */

	allocate_snapshot = true;

}

#else

static inline void do_allocate_snapshot(const char *name) { }

#endif



__init static void enable_instances(void)

{

	struct trace_array *tr;
@@ -10188,6 +10241,9 @@ __init static void enable_instances(void) 


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



		if (IS_ENABLED(CONFIG_TRACER_MAX_TRACE))

			do_allocate_snapshot(tok);



		tr = trace_array_get_by_name(tok);

		if (!tr) {

			pr_warn("Failed to create instance buffer %s\n", curr_str);
@@ -10335,10 +10391,19 @@ __init static int tracer_alloc_buffers(void) 


void __init ftrace_boot_snapshot(void)

{

	struct trace_array *tr;



	if (snapshot_at_boot) {

		tracing_snapshot();

		internal_trace_puts("** Boot snapshot taken **\n");

	}



	list_for_each_entry(tr, &ftrace_trace_arrays, list) {

		if (tr == &global_trace)

			continue;

		trace_array_puts(tr, "** Boot snapshot taken **\n");

		tracing_snapshot_instance(tr);

	}

}



void __init early_trace_init(void)