Commit 1bd25a6f authored by Steven Rostedt's avatar Steven Rostedt Committed by Steven Rostedt (Google)
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tracing: Show module names and addresses of last boot 

Add the last boot module's names and addresses to the last_boot_info file.
This only shows the module information from a previous boot. If the buffer
is started and is recording the current boot, this file still will only
show "current".

  ~# cat instances/boot_mapped/last_boot_info
  10c00000		[kernel]
  ffffffffc00ca000	usb_serial_simple
  ffffffffc00ae000	usbserial
  ffffffffc008b000	bfq

  ~# echo function > instances/boot_mapped/current_tracer
  ~# cat instances/boot_mapped/last_boot_info
  # Current

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: https://lore.kernel.org/20250305164609.299186021@goodmis.org


Signed-off-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
parent fd39e48f

kernel/trace/trace.c

+89 −13
Original line number Diff line number Diff line
@@ -5999,6 +5999,8 @@ struct trace_scratch { 
	struct trace_mod_entry	entries[];

};



static DEFINE_MUTEX(scratch_mutex);



static int save_mod(struct module *mod, void *data)

{

	struct trace_array *tr = data;
@@ -6039,6 +6041,7 @@ static void update_last_data(struct trace_array *tr) 
		       flex_array_size(tscratch, entries, tscratch->nr_entries));

		tscratch->nr_entries = 0;



		guard(mutex)(&scratch_mutex);

		module_for_each_mod(save_mod, tr);

	}
@@ -6876,15 +6879,47 @@ tracing_total_entries_read(struct file *filp, char __user *ubuf, 
	return simple_read_from_buffer(ubuf, cnt, ppos, buf, r);

}



static ssize_t

tracing_last_boot_read(struct file *filp, char __user *ubuf, size_t cnt, loff_t *ppos)

#define LAST_BOOT_HEADER ((void *)1)



static void *l_next(struct seq_file *m, void *v, loff_t *pos)

{

	struct trace_array *tr = filp->private_data;

	struct trace_array *tr = m->private;

	struct trace_scratch *tscratch = tr->scratch;

	struct seq_buf seq;

	char buf[64];

	unsigned int index = *pos;



	(*pos)++;



	seq_buf_init(&seq, buf, 64);

	if (*pos == 1)

		return LAST_BOOT_HEADER;



	/* Only show offsets of the last boot data */

	if (!tscratch || !(tr->flags & TRACE_ARRAY_FL_LAST_BOOT))

		return NULL;



	/* *pos 0 is for the header, 1 is for the first module */

	index--;



	if (index >= tscratch->nr_entries)

		return NULL;



	return &tscratch->entries[index];

}



static void *l_start(struct seq_file *m, loff_t *pos)

{

	mutex_lock(&scratch_mutex);



	return l_next(m, NULL, pos);

}



static void l_stop(struct seq_file *m, void *p)

{

	mutex_unlock(&scratch_mutex);

}



static void show_last_boot_header(struct seq_file *m, struct trace_array *tr)

{

	struct trace_scratch *tscratch = tr->scratch;



	/*

	 * Do not leak KASLR address. This only shows the KASLR address of
@@ -6894,11 +6929,52 @@ tracing_last_boot_read(struct file *filp, char __user *ubuf, size_t cnt, loff_t 
	 * should not be the same as the current boot.

	 */

	if (tscratch && (tr->flags & TRACE_ARRAY_FL_LAST_BOOT))

		seq_buf_printf(&seq, "%lx\t[kernel]\n", tscratch->kaslr_addr);

		seq_printf(m, "%lx\t[kernel]\n", tscratch->kaslr_addr);

	else

		seq_buf_puts(&seq, "# Current\n");

		seq_puts(m, "# Current\n");

}



	return simple_read_from_buffer(ubuf, cnt, ppos, buf, seq_buf_used(&seq));

static int l_show(struct seq_file *m, void *v)

{

	struct trace_array *tr = m->private;

	struct trace_mod_entry *entry = v;



	if (v == LAST_BOOT_HEADER) {

		show_last_boot_header(m, tr);

		return 0;

	}



	seq_printf(m, "%lx\t%s\n", entry->mod_addr, entry->mod_name);

	return 0;

}



static const struct seq_operations last_boot_seq_ops = {

	.start		= l_start,

	.next		= l_next,

	.stop		= l_stop,

	.show		= l_show,

};



static int tracing_last_boot_open(struct inode *inode, struct file *file)

{

	struct trace_array *tr = inode->i_private;

	struct seq_file *m;

	int ret;



	ret = tracing_check_open_get_tr(tr);

	if (ret)

		return ret;



	ret = seq_open(file, &last_boot_seq_ops);

	if (ret) {

		trace_array_put(tr);

		return ret;

	}



	m = file->private_data;

	m->private = tr;



	return 0;

}



static int tracing_buffer_meta_open(struct inode *inode, struct file *filp)
@@ -7527,10 +7603,10 @@ static const struct file_operations trace_time_stamp_mode_fops = { 
};



static const struct file_operations last_boot_fops = {

	.open		= tracing_open_generic_tr,

	.read		= tracing_last_boot_read,

	.llseek		= generic_file_llseek,

	.release	= tracing_release_generic_tr,

	.open		= tracing_last_boot_open,

	.read		= seq_read,

	.llseek		= seq_lseek,

	.release	= tracing_seq_release,

};



#ifdef CONFIG_TRACER_SNAPSHOT