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Commit 65f8c95e authored by Anton Vorontsov's avatar Anton Vorontsov
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pstore/ftrace: Convert to its own enable/disable debugfs knob 



With this patch we no longer reuse function tracer infrastructure, now
we register our own tracer back-end via a debugfs knob.

It's a bit more code, but that is the only downside. On the bright side we
have:

- Ability to make persistent_ram module removable (when needed, we can
  move ftrace_ops struct into a module). Note that persistent_ram is still
  not removable for other reasons, but with this patch it's just one
  thing less to worry about;

- Pstore part is more isolated from the generic function tracer. We tried
  it already by registering our own tracer in available_tracers, but that
  way we're loosing ability to see the traces while we record them to
  pstore. This solution is somewhere in the middle: we only register
  "internal ftracer" back-end, but not the "front-end";

- When there is only pstore tracing enabled, the kernel will only write
  to the pstore buffer, omitting function tracer buffer (which, of course,
  still can be enabled via 'echo function > current_tracer').

Suggested-by: default avatarSteven Rostedt <rostedt@goodmis.org>
Signed-off-by: default avatarAnton Vorontsov <anton.vorontsov@linaro.org>
parent b4a871bc

Documentation/ramoops.txt

+1 −3
Original line number Original line Diff line number Diff line
@@ -102,9 +102,7 @@ related hangs. The functions call chain log is stored in a "ftrace-ramoops" 
file. Here is an example of usage:

file. Here is an example of usage:





 # mount -t debugfs debugfs /sys/kernel/debug/

 # mount -t debugfs debugfs /sys/kernel/debug/

 # cd /sys/kernel/debug/tracing

 # echo 1 > /sys/kernel/debug/pstore/record_ftrace

 # echo function > current_tracer

 # echo 1 > options/func_pstore

 # reboot -f

 # reboot -f

 [...]

 [...]

 # mount -t pstore pstore /mnt/

 # mount -t pstore pstore /mnt/

fs/pstore/Kconfig

+1 −0
Original line number Original line Diff line number Diff line
@@ -23,6 +23,7 @@ config PSTORE_FTRACE 
	bool "Persistent function tracer"

	bool "Persistent function tracer"

	depends on PSTORE

	depends on PSTORE

	depends on FUNCTION_TRACER

	depends on FUNCTION_TRACER

	depends on DEBUG_FS

	help

	help

	  With this option kernel traces function calls into a persistent

	  With this option kernel traces function calls into a persistent

	  ram buffer that can be decoded and dumped after reboot through

	  ram buffer that can be decoded and dumped after reboot through

fs/pstore/ftrace.c

+95 −1
Original line number Original line Diff line number Diff line
@@ -17,19 +17,113 @@ 
#include <linux/percpu.h>

#include <linux/percpu.h>

#include <linux/smp.h>

#include <linux/smp.h>

#include <linux/atomic.h>

#include <linux/atomic.h>

#include <linux/types.h>

#include <linux/mutex.h>

#include <linux/ftrace.h>

#include <linux/fs.h>

#include <linux/debugfs.h>

#include <linux/err.h>

#include <linux/cache.h>

#include <asm/barrier.h>

#include <asm/barrier.h>

#include "internal.h"

#include "internal.h"





void notrace pstore_ftrace_call(unsigned long ip, unsigned long parent_ip)

static void notrace pstore_ftrace_call(unsigned long ip,

				       unsigned long parent_ip)

{

{

	unsigned long flags;

	struct pstore_ftrace_record rec = {};

	struct pstore_ftrace_record rec = {};





	if (unlikely(oops_in_progress))

	if (unlikely(oops_in_progress))

		return;

		return;





	local_irq_save(flags);



	rec.ip = ip;

	rec.ip = ip;

	rec.parent_ip = parent_ip;

	rec.parent_ip = parent_ip;

	pstore_ftrace_encode_cpu(&rec, raw_smp_processor_id());

	pstore_ftrace_encode_cpu(&rec, raw_smp_processor_id());

	psinfo->write_buf(PSTORE_TYPE_FTRACE, 0, NULL, 0, (void *)&rec,

	psinfo->write_buf(PSTORE_TYPE_FTRACE, 0, NULL, 0, (void *)&rec,

			  sizeof(rec), psinfo);

			  sizeof(rec), psinfo);



	local_irq_restore(flags);

}



static struct ftrace_ops pstore_ftrace_ops __read_mostly = {

	.func	= pstore_ftrace_call,

};



static DEFINE_MUTEX(pstore_ftrace_lock);

static bool pstore_ftrace_enabled;



static ssize_t pstore_ftrace_knob_write(struct file *f, const char __user *buf,

					size_t count, loff_t *ppos)

{

	u8 on;

	ssize_t ret;



	ret = kstrtou8_from_user(buf, count, 2, &on);

	if (ret)

		return ret;



	mutex_lock(&pstore_ftrace_lock);



	if (!on ^ pstore_ftrace_enabled)

		goto out;



	if (on)

		ret = register_ftrace_function(&pstore_ftrace_ops);

	else

		ret = unregister_ftrace_function(&pstore_ftrace_ops);

	if (ret) {

		pr_err("%s: unable to %sregister ftrace ops: %zd\n",

		       __func__, on ? "" : "un", ret);

		goto err;

	}



	pstore_ftrace_enabled = on;

out:

	ret = count;

err:

	mutex_unlock(&pstore_ftrace_lock);



	return ret;

}



static ssize_t pstore_ftrace_knob_read(struct file *f, char __user *buf,

				       size_t count, loff_t *ppos)

{

	char val[] = { '0' + pstore_ftrace_enabled, '\n' };



	return simple_read_from_buffer(buf, count, ppos, val, sizeof(val));

}



static const struct file_operations pstore_knob_fops = {

	.open	= simple_open,

	.read	= pstore_ftrace_knob_read,

	.write	= pstore_ftrace_knob_write,

};



void pstore_register_ftrace(void)

{

	struct dentry *dir;

	struct dentry *file;



	if (!psinfo->write_buf)

		return;



	dir = debugfs_create_dir("pstore", NULL);

	if (!dir) {

		pr_err("%s: unable to create pstore directory\n", __func__);

		return;

	}



	file = debugfs_create_file("record_ftrace", 0600, dir, NULL,

				   &pstore_knob_fops);

	if (!file) {

		pr_err("%s: unable to create record_ftrace file\n", __func__);

		goto err_file;

	}



	return;

err_file:

	debugfs_remove(dir);

}
 
}

fs/pstore/internal.h

+6 −0
Original line number Original line Diff line number Diff line
@@ -39,6 +39,12 @@ pstore_ftrace_decode_cpu(struct pstore_ftrace_record *rec) 
#endif

#endif

}

}





#ifdef CONFIG_PSTORE_FTRACE

extern void pstore_register_ftrace(void);

#else

static inline void pstore_register_ftrace(void) {}

#endif



extern struct pstore_info *psinfo;

extern struct pstore_info *psinfo;





extern void	pstore_set_kmsg_bytes(int);

extern void	pstore_set_kmsg_bytes(int);

fs/pstore/platform.c

+1 −0
Original line number Original line Diff line number Diff line
@@ -236,6 +236,7 @@ int pstore_register(struct pstore_info *psi) 




	kmsg_dump_register(&pstore_dumper);

	kmsg_dump_register(&pstore_dumper);

	pstore_register_console();

	pstore_register_console();

	pstore_register_ftrace();





	if (pstore_update_ms >= 0) {

	if (pstore_update_ms >= 0) {

		pstore_timer.expires = jiffies +

		pstore_timer.expires = jiffies +