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kernel debug: support resetting WARN*_ONCE

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I like _ONCE warnings because it's guaranteed that they don't flood the
log.

During testing I find it useful to reset the state of the once warnings,
so that I can rerun tests and see if they trigger again, or can
guarantee that a test run always hits the same warnings.

This patch adds a debugfs interface to reset all the _ONCE warnings so
that they appear again:

  echo 1 > /sys/kernel/debug/clear_warn_once

This is implemented by putting all the warning booleans into a special
section, and clearing it.

[akpm@linux-foundation.org: coding-style fixes]
Link: http://lkml.kernel.org/r/20171017221455.6740-1-andi@firstfloor.org
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Tested-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Andi Kleen
2017-11-17 15:27:03 -08:00
committed by Linus Torvalds
parent fb6cc4ac15
commit b1fca27d38
5 changed files with 42 additions and 3 deletions
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28
kernel/panic.c
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@@ -27,6 +27,8 @@
#include <linux/console.h>
#include <linux/bug.h>
#include <linux/ratelimit.h>
#include <linux/debugfs.h>
#include <asm/sections.h>
#define PANIC_TIMER_STEP 100
#define PANIC_BLINK_SPD 18
@@ -587,6 +589,32 @@ void warn_slowpath_null(const char *file, int line)
EXPORT_SYMBOL(warn_slowpath_null);
#endif
#ifdef CONFIG_BUG
/* Support resetting WARN*_ONCE state */
static int clear_warn_once_set(void *data, u64 val)
{
memset(__start_once, 0, __end_once - __start_once);
return 0;
}
DEFINE_SIMPLE_ATTRIBUTE(clear_warn_once_fops,
NULL,
clear_warn_once_set,
"%lld\n");
static __init int register_warn_debugfs(void)
{
/* Don't care about failure */
debugfs_create_file("clear_warn_once", 0644, NULL,
NULL, &clear_warn_once_fops);
return 0;
}
device_initcall(register_warn_debugfs);
#endif
#ifdef CONFIG_CC_STACKPROTECTOR
/*