Commit b1fca27d authored by Andi Kleen's avatar Andi Kleen Committed by Linus Torvalds
Browse files

kernel debug: support resetting WARN*_ONCE 

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: default avatarAndi Kleen <ak@linux.intel.com>
Tested-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent fb6cc4ac

Documentation/clearing-warn-once.txt

0 → 100644
+7 −0
Original line number Diff line number Diff line 


WARN_ONCE / WARN_ON_ONCE only print a warning once.



echo 1 > /sys/kernel/debug/clear_warn_once



clears the state and allows the warnings to print once again.

This can be useful after test suite runs to reproduce problems.

include/asm-generic/bug.h

+3 −3
Original line number Diff line number Diff line
@@ -130,7 +130,7 @@ void __warn(const char *file, int line, void *caller, unsigned taint, 


#ifndef WARN_ON_ONCE

#define WARN_ON_ONCE(condition)	({				\

	static bool __section(.data.unlikely) __warned;		\

	static bool __section(.data.once) __warned;		\

	int __ret_warn_once = !!(condition);			\

								\

	if (unlikely(__ret_warn_once && !__warned)) {		\
@@ -142,7 +142,7 @@ void __warn(const char *file, int line, void *caller, unsigned taint, 
#endif



#define WARN_ONCE(condition, format...)	({			\

	static bool __section(.data.unlikely) __warned;		\

	static bool __section(.data.once) __warned;		\

	int __ret_warn_once = !!(condition);			\

								\

	if (unlikely(__ret_warn_once && !__warned)) {		\
@@ -153,7 +153,7 @@ void __warn(const char *file, int line, void *caller, unsigned taint, 
})



#define WARN_TAINT_ONCE(condition, taint, format...)	({	\

	static bool __section(.data.unlikely) __warned;		\

	static bool __section(.data.once) __warned;		\

	int __ret_warn_once = !!(condition);			\

								\

	if (unlikely(__ret_warn_once && !__warned)) {		\

include/asm-generic/sections.h

+1 −0
Original line number Diff line number Diff line
@@ -44,6 +44,7 @@ extern char __entry_text_start[], __entry_text_end[]; 
extern char __start_rodata[], __end_rodata[];

extern char __irqentry_text_start[], __irqentry_text_end[];

extern char __softirqentry_text_start[], __softirqentry_text_end[];

extern char __start_once[], __end_once[];



/* Start and end of .ctors section - used for constructor calls. */

extern char __ctors_start[], __ctors_end[];

include/asm-generic/vmlinux.lds.h

+3 −0
Original line number Diff line number Diff line
@@ -223,6 +223,9 @@ 
	MEM_KEEP(init.data)						\

	MEM_KEEP(exit.data)						\

	*(.data.unlikely)						\

	VMLINUX_SYMBOL(__start_once) = .;				\

	*(.data.once)							\

	VMLINUX_SYMBOL(__end_once) = .;					\

	STRUCT_ALIGN();							\

	*(__tracepoints)						\

	/* implement dynamic printk debug */				\

kernel/panic.c

+28 −0
Original line number Diff line number Diff line
@@ -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



/*

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