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Date: Tue, 2 Aug 2016 13:40:05 -0700
From: Andi Kleen <andi@...stfloor.org>
To: akpm@...ux-foundation.org
Cc: linux-kernel@...r.kernel.org, Andi Kleen <ak@...ux.intel.com>
Subject: [PATCH] Support resetting WARN*_ONCE
From: Andi Kleen <ak@...ux.intel.com>
WARN*_ONCE warnings only appear once.
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 flags into
a special section, and clearing it.
Signed-off-by: Andi Kleen <ak@...ux.intel.com>
---
include/asm-generic/bug.h | 6 +++---
include/asm-generic/sections.h | 1 +
include/asm-generic/vmlinux.lds.h | 3 +++
kernel/panic.c | 24 ++++++++++++++++++++++++
4 files changed, 31 insertions(+), 3 deletions(-)
diff --git a/include/asm-generic/bug.h b/include/asm-generic/bug.h
index 6f96247226a4..4dae133b51c9 100644
--- a/include/asm-generic/bug.h
+++ b/include/asm-generic/bug.h
@@ -113,7 +113,7 @@ void __warn(const char *file, int line, void *caller, unsigned taint,
})
#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)) { \
@@ -124,7 +124,7 @@ void __warn(const char *file, int line, void *caller, unsigned taint,
})
#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)) { \
@@ -135,7 +135,7 @@ 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)) { \
diff --git a/include/asm-generic/sections.h b/include/asm-generic/sections.h
index af0254c09424..0e9826a4acab 100644
--- a/include/asm-generic/sections.h
+++ b/include/asm-generic/sections.h
@@ -36,6 +36,7 @@ extern char __per_cpu_load[], __per_cpu_start[], __per_cpu_end[];
extern char __kprobes_text_start[], __kprobes_text_end[];
extern char __entry_text_start[], __entry_text_end[];
extern char __start_rodata[], __end_rodata[];
+extern char __start_once[], __end_once[];
/* Start and end of .ctors section - used for constructor calls. */
extern char __ctors_start[], __ctors_end[];
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 6a67ab94b553..4b8d43b7c07f 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -204,6 +204,9 @@
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 */ \
diff --git a/kernel/panic.c b/kernel/panic.c
index 8aa74497cc5a..4f52356f1562 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -25,6 +25,7 @@
#include <linux/nmi.h>
#include <linux/console.h>
#include <linux/bug.h>
+#include <linux/debugfs.h>
#define PANIC_TIMER_STEP 100
#define PANIC_BLINK_SPD 18
@@ -553,6 +554,29 @@ void warn_slowpath_null(const char *file, int line)
EXPORT_SYMBOL(warn_slowpath_null);
#endif
+/* 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;
+}
+
+__initcall(register_warn_debugfs);
+
#ifdef CONFIG_CC_STACKPROTECTOR
/*
--
2.5.5
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