[RFC][PATCH] bug: Add _ONCE logic to report_bug()
From: Peter Zijlstra
Date: Sat Feb 25 2017 - 04:01:59 EST
Josh suggested moving the _ONCE logic inside the trap handler, using a
bit in the bug_entry::flags field, avoiding the need for the extra
variable.
Sadly this only works for WARN_ON_ONCE(), since the others have
printk() statements prior to triggering the trap.
Still, this saves some text and data:
text data bss dec hex filename
10469505 4443448 843776 15756729 f06db9 defconfig-build/vmlinux-ud0
10452803 4442616 843776 15739195 f0293b defconfig-build/vmlinux-ud0-once
(Only compile tested on x86_64 so far.)
Suggested-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
---
arch/arm64/include/asm/bug.h | 2 +-
arch/parisc/include/asm/bug.h | 8 ++++----
arch/powerpc/include/asm/bug.h | 4 ++--
arch/s390/include/asm/bug.h | 4 ++--
arch/sh/include/asm/bug.h | 4 ++--
arch/x86/include/asm/bug.h | 2 +-
include/asm-generic/bug.h | 18 +++++++++++++++++-
include/asm-generic/vmlinux.lds.h | 3 +--
include/linux/bug.h | 2 +-
lib/bug.c | 28 ++++++++++++++++++++--------
10 files changed, 51 insertions(+), 24 deletions(-)
--- a/arch/arm64/include/asm/bug.h
+++ b/arch/arm64/include/asm/bug.h
@@ -55,7 +55,7 @@ _BUGVERBOSE_LOCATION(__FILE__, __LINE__)
unreachable(); \
} while (0)
-#define __WARN_TAINT(taint) _BUG_FLAGS(BUGFLAG_TAINT(taint))
+#define __WARN_FLAGS(flags) _BUG_FLAGS(BUGFLAG_WARNING|(flags))
#endif /* ! CONFIG_GENERIC_BUG */
--- a/arch/parisc/include/asm/bug.h
+++ b/arch/parisc/include/asm/bug.h
@@ -46,7 +46,7 @@
#endif
#ifdef CONFIG_DEBUG_BUGVERBOSE
-#define __WARN_TAINT(taint) \
+#define __WARN_FLAGS(flags) \
do { \
asm volatile("\n" \
"1:\t" PARISC_BUG_BREAK_ASM "\n" \
@@ -56,11 +56,11 @@
"\t.org 2b+%c3\n" \
"\t.popsection" \
: : "i" (__FILE__), "i" (__LINE__), \
- "i" (BUGFLAG_TAINT(taint)), \
+ "i" (BUGFLAG_WARNING|(flags)), \
"i" (sizeof(struct bug_entry)) ); \
} while(0)
#else
-#define __WARN_TAINT(taint) \
+#define __WARN_FLAGS(flags) \
do { \
asm volatile("\n" \
"1:\t" PARISC_BUG_BREAK_ASM "\n" \
@@ -69,7 +69,7 @@
"\t.short %c0\n" \
"\t.org 2b+%c1\n" \
"\t.popsection" \
- : : "i" (BUGFLAG_TAINT(taint)), \
+ : : "i" (BUGFLAG_WARNING|(flags)), \
"i" (sizeof(struct bug_entry)) ); \
} while(0)
#endif
--- a/arch/powerpc/include/asm/bug.h
+++ b/arch/powerpc/include/asm/bug.h
@@ -85,12 +85,12 @@
} \
} while (0)
-#define __WARN_TAINT(taint) do { \
+#define __WARN_FLAGS(flags) do { \
__asm__ __volatile__( \
"1: twi 31,0,0\n" \
_EMIT_BUG_ENTRY \
: : "i" (__FILE__), "i" (__LINE__), \
- "i" (BUGFLAG_TAINT(taint)), \
+ "i" (BUGFLAG_WARNING|(flags)), \
"i" (sizeof(struct bug_entry))); \
} while (0)
--- a/arch/s390/include/asm/bug.h
+++ b/arch/s390/include/asm/bug.h
@@ -46,8 +46,8 @@
unreachable(); \
} while (0)
-#define __WARN_TAINT(taint) do { \
- __EMIT_BUG(BUGFLAG_TAINT(taint)); \
+#define __WARN_FLAGS(flags) do { \
+ __EMIT_BUG(BUGFLAG_WARNING|(flags)); \
} while (0)
#define WARN_ON(x) ({ \
--- a/arch/sh/include/asm/bug.h
+++ b/arch/sh/include/asm/bug.h
@@ -50,7 +50,7 @@ do { \
"i" (sizeof(struct bug_entry))); \
} while (0)
-#define __WARN_TAINT(taint) \
+#define __WARN_FLAGS(flags) \
do { \
__asm__ __volatile__ ( \
"1:\t.short %O0\n" \
@@ -59,7 +59,7 @@ do { \
: "n" (TRAPA_BUG_OPCODE), \
"i" (__FILE__), \
"i" (__LINE__), \
- "i" (BUGFLAG_TAINT(taint)), \
+ "i" (BUGFLAG_WARNING|(flags)), \
"i" (sizeof(struct bug_entry))); \
} while (0)
--- a/arch/x86/include/asm/bug.h
+++ b/arch/x86/include/asm/bug.h
@@ -64,7 +64,7 @@ do { \
unreachable(); \
} while (0)
-#define __WARN_TAINT(taint) _BUG_FLAGS(ASM_UD0, BUGFLAG_TAINT(taint))
+#define __WARN_FLAGS(flags) _BUG_FLAGS(ASM_UD0, BUGFLAG_WARNING|(flags))
#include <asm-generic/bug.h>
--- a/include/asm-generic/bug.h
+++ b/include/asm-generic/bug.h
@@ -5,6 +5,8 @@
#ifdef CONFIG_GENERIC_BUG
#define BUGFLAG_WARNING (1 << 0)
+#define BUGFLAG_ONCE (1 << 1)
+#define BUGFLAG_DONE (1 << 2)
#define BUGFLAG_TAINT(taint) (BUGFLAG_WARNING | ((taint) << 8))
#define BUG_GET_TAINT(bug) ((bug)->flags >> 8)
#endif
@@ -55,6 +57,18 @@ struct bug_entry {
#define BUG_ON(condition) do { if (unlikely(condition)) BUG(); } while (0)
#endif
+#ifdef __WARN_FLAGS
+#define __WARN_TAINT(taint) __WARN_FLAGS(BUGFLAG_TAINT(taint))
+#define __WARN_ONCE_TAINT(taint) __WARN_FLAGS(BUGFLAG_ONCE|BUGFLAG_TAINT(taint))
+
+#define WARN_ON_ONCE(condition) ({ \
+ int __ret_warn_on = !!(condition); \
+ if (unlikely(__ret_warn_on)) \
+ __WARN_ONCE_TAINT(TAINT_WARN); \
+ unlikely(__ret_warn_on); \
+})
+#endif
+
/*
* WARN(), WARN_ON(), WARN_ON_ONCE, and so on can be used to report
* significant issues that need prompt attention if they should ever
@@ -97,7 +111,7 @@ void __warn(const char *file, int line,
#endif
#ifndef WARN
-#define WARN(condition, format...) ({ \
+#define WARN(condition, format...) ({ \
int __ret_warn_on = !!(condition); \
if (unlikely(__ret_warn_on)) \
__WARN_printf(format); \
@@ -112,6 +126,7 @@ void __warn(const char *file, int line,
unlikely(__ret_warn_on); \
})
+#ifndef WARN_ON_ONCE
#define WARN_ON_ONCE(condition) ({ \
static bool __section(.data.unlikely) __warned; \
int __ret_warn_once = !!(condition); \
@@ -122,6 +137,7 @@ void __warn(const char *file, int line,
} \
unlikely(__ret_warn_once); \
})
+#endif
#define WARN_ONCE(condition, format...) ({ \
static bool __section(.data.unlikely) __warned; \
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -286,8 +286,6 @@
*(.rodata1) \
} \
\
- BUG_TABLE \
- \
/* PCI quirks */ \
.pci_fixup : AT(ADDR(.pci_fixup) - LOAD_OFFSET) { \
VMLINUX_SYMBOL(__start_pci_fixups_early) = .; \
@@ -855,6 +853,7 @@
READ_MOSTLY_DATA(cacheline) \
DATA_DATA \
CONSTRUCTORS \
+ BUG_TABLE \
}
#define INIT_TEXT_SECTION(inittext_align) \
--- a/include/linux/bug.h
+++ b/include/linux/bug.h
@@ -105,7 +105,7 @@ static inline int is_warning_bug(const s
return bug->flags & BUGFLAG_WARNING;
}
-const struct bug_entry *find_bug(unsigned long bugaddr);
+struct bug_entry *find_bug(unsigned long bugaddr);
enum bug_trap_type report_bug(unsigned long bug_addr, struct pt_regs *regs);
--- a/lib/bug.c
+++ b/lib/bug.c
@@ -47,7 +47,7 @@
#include <linux/sched.h>
#include <linux/rculist.h>
-extern const struct bug_entry __start___bug_table[], __stop___bug_table[];
+extern struct bug_entry __start___bug_table[], __stop___bug_table[];
static inline unsigned long bug_addr(const struct bug_entry *bug)
{
@@ -62,10 +62,10 @@ static inline unsigned long bug_addr(con
/* Updates are protected by module mutex */
static LIST_HEAD(module_bug_list);
-static const struct bug_entry *module_find_bug(unsigned long bugaddr)
+static struct bug_entry *module_find_bug(unsigned long bugaddr)
{
struct module *mod;
- const struct bug_entry *bug = NULL;
+ struct bug_entry *bug = NULL;
rcu_read_lock_sched();
list_for_each_entry_rcu(mod, &module_bug_list, bug_list) {
@@ -122,15 +122,15 @@ void module_bug_cleanup(struct module *m
#else
-static inline const struct bug_entry *module_find_bug(unsigned long bugaddr)
+static inline struct bug_entry *module_find_bug(unsigned long bugaddr)
{
return NULL;
}
#endif
-const struct bug_entry *find_bug(unsigned long bugaddr)
+struct bug_entry *find_bug(unsigned long bugaddr)
{
- const struct bug_entry *bug;
+ struct bug_entry *bug;
for (bug = __start___bug_table; bug < __stop___bug_table; ++bug)
if (bugaddr == bug_addr(bug))
@@ -141,9 +141,9 @@ const struct bug_entry *find_bug(unsigne
enum bug_trap_type report_bug(unsigned long bugaddr, struct pt_regs *regs)
{
- const struct bug_entry *bug;
+ struct bug_entry *bug;
const char *file;
- unsigned line, warning;
+ unsigned line, warning, once, done;
if (!is_valid_bugaddr(bugaddr))
return BUG_TRAP_TYPE_NONE;
@@ -164,6 +164,18 @@ enum bug_trap_type report_bug(unsigned l
line = bug->line;
#endif
warning = (bug->flags & BUGFLAG_WARNING) != 0;
+ once = (bug->flags & BUGFLAG_ONCE) != 0;
+ done = (bug->flags & BUGFLAG_DONE) != 0;
+
+ if (warning && once) {
+ if (done)
+ return BUG_TRAP_TYPE_WARN;
+
+ /*
+ * Since this is the only store, concurrency is not an issue.
+ */
+ bug->flags |= BUGFLAG_DONE;
+ }
}
if (warning) {