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linux-sg2042
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debug: Add _ONCE() logic to report_bug() 

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 a fair amount of text and some data:

  text         data       filename
  10682460     4530992    defconfig-build/vmlinux.orig
  10665111     4530096    defconfig-build/vmlinux.patched

Suggested-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Peter Zijlstra 2017-02-25 08:56:53 +01:00 committed by Ingo Molnar
parent 70579a86e3
commit 19d436268d
10 changed files with 52 additions and 25 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
arch/arm64/include/asm/bug.h
View File

@ -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 */

8
arch/parisc/include/asm/bug.h
View File

@ -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

4
arch/powerpc/include/asm/bug.h
View File

@ -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)

4
arch/s390/include/asm/bug.h
View File

@ -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) ({ \

4
arch/sh/include/asm/bug.h
View File

@ -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)

2
arch/x86/include/asm/bug.h
View File

@ -76,7 +76,7 @@ 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>

16
include/asm-generic/bug.h
View File

@ -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
@ -112,6 +126,7 @@ void __warn(const char *file, int line, void *caller, unsigned taint,
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, void *caller, unsigned taint,
} \
unlikely(__ret_warn_once); \
})
#endif
#define WARN_ONCE(condition, format...) ({ \
static bool __section(.data.unlikely) __warned; \

5
include/asm-generic/vmlinux.lds.h
View File

@ -286,8 +286,6 @@
*(.rodata1) \
} \
\
BUG_TABLE \
\
/* PCI quirks */ \
.pci_fixup : AT(ADDR(.pci_fixup) - LOAD_OFFSET) { \
VMLINUX_SYMBOL(__start_pci_fixups_early) = .; \
@ -855,7 +853,8 @@
READ_MOSTLY_DATA(cacheline) \
DATA_DATA \
CONSTRUCTORS \
}
} \
BUG_TABLE
#define INIT_TEXT_SECTION(inittext_align) \
. = ALIGN(inittext_align); \

2
include/linux/bug.h
View File

@ -105,7 +105,7 @@ static inline int is_warning_bug(const struct bug_entry *bug)
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);

28
lib/bug.c
View File

@ -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(const struct bug_entry *bug)
/* 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 *mod)
#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(unsigned long bugaddr)
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 long bugaddr, struct pt_regs *regs)
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) {