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Date: Tue, 16 Dec 2008 11:40:27 +0000
From: "Jan Beulich" <jbeulich@...ell.com>
To: <mingo@...e.hu>, <tglx@...utronix.de>,
<linux-kernel@...r.kernel.org>, <hpa@...or.com>
Cc: <linux-arch@...r.kernel.org>
Subject: [PATCH] allow bug table entries to use relative pointers (and
use it on x86-64)
This allows reducing the bug table size by half. Perhaps there are
other 64-bit architectures that could also make use of this.
Signed-off-by: Jan Beulich <jbeulich@...ell.com>
---
arch/x86/Kconfig | 4 ++++
arch/x86/include/asm/bug.h | 2 +-
include/asm-generic/bug.h | 8 ++++++++
lib/bug.c | 19 +++++++++++++++++--
4 files changed, 30 insertions(+), 3 deletions(-)
--- linux-2.6.28-rc8/arch/x86/Kconfig 2008-12-11 14:45:37.000000000 +0100
+++ 2.6.28-rc8-x86_64-bug-rel-addr/arch/x86/Kconfig 2008-12-01 14:10:32.000000000 +0100
@@ -87,6 +87,10 @@ config GENERIC_IOMAP
config GENERIC_BUG
def_bool y
depends on BUG
+ select GENERIC_BUG_RELATIVE_POINTERS if X86_64
+
+config GENERIC_BUG_RELATIVE_POINTERS
+ bool
config GENERIC_HWEIGHT
def_bool y
--- linux-2.6.28-rc8/arch/x86/include/asm/bug.h 2008-12-11 14:45:37.000000000 +0100
+++ 2.6.28-rc8-x86_64-bug-rel-addr/arch/x86/include/asm/bug.h 2008-12-01 14:12:17.000000000 +0100
@@ -9,7 +9,7 @@
#ifdef CONFIG_X86_32
# define __BUG_C0 "2:\t.long 1b, %c0\n"
#else
-# define __BUG_C0 "2:\t.quad 1b, %c0\n"
+# define __BUG_C0 "2:\t.long 1b - 2b, %c0 - 2b\n"
#endif
#define BUG() \
--- linux-2.6.28-rc8/include/asm-generic/bug.h 2008-12-11 14:46:04.000000000 +0100
+++ 2.6.28-rc8-x86_64-bug-rel-addr/include/asm-generic/bug.h 2008-12-01 14:13:35.000000000 +0100
@@ -8,9 +8,17 @@
#ifdef CONFIG_GENERIC_BUG
#ifndef __ASSEMBLY__
struct bug_entry {
+#ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
unsigned long bug_addr;
+#else
+ signed int bug_addr_disp;
+#endif
#ifdef CONFIG_DEBUG_BUGVERBOSE
+#ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
const char *file;
+#else
+ signed int file_disp;
+#endif
unsigned short line;
#endif
unsigned short flags;
--- linux-2.6.28-rc8/lib/bug.c 2008-07-13 23:51:29.000000000 +0200
+++ 2.6.28-rc8-x86_64-bug-rel-addr/lib/bug.c 2008-12-01 14:18:37.000000000 +0100
@@ -5,6 +5,8 @@
CONFIG_BUG - emit BUG traps. Nothing happens without this.
CONFIG_GENERIC_BUG - enable this code.
+ CONFIG_GENERIC_BUG_RELATIVE_POINTERS - use 32-bit pointers relative to
+ the containing struct bug_entry for bug_addr and file.
CONFIG_DEBUG_BUGVERBOSE - emit full file+line information for each BUG
CONFIG_BUG and CONFIG_DEBUG_BUGVERBOSE are potentially user-settable
@@ -43,6 +45,15 @@
extern const struct bug_entry __start___bug_table[], __stop___bug_table[];
+static inline unsigned long bug_addr(const struct bug_entry *bug)
+{
+#ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
+ return bug->bug_addr;
+#else
+ return (unsigned long)bug + bug->bug_addr_disp;
+#endif
+}
+
#ifdef CONFIG_MODULES
static LIST_HEAD(module_bug_list);
@@ -55,7 +66,7 @@ static const struct bug_entry *module_fi
unsigned i;
for (i = 0; i < mod->num_bugs; ++i, ++bug)
- if (bugaddr == bug->bug_addr)
+ if (bugaddr == bug_addr(bug))
return bug;
}
return NULL;
@@ -108,7 +119,7 @@ const struct bug_entry *find_bug(unsigne
const struct bug_entry *bug;
for (bug = __start___bug_table; bug < __stop___bug_table; ++bug)
- if (bugaddr == bug->bug_addr)
+ if (bugaddr == bug_addr(bug))
return bug;
return module_find_bug(bugaddr);
@@ -133,7 +144,11 @@ enum bug_trap_type report_bug(unsigned l
if (bug) {
#ifdef CONFIG_DEBUG_BUGVERBOSE
+#ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
file = bug->file;
+#else
+ file = (const char *)bug + bug->file_disp;
+#endif
line = bug->line;
#endif
warning = (bug->flags & BUGFLAG_WARNING) != 0;
--
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