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Date: Thu, 17 Feb 2011 17:03:26 +0000
From: "Jan Beulich" <JBeulich@...ell.com>
To: <mingo@...e.hu>, <tglx@...utronix.de>, <hpa@...or.com>
Cc: <tony.luck@...el.com>, <linux-kernel@...r.kernel.org>
Subject: [PATCH 2/3] x86-64: use relative 32-bit pointers in exception
tables
Convert exception table pointers from absolute 64-bit to relative 32-
bit ones, thus shrinking the table size by half. Rather than providing
an x86-64-specific extable implementation, generalize the common one
to deal with different ways of storing the pointers, which will allow
ia64's custom implementation to be dropped subsequently.
Signed-off-by: Jan Beulich <jbeulich@...ell.com>
Cc: Tony Luck <tony.luck@...el.com>
---
arch/Kconfig | 3 ++
arch/x86/Kconfig | 1
arch/x86/include/asm/asm.h | 8 +++---
arch/x86/include/asm/uaccess.h | 17 --------------
arch/x86/mm/extable.c | 8 ++++--
include/asm-generic/extable.h | 49 +++++++++++++++++++++++++++++++++++++++++
include/asm-generic/uaccess.h | 21 -----------------
lib/extable.c | 39 ++++++++++++++++++++++++++------
8 files changed, 96 insertions(+), 50 deletions(-)
--- 2.6.38-rc5-extable.orig/arch/Kconfig
+++ 2.6.38-rc5-extable/arch/Kconfig
@@ -61,6 +61,9 @@ config OPTPROBES
depends on KPROBES && HAVE_OPTPROBES
depends on !PREEMPT
+config EXTABLE_RELATIVE_POINTERS
+ bool
+
config HAVE_EFFICIENT_UNALIGNED_ACCESS
bool
help
--- 2.6.38-rc5-extable.orig/arch/x86/Kconfig
+++ 2.6.38-rc5-extable/arch/x86/Kconfig
@@ -11,6 +11,7 @@ config X86_32
config X86_64
def_bool 64BIT
+ select EXTABLE_RELATIVE_POINTERS
### Arch settings
config X86
--- 2.6.38-rc5-extable.orig/arch/x86/include/asm/asm.h
+++ 2.6.38-rc5-extable/arch/x86/include/asm/asm.h
@@ -41,14 +41,14 @@
#ifdef __ASSEMBLY__
# define _ASM_EXTABLE(from,to) \
__ASM_EX_SEC ; \
- _ASM_ALIGN ; \
- _ASM_PTR from , to ; \
+ .balign 4 ; \
+ .long from __ASM_SEL(,-.), to __ASM_SEL(,-.) ; \
.previous
#else
# define _ASM_EXTABLE(from,to) \
__ASM_EX_SEC \
- _ASM_ALIGN "\n" \
- _ASM_PTR #from "," #to "\n" \
+ " .balign 4\n" \
+ " .long " #from __ASM_SEL(,-.) "," #to __ASM_SEL(,-.) "\n" \
" .previous\n"
#endif
--- 2.6.38-rc5-extable.orig/arch/x86/include/asm/uaccess.h
+++ 2.6.38-rc5-extable/arch/x86/include/asm/uaccess.h
@@ -79,22 +79,7 @@
*/
#define access_ok(type, addr, size) (likely(__range_not_ok(addr, size) == 0))
-/*
- * The exception table consists of pairs of addresses: the first is the
- * address of an instruction that is allowed to fault, and the second is
- * the address at which the program should continue. No registers are
- * modified, so it is entirely up to the continuation code to figure out
- * what to do.
- *
- * All the routines below use bits of fixup code that are out of line
- * with the main instruction path. This means when everything is well,
- * we don't even have to jump over them. Further, they do not intrude
- * on our cache or tlb entries.
- */
-
-struct exception_table_entry {
- unsigned long insn, fixup;
-};
+#include <asm-generic/extable.h>
extern int fixup_exception(struct pt_regs *regs);
--- 2.6.38-rc5-extable.orig/arch/x86/mm/extable.c
+++ 2.6.38-rc5-extable/arch/x86/mm/extable.c
@@ -23,13 +23,15 @@ int fixup_exception(struct pt_regs *regs
fixup = search_exception_tables(regs->ip);
if (fixup) {
+ unsigned long addr = ex_fixup(fixup);
+
/* If fixup is less than 16, it means uaccess error */
- if (fixup->fixup < 16) {
+ if (addr < 16) {
current_thread_info()->uaccess_err = -EFAULT;
- regs->ip += fixup->fixup;
+ regs->ip += addr;
return 1;
}
- regs->ip = fixup->fixup;
+ regs->ip = addr;
return 1;
}
--- /dev/null
+++ 2.6.38-rc5-extable/include/asm-generic/extable.h
@@ -0,0 +1,49 @@
+#ifndef __ASM_GENERIC_EXTABLE_H
+#define __ASM_GENERIC_EXTABLE_H
+
+/*
+ * The exception table consists of pairs of addresses: the first is the
+ * address of an instruction that is allowed to fault, and the second is
+ * the address at which the program should continue. No registers are
+ * modified, so it is entirely up to the continuation code to figure out
+ * what to do.
+ *
+ * All the routines below use bits of fixup code that are out of line
+ * with the main instruction path. This means when everything is well,
+ * we don't even have to jump over them. Further, they do not intrude
+ * on our cache or tlb entries.
+ */
+
+struct exception_table_entry
+{
+#ifdef CONFIG_EXTABLE_RELATIVE_POINTERS
+ s32 insn_off, fixup_off;
+#else
+ unsigned long insn, fixup;
+#endif
+};
+
+#ifdef CONFIG_EXTABLE_RELATIVE_POINTERS
+#define EX_FIELD(ptr, field) \
+ ((unsigned long)&(ptr)->field##_off + (ptr)->field##_off)
+#else
+#define EX_FIELD(ptr, field) (ptr)->field
+#endif
+
+static inline unsigned long ex_insn(const struct exception_table_entry *x)
+{
+ return EX_FIELD(x, insn);
+}
+#define ex_insn ex_insn /* until all architectures have this accessor */
+
+static inline unsigned long ex_fixup(const struct exception_table_entry *x)
+{
+ return EX_FIELD(x, fixup);
+}
+
+#undef EX_FIELD
+
+/* Returns 0 if exception not found and fixup otherwise. */
+extern unsigned long search_exception_table(unsigned long);
+
+#endif /* __ASM_GENERIC_EXTABLE_H */
--- 2.6.38-rc5-extable.orig/include/asm-generic/uaccess.h
+++ 2.6.38-rc5-extable/include/asm-generic/uaccess.h
@@ -50,26 +50,7 @@ static inline int __access_ok(unsigned l
}
#endif
-/*
- * The exception table consists of pairs of addresses: the first is the
- * address of an instruction that is allowed to fault, and the second is
- * the address at which the program should continue. No registers are
- * modified, so it is entirely up to the continuation code to figure out
- * what to do.
- *
- * All the routines below use bits of fixup code that are out of line
- * with the main instruction path. This means when everything is well,
- * we don't even have to jump over them. Further, they do not intrude
- * on our cache or tlb entries.
- */
-
-struct exception_table_entry
-{
- unsigned long insn, fixup;
-};
-
-/* Returns 0 if exception not found and fixup otherwise. */
-extern unsigned long search_exception_table(unsigned long);
+#include "extable.h"
/*
* architectures with an MMU should override these two
--- 2.6.38-rc5-extable.orig/lib/extable.c
+++ 2.6.38-rc5-extable/lib/extable.c
@@ -14,6 +14,10 @@
#include <linux/sort.h>
#include <asm/uaccess.h>
+#ifndef ex_insn /* until all architectures have this accessor */
+#define ex_insn(x) (x)->insn
+#endif
+
#ifndef ARCH_HAS_SORT_EXTABLE
/*
* The exception table needs to be sorted so that the binary
@@ -24,20 +28,38 @@
static int cmp_ex(const void *a, const void *b)
{
const struct exception_table_entry *x = a, *y = b;
+ unsigned long xinsn = ex_insn(x);
+ unsigned long yinsn = ex_insn(y);
/* avoid overflow */
- if (x->insn > y->insn)
+ if (xinsn > yinsn)
return 1;
- if (x->insn < y->insn)
+ if (xinsn < yinsn)
return -1;
return 0;
}
+#ifdef CONFIG_EXTABLE_RELATIVE_POINTERS
+static void swap_ex(void *a, void *b, int size)
+{
+ struct exception_table_entry *x = a, *y = b, tmp;
+ long delta = b - a;
+
+ tmp = *x;
+ x->insn_off = y->insn_off + delta;
+ x->fixup_off = y->fixup_off + delta;
+ y->insn_off = tmp.insn_off - delta;
+ y->fixup_off = tmp.fixup_off - delta;
+}
+#else
+#define swap_ex NULL
+#endif
+
void sort_extable(struct exception_table_entry *start,
struct exception_table_entry *finish)
{
sort(start, finish - start, sizeof(struct exception_table_entry),
- cmp_ex, NULL);
+ cmp_ex, swap_ex);
}
#ifdef CONFIG_MODULES
@@ -48,13 +70,15 @@ void sort_extable(struct exception_table
void trim_init_extable(struct module *m)
{
/*trim the beginning*/
- while (m->num_exentries && within_module_init(m->extable[0].insn, m)) {
+ while (m->num_exentries &&
+ within_module_init(ex_insn(m->extable), m)) {
m->extable++;
m->num_exentries--;
}
/*trim the end*/
while (m->num_exentries &&
- within_module_init(m->extable[m->num_exentries-1].insn, m))
+ within_module_init(ex_insn(m->extable + m->num_exentries - 1),
+ m))
m->num_exentries--;
}
#endif /* CONFIG_MODULES */
@@ -68,6 +92,7 @@ void trim_init_extable(struct module *m)
* We use a binary search, and thus we assume that the table is
* already sorted.
*/
+#include <linux/kallsyms.h>//temp
const struct exception_table_entry *
search_extable(const struct exception_table_entry *first,
const struct exception_table_entry *last,
@@ -81,9 +106,9 @@ search_extable(const struct exception_ta
* careful, the distance between value and insn
* can be larger than MAX_LONG:
*/
- if (mid->insn < value)
+ if (ex_insn(mid) < value)
first = mid + 1;
- else if (mid->insn > value)
+ else if (ex_insn(mid) > value)
last = mid - 1;
else
return mid;
--
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