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-rw-r--r--arch/x86/include/asm/asm.h20
-rw-r--r--arch/x86/include/asm/uaccess.h17
-rw-r--r--arch/x86/mm/extable.c131
3 files changed, 146 insertions, 22 deletions
diff --git a/arch/x86/include/asm/asm.h b/arch/x86/include/asm/asm.h
index 0f15e8a..1c2d247 100644
--- a/arch/x86/include/asm/asm.h
+++ b/arch/x86/include/asm/asm.h
@@ -42,26 +42,30 @@
#ifdef __ASSEMBLY__
# define _ASM_EXTABLE(from,to) \
.pushsection "__ex_table","a" ; \
- _ASM_ALIGN ; \
- _ASM_PTR from , to ; \
+ .balign 8 ; \
+ .long (from) - . ; \
+ .long (to) - . ; \
.popsection
# define _ASM_EXTABLE_EX(from,to) \
.pushsection "__ex_table","a" ; \
- _ASM_ALIGN ; \
- _ASM_PTR from , (to) - (from) ; \
+ .balign 8 ; \
+ .long (from) - . ; \
+ .long (to) - . + 0x7ffffff0 ; \
.popsection
#else
# define _ASM_EXTABLE(from,to) \
" .pushsection \"__ex_table\",\"a\"\n" \
- _ASM_ALIGN "\n" \
- _ASM_PTR #from "," #to "\n" \
+ " .balign 8\n" \
+ " .long (" #from ") - .\n" \
+ " .long (" #to ") - .\n" \
" .popsection\n"
# define _ASM_EXTABLE_EX(from,to) \
" .pushsection \"__ex_table\",\"a\"\n" \
- _ASM_ALIGN "\n" \
- _ASM_PTR #from ",(" #to ")-(" #from ")\n" \
+ " .balign 8\n" \
+ " .long (" #from ") - .\n" \
+ " .long (" #to ") - . + 0x7ffffff0\n" \
" .popsection\n"
#endif
diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
index 4ee59dd..851fe0d 100644
--- a/arch/x86/include/asm/uaccess.h
+++ b/arch/x86/include/asm/uaccess.h
@@ -79,11 +79,12 @@
#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.
+ * The exception table consists of pairs of addresses relative to the
+ * exception table enty itself: 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,
@@ -92,10 +93,14 @@
*/
struct exception_table_entry {
- unsigned long insn, fixup;
+ int insn, fixup;
};
+/* This is not the generic standard exception_table_entry format */
+#define ARCH_HAS_SORT_EXTABLE
+#define ARCH_HAS_SEARCH_EXTABLE
extern int fixup_exception(struct pt_regs *regs);
+extern int early_fixup_exception(unsigned long *ip);
/*
* These are the main single-value transfer routines. They automatically
diff --git a/arch/x86/mm/extable.c b/arch/x86/mm/extable.c
index 5555675..903ec1e 100644
--- a/arch/x86/mm/extable.c
+++ b/arch/x86/mm/extable.c
@@ -1,11 +1,23 @@
#include <linux/module.h>
#include <linux/spinlock.h>
+#include <linux/sort.h>
#include <asm/uaccess.h>
+static inline unsigned long
+ex_insn_addr(const struct exception_table_entry *x)
+{
+ return (unsigned long)&x->insn + x->insn;
+}
+static inline unsigned long
+ex_fixup_addr(const struct exception_table_entry *x)
+{
+ return (unsigned long)&x->fixup + x->fixup;
+}
int fixup_exception(struct pt_regs *regs)
{
const struct exception_table_entry *fixup;
+ unsigned long new_ip;
#ifdef CONFIG_PNPBIOS
if (unlikely(SEGMENT_IS_PNP_CODE(regs->cs))) {
@@ -23,13 +35,14 @@ int fixup_exception(struct pt_regs *regs)
fixup = search_exception_tables(regs->ip);
if (fixup) {
- /* If fixup is less than 16, it means uaccess error */
- if (fixup->fixup < 16) {
+ new_ip = ex_fixup_addr(fixup);
+
+ if (fixup->fixup - fixup->insn >= 0x7ffffff0 - 4) {
+ /* Special hack for uaccess_err */
current_thread_info()->uaccess_err = 1;
- regs->ip += fixup->fixup;
- return 1;
+ new_ip -= 0x7ffffff0;
}
- regs->ip = fixup->fixup;
+ regs->ip = new_ip;
return 1;
}
@@ -40,15 +53,117 @@ int fixup_exception(struct pt_regs *regs)
int __init early_fixup_exception(unsigned long *ip)
{
const struct exception_table_entry *fixup;
+ unsigned long new_ip;
fixup = search_exception_tables(*ip);
if (fixup) {
- if (fixup->fixup < 16)
- return 0; /* Not supported during early boot */
+ new_ip = ex_fixup_addr(fixup);
+
+ if (fixup->fixup - fixup->insn >= 0x7ffffff0 - 4) {
+ /* uaccess handling not supported during early boot */
+ return 0;
+ }
- *ip = fixup->fixup;
+ *ip = new_ip;
return 1;
}
return 0;
}
+
+/*
+ * Search one exception table for an entry corresponding to the
+ * given instruction address, and return the address of the entry,
+ * or NULL if none is found.
+ * We use a binary search, and thus we assume that the table is
+ * already sorted.
+ */
+const struct exception_table_entry *
+search_extable(const struct exception_table_entry *first,
+ const struct exception_table_entry *last,
+ unsigned long value)
+{
+ while (first <= last) {
+ const struct exception_table_entry *mid;
+ unsigned long addr;
+
+ mid = ((last - first) >> 1) + first;
+ addr = ex_insn_addr(mid);
+ if (addr < value)
+ first = mid + 1;
+ else if (addr > value)
+ last = mid - 1;
+ else
+ return mid;
+ }
+ return NULL;
+}
+
+/*
+ * The exception table needs to be sorted so that the binary
+ * search that we use to find entries in it works properly.
+ * This is used both for the kernel exception table and for
+ * the exception tables of modules that get loaded.
+ *
+ */
+static int cmp_ex(const void *a, const void *b)
+{
+ const struct exception_table_entry *x = a, *y = b;
+
+ /*
+ * This value will always end up fittin in an int, because on
+ * both i386 and x86-64 the kernel symbol-reachable address
+ * space is < 2 GiB.
+ *
+ * This compare is only valid after normalization.
+ */
+ return x->insn - y->insn;
+}
+
+void sort_extable(struct exception_table_entry *start,
+ struct exception_table_entry *finish)
+{
+ struct exception_table_entry *p;
+ int i;
+
+ /* Convert all entries to being relative to the start of the section */
+ i = 0;
+ for (p = start; p < finish; p++) {
+ p->insn += i;
+ i += 4;
+ p->fixup += i;
+ i += 4;
+ }
+
+ sort(start, finish - start, sizeof(struct exception_table_entry),
+ cmp_ex, NULL);
+
+ /* Denormalize all entries */
+ i = 0;
+ for (p = start; p < finish; p++) {
+ p->insn -= i;
+ i += 4;
+ p->fixup -= i;
+ i += 4;
+ }
+}
+
+#ifdef CONFIG_MODULES
+/*
+ * If the exception table is sorted, any referring to the module init
+ * will be at the beginning or the end.
+ */
+void trim_init_extable(struct module *m)
+{
+ /*trim the beginning*/
+ while (m->num_exentries &&
+ within_module_init(ex_insn_addr(&m->extable[0]), m)) {
+ m->extable++;
+ m->num_exentries--;
+ }
+ /*trim the end*/
+ while (m->num_exentries &&
+ within_module_init(ex_insn_addr(&m->extable[m->num_exentries-1]), m))
+ m->num_exentries--;
+}
+#endif /* CONFIG_MODULES */
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