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authorLinus Torvalds <torvalds@linux-foundation.org>2012-05-23 10:44:35 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2012-05-23 10:44:35 -0700
commit269af9a1a08d368b46d72e74126564d04c354f7e (patch)
treef0f2a8dd54075edebbb728602822e2b7378588d0 /arch/x86/mm
parent8ca038dc10eec80f280d9d483f1835ac2763a787 (diff)
parent8b5ad472991796b2347464922c72de2ca5a028f3 (diff)
downloadop-kernel-dev-269af9a1a08d368b46d72e74126564d04c354f7e.zip
op-kernel-dev-269af9a1a08d368b46d72e74126564d04c354f7e.tar.gz
Merge branch 'x86-extable-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull exception table generation updates from Ingo Molnar: "The biggest change here is to allow the build-time sorting of the exception table, to speed up booting. This is achieved by the architecture enabling BUILDTIME_EXTABLE_SORT. This option is enabled for x86 and MIPS currently. On x86 a number of fixes and changes were needed to allow build-time sorting of the exception table, in particular a relocation invariant exception table format was needed. This required the abstracting out of exception table protocol and the removal of 20 years of accumulated assumptions about the x86 exception table format. While at it, this tree also cleans up various other aspects of exception handling, such as early(er) exception handling for rdmsr_safe() et al. All in one, as the result of these changes the x86 exception code is now pretty nice and modern. As an added bonus any regressions in this code will be early and violent crashes, so if you see any of those, you'll know whom to blame!" Fix up trivial conflicts in arch/{mips,x86}/Kconfig files due to nearby modifications of other core architecture options. * 'x86-extable-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (35 commits) Revert "x86, extable: Disable presorted exception table for now" scripts/sortextable: Handle relative entries, and other cleanups x86, extable: Switch to relative exception table entries x86, extable: Disable presorted exception table for now x86, extable: Add _ASM_EXTABLE_EX() macro x86, extable: Remove open-coded exception table entries in arch/x86/ia32/ia32entry.S x86, extable: Remove open-coded exception table entries in arch/x86/include/asm/xsave.h x86, extable: Remove open-coded exception table entries in arch/x86/include/asm/kvm_host.h x86, extable: Remove the now-unused __ASM_EX_SEC macros x86, extable: Remove open-coded exception table entries in arch/x86/xen/xen-asm_32.S x86, extable: Remove open-coded exception table entries in arch/x86/um/checksum_32.S x86, extable: Remove open-coded exception table entries in arch/x86/lib/usercopy_32.c x86, extable: Remove open-coded exception table entries in arch/x86/lib/putuser.S x86, extable: Remove open-coded exception table entries in arch/x86/lib/getuser.S x86, extable: Remove open-coded exception table entries in arch/x86/lib/csum-copy_64.S x86, extable: Remove open-coded exception table entries in arch/x86/lib/copy_user_nocache_64.S x86, extable: Remove open-coded exception table entries in arch/x86/lib/copy_user_64.S x86, extable: Remove open-coded exception table entries in arch/x86/lib/checksum_32.S x86, extable: Remove open-coded exception table entries in arch/x86/kernel/test_rodata.c x86, extable: Remove open-coded exception table entries in arch/x86/kernel/entry_64.S ...
Diffstat (limited to 'arch/x86/mm')
-rw-r--r--arch/x86/mm/extable.c142
1 files changed, 137 insertions, 5 deletions
diff --git a/arch/x86/mm/extable.c b/arch/x86/mm/extable.c
index 1fb85db..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))) {
@@ -23,15 +35,135 @@ 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;
}
return 0;
}
+
+/* Restricted version used during very early boot */
+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) {
+ new_ip = ex_fixup_addr(fixup);
+
+ if (fixup->fixup - fixup->insn >= 0x7ffffff0 - 4) {
+ /* uaccess handling not supported during early boot */
+ return 0;
+ }
+
+ *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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