1 files changed, 123 insertions, 8 deletions

diff --git a/arch/x86/mm/extable.c b/arch/x86/mm/extable.c
index 5555675dadb6..903ec1e9c326 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 */