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-rw-r--r--arch/x86/mm/extable.c169
1 files changed, 169 insertions, 0 deletions
diff --git a/arch/x86/mm/extable.c b/arch/x86/mm/extable.c
new file mode 100644
index 000000000..903ec1e9c
--- /dev/null
+++ b/arch/x86/mm/extable.c
@@ -0,0 +1,169 @@
+#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))) {
+ extern u32 pnp_bios_fault_eip, pnp_bios_fault_esp;
+ extern u32 pnp_bios_is_utter_crap;
+ pnp_bios_is_utter_crap = 1;
+ printk(KERN_CRIT "PNPBIOS fault.. attempting recovery.\n");
+ __asm__ volatile(
+ "movl %0, %%esp\n\t"
+ "jmp *%1\n\t"
+ : : "g" (pnp_bios_fault_esp), "g" (pnp_bios_fault_eip));
+ panic("do_trap: can't hit this");
+ }
+#endif
+
+ fixup = search_exception_tables(regs->ip);
+ if (fixup) {
+ new_ip = ex_fixup_addr(fixup);
+
+ if (fixup->fixup - fixup->insn >= 0x7ffffff0 - 4) {
+ /* Special hack for uaccess_err */
+ current_thread_info()->uaccess_err = 1;
+ new_ip -= 0x7ffffff0;
+ }
+ 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 */