x86_64, traps: Rework bad_iret

[pandora-kernel.git] / arch / x86 / kernel / traps.c

diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 48035e9..de801f2 100644 (file)
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -407,6 +407,35 @@ asmlinkage __visible struct pt_regs *sync_regs(struct pt_regs *eregs)
        return regs;
 }
 NOKPROBE_SYMBOL(sync_regs);
+
+struct bad_iret_stack {
+       void *error_entry_ret;
+       struct pt_regs regs;
+};
+
+asmlinkage __visible
+struct bad_iret_stack *fixup_bad_iret(struct bad_iret_stack *s)
+{
+       /*
+        * This is called from entry_64.S early in handling a fault
+        * caused by a bad iret to user mode.  To handle the fault
+        * correctly, we want move our stack frame to task_pt_regs
+        * and we want to pretend that the exception came from the
+        * iret target.
+        */
+       struct bad_iret_stack *new_stack =
+               container_of(task_pt_regs(current),
+                            struct bad_iret_stack, regs);
+
+       /* Copy the IRET target to the new stack. */
+       memmove(&new_stack->regs.ip, (void *)s->regs.sp, 5*8);
+
+       /* Copy the remainder of the stack from the current stack. */
+       memmove(new_stack, s, offsetof(struct bad_iret_stack, regs.ip));
+
+       BUG_ON(!user_mode_vm(&new_stack->regs));
+       return new_stack;
+}
 #endif
 
 /*