Merge branch 'x86-mpx-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git...

[cascardo/linux.git] / arch / x86 / kernel / traps.c

diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index f73fc4a..88900e2 100644 (file)
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -233,32 +233,40 @@ DO_ERROR(X86_TRAP_UD,     SIGILL,  "invalid opcode",              invalid_op)
 DO_ERROR(X86_TRAP_OLD_MF, SIGFPE,  "coprocessor segment overrun",coprocessor_segment_overrun)
 DO_ERROR(X86_TRAP_TS,     SIGSEGV, "invalid TSS",              invalid_TSS)
 DO_ERROR(X86_TRAP_NP,     SIGBUS,  "segment not present",      segment_not_present)
-#ifdef CONFIG_X86_32
 DO_ERROR(X86_TRAP_SS,     SIGBUS,  "stack segment",            stack_segment)
-#endif
 DO_ERROR(X86_TRAP_AC,     SIGBUS,  "alignment check",          alignment_check)
 
 #ifdef CONFIG_X86_64
 /* Runs on IST stack */
-dotraplinkage void do_stack_segment(struct pt_regs *regs, long error_code)
-{
-       enum ctx_state prev_state;
-
-       prev_state = exception_enter();
-       if (notify_die(DIE_TRAP, "stack segment", regs, error_code,
-                      X86_TRAP_SS, SIGBUS) != NOTIFY_STOP) {
-               preempt_conditional_sti(regs);
-               do_trap(X86_TRAP_SS, SIGBUS, "stack segment", regs, error_code, NULL);
-               preempt_conditional_cli(regs);
-       }
-       exception_exit(prev_state);
-}
-
 dotraplinkage void do_double_fault(struct pt_regs *regs, long error_code)
 {
        static const char str[] = "double fault";
        struct task_struct *tsk = current;
 
+#ifdef CONFIG_X86_ESPFIX64
+       extern unsigned char native_irq_return_iret[];
+
+       /*
+        * If IRET takes a non-IST fault on the espfix64 stack, then we
+        * end up promoting it to a doublefault.  In that case, modify
+        * the stack to make it look like we just entered the #GP
+        * handler from user space, similar to bad_iret.
+        */
+       if (((long)regs->sp >> PGDIR_SHIFT) == ESPFIX_PGD_ENTRY &&
+               regs->cs == __KERNEL_CS &&
+               regs->ip == (unsigned long)native_irq_return_iret)
+       {
+               struct pt_regs *normal_regs = task_pt_regs(current);
+
+               /* Fake a #GP(0) from userspace. */
+               memmove(&normal_regs->ip, (void *)regs->sp, 5*8);
+               normal_regs->orig_ax = 0;  /* Missing (lost) #GP error code */
+               regs->ip = (unsigned long)general_protection;
+               regs->sp = (unsigned long)&normal_regs->orig_ax;
+               return;
+       }
+#endif
+
        exception_enter();
        /* Return not checked because double check cannot be ignored */
        notify_die(DIE_TRAP, str, regs, error_code, X86_TRAP_DF, SIGSEGV);
@@ -462,7 +470,7 @@ NOKPROBE_SYMBOL(do_int3);
  * for scheduling or signal handling. The actual stack switch is done in
  * entry.S
  */
-asmlinkage __visible struct pt_regs *sync_regs(struct pt_regs *eregs)
+asmlinkage __visible notrace struct pt_regs *sync_regs(struct pt_regs *eregs)
 {
        struct pt_regs *regs = eregs;
        /* Did already sync */
@@ -482,6 +490,36 @@ 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 notrace
+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;
+}
+NOKPROBE_SYMBOL(fixup_bad_iret);
 #endif
 
 /*
@@ -861,7 +899,7 @@ void __init trap_init(void)
        set_intr_gate(X86_TRAP_OLD_MF, coprocessor_segment_overrun);
        set_intr_gate(X86_TRAP_TS, invalid_TSS);
        set_intr_gate(X86_TRAP_NP, segment_not_present);
-       set_intr_gate_ist(X86_TRAP_SS, &stack_segment, STACKFAULT_STACK);
+       set_intr_gate(X86_TRAP_SS, stack_segment);
        set_intr_gate(X86_TRAP_GP, general_protection);
        set_intr_gate(X86_TRAP_SPURIOUS, spurious_interrupt_bug);
        set_intr_gate(X86_TRAP_MF, coprocessor_error);