x86_64, traps: Rework bad_iret

[pandora-kernel.git] / arch / x86 / kernel / entry_64.S

diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index 7201785..9d28dba 100644 (file)
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -875,12 +875,14 @@ ENTRY(native_iret)
 
 .global native_irq_return_iret
 native_irq_return_iret:
 
 .global native_irq_return_iret
 native_irq_return_iret:

+       /*
+        * This may fault.  Non-paranoid faults on return to userspace are
+        * handled by fixup_bad_iret.  These include #SS, #GP, and #NP.
+        * Double-faults due to espfix64 are handled in do_double_fault.
+        * Other faults here are fatal.
+        */

        iretq
 
        iretq
 

-       .section __ex_table,"a"
-       .quad native_irq_return_iret, bad_iret
-       .previous
-

 #ifdef CONFIG_X86_ESPFIX64
 native_irq_return_ldt:
        pushq_cfi %rax
 #ifdef CONFIG_X86_ESPFIX64
 native_irq_return_ldt:
        pushq_cfi %rax


@@ -907,25 +909,6 @@ native_irq_return_ldt:
        jmp native_irq_return_iret
 #endif
 
        jmp native_irq_return_iret
 #endif
 

-       .section .fixup,"ax"
-bad_iret:
-       /*
-        * The iret traps when the %cs or %ss being restored is bogus.
-        * We've lost the original trap vector and error code.
-        * #GPF is the most likely one to get for an invalid selector.
-        * So pretend we completed the iret and took the #GPF in user mode.
-        *
-        * We are now running with the kernel GS after exception recovery.
-        * But error_entry expects us to have user GS to match the user %cs,
-        * so swap back.
-        */
-       pushq $0
-
-       SWAPGS
-       jmp general_protection
-
-       .previous
-

        /* edi: workmask, edx: work */
 retint_careful:
        CFI_RESTORE_STATE
        /* edi: workmask, edx: work */
 retint_careful:
        CFI_RESTORE_STATE


@@ -1463,16 +1446,15 @@ error_sti:
 
 /*
  * There are two places in the kernel that can potentially fault with
 
 /*
  * There are two places in the kernel that can potentially fault with

- * usergs. Handle them here. The exception handlers after iret run with
- * kernel gs again, so don't set the user space flag. B stepping K8s
- * sometimes report an truncated RIP for IRET exceptions returning to
- * compat mode. Check for these here too.
+ * usergs. Handle them here.  B stepping K8s sometimes report a
+ * truncated RIP for IRET exceptions returning to compat mode. Check
+ * for these here too.

  */
 error_kernelspace:
        incl %ebx
        leaq native_irq_return_iret(%rip),%rcx
        cmpq %rcx,RIP+8(%rsp)
  */
 error_kernelspace:
        incl %ebx
        leaq native_irq_return_iret(%rip),%rcx
        cmpq %rcx,RIP+8(%rsp)

-       je error_swapgs
+       je error_bad_iret

        movl %ecx,%eax  /* zero extend */
        cmpq %rax,RIP+8(%rsp)
        je bstep_iret
        movl %ecx,%eax  /* zero extend */
        cmpq %rax,RIP+8(%rsp)
        je bstep_iret


@@ -1483,7 +1465,15 @@ error_kernelspace:
 bstep_iret:
        /* Fix truncated RIP */
        movq %rcx,RIP+8(%rsp)
 bstep_iret:
        /* Fix truncated RIP */
        movq %rcx,RIP+8(%rsp)

-       jmp error_swapgs
+       /* fall through */
+
+error_bad_iret:
+       SWAPGS
+       mov %rsp,%rdi
+       call fixup_bad_iret
+       mov %rax,%rsp
+       decl %ebx       /* Return to usergs */
+       jmp error_sti

        CFI_ENDPROC
 END(error_entry)
 
        CFI_ENDPROC
 END(error_entry)