Commit a57dae3a authored Feb 06, 2008 by Roland McGrath Committed by Ingo Molnar Feb 06, 2008

x86: fix iret exception recovery on 64-bit



This change broke recovery of exceptions in iret:

   commit 72fe4858
   Author: Glauber de Oliveira Costa <gcosta@redhat.com>

       x86: replace privileged instructions with paravirt macros

The ENTRY(native_iret) macro adds alignment padding before the iretq
instruction, so "iret_label" no longer points exactly at the instruction.
It was sloppy to leave the old "iret_label" label behind when replacing
its nearby use.  Removing it would have revealed the other use of the
label later in the file, and upon noticing that use, anyone exercising
the minimum of attention to detail expected of anyone touching this
subtle code would realize it needed to change as well.

Signed-off-by: Roland McGrath <roland@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

parent b5556a67

arch/x86/kernel/entry_64.S

+1 −2

Original line number	Diff line number	Diff line
		@@ -582,7 +582,6 @@ retint_restore_args: /* return to kernel space */
		TRACE_IRQS_IRETQ
		restore_args:
		RESTORE_ARGS 0,8,0
		iret_label:
		#ifdef CONFIG_PARAVIRT
		INTERRUPT_RETURN
		#endif
		@@ -920,7 +919,7 @@ error_kernelspace:
		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. */
		leaq iret_label(%rip),%rbp
		leaq native_iret(%rip),%rbp
		cmpq %rbp,RIP(%rsp)
		je error_swapgs
		movl %ebp,%ebp /* zero extend */