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x86: fix iret exception recovery on 64-bit

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This change broke recovery of exceptions in iret:

   commit 72fe485854
   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>
This commit is contained in:
Roland McGrath 2008-02-06 22:39:45 +01:00 committed by Ingo Molnar
parent b5556a67f0
commit a57dae3aa4
1 changed files with 1 additions and 2 deletions
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3
arch/x86/kernel/entry_64.S
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@ -582,7 +582,6 @@ retint_restore_args: /* return to kernel space */
TRACE_IRQS_IRETQ TRACE_IRQS_IRETQ
restore_args: restore_args:
RESTORE_ARGS 0,8,0 RESTORE_ARGS 0,8,0
iret_label:
#ifdef CONFIG_PARAVIRT #ifdef CONFIG_PARAVIRT
INTERRUPT_RETURN INTERRUPT_RETURN
#endif #endif
@ -920,7 +919,7 @@ error_kernelspace:
iret run with kernel gs again, so don't set the user space flag. iret run with kernel gs again, so don't set the user space flag.
B stepping K8s sometimes report an truncated RIP for IRET B stepping K8s sometimes report an truncated RIP for IRET
exceptions returning to compat mode. Check for these here too. */ exceptions returning to compat mode. Check for these here too. */
leaq iret_label(%rip),%rbp leaq native_iret(%rip),%rbp
cmpq %rbp,RIP(%rsp) cmpq %rbp,RIP(%rsp)
je error_swapgs je error_swapgs
movl %ebp,%ebp /* zero extend */ movl %ebp,%ebp /* zero extend */