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x86_64/entry/xen: Do not invoke espfix64 on Xen

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This moves the espfix64 logic into native_iret.  To make this work,
it gets rid of the native patch for INTERRUPT_RETURN:
INTERRUPT_RETURN on native kernels is now 'jmp native_iret'.

This changes the 16-bit SS behavior on Xen from OOPSing to leaking
some bits of the Xen hypervisor's RSP (I think).

[ hpa: this is a nonzero cost on native, but probably not enough to
  measure. Xen needs to fix this in their own code, probably doing
  something equivalent to espfix64. ]

Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Link: http://lkml.kernel.org/r/7b8f1d8ef6597cb16ae004a43c56980a7de3cf94.1406129132.git.luto@amacapital.net
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Cc: <stable@vger.kernel.org>
This commit is contained in:
Andy Lutomirski
2014-07-23 08:34:11 -07:00
committed by H. Peter Anvin
parent 64aa90f26c
commit 7209a75d20
3 changed files with 11 additions and 21 deletions
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2
arch/x86/include/asm/irqflags.h
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@@ -129,7 +129,7 @@ static inline notrace unsigned long arch_local_irq_save(void)
#define PARAVIRT_ADJUST_EXCEPTION_FRAME /* */
#define INTERRUPT_RETURN iretq
#define INTERRUPT_RETURN jmp native_iret
#define USERGS_SYSRET64 \
swapgs; \
sysretq;