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Commit 162e6df4 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

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

Pull x86 fixes from Thomas Gleixner:
 "Two bugfixes from Andy addressing at least some of the subtle NMI
  related wreckage which has been reported by Sasha Levin"

* 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/nmi/64: Fix a paravirt stack-clobbering bug in the NMI code
  x86/paravirt: Replace the paravirt nop with a bona fide empty function
parents 5a6bdf06 83c133cf

arch/x86/entry/entry_64.S

+15 −1
Original line number Diff line number Diff line
@@ -1128,7 +1128,18 @@ END(error_exit) 


/* Runs on exception stack */

ENTRY(nmi)

	/*

	 * Fix up the exception frame if we're on Xen.

	 * PARAVIRT_ADJUST_EXCEPTION_FRAME is guaranteed to push at most

	 * one value to the stack on native, so it may clobber the rdx

	 * scratch slot, but it won't clobber any of the important

	 * slots past it.

	 *

	 * Xen is a different story, because the Xen frame itself overlaps

	 * the "NMI executing" variable.

	 */

	PARAVIRT_ADJUST_EXCEPTION_FRAME



	/*

	 * We allow breakpoints in NMIs. If a breakpoint occurs, then

	 * the iretq it performs will take us out of NMI context.
@@ -1179,9 +1190,12 @@ ENTRY(nmi) 
	 * we don't want to enable interrupts, because then we'll end

	 * up in an awkward situation in which IRQs are on but NMIs

	 * are off.

	 *

	 * We also must not push anything to the stack before switching

	 * stacks lest we corrupt the "NMI executing" variable.

	 */



	SWAPGS

	SWAPGS_UNSAFE_STACK

	cld

	movq	%rsp, %rdx

	movq	PER_CPU_VAR(cpu_current_top_of_stack), %rsp

arch/x86/kernel/paravirt.c

+12 −4
Original line number Diff line number Diff line
@@ -41,10 +41,18 @@ 
#include <asm/timer.h>

#include <asm/special_insns.h>



/* nop stub */

void _paravirt_nop(void)

{

}

/*

 * nop stub, which must not clobber anything *including the stack* to

 * avoid confusing the entry prologues.

 */

extern void _paravirt_nop(void);

asm (".pushsection .entry.text, \"ax\"\n"

     ".global _paravirt_nop\n"

     "_paravirt_nop:\n\t"

     "ret\n\t"

     ".size _paravirt_nop, . - _paravirt_nop\n\t"

     ".type _paravirt_nop, @function\n\t"

     ".popsection");



/* identity function, which can be inlined */

u32 _paravirt_ident_32(u32 x)