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Commit a00394f8 authored by Jeremy Fitzhardinge's avatar Jeremy Fitzhardinge Committed by Ingo Molnar
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x86, 64-bit: swapgs pvop with a user-stack can never be called 



It's never safe to call a swapgs pvop when the user stack is current -
it must be inline replaced.  Rather than making a call, the
SWAPGS_UNSAFE_STACK pvop always just puts "swapgs" as a placeholder,
which must either be replaced inline or trap'n'emulated (somehow).

Signed-off-by: default avatarJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: xen-devel <xen-devel@lists.xensource.com>
Cc: Stephen Tweedie <sct@redhat.com>
Cc: Eduardo Habkost <ehabkost@redhat.com>
Cc: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 66804154

include/asm-x86/irqflags.h

+1 −1
Original line number Diff line number Diff line
@@ -111,6 +111,7 @@ static inline unsigned long __raw_local_irq_save(void) 
#define DISABLE_INTERRUPTS(x)	cli



#ifdef CONFIG_X86_64

#define SWAPGS_UNSAFE_STACK	swapgs

#define INTERRUPT_RETURN	iretq

#define USERGS_SYSRET64				\

	swapgs;					\
@@ -185,7 +186,6 @@ static inline void trace_hardirqs_fixup(void) 
 * Either way, this is a good way to document that we don't

 * have a reliable stack. x86_64 only.

 */

#define SWAPGS_UNSAFE_STACK	swapgs

#define ARCH_TRACE_IRQS_ON		call trace_hardirqs_on_thunk

#define ARCH_TRACE_IRQS_OFF		call trace_hardirqs_off_thunk

#define ARCH_LOCKDEP_SYS_EXIT		call lockdep_sys_exit_thunk

include/asm-x86/paravirt.h

+10 −0
Original line number Diff line number Diff line
@@ -1522,6 +1522,16 @@ static inline unsigned long __raw_local_irq_save(void) 




#else	/* !CONFIG_X86_32 */



/*

 * If swapgs is used while the userspace stack is still current,

 * there's no way to call a pvop.  The PV replacement *must* be

 * inlined, or the swapgs instruction must be trapped and emulated.

 */

#define SWAPGS_UNSAFE_STACK						\

	PARA_SITE(PARA_PATCH(pv_cpu_ops, PV_CPU_swapgs), CLBR_NONE,	\

		  swapgs)



#define SWAPGS								\

	PARA_SITE(PARA_PATCH(pv_cpu_ops, PV_CPU_swapgs), CLBR_NONE,	\

		  PV_SAVE_REGS;						\