diff options
| author | Jeremy Fitzhardinge <jeremy@goop.org> | 2008-06-25 00:19:30 -0400 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2008-07-08 13:15:56 +0200 |
| commit | a00394f81f419beb6fb9f7023bd4d15913dc625d (patch) | |
| tree | 0faef5a52c4244173a3669bc646ef12bb79d6bc6 | |
| parent | 6680415481c7bd38967cf7488787f509f17ba307 (diff) | |
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: Jeremy 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: Ingo Molnar <mingo@elte.hu>
| -rw-r--r-- | include/asm-x86/irqflags.h | 2 | ||||
| -rw-r--r-- | include/asm-x86/paravirt.h | 10 |
2 files changed, 11 insertions, 1 deletions
diff --git a/include/asm-x86/irqflags.h b/include/asm-x86/irqflags.h index ea9bd2635d59..d17e1f623dbb 100644 --- a/include/asm-x86/irqflags.h +++ b/include/asm-x86/irqflags.h @@ -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 diff --git a/include/asm-x86/paravirt.h b/include/asm-x86/paravirt.h index 33f72f8fe757..3286a0c63b42 100644 --- a/include/asm-x86/paravirt.h +++ b/include/asm-x86/paravirt.h @@ -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; \ |