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authorJeremy Fitzhardinge <jeremy@goop.org>2008-06-25 00:19:30 -0400
committerIngo Molnar <mingo@elte.hu>2008-07-08 13:15:56 +0200
commita00394f81f419beb6fb9f7023bd4d15913dc625d (patch)
tree0faef5a52c4244173a3669bc646ef12bb79d6bc6
parent6680415481c7bd38967cf7488787f509f17ba307 (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.h2
-rw-r--r--include/asm-x86/paravirt.h10
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; \