x86/paravirt: Use normal calling sequences for irq enable/disable

Bastian Blank reported a boot crash with stackprotector enabled,
and debugged it back to edx register corruption.

For historical reasons irq enable/disable/save/restore had special
calling sequences to make them more efficient.  With the more
recent introduction of higher-level and more general optimisations
this is no longer necessary so we can just use the normal PVOP_
macros.

This fixes some residual bugs in the old implementations which left
edx liable to inadvertent clobbering. Also, fix some bugs in
__PVOP_VCALLEESAVE which were revealed by actual use.

Reported-by: Bastian Blank <bastian@waldi.eu.org>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: Stable Kernel <stable@kernel.org>
Cc: Xen-devel <xen-devel@lists.xensource.com>
LKML-Reference: <4AD3BC9B.7040501@goop.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

2 files changed, 10 insertions, 28 deletions

diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
index 8aebcc41041d..efb38994859c 100644
--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -840,42 +840,22 @@ static __always_inline void __raw_spin_unlock(struct raw_spinlock *lock)
 
 static inline unsigned long __raw_local_save_flags(void)
 {
-        unsigned long f;
-
-        asm volatile(paravirt_alt(PARAVIRT_CALL)
-                     : "=a"(f)
-                     : paravirt_type(pv_irq_ops.save_fl),
-                       paravirt_clobber(CLBR_EAX)
-                     : "memory", "cc");
-        return f;
+        return PVOP_CALLEE0(unsigned long, pv_irq_ops.save_fl);
 }
 
 static inline void raw_local_irq_restore(unsigned long f)
 {
-        asm volatile(paravirt_alt(PARAVIRT_CALL)
-                     : "=a"(f)
-                     : PV_FLAGS_ARG(f),
-                       paravirt_type(pv_irq_ops.restore_fl),
-                       paravirt_clobber(CLBR_EAX)
-                     : "memory", "cc");
+        PVOP_VCALLEE1(pv_irq_ops.restore_fl, f);
 }
 
 static inline void raw_local_irq_disable(void)
 {
-        asm volatile(paravirt_alt(PARAVIRT_CALL)
-                     :
-                     : paravirt_type(pv_irq_ops.irq_disable),
-                       paravirt_clobber(CLBR_EAX)
-                     : "memory", "eax", "cc");
+        PVOP_VCALLEE0(pv_irq_ops.irq_disable);
 }
 
 static inline void raw_local_irq_enable(void)
 {
-        asm volatile(paravirt_alt(PARAVIRT_CALL)
-                     :
-                     : paravirt_type(pv_irq_ops.irq_enable),
-                       paravirt_clobber(CLBR_EAX)
-                     : "memory", "eax", "cc");
+        PVOP_VCALLEE0(pv_irq_ops.irq_enable);
 }
 
 static inline unsigned long __raw_local_irq_save(void)
diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/paravirt_types.h
index dd0f5b32489d..9357473c8da0 100644
--- a/arch/x86/include/asm/paravirt_types.h
+++ b/arch/x86/include/asm/paravirt_types.h
@@ -494,10 +494,11 @@ int paravirt_disable_iospace(void);
 #define EXTRA_CLOBBERS
 #define VEXTRA_CLOBBERS
 #else  /* CONFIG_X86_64 */
+/* [re]ax isn't an arg, but the return val */
 #define PVOP_VCALL_ARGS                                 \
         unsigned long __edi = __edi, __esi = __esi,     \
-                __edx = __edx, __ecx = __ecx
-#define PVOP_CALL_ARGS          PVOP_VCALL_ARGS, __eax
+                __edx = __edx, __ecx = __ecx, __eax = __eax
+#define PVOP_CALL_ARGS          PVOP_VCALL_ARGS
 
 #define PVOP_CALL_ARG1(x)               "D" ((unsigned long)(x))
 #define PVOP_CALL_ARG2(x)               "S" ((unsigned long)(x))
@@ -509,6 +510,7 @@ int paravirt_disable_iospace(void);
                                 "=c" (__ecx)
 #define PVOP_CALL_CLOBBERS      PVOP_VCALL_CLOBBERS, "=a" (__eax)
 
+/* void functions are still allowed [re]ax for scratch */
 #define PVOP_VCALLEE_CLOBBERS   "=a" (__eax)
 #define PVOP_CALLEE_CLOBBERS    PVOP_VCALLEE_CLOBBERS
 
@@ -583,8 +585,8 @@ int paravirt_disable_iospace(void);
                        VEXTRA_CLOBBERS,                                 \
                        pre, post, ##__VA_ARGS__)
 
-#define __PVOP_VCALLEESAVE(rettype, op, pre, post, ...)                 \
-        ____PVOP_CALL(rettype, op.func, CLBR_RET_REG,                   \
+#define __PVOP_VCALLEESAVE(op, pre, post, ...)                          \
+        ____PVOP_VCALL(op.func, CLBR_RET_REG,                           \
                       PVOP_VCALLEE_CLOBBERS, ,                          \
                       pre, post, ##__VA_ARGS__)