x86/fpu/xstate: Use explicit parameter in xstate_fault()

While looking at xstate.h it took me some time to realize that
'xstate_fault' uses 'err' as a silent parameter. This is not
obvious at the call site, at all.

Make it an explicit macro argument, so that the syntactic
connection is easier to see. Also explain xstate_fault()
a bit.

Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/x86/include/asm/fpu/xstate.h b/arch/x86/include/asm/fpu/xstate.h
index 8f336d2ae1262ab2a357e2c9451f9b4377f9592d..a6e07bb3152666261494f71263916a5382e58d0a 100644 (file)
--- a/arch/x86/include/asm/fpu/xstate.h
+++ b/arch/x86/include/asm/fpu/xstate.h
@@ -47,12 +47,18 @@ extern void update_regset_xstate_info(unsigned int size, u64 xstate_mask);
 #define XRSTOR         ".byte " REX_PREFIX "0x0f,0xae,0x2f"
 #define XRSTORS                ".byte " REX_PREFIX "0x0f,0xc7,0x1f"
 
-#define xstate_fault   ".section .fixup,\"ax\"\n"      \
-                       "3:  movl $-1,%[err]\n"         \
-                       "    jmp  2b\n"                 \
-                       ".previous\n"                   \
-                       _ASM_EXTABLE(1b, 3b)            \
-                       : [err] "=r" (err)
+/* xstate instruction fault handler: */
+#define xstate_fault(__err)            \
+                                       \
+       ".section .fixup,\"ax\"\n"      \
+                                       \
+       "3:  movl $-1,%[err]\n"         \
+       "    jmp  2b\n"                 \
+                                       \
+       ".previous\n"                   \
+                                       \
+       _ASM_EXTABLE(1b, 3b)            \
+       : [err] "=r" (__err)
 
 /*
  * This function is called only during boot time when x86 caps are not set
@@ -70,13 +76,13 @@ static inline int copy_xregs_to_kernel_booting(struct xregs_state *fx)
        if (boot_cpu_has(X86_FEATURE_XSAVES))
                asm volatile("1:"XSAVES"\n\t"
                        "2:\n\t"
-                            xstate_fault
+                            xstate_fault(err)
                        : "D" (fx), "m" (*fx), "a" (lmask), "d" (hmask)
                        :   "memory");
        else
                asm volatile("1:"XSAVE"\n\t"
                        "2:\n\t"
-                            xstate_fault
+                            xstate_fault(err)
                        : "D" (fx), "m" (*fx), "a" (lmask), "d" (hmask)
                        :   "memory");
        return err;
@@ -97,13 +103,13 @@ static inline int copy_kernel_to_xregs_booting(struct xregs_state *fx, u64 mask)
        if (boot_cpu_has(X86_FEATURE_XSAVES))
                asm volatile("1:"XRSTORS"\n\t"
                        "2:\n\t"
-                            xstate_fault
+                            xstate_fault(err)
                        : "D" (fx), "m" (*fx), "a" (lmask), "d" (hmask)
                        :   "memory");
        else
                asm volatile("1:"XRSTOR"\n\t"
                        "2:\n\t"
-                            xstate_fault
+                            xstate_fault(err)
                        : "D" (fx), "m" (*fx), "a" (lmask), "d" (hmask)
                        :   "memory");
        return err;
@@ -141,7 +147,7 @@ static inline int copy_xregs_to_kernel(struct xregs_state *fx)
                [fx] "D" (fx), "a" (lmask), "d" (hmask) :
                "memory");
        asm volatile("2:\n\t"
-                    xstate_fault
+                    xstate_fault(err)
                     : "0" (0)
                     : "memory");
 
@@ -169,7 +175,7 @@ static inline int copy_kernel_to_xregs(struct xregs_state *fx, u64 mask)
                : "memory");
 
        asm volatile("2:\n"
-                    xstate_fault
+                    xstate_fault(err)
                     : "0" (0)
                     : "memory");
 
@@ -201,7 +207,7 @@ static inline int copy_xregs_to_user(struct xregs_state __user *buf)
        __asm__ __volatile__(ASM_STAC "\n"
                             "1:"XSAVE"\n"
                             "2: " ASM_CLAC "\n"
-                            xstate_fault
+                            xstate_fault(err)
                             : "D" (buf), "a" (-1), "d" (-1), "0" (0)
                             : "memory");
        return err;
@@ -220,7 +226,7 @@ static inline int copy_user_to_xregs(struct xregs_state __user *buf, u64 mask)
        __asm__ __volatile__(ASM_STAC "\n"
                             "1:"XRSTOR"\n"
                             "2: " ASM_CLAC "\n"
-                            xstate_fault
+                            xstate_fault(err)
                             : "D" (xstate), "a" (lmask), "d" (hmask), "0" (0)
                             : "memory");       /* memory required? */
        return err;