[PATCH v2 1/6] x86: replace __ASM_{CL,ST}AC

[Jan Beulich <jbeulich@xxxxxxxx>]

Introduce proper assembler macros instead, enabled only when the
assembler itself doesn't support the insns. To avoid duplicating the
macros for assembly and C files, have them processed into asm-macros.h.
This in turn requires adding a multiple inclusion guard when generating
that header.

No change to generated code.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>

--- a/xen/arch/x86/Makefile
+++ b/xen/arch/x86/Makefile
@@ -243,7 +243,10 @@ $(BASEDIR)/include/asm-x86/asm-macros.h:
        echo '#if 0' >$@.new
        echo '.if 0' >>$@.new
        echo '#endif' >>$@.new
+       echo '#ifndef __ASM_MACROS_H__' >>$@.new
+       echo '#define __ASM_MACROS_H__' >>$@.new
        echo 'asm ( ".include \"$@\"" );' >>$@.new
+       echo '#endif /* __ASM_MACROS_H__ */' >>$@.new
        echo '#if 0' >>$@.new
        echo '.endif' >>$@.new
        cat $< >>$@.new
--- a/xen/arch/x86/arch.mk
+++ b/xen/arch/x86/arch.mk
@@ -20,6 +20,7 @@ $(call as-option-add,CFLAGS,CC,"rdrand %
 $(call as-option-add,CFLAGS,CC,"rdfsbase %rax",-DHAVE_AS_FSGSBASE)
 $(call as-option-add,CFLAGS,CC,"xsaveopt (%rax)",-DHAVE_AS_XSAVEOPT)
 $(call as-option-add,CFLAGS,CC,"rdseed %eax",-DHAVE_AS_RDSEED)
+$(call as-option-add,CFLAGS,CC,"clac",-DHAVE_AS_CLAC_STAC)
 $(call as-option-add,CFLAGS,CC,"clwb (%rax)",-DHAVE_AS_CLWB)
 $(call as-option-add,CFLAGS,CC,".equ \"x\"$$(comma)1",-DHAVE_AS_QUOTED_SYM)
 $(call as-option-add,CFLAGS,CC,"invpcid (%rax)$$(comma)%rax",-DHAVE_AS_INVPCID)
--- a/xen/arch/x86/asm-macros.c
+++ b/xen/arch/x86/asm-macros.c
@@ -1 +1,2 @@
+#include <asm/asm-defns.h>
 #include <asm/alternative-asm.h>
--- /dev/null
+++ b/xen/include/asm-x86/asm-defns.h
@@ -0,0 +1,9 @@
+#ifndef HAVE_AS_CLAC_STAC
+.macro clac
+    .byte 0x0f, 0x01, 0xca
+.endm
+
+.macro stac
+    .byte 0x0f, 0x01, 0xcb
+.endm
+#endif
--- a/xen/include/asm-x86/asm_defns.h
+++ b/xen/include/asm-x86/asm_defns.h
@@ -13,10 +13,12 @@
 #include <asm/alternative.h>
 
 #ifdef __ASSEMBLY__
+#include <asm/asm-defns.h>
 #ifndef CONFIG_INDIRECT_THUNK
 .equ CONFIG_INDIRECT_THUNK, 0
 #endif
 #else
+#include <asm/asm-macros.h>
 asm ( "\t.equ CONFIG_INDIRECT_THUNK, "
       __stringify(IS_ENABLED(CONFIG_INDIRECT_THUNK)) );
 #endif
@@ -200,34 +202,27 @@ register unsigned long current_stack_poi
 
 #endif
 
-/* "Raw" instruction opcodes */
-#define __ASM_CLAC      ".byte 0x0f,0x01,0xca"
-#define __ASM_STAC      ".byte 0x0f,0x01,0xcb"
-
 #ifdef __ASSEMBLY__
 .macro ASM_STAC
-    ALTERNATIVE "", __ASM_STAC, X86_FEATURE_XEN_SMAP
+    ALTERNATIVE "", stac, X86_FEATURE_XEN_SMAP
 .endm
 .macro ASM_CLAC
-    ALTERNATIVE "", __ASM_CLAC, X86_FEATURE_XEN_SMAP
+    ALTERNATIVE "", clac, X86_FEATURE_XEN_SMAP
 .endm
 #else
 static always_inline void clac(void)
 {
     /* Note: a barrier is implicit in alternative() */
-    alternative("", __ASM_CLAC, X86_FEATURE_XEN_SMAP);
+    alternative("", "clac", X86_FEATURE_XEN_SMAP);
 }
 
 static always_inline void stac(void)
 {
     /* Note: a barrier is implicit in alternative() */
-    alternative("", __ASM_STAC, X86_FEATURE_XEN_SMAP);
+    alternative("", "stac", X86_FEATURE_XEN_SMAP);
 }
 #endif
 
-#undef __ASM_STAC
-#undef __ASM_CLAC
-
 #ifdef __ASSEMBLY__
 .macro SAVE_ALL op, compat=0
 .ifeqs "\op", "CLAC"