criu: arch, x86 -- A few style tuneup in mixed call code

 - use entry/end from linkage
 - use macros for segments
 - use C style comments
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Reviewed-by: Dmitry Safonov <dsafonov@virtuozzo.com>
Tested-by: Dmitry Safonov <dsafonov@virtuozzo.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

criu/arch/x86/Makefile

@@ -3,6 +3,10 @@ builtin-name		:= crtools.built-in.o
 ccflags-y		+= -iquote $(obj) -iquote $(SRC_DIR) -iquote $(obj)/include
 ccflags-y		+= -iquote $(SRC_DIR)/criu/include -iquote $(SRC_DIR)/include
 
+asflags-y		+= -Wstrict-prototypes -Wa,--noexecstack
+asflags-y		+= -D__ASSEMBLY__ -nostdlib -fomit-frame-pointer
+asflags-y		+= -iquote $(obj)/include
+
 obj-y			+= cpu.o
 obj-y			+= crtools.o
 obj-y			+= sigframe.o

criu/arch/x86/call32.S

@@ -16,15 +16,19 @@
  * the fly.
  */
 
-	.text
+#include "common/asm/linkage.h"
+
+#define __USER32_CS	0x23
+#define __USER_CS	0x33
 
-	.global call32_from_64
-	.type call32_from_64, @function
-call32_from_64:
-	// rdi: stack to use
-	// esi: function to call
+	.text
 
-	// Save registers
+/*
+ * @rdi: Stack to use
+ * @esi: Pointer to function for calling
+ */
+ENTRY(call32_from_64)
+	/* Callee-saving registers due to ABI */
 	pushq %rbx
 	pushq %rbp
 	pushq %r12
@@ -33,30 +37,29 @@ call32_from_64:
 	pushq %r15
 	pushfq
 
-	// Switch stacks
+	/* Switch stacks */
 	sub $8, %rdi
 	mov %rsp,(%rdi)
 	mov %rdi,%rsp
 
-	// Switch to compatibility mode
-	pushq $0x23  /* USER32_CS */
+	/* Switch into compatibility mode */
+	pushq $__USER32_CS
 	pushq $1f
 	lretq
 
 1:
 	.code32
-	// Call the function
+	/* Run function and switch back */
 	call *%esi
-	// Switch back to long mode
-	jmp $0x33,$1f
+	jmp $__USER_CS,$1f
 	.code64
 
 1:
-	// Restore the stack
+	/* Restore the stack */
 	mov (%rsp),%rsp
 	add $8, %rdi
 
-	// Restore registers
+	/* Restore registers */
 	popfq
 	popq %r15
 	popq %r14
@@ -64,7 +67,5 @@ call32_from_64:
 	popq %r12
 	popq %rbp
 	popq %rbx
-
 	ret
-
-.size call32_from_64, .-call32_from_64
+END(call32_from_64)

criu/arch/x86/parasite-head-64.S

-#include "asm/linkage.h"
+#include "common/asm/linkage.h"
 #include "parasite.h"
 
 	.section .head.text, "ax"