arm64: Add ASM_BUG()

Currently. we can only use BUG() from C code, though there are
situations where we would like an equivalent mechanism in assembly code.

This patch refactors our BUG() definition such that it can be used in
either C or assembly, in the form of a new ASM_BUG().

The refactoring requires the removal of escape sequences, such as '\n'
and '\t', but these aren't strictly necessary as we can use ';' to
terminate assembler statements.

The low-level assembly is factored out into <asm/asm-bug.h>, with
<asm/bug.h> retained as the C wrapper.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dave Martin <dave.martin@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Will Deacon <will.deacon@arm.com>

arch/arm64/include/asm/bug.h

@@ -18,41 +18,12 @@
 #ifndef _ARCH_ARM64_ASM_BUG_H
 #define _ARCH_ARM64_ASM_BUG_H
 
-#include <asm/brk-imm.h>
+#include <linux/stringify.h>
 
-#ifdef CONFIG_DEBUG_BUGVERBOSE
-#define _BUGVERBOSE_LOCATION(file, line) __BUGVERBOSE_LOCATION(file, line)
-#define __BUGVERBOSE_LOCATION(file, line)				\
-		".pushsection .rodata.str,\"aMS\",@progbits,1\n"	\
-	"2:	.string \"" file "\"\n\t"				\
-		".popsection\n\t"					\
-									\
-		".long 2b - 0b\n\t"					\
-		".short " #line "\n\t"
-#else
-#define _BUGVERBOSE_LOCATION(file, line)
-#endif
-
-#ifdef CONFIG_GENERIC_BUG
-
-#define __BUG_ENTRY(flags) 				\
-		".pushsection __bug_table,\"aw\"\n\t"	\
-		".align 2\n\t"				\
-	"0:	.long 1f - 0b\n\t"			\
-_BUGVERBOSE_LOCATION(__FILE__, __LINE__)		\
-		".short " #flags "\n\t"			\
-		".popsection\n"				\
-	"1:	"
-#else
-#define __BUG_ENTRY(flags) ""
-#endif
+#include <asm/asm-bug.h>
 
 #define __BUG_FLAGS(flags)				\
-	asm volatile (					\
-		__BUG_ENTRY(flags)			\
-		"brk %[imm]" :: [imm] "i" (BUG_BRK_IMM)	\
-	);
-
+	asm volatile (__stringify(ASM_BUG_FLAGS(flags)));
 
 #define BUG() do {					\
 	__BUG_FLAGS(0);					\