arm64: Work around broken .inst when defective gas is detected

.inst being largely broken with older binutils, it'd be better not
to emit it altogether when detecting such configuration (as it
leads to all kind of horrors when using alternatives).

Generalize the __emit_inst macro and use it extensively in
asm/sysreg.h, and make it generate a .long when a broken gas is
detected. The disassembly will be crap, but at least we can write
semi-sane code.
Acked-by: NWill Deacon <will.deacon@arm.com>
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

arch/arm64/include/asm/sysreg.h

@@ -35,12 +35,33 @@
 #define sys_reg(op0, op1, crn, crm, op2) \
 	((((op0)&3)<<19)|((op1)<<16)|((crn)<<12)|((crm)<<8)|((op2)<<5))
 
+#ifndef CONFIG_BROKEN_GAS_INST
+
 #ifdef __ASSEMBLY__
 #define __emit_inst(x)			.inst (x)
 #else
 #define __emit_inst(x)			".inst " __stringify((x)) "\n\t"
 #endif
 
+#else  /* CONFIG_BROKEN_GAS_INST */
+
+#ifndef CONFIG_CPU_BIG_ENDIAN
+#define __INSTR_BSWAP(x)		(x)
+#else  /* CONFIG_CPU_BIG_ENDIAN */
+#define __INSTR_BSWAP(x)		((((x) << 24) & 0xff000000)	| \
+					 (((x) <<  8) & 0x00ff0000)	| \
+					 (((x) >>  8) & 0x0000ff00)	| \
+					 (((x) >> 24) & 0x000000ff))
+#endif	/* CONFIG_CPU_BIG_ENDIAN */
+
+#ifdef __ASSEMBLY__
+#define __emit_inst(x)			.long __INSTR_BSWAP(x)
+#else  /* __ASSEMBLY__ */
+#define __emit_inst(x)			".long " __stringify(__INSTR_BSWAP(x)) "\n\t"
+#endif	/* __ASSEMBLY__ */
+
+#endif	/* CONFIG_BROKEN_GAS_INST */
+
 #define SYS_MIDR_EL1			sys_reg(3, 0, 0, 0, 0)
 #define SYS_MPIDR_EL1			sys_reg(3, 0, 0, 0, 5)
 #define SYS_REVIDR_EL1			sys_reg(3, 0, 0, 0, 6)
@@ -232,11 +253,11 @@
 	.equ	.L__reg_num_xzr, 31
 
 	.macro	mrs_s, rt, sreg
-	.inst	0xd5200000|(\sreg)|(.L__reg_num_\rt)
+	 __emit_inst(0xd5200000|(\sreg)|(.L__reg_num_\rt))
 	.endm
 
 	.macro	msr_s, sreg, rt
-	.inst	0xd5000000|(\sreg)|(.L__reg_num_\rt)
+	__emit_inst(0xd5000000|(\sreg)|(.L__reg_num_\rt))
 	.endm
 
 #else
@@ -250,11 +271,11 @@ asm(
 "	.equ	.L__reg_num_xzr, 31\n"
 "\n"
 "	.macro	mrs_s, rt, sreg\n"
-"	.inst	0xd5200000|(\\sreg)|(.L__reg_num_\\rt)\n"
+	__emit_inst(0xd5200000|(\\sreg)|(.L__reg_num_\\rt))
 "	.endm\n"
 "\n"
 "	.macro	msr_s, sreg, rt\n"
-"	.inst	0xd5000000|(\\sreg)|(.L__reg_num_\\rt)\n"
+	__emit_inst(0xd5000000|(\\sreg)|(.L__reg_num_\\rt))
 "	.endm\n"
 );