s390/alternatives: provide identical sized orginal/alternative sequences

Explicitly provide identical sized original/alternative instruction
sequences. This way there is no need for the s390 specific alternatives
infrastructure to generate padding sequences.
The code which generates such sequences will be removed with a follow on
patch.

Acked-by: Vasily Gorbik <gor@linux.ibm.com>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Link: https://lore.kernel.org/r/20220511120532.2228616-2-hca@linux.ibm.com
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

arch/s390/include/asm/spinlock.h

@@ -79,7 +79,7 @@ static inline void arch_spin_unlock(arch_spinlock_t *lp)
 	typecheck(int, lp->lock);
 	kcsan_release();
 	asm_inline volatile(
-		ALTERNATIVE("", ".insn rre,0xb2fa0000,7,0", 49)	/* NIAI 7 */
+		ALTERNATIVE("nop", ".insn rre,0xb2fa0000,7,0", 49) /* NIAI 7 */
 		"	sth	%1,%0\n"
 		: "=R" (((unsigned short *) &lp->lock)[1])
 		: "d" (0) : "cc", "memory");

arch/s390/kernel/entry.S

@@ -53,19 +53,19 @@ STACK_INIT = STACK_SIZE - STACK_FRAME_OVERHEAD - __PT_SIZE
 _LPP_OFFSET	= __LC_LPP
 
 	.macro STBEAR address
-	ALTERNATIVE "", ".insn	s,0xb2010000,\address", 193
+	ALTERNATIVE "nop", ".insn s,0xb2010000,\address", 193
 	.endm
 
 	.macro LBEAR address
-	ALTERNATIVE "", ".insn	s,0xb2000000,\address", 193
+	ALTERNATIVE "nop", ".insn s,0xb2000000,\address", 193
 	.endm
 
 	.macro LPSWEY address,lpswe
-	ALTERNATIVE "b \lpswe", ".insn siy,0xeb0000000071,\address,0", 193
+	ALTERNATIVE "b \lpswe; nopr", ".insn siy,0xeb0000000071,\address,0", 193
 	.endm
 
 	.macro MBEAR reg
-	ALTERNATIVE "", __stringify(mvc __PT_LAST_BREAK(8,\reg),__LC_LAST_BREAK), 193
+	ALTERNATIVE "brcl 0,0", __stringify(mvc __PT_LAST_BREAK(8,\reg),__LC_LAST_BREAK), 193
 	.endm
 
 	.macro	CHECK_STACK savearea
@@ -121,16 +121,16 @@ _LPP_OFFSET	= __LC_LPP
 	.endm
 
 	.macro BPOFF
-	ALTERNATIVE "", ".insn rrf,0xb2e80000,0,0,12,0", 82
+	ALTERNATIVE "nop", ".insn rrf,0xb2e80000,0,0,12,0", 82
 	.endm
 
 	.macro BPON
-	ALTERNATIVE "", ".insn rrf,0xb2e80000,0,0,13,0", 82
+	ALTERNATIVE "nop", ".insn rrf,0xb2e80000,0,0,13,0", 82
 	.endm
 
 	.macro BPENTER tif_ptr,tif_mask
 	ALTERNATIVE "TSTMSK \tif_ptr,\tif_mask; jz .+8; .insn rrf,0xb2e80000,0,0,13,0", \
-		    "", 82
+		    "j .+12; nop; nop", 82
 	.endm
 
 	.macro BPEXIT tif_ptr,tif_mask
@@ -226,7 +226,7 @@ ENTRY(__switch_to)
 	aghi	%r3,__TASK_pid
 	mvc	__LC_CURRENT_PID(4,%r0),0(%r3)	# store pid of next
 	lmg	%r6,%r15,__SF_GPRS(%r15)	# load gprs of next task
-	ALTERNATIVE "", "lpp _LPP_OFFSET", 40
+	ALTERNATIVE "nop", "lpp _LPP_OFFSET", 40
 	BR_EX	%r14
 ENDPROC(__switch_to)
 
@@ -610,7 +610,7 @@ ENTRY(mcck_int_handler)
 	jno	0f
 	BPEXIT	__TI_flags(%r12),_TIF_ISOLATE_BP
 	stpt	__LC_EXIT_TIMER
-0:	ALTERNATIVE "", __stringify(lghi %r12,__LC_LAST_BREAK_SAVE_AREA),193
+0:	ALTERNATIVE "nop", __stringify(lghi %r12,__LC_LAST_BREAK_SAVE_AREA),193
 	LBEAR	0(%r12)
 	lmg	%r11,%r15,__PT_R11(%r11)
 	LPSWEY	__LC_RETURN_MCCK_PSW,__LC_RETURN_MCCK_LPSWE
@@ -646,7 +646,7 @@ ENTRY(mcck_int_handler)
 ENDPROC(mcck_int_handler)
 
 ENTRY(restart_int_handler)
-	ALTERNATIVE "", "lpp _LPP_OFFSET", 40
+	ALTERNATIVE "nop", "lpp _LPP_OFFSET", 40
 	stg	%r15,__LC_SAVE_AREA_RESTART
 	TSTMSK	__LC_RESTART_FLAGS,RESTART_FLAG_CTLREGS,4
 	jz	0f

arch/s390/lib/spinlock.c

@@ -75,7 +75,7 @@ static inline int arch_load_niai4(int *lock)
 	int owner;
 
 	asm_inline volatile(
-		ALTERNATIVE("", ".insn rre,0xb2fa0000,4,0", 49)	/* NIAI 4 */
+		ALTERNATIVE("nop", ".insn rre,0xb2fa0000,4,0", 49) /* NIAI 4 */
 		"	l	%0,%1\n"
 		: "=d" (owner) : "Q" (*lock) : "memory");
 	return owner;
@@ -86,7 +86,7 @@ static inline int arch_cmpxchg_niai8(int *lock, int old, int new)
 	int expected = old;
 
 	asm_inline volatile(
-		ALTERNATIVE("", ".insn rre,0xb2fa0000,8,0", 49)	/* NIAI 8 */
+		ALTERNATIVE("nop", ".insn rre,0xb2fa0000,8,0", 49) /* NIAI 8 */
 		"	cs	%0,%3,%1\n"
 		: "=d" (old), "=Q" (*lock)
 		: "0" (old), "d" (new), "Q" (*lock)