s390/alternatives: Rework to allow for callbacks

Rework alternatives to allow for callbacks. With this every
alternative entry has additional data encoded:

- When (aka context) an alternative is supposed to be applied

- The type of an alternative, which allows for type specific handling
  and callbacks

- Extra type specific payload (patch information), which can be passed
  to callbacks in order to decide if an alternative should be applied
  or not

With this only the "late" context is implemented, which means there is
no change to the previous behaviour. All code is just converted to the
more generic new infrastructure.

Reviewed-by: Alexander Gordeev <agordeev@linux.ibm.com>
Tested-by: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

2 files changed, 27 insertions, 25 deletions

diff --git a/arch/s390/kernel/alternative.c b/arch/s390/kernel/alternative.c
index 33debc2a26c9..ecabdff89bce 100644
--- a/arch/s390/kernel/alternative.c
+++ b/arch/s390/kernel/alternative.c
@@ -1,31 +1,33 @@
 // SPDX-License-Identifier: GPL-2.0
-#include <linux/module.h>
+
+#include <linux/uaccess.h>
 #include <asm/alternative.h>
 #include <asm/facility.h>
-#include <asm/nospec-branch.h>
 
-void __init_or_module apply_alternatives(struct alt_instr *start,
-					 struct alt_instr *end)
+void __apply_alternatives(struct alt_instr *start, struct alt_instr *end, unsigned int ctx)
 {
-	struct alt_instr *a;
 	u8 *instr, *replacement;
+	struct alt_instr *a;
+	bool replace;
 
 	/*
 	 * The scan order should be from start to end. A later scanned
 	 * alternative code can overwrite previously scanned alternative code.
 	 */
 	for (a = start; a < end; a++) {
+		if (!(a->ctx & ctx))
+			continue;
+		switch (a->type) {
+		case ALT_TYPE_FACILITY:
+			replace = __test_facility(a->data, alt_stfle_fac_list);
+			break;
+		default:
+			replace = false;
+		}
+		if (!replace)
+			continue;
 		instr = (u8 *)&a->instr_offset + a->instr_offset;
 		replacement = (u8 *)&a->repl_offset + a->repl_offset;
-
-		if (!__test_facility(a->feature, alt_stfle_fac_list))
-			continue;
 		s390_kernel_write(instr, replacement, a->instrlen);
 	}
 }
-
-extern struct alt_instr __alt_instructions[], __alt_instructions_end[];
-void __init apply_alternative_instructions(void)
-{
-	apply_alternatives(__alt_instructions, __alt_instructions_end);
-}
diff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.S
index 866917ff013f..90027a57a524 100644
--- a/arch/s390/kernel/entry.S
+++ b/arch/s390/kernel/entry.S
@@ -32,19 +32,19 @@
 _LPP_OFFSET	= __LC_LPP
 
 	.macro STBEAR address
-	ALTERNATIVE "nop", ".insn s,0xb2010000,\address", 193
+	ALTERNATIVE "nop", ".insn s,0xb2010000,\address", ALT_FACILITY(193)
 	.endm
 
 	.macro LBEAR address
-	ALTERNATIVE "nop", ".insn s,0xb2000000,\address", 193
+	ALTERNATIVE "nop", ".insn s,0xb2000000,\address", ALT_FACILITY(193)
 	.endm
 
 	.macro LPSWEY address,lpswe
-	ALTERNATIVE "b \lpswe; nopr", ".insn siy,0xeb0000000071,\address,0", 193
+	ALTERNATIVE "b \lpswe; nopr", ".insn siy,0xeb0000000071,\address,0", ALT_FACILITY(193)
 	.endm
 
 	.macro MBEAR reg
-	ALTERNATIVE "brcl 0,0", __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), ALT_FACILITY(193)
 	.endm
 
 	.macro	CHECK_STACK savearea
@@ -100,22 +100,22 @@ _LPP_OFFSET	= __LC_LPP
 	.endm
 
 	.macro BPOFF
-	ALTERNATIVE "nop", ".insn rrf,0xb2e80000,0,0,12,0", 82
+	ALTERNATIVE "nop", ".insn rrf,0xb2e80000,0,0,12,0", ALT_FACILITY(82)
 	.endm
 
 	.macro BPON
-	ALTERNATIVE "nop", ".insn rrf,0xb2e80000,0,0,13,0", 82
+	ALTERNATIVE "nop", ".insn rrf,0xb2e80000,0,0,13,0", ALT_FACILITY(82)
 	.endm
 
 	.macro BPENTER tif_ptr,tif_mask
 	ALTERNATIVE "TSTMSK \tif_ptr,\tif_mask; jz .+8; .insn rrf,0xb2e80000,0,0,13,0", \
-		    "j .+12; nop; nop", 82
+		    "j .+12; nop; nop", ALT_FACILITY(82)
 	.endm
 
 	.macro BPEXIT tif_ptr,tif_mask
 	TSTMSK	\tif_ptr,\tif_mask
 	ALTERNATIVE "jz .+8;  .insn rrf,0xb2e80000,0,0,12,0", \
-		    "jnz .+8; .insn rrf,0xb2e80000,0,0,13,0", 82
+		    "jnz .+8; .insn rrf,0xb2e80000,0,0,13,0", ALT_FACILITY(82)
 	.endm
 
 #if IS_ENABLED(CONFIG_KVM)
@@ -169,7 +169,7 @@ SYM_FUNC_START(__switch_to_asm)
 	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 "nop", "lpp _LPP_OFFSET", 40
+	ALTERNATIVE "nop", "lpp _LPP_OFFSET", ALT_FACILITY(40)
 	BR_EX	%r14
 SYM_FUNC_END(__switch_to_asm)
 
@@ -515,7 +515,7 @@ SYM_CODE_START(mcck_int_handler)
 	jno	0f
 	BPON
 	stpt	__LC_EXIT_TIMER
-0:	ALTERNATIVE "nop", __stringify(lghi %r12,__LC_LAST_BREAK_SAVE_AREA),193
+0:	ALTERNATIVE "nop", __stringify(lghi %r12,__LC_LAST_BREAK_SAVE_AREA), ALT_FACILITY(193)
 	LBEAR	0(%r12)
 	lmg	%r11,%r15,__PT_R11(%r11)
 	LPSWEY	__LC_RETURN_MCCK_PSW,__LC_RETURN_MCCK_LPSWE
@@ -551,7 +551,7 @@ SYM_CODE_START(mcck_int_handler)
 SYM_CODE_END(mcck_int_handler)
 
 SYM_CODE_START(restart_int_handler)
-	ALTERNATIVE "nop", "lpp _LPP_OFFSET", 40
+	ALTERNATIVE "nop", "lpp _LPP_OFFSET", ALT_FACILITY(40)
 	stg	%r15,__LC_SAVE_AREA_RESTART
 	TSTMSK	__LC_RESTART_FLAGS,RESTART_FLAG_CTLREGS,4
 	jz	0f