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>

3 files changed, 63 insertions, 7 deletions

diff --git a/arch/s390/include/asm/alternative.h b/arch/s390/include/asm/alternative.h
index 16de33750d6c..5b931070be16 100644
--- a/arch/s390/include/asm/alternative.h
+++ b/arch/s390/include/asm/alternative.h
@@ -2,6 +2,44 @@
 #ifndef _ASM_S390_ALTERNATIVE_H
 #define _ASM_S390_ALTERNATIVE_H
 
+/*
+ * Each alternative comes with a 32 bit feature field:
+ *	union {
+ *		u32 feature;
+ *		struct {
+ *			u32 ctx	 : 4;
+ *			u32 type : 8;
+ *			u32 data : 20;
+ *		};
+ *	}
+ *
+ * @ctx is a bitfield, where only one bit must be set. Each bit defines
+ * in which context an alternative is supposed to be applied to the
+ * kernel image:
+ *
+ * - from the decompressor before the kernel itself is executed
+ * - from early kernel code from within the kernel
+ *
+ * @type is a number which defines the type and with that the type
+ * specific alternative patching.
+ *
+ * @data is additional type specific information which defines if an
+ * alternative should be applied.
+ */
+
+#define ALT_CTX_LATE		1
+#define ALT_CTX_ALL		ALT_CTX_LATE
+
+#define ALT_TYPE_FACILITY	0
+
+#define ALT_DATA_SHIFT		0
+#define ALT_TYPE_SHIFT		20
+#define ALT_CTX_SHIFT		28
+
+#define ALT_FACILITY(facility)		(ALT_CTX_LATE << ALT_CTX_SHIFT		| \
+					 ALT_TYPE_FACILITY << ALT_TYPE_SHIFT	| \
+					 (facility) << ALT_DATA_SHIFT)
+
 #ifndef __ASSEMBLY__
 
 #include <linux/types.h>
@@ -11,12 +49,30 @@
 struct alt_instr {
 	s32 instr_offset;	/* original instruction */
 	s32 repl_offset;	/* offset to replacement instruction */
-	u16 feature;		/* feature required for replacement */
+	union {
+		u32 feature;	/* feature required for replacement */
+		struct {
+			u32 ctx	 : 4;  /* context */
+			u32 type : 8;  /* type of alternative */
+			u32 data : 20; /* patching information */
+		};
+	};
 	u8  instrlen;		/* length of original instruction */
 } __packed;
 
-void apply_alternative_instructions(void);
-void apply_alternatives(struct alt_instr *start, struct alt_instr *end);
+extern struct alt_instr __alt_instructions[], __alt_instructions_end[];
+
+void __apply_alternatives(struct alt_instr *start, struct alt_instr *end, unsigned int ctx);
+
+static inline void apply_alternative_instructions(void)
+{
+	__apply_alternatives(__alt_instructions, __alt_instructions_end, ALT_CTX_LATE);
+}
+
+static inline void apply_alternatives(struct alt_instr *start, struct alt_instr *end)
+{
+	__apply_alternatives(start, end, ALT_CTX_ALL);
+}
 
 /*
  * +---------------------------------+
@@ -51,7 +107,7 @@ void apply_alternatives(struct alt_instr *start, struct alt_instr *end);
 #define ALTINSTR_ENTRY(feature, num)					\
 	"\t.long 661b - .\n"			/* old instruction */	\
 	"\t.long " b_altinstr(num)"b - .\n"	/* alt instruction */	\
-	"\t.word " __stringify(feature) "\n"	/* feature	   */	\
+	"\t.long " __stringify(feature) "\n"	/* feature	   */	\
 	"\t.byte " oldinstr_len "\n"		/* instruction len */	\
 	"\t.org . - (" oldinstr_len ") & 1\n"				\
 	"\t.org . - (" oldinstr_len ") + (" altinstr_len(num) ")\n"	\
@@ -127,7 +183,7 @@ void apply_alternatives(struct alt_instr *start, struct alt_instr *end);
 .macro alt_entry orig_start, orig_end, alt_start, alt_end, feature
 	.long	\orig_start - .
 	.long	\alt_start - .
-	.word	\feature
+	.long	\feature
 	.byte	\orig_end - \orig_start
 	.org	. - ( \orig_end - \orig_start ) & 1
 	.org	. - ( \orig_end - \orig_start ) + ( \alt_end - \alt_start )
diff --git a/arch/s390/include/asm/processor.h b/arch/s390/include/asm/processor.h
index 5debb12614ad..8a52554f49f0 100644
--- a/arch/s390/include/asm/processor.h
+++ b/arch/s390/include/asm/processor.h
@@ -419,7 +419,7 @@ static __always_inline bool regs_irqs_disabled(struct pt_regs *regs)
 
 static __always_inline void bpon(void)
 {
-	asm volatile(ALTERNATIVE("nop", ".insn	rrf,0xb2e80000,0,0,13,0", 82));
+	asm volatile(ALTERNATIVE("nop", ".insn	rrf,0xb2e80000,0,0,13,0", ALT_FACILITY(82)));
 }
 
 #endif /* __ASSEMBLY__ */
diff --git a/arch/s390/include/asm/spinlock.h b/arch/s390/include/asm/spinlock.h
index 3e43c90ff135..77d5e804af93 100644
--- a/arch/s390/include/asm/spinlock.h
+++ b/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("nop", ".insn rre,0xb2fa0000,7,0", 49) /* NIAI 7 */
+		ALTERNATIVE("nop", ".insn rre,0xb2fa0000,7,0", ALT_FACILITY(49)) /* NIAI 7 */
 		"	sth	%1,%0\n"
 		: "=R" (((unsigned short *) &lp->lock)[1])
 		: "d" (0) : "cc", "memory");