1 files changed, 238 insertions, 0 deletions
diff --git a/arch/s390/include/asm/alternative.h b/arch/s390/include/asm/alternative.h
new file mode 100644
index 000000000000..1c56480def9e
--- /dev/null
+++ b/arch/s390/include/asm/alternative.h
@@ -0,0 +1,238 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#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_EARLY		1
+#define ALT_CTX_LATE		2
+#define ALT_CTX_ALL		(ALT_CTX_EARLY | ALT_CTX_LATE)
+
+#define ALT_TYPE_FACILITY	0
+#define ALT_TYPE_FEATURE	1
+#define ALT_TYPE_SPEC		2
+
+#define ALT_DATA_SHIFT		0
+#define ALT_TYPE_SHIFT		20
+#define ALT_CTX_SHIFT		28
+
+#define ALT_FACILITY(facility)		(ALT_CTX_EARLY << ALT_CTX_SHIFT		| \
+					 ALT_TYPE_FACILITY << ALT_TYPE_SHIFT	| \
+					 (facility) << ALT_DATA_SHIFT)
+
+#define ALT_FEATURE(feature)		(ALT_CTX_EARLY << ALT_CTX_SHIFT		| \
+					 ALT_TYPE_FEATURE << ALT_TYPE_SHIFT	| \
+					 (feature) << ALT_DATA_SHIFT)
+
+#define ALT_SPEC(facility)		(ALT_CTX_LATE << ALT_CTX_SHIFT		| \
+					 ALT_TYPE_SPEC << ALT_TYPE_SHIFT	| \
+					 (facility) << ALT_DATA_SHIFT)
+
+#ifndef __ASSEMBLER__
+
+#include <linux/types.h>
+#include <linux/stddef.h>
+#include <linux/stringify.h>
+
+struct alt_instr {
+	s32 instr_offset;	/* original instruction */
+	s32 repl_offset;	/* offset to replacement instruction */
+	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;
+
+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);
+}
+
+/*
+ * +---------------------------------+
+ * |661:			     |662:
+ * | oldinstr			     |
+ * +---------------------------------+
+ *
+ * .altinstr_replacement section
+ * +---------------------------------+
+ * |6641:			     |6651:
+ * | alternative instr 1	     |
+ * +---------------------------------+
+ * |6642:			     |6652:
+ * | alternative instr 2	     |
+ * +---------------------------------+
+ *
+ * .altinstructions section
+ * +---------------------------------+
+ * | alt_instr entries for each      |
+ * | alternative instr		     |
+ * +---------------------------------+
+ */
+
+#define b_altinstr(num)		"664"#num
+#define e_altinstr(num)		"665"#num
+#define oldinstr_len		"662b-661b"
+#define altinstr_len(num)	e_altinstr(num)"b-"b_altinstr(num)"b"
+
+#define OLDINSTR(oldinstr) \
+	"661:\n\t" oldinstr "\n662:\n"
+
+#define ALTINSTR_ENTRY(feature, num)					\
+	"\t.long 661b - .\n"			/* old instruction */	\
+	"\t.long " b_altinstr(num)"b - .\n"	/* alt instruction */	\
+	"\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"	\
+	"\t.org . - (" altinstr_len(num) ") + (" oldinstr_len ")\n"
+
+#define ALTINSTR_REPLACEMENT(altinstr, num)	/* replacement */	\
+	b_altinstr(num)":\n\t" altinstr "\n" e_altinstr(num) ":\n"
+
+/* alternative assembly primitive: */
+#define ALTERNATIVE(oldinstr, altinstr, feature) \
+	".pushsection .altinstr_replacement, \"ax\"\n"			\
+	ALTINSTR_REPLACEMENT(altinstr, 1)				\
+	".popsection\n"							\
+	OLDINSTR(oldinstr)						\
+	".pushsection .altinstructions,\"a\"\n"				\
+	ALTINSTR_ENTRY(feature, 1)					\
+	".popsection\n"
+
+#define ALTERNATIVE_2(oldinstr, altinstr1, feature1, altinstr2, feature2)\
+	".pushsection .altinstr_replacement, \"ax\"\n"			\
+	ALTINSTR_REPLACEMENT(altinstr1, 1)				\
+	ALTINSTR_REPLACEMENT(altinstr2, 2)				\
+	".popsection\n"							\
+	OLDINSTR(oldinstr)						\
+	".pushsection .altinstructions,\"a\"\n"				\
+	ALTINSTR_ENTRY(feature1, 1)					\
+	ALTINSTR_ENTRY(feature2, 2)					\
+	".popsection\n"
+
+/*
+ * Alternative instructions for different CPU types or capabilities.
+ *
+ * This allows to use optimized instructions even on generic binary
+ * kernels.
+ *
+ * oldinstr is padded with jump and nops at compile time if altinstr is
+ * longer. altinstr is padded with jump and nops at run-time during patching.
+ *
+ * For non barrier like inlines please define new variants
+ * without volatile and memory clobber.
+ */
+#define alternative(oldinstr, altinstr, feature)			\
+	asm_inline volatile(ALTERNATIVE(oldinstr, altinstr, feature) : : : "memory")
+
+#define alternative_2(oldinstr, altinstr1, feature1, altinstr2, feature2) \
+	asm_inline volatile(ALTERNATIVE_2(oldinstr, altinstr1, feature1,   \
+				   altinstr2, feature2) ::: "memory")
+
+/* Alternative inline assembly with input. */
+#define alternative_input(oldinstr, newinstr, feature, input...)	\
+	asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, feature)	\
+		: : input)
+
+/* Like alternative_input, but with a single output argument */
+#define alternative_io(oldinstr, altinstr, feature, output, input...)	\
+	asm_inline volatile(ALTERNATIVE(oldinstr, altinstr, feature)	\
+		: output : input)
+
+/* Use this macro if more than one output parameter is needed. */
+#define ASM_OUTPUT2(a...) a
+
+/* Use this macro if clobbers are needed without inputs. */
+#define ASM_NO_INPUT_CLOBBER(clobber...) : clobber
+
+#else  /* __ASSEMBLER__ */
+
+/*
+ * Issue one struct alt_instr descriptor entry (need to put it into
+ * the section .altinstructions, see below). This entry contains
+ * enough information for the alternatives patching code to patch an
+ * instruction. See apply_alternatives().
+ */
+.macro alt_entry orig_start, orig_end, alt_start, alt_end, feature
+	.long	\orig_start - .
+	.long	\alt_start - .
+	.long	\feature
+	.byte	\orig_end - \orig_start
+	.org	. - ( \orig_end - \orig_start ) & 1
+	.org	. - ( \orig_end - \orig_start ) + ( \alt_end - \alt_start )
+	.org	. - ( \alt_end - \alt_start ) + ( \orig_end - \orig_start )
+.endm
+
+/*
+ * Define an alternative between two instructions. If @feature is
+ * present, early code in apply_alternatives() replaces @oldinstr with
+ * @newinstr.
+ */
+.macro ALTERNATIVE oldinstr, newinstr, feature
+	.pushsection .altinstr_replacement,"ax"
+770:	\newinstr
+771:	.popsection
+772:	\oldinstr
+773:	.pushsection .altinstructions,"a"
+	alt_entry 772b, 773b, 770b, 771b, \feature
+	.popsection
+.endm
+
+/*
+ * Define an alternative between two instructions. If @feature is
+ * present, early code in apply_alternatives() replaces @oldinstr with
+ * @newinstr.
+ */
+.macro ALTERNATIVE_2 oldinstr, newinstr1, feature1, newinstr2, feature2
+	.pushsection .altinstr_replacement,"ax"
+770:	\newinstr1
+771:	\newinstr2
+772:	.popsection
+773:	\oldinstr
+774:	.pushsection .altinstructions,"a"
+	alt_entry 773b, 774b, 770b, 771b,\feature1
+	alt_entry 773b, 774b, 771b, 772b,\feature2
+	.popsection
+.endm
+
+#endif /* __ASSEMBLER__ */
+
+#endif /* _ASM_S390_ALTERNATIVE_H */