1 files changed, 120 insertions, 0 deletions
diff --git a/arch/s390/include/asm/alternative.h b/arch/s390/include/asm/alternative.h
new file mode 100644
index 0000000000..904dd049f9
--- /dev/null
+++ b/arch/s390/include/asm/alternative.h
@@ -0,0 +1,120 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_S390_ALTERNATIVE_H
+#define _ASM_S390_ALTERNATIVE_H
+
+#ifndef __ASSEMBLY__
+
+#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 */
+	u16 facility;		/* facility bit set for replacement */
+	u8  instrlen;		/* length of original instruction */
+} __packed;
+
+void apply_alternative_instructions(void);
+void apply_alternatives(struct alt_instr *start, struct alt_instr *end);
+
+/*
+ * +---------------------------------+
+ * |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(facility, num)					\
+	"\t.long 661b - .\n"			/* old instruction */	\
+	"\t.long " b_altinstr(num)"b - .\n"	/* alt instruction */	\
+	"\t.word " __stringify(facility) "\n"	/* facility bit    */	\
+	"\t.byte " oldinstr_len "\n"		/* instruction len */	\
+	"\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, facility) \
+	".pushsection .altinstr_replacement, \"ax\"\n"			\
+	ALTINSTR_REPLACEMENT(altinstr, 1)				\
+	".popsection\n"							\
+	OLDINSTR(oldinstr)						\
+	".pushsection .altinstructions,\"a\"\n"				\
+	ALTINSTR_ENTRY(facility, 1)					\
+	".popsection\n"
+
+#define ALTERNATIVE_2(oldinstr, altinstr1, facility1, altinstr2, facility2)\
+	".pushsection .altinstr_replacement, \"ax\"\n"			\
+	ALTINSTR_REPLACEMENT(altinstr1, 1)				\
+	ALTINSTR_REPLACEMENT(altinstr2, 2)				\
+	".popsection\n"							\
+	OLDINSTR(oldinstr)						\
+	".pushsection .altinstructions,\"a\"\n"				\
+	ALTINSTR_ENTRY(facility1, 1)					\
+	ALTINSTR_ENTRY(facility2, 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, facility)			\
+	asm_inline volatile(ALTERNATIVE(oldinstr, altinstr, facility) : : : "memory")
+
+#define alternative_2(oldinstr, altinstr1, facility1, altinstr2, facility2) \
+	asm_inline volatile(ALTERNATIVE_2(oldinstr, altinstr1, facility1,   \
+				   altinstr2, facility2) ::: "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, facility, output, input...)	\
+	asm_inline volatile(ALTERNATIVE(oldinstr, altinstr, facility)	\
+		: 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
+
+#endif /* __ASSEMBLY__ */
+
+#endif /* _ASM_S390_ALTERNATIVE_H */