1 files changed, 150 insertions, 0 deletions
diff --git a/arch/s390/include/asm/alternative.h b/arch/s390/include/asm/alternative.h
new file mode 100644
index 000000000..c2cf7bcde
--- /dev/null
+++ b/arch/s390/include/asm/alternative.h
@@ -0,0 +1,150 @@
+/* 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 */
+	u8  replacementlen;	/* length of new instruction */
+} __packed;
+
+void apply_alternative_instructions(void);
+void apply_alternatives(struct alt_instr *start, struct alt_instr *end);
+
+/*
+ * |661:       |662:	  |6620      |663:
+ * +-----------+---------------------+
+ * | oldinstr  | oldinstr_padding    |
+ * |	       +----------+----------+
+ * |	       |	  |	     |
+ * |	       | >6 bytes |6/4/2 nops|
+ * |	       |6 bytes jg----------->
+ * +-----------+---------------------+
+ *		 ^^ static padding ^^
+ *
+ * .altinstr_replacement section
+ * +---------------------+-----------+
+ * |6641:			     |6651:
+ * | alternative instr 1	     |
+ * +-----------+---------+- - - - - -+
+ * |6642:		 |6652:      |
+ * | alternative instr 2 | padding
+ * +---------------------+- - - - - -+
+ *			  ^ runtime ^
+ *
+ * .altinstructions section
+ * +---------------------------------+
+ * | alt_instr entries for each      |
+ * | alternative instr		     |
+ * +---------------------------------+
+ */
+
+#define b_altinstr(num)	"664"#num
+#define e_altinstr(num)	"665"#num
+
+#define e_oldinstr_pad_end	"663"
+#define oldinstr_len		"662b-661b"
+#define oldinstr_total_len	e_oldinstr_pad_end"b-661b"
+#define altinstr_len(num)	e_altinstr(num)"b-"b_altinstr(num)"b"
+#define oldinstr_pad_len(num) \
+	"-(((" altinstr_len(num) ")-(" oldinstr_len ")) > 0) * " \
+	"((" altinstr_len(num) ")-(" oldinstr_len "))"
+
+#define INSTR_LEN_SANITY_CHECK(len)					\
+	".if " len " > 254\n"						\
+	"\t.error \"cpu alternatives does not support instructions "	\
+		"blocks > 254 bytes\"\n"				\
+	".endif\n"							\
+	".if (" len ") %% 2\n"						\
+	"\t.error \"cpu alternatives instructions length is odd\"\n"	\
+	".endif\n"
+
+#define OLDINSTR_PADDING(oldinstr, num)					\
+	".if " oldinstr_pad_len(num) " > 6\n"				\
+	"\tjg " e_oldinstr_pad_end "f\n"				\
+	"6620:\n"							\
+	"\t.fill (" oldinstr_pad_len(num) " - (6620b-662b)) / 2, 2, 0x0700\n" \
+	".else\n"							\
+	"\t.fill " oldinstr_pad_len(num) " / 6, 6, 0xc0040000\n"	\
+	"\t.fill " oldinstr_pad_len(num) " %% 6 / 4, 4, 0x47000000\n"	\
+	"\t.fill " oldinstr_pad_len(num) " %% 6 %% 4 / 2, 2, 0x0700\n"	\
+	".endif\n"
+
+#define OLDINSTR(oldinstr, num)						\
+	"661:\n\t" oldinstr "\n662:\n"					\
+	OLDINSTR_PADDING(oldinstr, num)					\
+	e_oldinstr_pad_end ":\n"					\
+	INSTR_LEN_SANITY_CHECK(oldinstr_len)
+
+#define OLDINSTR_2(oldinstr, num1, num2)				\
+	"661:\n\t" oldinstr "\n662:\n"					\
+	".if " altinstr_len(num1) " < " altinstr_len(num2) "\n"		\
+	OLDINSTR_PADDING(oldinstr, num2)				\
+	".else\n"							\
+	OLDINSTR_PADDING(oldinstr, num1)				\
+	".endif\n"							\
+	e_oldinstr_pad_end ":\n"					\
+	INSTR_LEN_SANITY_CHECK(oldinstr_len)
+
+#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_total_len "\n"	/* source len	   */	\
+	"\t.byte " altinstr_len(num) "\n"	/* alt instruction len */
+
+#define ALTINSTR_REPLACEMENT(altinstr, num)	/* replacement */	\
+	b_altinstr(num)":\n\t" altinstr "\n" e_altinstr(num) ":\n"	\
+	INSTR_LEN_SANITY_CHECK(altinstr_len(num))
+
+/* alternative assembly primitive: */
+#define ALTERNATIVE(oldinstr, altinstr, facility) \
+	".pushsection .altinstr_replacement, \"ax\"\n"			\
+	ALTINSTR_REPLACEMENT(altinstr, 1)				\
+	".popsection\n"							\
+	OLDINSTR(oldinstr, 1)						\
+	".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_2(oldinstr, 1, 2)					\
+	".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 volatile(ALTERNATIVE(oldinstr, altinstr, facility) : : : "memory")
+
+#define alternative_2(oldinstr, altinstr1, facility1, altinstr2, facility2) \
+	asm volatile(ALTERNATIVE_2(oldinstr, altinstr1, facility1,	    \
+				   altinstr2, facility2) ::: "memory")
+
+#endif /* __ASSEMBLY__ */
+
+#endif /* _ASM_S390_ALTERNATIVE_H */