1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef _ASM_S390_ALTERNATIVE_H
3 #define _ASM_S390_ALTERNATIVE_H
4 
5 #ifndef __ASSEMBLY__
6 
7 #include <linux/types.h>
8 #include <linux/stddef.h>
9 #include <linux/stringify.h>
10 
11 struct alt_instr {
12 	s32 instr_offset;	/* original instruction */
13 	s32 repl_offset;	/* offset to replacement instruction */
14 	u16 facility;		/* facility bit set for replacement */
15 	u8  instrlen;		/* length of original instruction */
16 } __packed;
17 
18 void apply_alternative_instructions(void);
19 void apply_alternatives(struct alt_instr *start, struct alt_instr *end);
20 
21 /*
22  * +---------------------------------+
23  * |661:			     |662:
24  * | oldinstr			     |
25  * +---------------------------------+
26  *
27  * .altinstr_replacement section
28  * +---------------------------------+
29  * |6641:			     |6651:
30  * | alternative instr 1	     |
31  * +---------------------------------+
32  * |6642:			     |6652:
33  * | alternative instr 2	     |
34  * +---------------------------------+
35  *
36  * .altinstructions section
37  * +---------------------------------+
38  * | alt_instr entries for each      |
39  * | alternative instr		     |
40  * +---------------------------------+
41  */
42 
43 #define b_altinstr(num)		"664"#num
44 #define e_altinstr(num)		"665"#num
45 #define oldinstr_len		"662b-661b"
46 #define altinstr_len(num)	e_altinstr(num)"b-"b_altinstr(num)"b"
47 
48 #define OLDINSTR(oldinstr) \
49 	"661:\n\t" oldinstr "\n662:\n"
50 
51 #define ALTINSTR_ENTRY(facility, num)					\
52 	"\t.long 661b - .\n"			/* old instruction */	\
53 	"\t.long " b_altinstr(num)"b - .\n"	/* alt instruction */	\
54 	"\t.word " __stringify(facility) "\n"	/* facility bit    */	\
55 	"\t.byte " oldinstr_len "\n"		/* instruction len */	\
56 	"\t.org . - (" oldinstr_len ") + (" altinstr_len(num) ")\n"	\
57 	"\t.org . - (" altinstr_len(num) ") + (" oldinstr_len ")\n"
58 
59 #define ALTINSTR_REPLACEMENT(altinstr, num)	/* replacement */	\
60 	b_altinstr(num)":\n\t" altinstr "\n" e_altinstr(num) ":\n"
61 
62 /* alternative assembly primitive: */
63 #define ALTERNATIVE(oldinstr, altinstr, facility) \
64 	".pushsection .altinstr_replacement, \"ax\"\n"			\
65 	ALTINSTR_REPLACEMENT(altinstr, 1)				\
66 	".popsection\n"							\
67 	OLDINSTR(oldinstr)						\
68 	".pushsection .altinstructions,\"a\"\n"				\
69 	ALTINSTR_ENTRY(facility, 1)					\
70 	".popsection\n"
71 
72 #define ALTERNATIVE_2(oldinstr, altinstr1, facility1, altinstr2, facility2)\
73 	".pushsection .altinstr_replacement, \"ax\"\n"			\
74 	ALTINSTR_REPLACEMENT(altinstr1, 1)				\
75 	ALTINSTR_REPLACEMENT(altinstr2, 2)				\
76 	".popsection\n"							\
77 	OLDINSTR(oldinstr)						\
78 	".pushsection .altinstructions,\"a\"\n"				\
79 	ALTINSTR_ENTRY(facility1, 1)					\
80 	ALTINSTR_ENTRY(facility2, 2)					\
81 	".popsection\n"
82 
83 /*
84  * Alternative instructions for different CPU types or capabilities.
85  *
86  * This allows to use optimized instructions even on generic binary
87  * kernels.
88  *
89  * oldinstr is padded with jump and nops at compile time if altinstr is
90  * longer. altinstr is padded with jump and nops at run-time during patching.
91  *
92  * For non barrier like inlines please define new variants
93  * without volatile and memory clobber.
94  */
95 #define alternative(oldinstr, altinstr, facility)			\
96 	asm_inline volatile(ALTERNATIVE(oldinstr, altinstr, facility) : : : "memory")
97 
98 #define alternative_2(oldinstr, altinstr1, facility1, altinstr2, facility2) \
99 	asm_inline volatile(ALTERNATIVE_2(oldinstr, altinstr1, facility1,   \
100 				   altinstr2, facility2) ::: "memory")
101 
102 /* Alternative inline assembly with input. */
103 #define alternative_input(oldinstr, newinstr, feature, input...)	\
104 	asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, feature)	\
105 		: : input)
106 
107 /* Like alternative_input, but with a single output argument */
108 #define alternative_io(oldinstr, altinstr, facility, output, input...)	\
109 	asm_inline volatile(ALTERNATIVE(oldinstr, altinstr, facility)	\
110 		: output : input)
111 
112 /* Use this macro if more than one output parameter is needed. */
113 #define ASM_OUTPUT2(a...) a
114 
115 /* Use this macro if clobbers are needed without inputs. */
116 #define ASM_NO_INPUT_CLOBBER(clobber...) : clobber
117 
118 #endif /* __ASSEMBLY__ */
119 
120 #endif /* _ASM_S390_ALTERNATIVE_H */
121