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 	u8  replacementlen;	/* length of new instruction */
17 } __packed;
18 
19 void apply_alternative_instructions(void);
20 void apply_alternatives(struct alt_instr *start, struct alt_instr *end);
21 
22 /*
23  * |661:       |662:	  |6620      |663:
24  * +-----------+---------------------+
25  * | oldinstr  | oldinstr_padding    |
26  * |	       +----------+----------+
27  * |	       |	  |	     |
28  * |	       | >6 bytes |6/4/2 nops|
29  * |	       |6 bytes jg----------->
30  * +-----------+---------------------+
31  *		 ^^ static padding ^^
32  *
33  * .altinstr_replacement section
34  * +---------------------+-----------+
35  * |6641:			     |6651:
36  * | alternative instr 1	     |
37  * +-----------+---------+- - - - - -+
38  * |6642:		 |6652:      |
39  * | alternative instr 2 | padding
40  * +---------------------+- - - - - -+
41  *			  ^ runtime ^
42  *
43  * .altinstructions section
44  * +---------------------------------+
45  * | alt_instr entries for each      |
46  * | alternative instr		     |
47  * +---------------------------------+
48  */
49 
50 #define b_altinstr(num)	"664"#num
51 #define e_altinstr(num)	"665"#num
52 
53 #define e_oldinstr_pad_end	"663"
54 #define oldinstr_len		"662b-661b"
55 #define oldinstr_total_len	e_oldinstr_pad_end"b-661b"
56 #define altinstr_len(num)	e_altinstr(num)"b-"b_altinstr(num)"b"
57 #define oldinstr_pad_len(num) \
58 	"-(((" altinstr_len(num) ")-(" oldinstr_len ")) > 0) * " \
59 	"((" altinstr_len(num) ")-(" oldinstr_len "))"
60 
61 #define INSTR_LEN_SANITY_CHECK(len)					\
62 	".if " len " > 254\n"						\
63 	"\t.error \"cpu alternatives does not support instructions "	\
64 		"blocks > 254 bytes\"\n"				\
65 	".endif\n"							\
66 	".if (" len ") %% 2\n"						\
67 	"\t.error \"cpu alternatives instructions length is odd\"\n"	\
68 	".endif\n"
69 
70 #define OLDINSTR_PADDING(oldinstr, num)					\
71 	".if " oldinstr_pad_len(num) " > 6\n"				\
72 	"\tjg " e_oldinstr_pad_end "f\n"				\
73 	"6620:\n"							\
74 	"\t.fill (" oldinstr_pad_len(num) " - (6620b-662b)) / 2, 2, 0x0700\n" \
75 	".else\n"							\
76 	"\t.fill " oldinstr_pad_len(num) " / 6, 6, 0xc0040000\n"	\
77 	"\t.fill " oldinstr_pad_len(num) " %% 6 / 4, 4, 0x47000000\n"	\
78 	"\t.fill " oldinstr_pad_len(num) " %% 6 %% 4 / 2, 2, 0x0700\n"	\
79 	".endif\n"
80 
81 #define OLDINSTR(oldinstr, num)						\
82 	"661:\n\t" oldinstr "\n662:\n"					\
83 	OLDINSTR_PADDING(oldinstr, num)					\
84 	e_oldinstr_pad_end ":\n"					\
85 	INSTR_LEN_SANITY_CHECK(oldinstr_len)
86 
87 #define OLDINSTR_2(oldinstr, num1, num2)				\
88 	"661:\n\t" oldinstr "\n662:\n"					\
89 	".if " altinstr_len(num1) " < " altinstr_len(num2) "\n"		\
90 	OLDINSTR_PADDING(oldinstr, num2)				\
91 	".else\n"							\
92 	OLDINSTR_PADDING(oldinstr, num1)				\
93 	".endif\n"							\
94 	e_oldinstr_pad_end ":\n"					\
95 	INSTR_LEN_SANITY_CHECK(oldinstr_len)
96 
97 #define ALTINSTR_ENTRY(facility, num)					\
98 	"\t.long 661b - .\n"			/* old instruction */	\
99 	"\t.long " b_altinstr(num)"b - .\n"	/* alt instruction */	\
100 	"\t.word " __stringify(facility) "\n"	/* facility bit    */	\
101 	"\t.byte " oldinstr_total_len "\n"	/* source len	   */	\
102 	"\t.byte " altinstr_len(num) "\n"	/* alt instruction len */
103 
104 #define ALTINSTR_REPLACEMENT(altinstr, num)	/* replacement */	\
105 	b_altinstr(num)":\n\t" altinstr "\n" e_altinstr(num) ":\n"	\
106 	INSTR_LEN_SANITY_CHECK(altinstr_len(num))
107 
108 /* alternative assembly primitive: */
109 #define ALTERNATIVE(oldinstr, altinstr, facility) \
110 	".pushsection .altinstr_replacement, \"ax\"\n"			\
111 	ALTINSTR_REPLACEMENT(altinstr, 1)				\
112 	".popsection\n"							\
113 	OLDINSTR(oldinstr, 1)						\
114 	".pushsection .altinstructions,\"a\"\n"				\
115 	ALTINSTR_ENTRY(facility, 1)					\
116 	".popsection\n"
117 
118 #define ALTERNATIVE_2(oldinstr, altinstr1, facility1, altinstr2, facility2)\
119 	".pushsection .altinstr_replacement, \"ax\"\n"			\
120 	ALTINSTR_REPLACEMENT(altinstr1, 1)				\
121 	ALTINSTR_REPLACEMENT(altinstr2, 2)				\
122 	".popsection\n"							\
123 	OLDINSTR_2(oldinstr, 1, 2)					\
124 	".pushsection .altinstructions,\"a\"\n"				\
125 	ALTINSTR_ENTRY(facility1, 1)					\
126 	ALTINSTR_ENTRY(facility2, 2)					\
127 	".popsection\n"
128 
129 /*
130  * Alternative instructions for different CPU types or capabilities.
131  *
132  * This allows to use optimized instructions even on generic binary
133  * kernels.
134  *
135  * oldinstr is padded with jump and nops at compile time if altinstr is
136  * longer. altinstr is padded with jump and nops at run-time during patching.
137  *
138  * For non barrier like inlines please define new variants
139  * without volatile and memory clobber.
140  */
141 #define alternative(oldinstr, altinstr, facility)			\
142 	asm volatile(ALTERNATIVE(oldinstr, altinstr, facility) : : : "memory")
143 
144 #define alternative_2(oldinstr, altinstr1, facility1, altinstr2, facility2) \
145 	asm volatile(ALTERNATIVE_2(oldinstr, altinstr1, facility1,	    \
146 				   altinstr2, facility2) ::: "memory")
147 
148 #endif /* __ASSEMBLY__ */
149 
150 #endif /* _ASM_S390_ALTERNATIVE_H */
151