1 #ifndef __ASM_ALTERNATIVE_H
2 #define __ASM_ALTERNATIVE_H
6 #include <linux/init.h>
7 #include <linux/kconfig.h>
8 #include <linux/types.h>
9 #include <linux/stddef.h>
10 #include <linux/stringify.h>
13 s32 orig_offset
; /* offset to original instruction */
14 s32 alt_offset
; /* offset to replacement instruction */
15 u16 cpufeature
; /* cpufeature bit set for replacement */
16 u8 orig_len
; /* size of original instruction(s) */
17 u8 alt_len
; /* size of new instruction(s), <= orig_len */
20 void __init
apply_alternatives_all(void);
21 void apply_alternatives(void *start
, size_t length
);
23 #define ALTINSTR_ENTRY(feature) \
24 " .word 661b - .\n" /* label */ \
25 " .word 663f - .\n" /* new instruction */ \
26 " .hword " __stringify(feature) "\n" /* feature bit */ \
27 " .byte 662b-661b\n" /* source len */ \
28 " .byte 664f-663f\n" /* replacement len */
31 * alternative assembly primitive:
33 * If any of these .org directive fail, it means that insn1 and insn2
34 * don't have the same length. This used to be written as
36 * .if ((664b-663b) != (662b-661b))
37 * .error "Alternatives instruction length mismatch"
40 * but most assemblers die if insn1 or insn2 have a .inst. This should
41 * be fixed in a binutils release posterior to 2.25.51.0.2 (anything
42 * containing commit 4e4d08cf7399b606 or c1baaddf8861).
44 #define __ALTERNATIVE_CFG(oldinstr, newinstr, feature, cfg_enabled) \
45 ".if "__stringify(cfg_enabled)" == 1\n" \
49 ".pushsection .altinstructions,\"a\"\n" \
50 ALTINSTR_ENTRY(feature) \
52 ".pushsection .altinstr_replacement, \"a\"\n" \
57 ".org . - (664b-663b) + (662b-661b)\n\t" \
58 ".org . - (662b-661b) + (664b-663b)\n" \
61 #define _ALTERNATIVE_CFG(oldinstr, newinstr, feature, cfg, ...) \
62 __ALTERNATIVE_CFG(oldinstr, newinstr, feature, IS_ENABLED(cfg))
66 .macro altinstruction_entry orig_offset alt_offset feature orig_len alt_len
67 .word \orig_offset
- .
74 .macro alternative_insn insn1
, insn2
, cap
, enable
= 1
77 662: .pushsection
.altinstructions
, "a"
78 altinstruction_entry
661b
, 663f
, \cap
, 662b
-661b
, 664f
-663f
80 .pushsection
.altinstr_replacement
, "ax"
83 .org
. - (664b
-663b
) + (662b
-661b
)
84 .org
. - (662b
-661b
) + (664b
-663b
)
89 * Begin an alternative code sequence.
91 * The code that follows this macro will be assembled and linked as
92 * normal. There are no restrictions on this code.
94 .macro alternative_if_not cap
, enable
= 1
96 .pushsection
.altinstructions
, "a"
97 altinstruction_entry
661f
, 663f
, \cap
, 662f
-661f
, 664f
-663f
104 * Provide the alternative code sequence.
106 * The code that follows this macro is assembled into a special
107 * section to be used for dynamic patching. Code that follows this
110 * 1. Be exactly the same length (in bytes) as the default code
113 * 2. Not contain a branch target that is used outside of the
114 * alternative sequence it is defined in (branches into an
115 * alternative sequence are not fixed up).
117 .macro alternative_else
, enable
= 1
119 662: .pushsection
.altinstr_replacement
, "ax"
125 * Complete an alternative code sequence.
127 .macro alternative_endif
, enable
= 1
130 .org
. - (664b
-663b
) + (662b
-661b
)
131 .org
. - (662b
-661b
) + (664b
-663b
)
135 #define _ALTERNATIVE_CFG(insn1, insn2, cap, cfg, ...) \
136 alternative_insn insn1, insn2, cap, IS_ENABLED(cfg)
139 #endif /* __ASSEMBLY__ */
142 * Usage: asm(ALTERNATIVE(oldinstr, newinstr, feature));
144 * Usage: asm(ALTERNATIVE(oldinstr, newinstr, feature, CONFIG_FOO));
145 * N.B. If CONFIG_FOO is specified, but not selected, the whole block
146 * will be omitted, including oldinstr.
148 #define ALTERNATIVE(oldinstr, newinstr, ...) \
149 _ALTERNATIVE_CFG(oldinstr, newinstr, __VA_ARGS__, 1)
151 #endif /* __ASM_ALTERNATIVE_H */