1 #ifndef _ASM_X86_ALTERNATIVE_H
2 #define _ASM_X86_ALTERNATIVE_H
4 #include <linux/types.h>
5 #include <linux/stddef.h>
6 #include <linux/stringify.h>
10 * Alternative inline assembly for SMP.
12 * The LOCK_PREFIX macro defined here replaces the LOCK and
13 * LOCK_PREFIX macros used everywhere in the source tree.
15 * SMP alternatives use the same data structures as the other
16 * alternatives and the X86_FEATURE_UP flag to indicate the case of a
17 * UP system running a SMP kernel. The existing apply_alternatives()
18 * works fine for patching a SMP kernel for UP.
20 * The SMP alternative tables can be kept after boot and contain both
21 * UP and SMP versions of the instructions to allow switching back to
22 * SMP at runtime, when hotplugging in a new CPU, which is especially
23 * useful in virtualized environments.
25 * The very common lock prefix is handled as special case in a
26 * separate table which is a pure address list without replacement ptr
27 * and size information. That keeps the table sizes small.
31 #define LOCK_PREFIX_HERE \
32 ".section .smp_locks,\"a\"\n" \
34 ".long 671f - .\n" /* offset */ \
38 #define LOCK_PREFIX LOCK_PREFIX_HERE "\n\tlock; "
40 #else /* ! CONFIG_SMP */
41 #define LOCK_PREFIX_HERE ""
42 #define LOCK_PREFIX ""
46 s32 instr_offset; /* original instruction */
47 s32 repl_offset; /* offset to replacement instruction */
48 u16 cpuid; /* cpuid bit set for replacement */
49 u8 instrlen; /* length of original instruction */
50 u8 replacementlen; /* length of new instruction */
51 u8 padlen; /* length of build-time padding */
54 extern void alternative_instructions(void);
55 extern void apply_alternatives(struct alt_instr *start, struct alt_instr *end);
60 extern void alternatives_smp_module_add(struct module *mod, char *name,
61 void *locks, void *locks_end,
62 void *text, void *text_end);
63 extern void alternatives_smp_module_del(struct module *mod);
64 extern void alternatives_enable_smp(void);
65 extern int alternatives_text_reserved(void *start, void *end);
66 extern bool skip_smp_alternatives;
68 static inline void alternatives_smp_module_add(struct module *mod, char *name,
69 void *locks, void *locks_end,
70 void *text, void *text_end) {}
71 static inline void alternatives_smp_module_del(struct module *mod) {}
72 static inline void alternatives_enable_smp(void) {}
73 static inline int alternatives_text_reserved(void *start, void *end)
77 #endif /* CONFIG_SMP */
79 #define b_replacement(num) "664"#num
80 #define e_replacement(num) "665"#num
82 #define alt_end_marker "663"
83 #define alt_slen "662b-661b"
84 #define alt_pad_len alt_end_marker"b-662b"
85 #define alt_total_slen alt_end_marker"b-661b"
86 #define alt_rlen(num) e_replacement(num)"f-"b_replacement(num)"f"
88 #define __OLDINSTR(oldinstr, num) \
89 "661:\n\t" oldinstr "\n662:\n" \
90 ".skip -(((" alt_rlen(num) ")-(" alt_slen ")) > 0) * " \
91 "((" alt_rlen(num) ")-(" alt_slen ")),0x90\n"
93 #define OLDINSTR(oldinstr, num) \
94 __OLDINSTR(oldinstr, num) \
98 * Pad the second replacement alternative with additional NOPs if it is
99 * additionally longer than the first replacement alternative.
101 #define OLDINSTR_2(oldinstr, num1, num2) \
102 __OLDINSTR(oldinstr, num1) \
103 ".skip -(((" alt_rlen(num2) ")-(" alt_rlen(num1) ")-(662b-661b)) > 0) * " \
104 "((" alt_rlen(num2) ")-(" alt_rlen(num1) ")-(662b-661b)),0x90\n" \
107 #define ALTINSTR_ENTRY(feature, num) \
108 " .long 661b - .\n" /* label */ \
109 " .long " b_replacement(num)"f - .\n" /* new instruction */ \
110 " .word " __stringify(feature) "\n" /* feature bit */ \
111 " .byte " alt_total_slen "\n" /* source len */ \
112 " .byte " alt_rlen(num) "\n" /* replacement len */ \
113 " .byte " alt_pad_len "\n" /* pad len */
115 #define ALTINSTR_REPLACEMENT(newinstr, feature, num) /* replacement */ \
116 b_replacement(num)":\n\t" newinstr "\n" e_replacement(num) ":\n\t"
118 /* alternative assembly primitive: */
119 #define ALTERNATIVE(oldinstr, newinstr, feature) \
120 OLDINSTR(oldinstr, 1) \
121 ".pushsection .altinstructions,\"a\"\n" \
122 ALTINSTR_ENTRY(feature, 1) \
124 ".pushsection .altinstr_replacement, \"ax\"\n" \
125 ALTINSTR_REPLACEMENT(newinstr, feature, 1) \
128 #define ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2)\
129 OLDINSTR_2(oldinstr, 1, 2) \
130 ".pushsection .altinstructions,\"a\"\n" \
131 ALTINSTR_ENTRY(feature1, 1) \
132 ALTINSTR_ENTRY(feature2, 2) \
134 ".pushsection .altinstr_replacement, \"ax\"\n" \
135 ALTINSTR_REPLACEMENT(newinstr1, feature1, 1) \
136 ALTINSTR_REPLACEMENT(newinstr2, feature2, 2) \
140 * This must be included *after* the definition of ALTERNATIVE due to
141 * <asm/arch_hweight.h>
143 #include <asm/cpufeature.h>
146 * Alternative instructions for different CPU types or capabilities.
148 * This allows to use optimized instructions even on generic binary
151 * length of oldinstr must be longer or equal the length of newinstr
152 * It can be padded with nops as needed.
154 * For non barrier like inlines please define new variants
155 * without volatile and memory clobber.
157 #define alternative(oldinstr, newinstr, feature) \
158 asm volatile (ALTERNATIVE(oldinstr, newinstr, feature) : : : "memory")
160 #define alternative_2(oldinstr, newinstr1, feature1, newinstr2, feature2) \
161 asm volatile(ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2) ::: "memory")
164 * Alternative inline assembly with input.
167 * No memory clobber here.
168 * Argument numbers start with 1.
169 * Best is to use constraints that are fixed size (like (%1) ... "r")
170 * If you use variable sized constraints like "m" or "g" in the
171 * replacement make sure to pad to the worst case length.
172 * Leaving an unused argument 0 to keep API compatibility.
174 #define alternative_input(oldinstr, newinstr, feature, input...) \
175 asm volatile (ALTERNATIVE(oldinstr, newinstr, feature) \
176 : : "i" (0), ## input)
178 /* Like alternative_input, but with a single output argument */
179 #define alternative_io(oldinstr, newinstr, feature, output, input...) \
180 asm volatile (ALTERNATIVE(oldinstr, newinstr, feature) \
181 : output : "i" (0), ## input)
183 /* Like alternative_io, but for replacing a direct call with another one. */
184 #define alternative_call(oldfunc, newfunc, feature, output, input...) \
185 asm volatile (ALTERNATIVE("call %P[old]", "call %P[new]", feature) \
186 : output : [old] "i" (oldfunc), [new] "i" (newfunc), ## input)
189 * use this macro(s) if you need more than one output parameter
192 #define ASM_OUTPUT2(a...) a
194 struct paravirt_patch_site;
195 #ifdef CONFIG_PARAVIRT
196 void apply_paravirt(struct paravirt_patch_site *start,
197 struct paravirt_patch_site *end);
199 static inline void apply_paravirt(struct paravirt_patch_site *start,
200 struct paravirt_patch_site *end)
202 #define __parainstructions NULL
203 #define __parainstructions_end NULL
206 extern void *text_poke_early(void *addr, const void *opcode, size_t len);
209 * Clear and restore the kernel write-protection flag on the local CPU.
210 * Allows the kernel to edit read-only pages.
211 * Side-effect: any interrupt handler running between save and restore will have
212 * the ability to write to read-only pages.
215 * Code patching in the UP case is safe if NMIs and MCE handlers are stopped and
216 * no thread can be preempted in the instructions being modified (no iret to an
217 * invalid instruction possible) or if the instructions are changed from a
218 * consistent state to another consistent state atomically.
219 * More care must be taken when modifying code in the SMP case because of
220 * Intel's errata. text_poke_smp() takes care that errata, but still
221 * doesn't support NMI/MCE handler code modifying.
222 * On the local CPU you need to be protected again NMI or MCE handlers seeing an
223 * inconsistent instruction while you patch.
225 struct text_poke_param {
231 extern void *text_poke(void *addr, const void *opcode, size_t len);
232 extern void *text_poke_smp(void *addr, const void *opcode, size_t len);
233 extern void text_poke_smp_batch(struct text_poke_param *params, int n);
235 #endif /* _ASM_X86_ALTERNATIVE_H */