1 #ifndef _ASM_X86_ALTERNATIVE_H
2 #define _ASM_X86_ALTERNATIVE_H
3
4 #ifndef __ASSEMBLY__
5
6 #include <linux/types.h>
7 #include <linux/stddef.h>
8 #include <linux/stringify.h>
9 #include <asm/asm.h>
10 #include <asm/ptrace.h>
11
12 /*
13 * Alternative inline assembly for SMP.
14 *
15 * The LOCK_PREFIX macro defined here replaces the LOCK and
16 * LOCK_PREFIX macros used everywhere in the source tree.
17 *
18 * SMP alternatives use the same data structures as the other
19 * alternatives and the X86_FEATURE_UP flag to indicate the case of a
20 * UP system running a SMP kernel. The existing apply_alternatives()
21 * works fine for patching a SMP kernel for UP.
22 *
23 * The SMP alternative tables can be kept after boot and contain both
24 * UP and SMP versions of the instructions to allow switching back to
25 * SMP at runtime, when hotplugging in a new CPU, which is especially
26 * useful in virtualized environments.
27 *
28 * The very common lock prefix is handled as special case in a
29 * separate table which is a pure address list without replacement ptr
30 * and size information. That keeps the table sizes small.
31 */
32
33 #ifdef CONFIG_SMP
34 #define LOCK_PREFIX_HERE \
35 ".pushsection .smp_locks,\"a\"\n" \
36 ".balign 4\n" \
37 ".long 671f - .\n" /* offset */ \
38 ".popsection\n" \
39 "671:"
40
41 #define LOCK_PREFIX LOCK_PREFIX_HERE "\n\tlock; "
42
43 #else /* ! CONFIG_SMP */
44 #define LOCK_PREFIX_HERE ""
45 #define LOCK_PREFIX ""
46 #endif
47
48 struct alt_instr {
49 s32 instr_offset; /* original instruction */
50 s32 repl_offset; /* offset to replacement instruction */
51 u16 cpuid; /* cpuid bit set for replacement */
52 u8 instrlen; /* length of original instruction */
53 u8 replacementlen; /* length of new instruction */
54 u8 padlen; /* length of build-time padding */
55 } __packed;
56
57 /*
58 * Debug flag that can be tested to see whether alternative
59 * instructions were patched in already:
60 */
61 extern int alternatives_patched;
62
63 extern void alternative_instructions(void);
64 extern void apply_alternatives(struct alt_instr *start, struct alt_instr *end);
65
66 struct module;
67
68 #ifdef CONFIG_SMP
69 extern void alternatives_smp_module_add(struct module *mod, char *name,
70 void *locks, void *locks_end,
71 void *text, void *text_end);
72 extern void alternatives_smp_module_del(struct module *mod);
73 extern void alternatives_enable_smp(void);
74 extern int alternatives_text_reserved(void *start, void *end);
75 extern bool skip_smp_alternatives;
76 #else
alternatives_smp_module_add(struct module * mod,char * name,void * locks,void * locks_end,void * text,void * text_end)77 static inline void alternatives_smp_module_add(struct module *mod, char *name,
78 void *locks, void *locks_end,
79 void *text, void *text_end) {}
alternatives_smp_module_del(struct module * mod)80 static inline void alternatives_smp_module_del(struct module *mod) {}
alternatives_enable_smp(void)81 static inline void alternatives_enable_smp(void) {}
alternatives_text_reserved(void * start,void * end)82 static inline int alternatives_text_reserved(void *start, void *end)
83 {
84 return 0;
85 }
86 #endif /* CONFIG_SMP */
87
88 #define b_replacement(num) "664"#num
89 #define e_replacement(num) "665"#num
90
91 #define alt_end_marker "663"
92 #define alt_slen "662b-661b"
93 #define alt_pad_len alt_end_marker"b-662b"
94 #define alt_total_slen alt_end_marker"b-661b"
95 #define alt_rlen(num) e_replacement(num)"f-"b_replacement(num)"f"
96
97 #define __OLDINSTR(oldinstr, num) \
98 "661:\n\t" oldinstr "\n662:\n" \
99 ".skip -(((" alt_rlen(num) ")-(" alt_slen ")) > 0) * " \
100 "((" alt_rlen(num) ")-(" alt_slen ")),0x90\n"
101
102 #define OLDINSTR(oldinstr, num) \
103 __OLDINSTR(oldinstr, num) \
104 alt_end_marker ":\n"
105
106 /*
107 * gas compatible max based on the idea from:
108 * http://graphics.stanford.edu/~seander/bithacks.html#IntegerMinOrMax
109 *
110 * The additional "-" is needed because gas uses a "true" value of -1.
111 */
112 #define alt_max_short(a, b) "((" a ") ^ (((" a ") ^ (" b ")) & -(-((" a ") < (" b ")))))"
113
114 /*
115 * Pad the second replacement alternative with additional NOPs if it is
116 * additionally longer than the first replacement alternative.
117 */
118 #define OLDINSTR_2(oldinstr, num1, num2) \
119 "661:\n\t" oldinstr "\n662:\n" \
120 ".skip -((" alt_max_short(alt_rlen(num1), alt_rlen(num2)) " - (" alt_slen ")) > 0) * " \
121 "(" alt_max_short(alt_rlen(num1), alt_rlen(num2)) " - (" alt_slen ")), 0x90\n" \
122 alt_end_marker ":\n"
123
124 #define ALTINSTR_ENTRY(feature, num) \
125 " .long 661b - .\n" /* label */ \
126 " .long " b_replacement(num)"f - .\n" /* new instruction */ \
127 " .word " __stringify(feature) "\n" /* feature bit */ \
128 " .byte " alt_total_slen "\n" /* source len */ \
129 " .byte " alt_rlen(num) "\n" /* replacement len */ \
130 " .byte " alt_pad_len "\n" /* pad len */
131
132 #define ALTINSTR_REPLACEMENT(newinstr, feature, num) /* replacement */ \
133 b_replacement(num)":\n\t" newinstr "\n" e_replacement(num) ":\n\t"
134
135 /* alternative assembly primitive: */
136 #define ALTERNATIVE(oldinstr, newinstr, feature) \
137 OLDINSTR(oldinstr, 1) \
138 ".pushsection .altinstructions,\"a\"\n" \
139 ALTINSTR_ENTRY(feature, 1) \
140 ".popsection\n" \
141 ".pushsection .altinstr_replacement, \"ax\"\n" \
142 ALTINSTR_REPLACEMENT(newinstr, feature, 1) \
143 ".popsection\n"
144
145 #define ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2)\
146 OLDINSTR_2(oldinstr, 1, 2) \
147 ".pushsection .altinstructions,\"a\"\n" \
148 ALTINSTR_ENTRY(feature1, 1) \
149 ALTINSTR_ENTRY(feature2, 2) \
150 ".popsection\n" \
151 ".pushsection .altinstr_replacement, \"ax\"\n" \
152 ALTINSTR_REPLACEMENT(newinstr1, feature1, 1) \
153 ALTINSTR_REPLACEMENT(newinstr2, feature2, 2) \
154 ".popsection\n"
155
156 /*
157 * Alternative instructions for different CPU types or capabilities.
158 *
159 * This allows to use optimized instructions even on generic binary
160 * kernels.
161 *
162 * length of oldinstr must be longer or equal the length of newinstr
163 * It can be padded with nops as needed.
164 *
165 * For non barrier like inlines please define new variants
166 * without volatile and memory clobber.
167 */
168 #define alternative(oldinstr, newinstr, feature) \
169 asm volatile (ALTERNATIVE(oldinstr, newinstr, feature) : : : "memory")
170
171 #define alternative_2(oldinstr, newinstr1, feature1, newinstr2, feature2) \
172 asm volatile(ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2) ::: "memory")
173
174 /*
175 * Alternative inline assembly with input.
176 *
177 * Pecularities:
178 * No memory clobber here.
179 * Argument numbers start with 1.
180 * Best is to use constraints that are fixed size (like (%1) ... "r")
181 * If you use variable sized constraints like "m" or "g" in the
182 * replacement make sure to pad to the worst case length.
183 * Leaving an unused argument 0 to keep API compatibility.
184 */
185 #define alternative_input(oldinstr, newinstr, feature, input...) \
186 asm volatile (ALTERNATIVE(oldinstr, newinstr, feature) \
187 : : "i" (0), ## input)
188
189 /*
190 * This is similar to alternative_input. But it has two features and
191 * respective instructions.
192 *
193 * If CPU has feature2, newinstr2 is used.
194 * Otherwise, if CPU has feature1, newinstr1 is used.
195 * Otherwise, oldinstr is used.
196 */
197 #define alternative_input_2(oldinstr, newinstr1, feature1, newinstr2, \
198 feature2, input...) \
199 asm volatile(ALTERNATIVE_2(oldinstr, newinstr1, feature1, \
200 newinstr2, feature2) \
201 : : "i" (0), ## input)
202
203 /* Like alternative_input, but with a single output argument */
204 #define alternative_io(oldinstr, newinstr, feature, output, input...) \
205 asm volatile (ALTERNATIVE(oldinstr, newinstr, feature) \
206 : output : "i" (0), ## input)
207
208 /* Like alternative_io, but for replacing a direct call with another one. */
209 #define alternative_call(oldfunc, newfunc, feature, output, input...) \
210 asm volatile (ALTERNATIVE("call %P[old]", "call %P[new]", feature) \
211 : output : [old] "i" (oldfunc), [new] "i" (newfunc), ## input)
212
213 /*
214 * Like alternative_call, but there are two features and respective functions.
215 * If CPU has feature2, function2 is used.
216 * Otherwise, if CPU has feature1, function1 is used.
217 * Otherwise, old function is used.
218 */
219 #define alternative_call_2(oldfunc, newfunc1, feature1, newfunc2, feature2, \
220 output, input...) \
221 asm volatile (ALTERNATIVE_2("call %P[old]", "call %P[new1]", feature1,\
222 "call %P[new2]", feature2) \
223 : output : [old] "i" (oldfunc), [new1] "i" (newfunc1), \
224 [new2] "i" (newfunc2), ## input)
225
226 /*
227 * use this macro(s) if you need more than one output parameter
228 * in alternative_io
229 */
230 #define ASM_OUTPUT2(a...) a
231
232 /*
233 * use this macro if you need clobbers but no inputs in
234 * alternative_{input,io,call}()
235 */
236 #define ASM_NO_INPUT_CLOBBER(clbr...) "i" (0) : clbr
237
238 struct paravirt_patch_site;
239 #ifdef CONFIG_PARAVIRT
240 void apply_paravirt(struct paravirt_patch_site *start,
241 struct paravirt_patch_site *end);
242 #else
apply_paravirt(struct paravirt_patch_site * start,struct paravirt_patch_site * end)243 static inline void apply_paravirt(struct paravirt_patch_site *start,
244 struct paravirt_patch_site *end)
245 {}
246 #define __parainstructions NULL
247 #define __parainstructions_end NULL
248 #endif
249
250 extern void *text_poke_early(void *addr, const void *opcode, size_t len);
251
252 /*
253 * Clear and restore the kernel write-protection flag on the local CPU.
254 * Allows the kernel to edit read-only pages.
255 * Side-effect: any interrupt handler running between save and restore will have
256 * the ability to write to read-only pages.
257 *
258 * Warning:
259 * Code patching in the UP case is safe if NMIs and MCE handlers are stopped and
260 * no thread can be preempted in the instructions being modified (no iret to an
261 * invalid instruction possible) or if the instructions are changed from a
262 * consistent state to another consistent state atomically.
263 * On the local CPU you need to be protected again NMI or MCE handlers seeing an
264 * inconsistent instruction while you patch.
265 */
266 extern void *text_poke(void *addr, const void *opcode, size_t len);
267 extern int poke_int3_handler(struct pt_regs *regs);
268 extern void *text_poke_bp(void *addr, const void *opcode, size_t len, void *handler);
269
270 #endif /* __ASSEMBLY__ */
271
272 #endif /* _ASM_X86_ALTERNATIVE_H */
273