1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef _ASM_X86_ALTERNATIVE_H
3 #define _ASM_X86_ALTERNATIVE_H
4
5 #include <linux/types.h>
6 #include <linux/stringify.h>
7 #include <linux/objtool.h>
8 #include <asm/asm.h>
9 #include <asm/bug.h>
10
11 #define ALT_FLAGS_SHIFT 16
12
13 #define ALT_FLAG_NOT (1 << 0)
14 #define ALT_NOT(feature) ((ALT_FLAG_NOT << ALT_FLAGS_SHIFT) | (feature))
15 #define ALT_FLAG_DIRECT_CALL (1 << 1)
16 #define ALT_DIRECT_CALL(feature) ((ALT_FLAG_DIRECT_CALL << ALT_FLAGS_SHIFT) | (feature))
17 #define ALT_CALL_ALWAYS ALT_DIRECT_CALL(X86_FEATURE_ALWAYS)
18
19 #ifndef __ASSEMBLER__
20
21 #include <linux/stddef.h>
22
23 /*
24 * Alternative inline assembly for SMP.
25 *
26 * The LOCK_PREFIX macro defined here replaces the LOCK and
27 * LOCK_PREFIX macros used everywhere in the source tree.
28 *
29 * SMP alternatives use the same data structures as the other
30 * alternatives and the X86_FEATURE_UP flag to indicate the case of a
31 * UP system running a SMP kernel. The existing apply_alternatives()
32 * works fine for patching a SMP kernel for UP.
33 *
34 * The SMP alternative tables can be kept after boot and contain both
35 * UP and SMP versions of the instructions to allow switching back to
36 * SMP at runtime, when hotplugging in a new CPU, which is especially
37 * useful in virtualized environments.
38 *
39 * The very common lock prefix is handled as special case in a
40 * separate table which is a pure address list without replacement ptr
41 * and size information. That keeps the table sizes small.
42 */
43
44 #ifdef CONFIG_SMP
45 #define LOCK_PREFIX_HERE \
46 ".pushsection .smp_locks,\"a\"\n" \
47 ".balign 4\n" \
48 ".long 671f - .\n" /* offset */ \
49 ".popsection\n" \
50 "671:"
51
52 #define LOCK_PREFIX LOCK_PREFIX_HERE "\n\tlock "
53
54 #else /* ! CONFIG_SMP */
55 #define LOCK_PREFIX_HERE ""
56 #define LOCK_PREFIX ""
57 #endif
58
59 /*
60 * The patching flags are part of the upper bits of the @ft_flags parameter when
61 * specifying them. The split is currently like this:
62 *
63 * [31... flags ...16][15... CPUID feature bit ...0]
64 *
65 * but since this is all hidden in the macros argument being split, those fields can be
66 * extended in the future to fit in a u64 or however the need arises.
67 */
68 struct alt_instr {
69 s32 instr_offset; /* original instruction */
70 s32 repl_offset; /* offset to replacement instruction */
71
72 union {
73 struct {
74 u32 cpuid: 16; /* CPUID bit set for replacement */
75 u32 flags: 16; /* patching control flags */
76 };
77 u32 ft_flags;
78 };
79
80 u8 instrlen; /* length of original instruction */
81 u8 replacementlen; /* length of new instruction */
82 } __packed;
83
84 extern struct alt_instr __alt_instructions[], __alt_instructions_end[];
85
86 /*
87 * Debug flag that can be tested to see whether alternative
88 * instructions were patched in already:
89 */
90 extern int alternatives_patched;
91
92 extern void alternative_instructions(void);
93 extern void apply_alternatives(struct alt_instr *start, struct alt_instr *end);
94 extern void apply_retpolines(s32 *start, s32 *end);
95 extern void apply_returns(s32 *start, s32 *end);
96 extern void apply_seal_endbr(s32 *start, s32 *end);
97 extern void apply_fineibt(s32 *start_retpoline, s32 *end_retpoine,
98 s32 *start_cfi, s32 *end_cfi);
99
100 struct module;
101
102 struct callthunk_sites {
103 s32 *call_start, *call_end;
104 };
105
106 #ifdef CONFIG_CALL_THUNKS
107 extern void callthunks_patch_builtin_calls(void);
108 extern void callthunks_patch_module_calls(struct callthunk_sites *sites,
109 struct module *mod);
110 extern void *callthunks_translate_call_dest(void *dest);
111 extern int x86_call_depth_emit_accounting(u8 **pprog, void *func, void *ip);
112 #else
callthunks_patch_builtin_calls(void)113 static __always_inline void callthunks_patch_builtin_calls(void) {}
114 static __always_inline void
callthunks_patch_module_calls(struct callthunk_sites * sites,struct module * mod)115 callthunks_patch_module_calls(struct callthunk_sites *sites,
116 struct module *mod) {}
callthunks_translate_call_dest(void * dest)117 static __always_inline void *callthunks_translate_call_dest(void *dest)
118 {
119 return dest;
120 }
x86_call_depth_emit_accounting(u8 ** pprog,void * func,void * ip)121 static __always_inline int x86_call_depth_emit_accounting(u8 **pprog,
122 void *func, void *ip)
123 {
124 return 0;
125 }
126 #endif
127
128 #ifdef CONFIG_MITIGATION_ITS
129 extern void its_init_mod(struct module *mod);
130 extern void its_fini_mod(struct module *mod);
131 extern void its_free_mod(struct module *mod);
132 extern u8 *its_static_thunk(int reg);
133 #else /* CONFIG_MITIGATION_ITS */
its_init_mod(struct module * mod)134 static inline void its_init_mod(struct module *mod) { }
its_fini_mod(struct module * mod)135 static inline void its_fini_mod(struct module *mod) { }
its_free_mod(struct module * mod)136 static inline void its_free_mod(struct module *mod) { }
its_static_thunk(int reg)137 static inline u8 *its_static_thunk(int reg)
138 {
139 WARN_ONCE(1, "ITS not compiled in");
140
141 return NULL;
142 }
143 #endif
144
145 #if defined(CONFIG_MITIGATION_RETHUNK) && defined(CONFIG_OBJTOOL)
146 extern bool cpu_wants_rethunk(void);
147 extern bool cpu_wants_rethunk_at(void *addr);
148 #else
cpu_wants_rethunk(void)149 static __always_inline bool cpu_wants_rethunk(void)
150 {
151 return false;
152 }
cpu_wants_rethunk_at(void * addr)153 static __always_inline bool cpu_wants_rethunk_at(void *addr)
154 {
155 return false;
156 }
157 #endif
158
159 #ifdef CONFIG_SMP
160 extern void alternatives_smp_module_add(struct module *mod, char *name,
161 void *locks, void *locks_end,
162 void *text, void *text_end);
163 extern void alternatives_smp_module_del(struct module *mod);
164 extern void alternatives_enable_smp(void);
165 extern int alternatives_text_reserved(void *start, void *end);
166 extern bool skip_smp_alternatives;
167 #else
alternatives_smp_module_add(struct module * mod,char * name,void * locks,void * locks_end,void * text,void * text_end)168 static inline void alternatives_smp_module_add(struct module *mod, char *name,
169 void *locks, void *locks_end,
170 void *text, void *text_end) {}
alternatives_smp_module_del(struct module * mod)171 static inline void alternatives_smp_module_del(struct module *mod) {}
alternatives_enable_smp(void)172 static inline void alternatives_enable_smp(void) {}
alternatives_text_reserved(void * start,void * end)173 static inline int alternatives_text_reserved(void *start, void *end)
174 {
175 return 0;
176 }
177 #endif /* CONFIG_SMP */
178
179 #define ALT_CALL_INSTR "call BUG_func"
180
181 #define alt_slen "772b-771b"
182 #define alt_total_slen "773b-771b"
183 #define alt_rlen "775f-774f"
184
185 #define OLDINSTR(oldinstr) \
186 "# ALT: oldinstr\n" \
187 "771:\n\t" oldinstr "\n772:\n" \
188 "# ALT: padding\n" \
189 ".skip -(((" alt_rlen ")-(" alt_slen ")) > 0) * " \
190 "((" alt_rlen ")-(" alt_slen ")),0x90\n" \
191 "773:\n"
192
193 #define ALTINSTR_ENTRY(ft_flags) \
194 ".pushsection .altinstructions,\"a\"\n" \
195 " .long 771b - .\n" /* label */ \
196 " .long 774f - .\n" /* new instruction */ \
197 " .4byte " __stringify(ft_flags) "\n" /* feature + flags */ \
198 " .byte " alt_total_slen "\n" /* source len */ \
199 " .byte " alt_rlen "\n" /* replacement len */ \
200 ".popsection\n"
201
202 #define ALTINSTR_REPLACEMENT(newinstr) /* replacement */ \
203 ".pushsection .altinstr_replacement, \"ax\"\n" \
204 "# ALT: replacement\n" \
205 "774:\n\t" newinstr "\n775:\n" \
206 ".popsection\n"
207
208 /* alternative assembly primitive: */
209 #define ALTERNATIVE(oldinstr, newinstr, ft_flags) \
210 OLDINSTR(oldinstr) \
211 ALTINSTR_ENTRY(ft_flags) \
212 ALTINSTR_REPLACEMENT(newinstr)
213
214 #define ALTERNATIVE_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) \
215 ALTERNATIVE(ALTERNATIVE(oldinstr, newinstr1, ft_flags1), newinstr2, ft_flags2)
216
217 /* If @feature is set, patch in @newinstr_yes, otherwise @newinstr_no. */
218 #define ALTERNATIVE_TERNARY(oldinstr, ft_flags, newinstr_yes, newinstr_no) \
219 ALTERNATIVE_2(oldinstr, newinstr_no, X86_FEATURE_ALWAYS, newinstr_yes, ft_flags)
220
221 #define ALTERNATIVE_3(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2, \
222 newinstr3, ft_flags3) \
223 ALTERNATIVE(ALTERNATIVE_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2), \
224 newinstr3, ft_flags3)
225
226 /*
227 * Alternative instructions for different CPU types or capabilities.
228 *
229 * This allows to use optimized instructions even on generic binary
230 * kernels.
231 *
232 * length of oldinstr must be longer or equal the length of newinstr
233 * It can be padded with nops as needed.
234 *
235 * For non barrier like inlines please define new variants
236 * without volatile and memory clobber.
237 */
238 #define alternative(oldinstr, newinstr, ft_flags) \
239 asm_inline volatile(ALTERNATIVE(oldinstr, newinstr, ft_flags) : : : "memory")
240
241 #define alternative_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) \
242 asm_inline volatile(ALTERNATIVE_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) ::: "memory")
243
244 /*
245 * Alternative inline assembly with input.
246 *
247 * Peculiarities:
248 * No memory clobber here.
249 * Argument numbers start with 1.
250 * Leaving an unused argument 0 to keep API compatibility.
251 */
252 #define alternative_input(oldinstr, newinstr, ft_flags, input...) \
253 asm_inline volatile(ALTERNATIVE(oldinstr, newinstr, ft_flags) \
254 : : "i" (0), ## input)
255
256 /* Like alternative_input, but with a single output argument */
257 #define alternative_io(oldinstr, newinstr, ft_flags, output, input...) \
258 asm_inline volatile(ALTERNATIVE(oldinstr, newinstr, ft_flags) \
259 : output : "i" (0), ## input)
260
261 /*
262 * Like alternative_io, but for replacing a direct call with another one.
263 *
264 * Use the %c operand modifier which is the generic way to print a bare
265 * constant expression with all syntax-specific punctuation omitted. %P
266 * is the x86-specific variant which can handle constants too, for
267 * historical reasons, but it should be used primarily for PIC
268 * references: i.e., if used for a function, it would add the PLT
269 * suffix.
270 */
271 #define alternative_call(oldfunc, newfunc, ft_flags, output, input, clobbers...) \
272 asm_inline volatile(ALTERNATIVE("call %c[old]", "call %c[new]", ft_flags) \
273 : ALT_OUTPUT_SP(output) \
274 : [old] "i" (oldfunc), [new] "i" (newfunc) \
275 COMMA(input) \
276 : clobbers)
277
278 /*
279 * Like alternative_call, but there are two features and respective functions.
280 * If CPU has feature2, function2 is used.
281 * Otherwise, if CPU has feature1, function1 is used.
282 * Otherwise, old function is used.
283 */
284 #define alternative_call_2(oldfunc, newfunc1, ft_flags1, newfunc2, ft_flags2, \
285 output, input, clobbers...) \
286 asm_inline volatile(ALTERNATIVE_2("call %c[old]", "call %c[new1]", ft_flags1, \
287 "call %c[new2]", ft_flags2) \
288 : ALT_OUTPUT_SP(output) \
289 : [old] "i" (oldfunc), [new1] "i" (newfunc1), \
290 [new2] "i" (newfunc2) \
291 COMMA(input) \
292 : clobbers)
293
294 #define ALT_OUTPUT_SP(...) ASM_CALL_CONSTRAINT, ## __VA_ARGS__
295
296 /* Macro for creating assembler functions avoiding any C magic. */
297 #define DEFINE_ASM_FUNC(func, instr, sec) \
298 asm (".pushsection " #sec ", \"ax\"\n" \
299 ".global " #func "\n\t" \
300 ".type " #func ", @function\n\t" \
301 ASM_FUNC_ALIGN "\n" \
302 #func ":\n\t" \
303 ASM_ENDBR \
304 instr "\n\t" \
305 ASM_RET \
306 ".size " #func ", . - " #func "\n\t" \
307 ".popsection")
308
309 void BUG_func(void);
310 void nop_func(void);
311
312 #else /* __ASSEMBLER__ */
313
314 #ifdef CONFIG_SMP
315 .macro LOCK_PREFIX
316 672: lock
317 .pushsection .smp_locks,"a"
318 .balign 4
319 .long 672b - .
320 .popsection
321 .endm
322 #else
323 .macro LOCK_PREFIX
324 .endm
325 #endif
326
327 /*
328 * Issue one struct alt_instr descriptor entry (need to put it into
329 * the section .altinstructions, see below). This entry contains
330 * enough information for the alternatives patching code to patch an
331 * instruction. See apply_alternatives().
332 */
333 .macro altinstr_entry orig alt ft_flags orig_len alt_len
334 .long \orig - .
335 .long \alt - .
336 .4byte \ft_flags
337 .byte \orig_len
338 .byte \alt_len
339 .endm
340
341 .macro ALT_CALL_INSTR
342 call BUG_func
343 .endm
344
345 /*
346 * Define an alternative between two instructions. If @feature is
347 * present, early code in apply_alternatives() replaces @oldinstr with
348 * @newinstr. ".skip" directive takes care of proper instruction padding
349 * in case @newinstr is longer than @oldinstr.
350 */
351 #define __ALTERNATIVE(oldinst, newinst, flag) \
352 740: \
353 oldinst ; \
354 741: \
355 .skip -(((744f-743f)-(741b-740b)) > 0) * ((744f-743f)-(741b-740b)),0x90 ;\
356 742: \
357 .pushsection .altinstructions,"a" ; \
358 altinstr_entry 740b,743f,flag,742b-740b,744f-743f ; \
359 .popsection ; \
360 .pushsection .altinstr_replacement,"ax" ; \
361 743: \
362 newinst ; \
363 744: \
364 .popsection ;
365
366 .macro ALTERNATIVE oldinstr, newinstr, ft_flags
367 __ALTERNATIVE(\oldinstr, \newinstr, \ft_flags)
368 .endm
369
370 #define old_len 141b-140b
371 #define new_len1 144f-143f
372 #define new_len2 145f-144f
373 #define new_len3 146f-145f
374
375 /*
376 * Same as ALTERNATIVE macro above but for two alternatives. If CPU
377 * has @feature1, it replaces @oldinstr with @newinstr1. If CPU has
378 * @feature2, it replaces @oldinstr with @feature2.
379 */
380 .macro ALTERNATIVE_2 oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2
381 __ALTERNATIVE(__ALTERNATIVE(\oldinstr, \newinstr1, \ft_flags1),
382 \newinstr2, \ft_flags2)
383 .endm
384
385 .macro ALTERNATIVE_3 oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2, newinstr3, ft_flags3
386 __ALTERNATIVE(ALTERNATIVE_2(\oldinstr, \newinstr1, \ft_flags1, \newinstr2, \ft_flags2),
387 \newinstr3, \ft_flags3)
388 .endm
389
390 /* If @feature is set, patch in @newinstr_yes, otherwise @newinstr_no. */
391 #define ALTERNATIVE_TERNARY(oldinstr, ft_flags, newinstr_yes, newinstr_no) \
392 ALTERNATIVE_2 oldinstr, newinstr_no, X86_FEATURE_ALWAYS, \
393 newinstr_yes, ft_flags
394
395 #endif /* __ASSEMBLER__ */
396
397 #endif /* _ASM_X86_ALTERNATIVE_H */
398