cf5961ca867746ae2eadb4a2b6f2c9068cec48c4
[muen/linux.git] / arch / x86 / include / asm / alternative.h
1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef _ASM_X86_ALTERNATIVE_H
3 #define _ASM_X86_ALTERNATIVE_H
4
5 #ifndef __ASSEMBLY__
6
7 #include <linux/types.h>
8 #include <linux/stddef.h>
9 #include <linux/stringify.h>
10 #include <asm/asm.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
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) {}
80 static inline void alternatives_smp_module_del(struct module *mod) {}
81 static inline void alternatives_enable_smp(void) {}
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 {                                                                             \
222         asm volatile (ALTERNATIVE_2("call %P[old]", "call %P[new1]", feature1,\
223                 "call %P[new2]", feature2)                                    \
224                 : output, ASM_CALL_CONSTRAINT                                 \
225                 : [old] "i" (oldfunc), [new1] "i" (newfunc1),                 \
226                   [new2] "i" (newfunc2), ## input);                           \
227 }
228
229 /*
230  * use this macro(s) if you need more than one output parameter
231  * in alternative_io
232  */
233 #define ASM_OUTPUT2(a...) a
234
235 /*
236  * use this macro if you need clobbers but no inputs in
237  * alternative_{input,io,call}()
238  */
239 #define ASM_NO_INPUT_CLOBBER(clbr...) "i" (0) : clbr
240
241 #endif /* __ASSEMBLY__ */
242
243 #endif /* _ASM_X86_ALTERNATIVE_H */