1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
|
/* x86 CPU feature tuning.
This file is part of the GNU C Library.
Copyright (C) 2017-2023 Free Software Foundation, Inc.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#if HAVE_TUNABLES
# define TUNABLE_NAMESPACE cpu
# include <stdbool.h>
# include <stdint.h>
# include <unistd.h> /* Get STDOUT_FILENO for _dl_printf. */
# include <elf/dl-tunables.h>
# include <string.h>
# include <cpu-features.h>
# include <ldsodefs.h>
/* We can't use IFUNC memcmp nor strlen in init_cpu_features from libc.a
since IFUNC must be set up by init_cpu_features. */
# if defined USE_MULTIARCH && !defined SHARED
# ifdef __x86_64__
/* DEFAULT_MEMCMP by sysdeps/x86_64/memcmp-isa-default-impl.h. */
# include <sysdeps/x86_64/memcmp-isa-default-impl.h>
# else
# define DEFAULT_MEMCMP __memcmp_ia32
# endif
extern __typeof (memcmp) DEFAULT_MEMCMP;
# else
# define DEFAULT_MEMCMP memcmp
# endif
# define CHECK_GLIBC_IFUNC_CPU_OFF(f, cpu_features, name, len) \
_Static_assert (sizeof (#name) - 1 == len, #name " != " #len); \
if (!DEFAULT_MEMCMP (f, #name, len)) \
{ \
CPU_FEATURE_UNSET (cpu_features, name) \
break; \
}
/* Disable a preferred feature NAME. We don't enable a preferred feature
which isn't available. */
# define CHECK_GLIBC_IFUNC_PREFERRED_OFF(f, cpu_features, name, len) \
_Static_assert (sizeof (#name) - 1 == len, #name " != " #len); \
if (!DEFAULT_MEMCMP (f, #name, len)) \
{ \
cpu_features->preferred[index_arch_##name] \
&= ~bit_arch_##name; \
break; \
}
/* Enable/disable a preferred feature NAME. */
# define CHECK_GLIBC_IFUNC_PREFERRED_BOTH(f, cpu_features, name, \
disable, len) \
_Static_assert (sizeof (#name) - 1 == len, #name " != " #len); \
if (!DEFAULT_MEMCMP (f, #name, len)) \
{ \
if (disable) \
cpu_features->preferred[index_arch_##name] &= ~bit_arch_##name; \
else \
cpu_features->preferred[index_arch_##name] |= bit_arch_##name; \
break; \
}
/* Enable/disable a preferred feature NAME. Enable a preferred feature
only if the feature NEED is usable. */
# define CHECK_GLIBC_IFUNC_PREFERRED_NEED_BOTH(f, cpu_features, name, \
need, disable, len) \
_Static_assert (sizeof (#name) - 1 == len, #name " != " #len); \
if (!DEFAULT_MEMCMP (f, #name, len)) \
{ \
if (disable) \
cpu_features->preferred[index_arch_##name] &= ~bit_arch_##name; \
else if (CPU_FEATURE_USABLE_P (cpu_features, need)) \
cpu_features->preferred[index_arch_##name] |= bit_arch_##name; \
break; \
}
attribute_hidden
void
TUNABLE_CALLBACK (set_hwcaps) (tunable_val_t *valp)
{
/* The current IFUNC selection is based on microbenchmarks in glibc.
It should give the best performance for most workloads. But other
choices may have better performance for a particular workload or on
the hardware which wasn't available when the selection was made.
The environment variable:
GLIBC_TUNABLES=glibc.cpu.hwcaps=-xxx,yyy,-zzz,....
can be used to enable CPU/ARCH feature yyy, disable CPU/ARCH feature
yyy and zzz, where the feature name is case-sensitive and has to
match the ones in cpu-features.h. It can be used by glibc developers
to tune for a new processor or override the IFUNC selection to
improve performance for a particular workload.
NOTE: the IFUNC selection may change over time. Please check all
multiarch implementations when experimenting. */
const char *p = valp->strval;
struct cpu_features *cpu_features = &GLRO(dl_x86_cpu_features);
size_t len;
do
{
const char *c, *n;
bool disable;
size_t nl;
for (c = p; *c != ','; c++)
if (*c == '\0')
break;
len = c - p;
disable = *p == '-';
if (disable)
{
n = p + 1;
nl = len - 1;
}
else
{
n = p;
nl = len;
}
switch (nl)
{
default:
break;
case 3:
if (disable)
{
CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, AVX, 3);
CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, CX8, 3);
CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, FMA, 3);
CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, HTT, 3);
CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, IBT, 3);
CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, RTM, 3);
}
break;
case 4:
if (disable)
{
CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, AVX2, 4);
CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, BMI1, 4);
CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, BMI2, 4);
CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, CMOV, 4);
CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, ERMS, 4);
CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, FMA4, 4);
CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, SSE2, 4);
CHECK_GLIBC_IFUNC_PREFERRED_OFF (n, cpu_features, I586, 4);
CHECK_GLIBC_IFUNC_PREFERRED_OFF (n, cpu_features, I686, 4);
}
break;
case 5:
if (disable)
{
CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, LZCNT, 5);
CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, MOVBE, 5);
CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, SHSTK, 5);
CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, SSSE3, 5);
CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, XSAVE, 5);
}
break;
case 6:
if (disable)
{
CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, POPCNT, 6);
CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, SSE4_1, 6);
CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, SSE4_2, 6);
if (!DEFAULT_MEMCMP (n, "XSAVEC", 6))
{
/* Update xsave_state_size to XSAVE state size. */
cpu_features->xsave_state_size
= cpu_features->xsave_state_full_size;
CPU_FEATURE_UNSET (cpu_features, XSAVEC);
}
}
break;
case 7:
if (disable)
{
CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, AVX512F, 7);
CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, OSXSAVE, 7);
}
break;
case 8:
if (disable)
{
CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, AVX512CD, 8);
CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, AVX512BW, 8);
CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, AVX512DQ, 8);
CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, AVX512ER, 8);
CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, AVX512PF, 8);
CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, AVX512VL, 8);
}
CHECK_GLIBC_IFUNC_PREFERRED_BOTH (n, cpu_features, Slow_BSF,
disable, 8);
break;
case 11:
{
CHECK_GLIBC_IFUNC_PREFERRED_BOTH (n, cpu_features,
Prefer_ERMS,
disable, 11);
CHECK_GLIBC_IFUNC_PREFERRED_BOTH (n, cpu_features,
Prefer_FSRM,
disable, 11);
CHECK_GLIBC_IFUNC_PREFERRED_NEED_BOTH (n, cpu_features,
Slow_SSE4_2,
SSE4_2,
disable, 11);
}
break;
case 15:
{
CHECK_GLIBC_IFUNC_PREFERRED_BOTH (n, cpu_features,
Fast_Rep_String,
disable, 15);
}
break;
case 16:
{
CHECK_GLIBC_IFUNC_PREFERRED_NEED_BOTH
(n, cpu_features, Prefer_No_AVX512, AVX512F,
disable, 16);
}
break;
case 18:
{
CHECK_GLIBC_IFUNC_PREFERRED_BOTH (n, cpu_features,
Fast_Copy_Backward,
disable, 18);
}
break;
case 19:
{
CHECK_GLIBC_IFUNC_PREFERRED_BOTH (n, cpu_features,
Fast_Unaligned_Load,
disable, 19);
CHECK_GLIBC_IFUNC_PREFERRED_BOTH (n, cpu_features,
Fast_Unaligned_Copy,
disable, 19);
}
break;
case 20:
{
CHECK_GLIBC_IFUNC_PREFERRED_NEED_BOTH
(n, cpu_features, Prefer_No_VZEROUPPER, AVX, disable,
20);
}
break;
case 23:
{
CHECK_GLIBC_IFUNC_PREFERRED_NEED_BOTH
(n, cpu_features, AVX_Fast_Unaligned_Load, AVX,
disable, 23);
}
break;
case 24:
{
CHECK_GLIBC_IFUNC_PREFERRED_NEED_BOTH
(n, cpu_features, MathVec_Prefer_No_AVX512, AVX512F,
disable, 24);
}
break;
case 26:
{
CHECK_GLIBC_IFUNC_PREFERRED_NEED_BOTH
(n, cpu_features, Prefer_PMINUB_for_stringop, SSE2,
disable, 26);
}
break;
}
p += len + 1;
}
while (*p != '\0');
}
# if CET_ENABLED
attribute_hidden
void
TUNABLE_CALLBACK (set_x86_ibt) (tunable_val_t *valp)
{
if (DEFAULT_MEMCMP (valp->strval, "on", sizeof ("on")) == 0)
GL(dl_x86_feature_control).ibt = cet_always_on;
else if (DEFAULT_MEMCMP (valp->strval, "off", sizeof ("off")) == 0)
GL(dl_x86_feature_control).ibt = cet_always_off;
else if (DEFAULT_MEMCMP (valp->strval, "permissive",
sizeof ("permissive")) == 0)
GL(dl_x86_feature_control).ibt = cet_permissive;
}
attribute_hidden
void
TUNABLE_CALLBACK (set_x86_shstk) (tunable_val_t *valp)
{
if (DEFAULT_MEMCMP (valp->strval, "on", sizeof ("on")) == 0)
GL(dl_x86_feature_control).shstk = cet_always_on;
else if (DEFAULT_MEMCMP (valp->strval, "off", sizeof ("off")) == 0)
GL(dl_x86_feature_control).shstk = cet_always_off;
else if (DEFAULT_MEMCMP (valp->strval, "permissive",
sizeof ("permissive")) == 0)
GL(dl_x86_feature_control).shstk = cet_permissive;
}
# endif
#endif
|
