sysdeps/x86/cpu-tunables.c

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