sysdeps/s390/cpu-features.c

   1 /* Initialize cpu feature data.  s390x version.
   2    Copyright (C) 2023-2024 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   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 #include <cpu-features.h>
  20
  21 #include <elf/dl-tunables.h>
  22 #include <ifunc-memcmp.h>
  23 #include <string.h>
  24 #include <dl-symbol-redir-ifunc.h>
  25 #include <dl-tunables-parse.h>
  26
  27 #define S390_COPY_CPU_FEATURES(SRC_PTR, DEST_PTR)       \
  28   (DEST_PTR)->hwcap = (SRC_PTR)->hwcap;                 \
  29   (DEST_PTR)->stfle_bits[0] = (SRC_PTR)->stfle_bits[0];
  30
  31 static void
  32 TUNABLE_CALLBACK (set_hwcaps) (tunable_val_t *valp)
  33 {
  34   /* The current IFUNC selection is always using the most recent
  35      features which are available via AT_HWCAP or STFLE-bits.  But in
  36      some scenarios it is useful to adjust this selection.
  37
  38      The environment variable:
  39
  40      GLIBC_TUNABLES=glibc.cpu.hwcaps=-xxx,yyy,zzz,....
  41
  42      can be used to enable HWCAP/STFLE feature yyy, disable HWCAP/STFLE feature
  43      xxx, where the feature name is case-sensitive and has to match the ones
  44      used below.  Furthermore, the ARCH-level zzz can be used to set various
  45      HWCAP/STFLE features at once.  */
  46
  47   /* Copy the features from dl_s390_cpu_features, which contains the features
  48      provided by AT_HWCAP and stfle-instruction.  */
  49   struct cpu_features *cpu_features = &GLRO(dl_s390_cpu_features);
  50   struct cpu_features cpu_features_orig;
  51   S390_COPY_CPU_FEATURES (cpu_features, &cpu_features_orig);
  52   struct cpu_features cpu_features_curr;
  53   S390_COPY_CPU_FEATURES (cpu_features, &cpu_features_curr);
  54
  55   struct tunable_str_comma_state_t ts;
  56   tunable_str_comma_init (&ts, valp);
  57
  58   struct tunable_str_comma_t t;
  59   while (tunable_str_comma_next (&ts, &t))
  60     {
  61       if (t.len == 0)
  62         continue;
  63
  64       /* Handle only the features here which are really used in the
  65          IFUNC-resolvers.  All others are ignored as the values are only used
  66          inside glibc.  */
  67       bool reset_features = false;
  68       unsigned long int hwcap_mask = 0UL;
  69       unsigned long long stfle_bits0_mask = 0ULL;
  70       bool disable = t.disable;
  71
  72       if (tunable_str_comma_strcmp_cte (&t, "zEC12")
  73           || tunable_str_comma_strcmp_cte (&t, "arch10"))
  74         {
  75           reset_features = true;
  76           disable = true;
  77           hwcap_mask = HWCAP_S390_VXRS | HWCAP_S390_VXRS_EXT
  78             | HWCAP_S390_VXRS_EXT2;
  79           stfle_bits0_mask = S390_STFLE_MASK_ARCH13_MIE3;
  80         }
  81       else if (tunable_str_comma_strcmp_cte (&t, "z13")
  82                || tunable_str_comma_strcmp_cte (&t, "arch11"))
  83         {
  84           reset_features = true;
  85           disable = true;
  86           hwcap_mask = HWCAP_S390_VXRS_EXT | HWCAP_S390_VXRS_EXT2;
  87           stfle_bits0_mask = S390_STFLE_MASK_ARCH13_MIE3;
  88         }
  89       else if (tunable_str_comma_strcmp_cte (&t, "z14")
  90                || tunable_str_comma_strcmp_cte (&t, "arch12"))
  91         {
  92           reset_features = true;
  93           disable = true;
  94           hwcap_mask = HWCAP_S390_VXRS_EXT2;
  95           stfle_bits0_mask = S390_STFLE_MASK_ARCH13_MIE3;
  96         }
  97       else if (tunable_str_comma_strcmp_cte (&t, "z15")
  98                || tunable_str_comma_strcmp_cte (&t, "z16")
  99                || tunable_str_comma_strcmp_cte (&t, "arch13")
 100                || tunable_str_comma_strcmp_cte (&t, "arch14"))
 101         {
 102           /* For z15 or newer we don't have to disable something, but we have
 103              to reset to the original values.  */
 104           reset_features = true;
 105         }
 106       else if (tunable_str_comma_strcmp_cte (&t, "HWCAP_S390_VXRS"))
 107         {
 108           hwcap_mask = HWCAP_S390_VXRS;
 109           if (t.disable)
 110             hwcap_mask |= HWCAP_S390_VXRS_EXT | HWCAP_S390_VXRS_EXT2;
 111         }
 112       else if (tunable_str_comma_strcmp_cte (&t, "HWCAP_S390_VXRS_EXT"))
 113         {
 114           hwcap_mask = HWCAP_S390_VXRS_EXT;
 115           if (t.disable)
 116             hwcap_mask |= HWCAP_S390_VXRS_EXT2;
 117           else
 118             hwcap_mask |= HWCAP_S390_VXRS;
 119         }
 120       else if (tunable_str_comma_strcmp_cte (&t, "HWCAP_S390_VXRS_EXT2"))
 121         {
 122           hwcap_mask = HWCAP_S390_VXRS_EXT2;
 123           if (!t.disable)
 124             hwcap_mask |= HWCAP_S390_VXRS | HWCAP_S390_VXRS_EXT;
 125         }
 126       else if (tunable_str_comma_strcmp_cte (&t, "STFLE_MIE3"))
 127         stfle_bits0_mask = S390_STFLE_MASK_ARCH13_MIE3;
 128
 129       /* Perform the actions determined above.  */
 130       if (reset_features)
 131         {
 132           S390_COPY_CPU_FEATURES (&cpu_features_orig, &cpu_features_curr);
 133         }
 134
 135       if (hwcap_mask != 0UL)
 136         {
 137           if (disable)
 138             cpu_features_curr.hwcap &= ~hwcap_mask;
 139           else
 140             cpu_features_curr.hwcap |= hwcap_mask;
 141         }
 142
 143       if (stfle_bits0_mask != 0ULL)
 144         {
 145           if (disable)
 146             cpu_features_curr.stfle_bits[0] &= ~stfle_bits0_mask;
 147           else
 148             cpu_features_curr.stfle_bits[0] |= stfle_bits0_mask;
 149         }
 150     }
 151
 152   /* Copy back the features after checking that no unsupported features were
 153      enabled by user.  */
 154   cpu_features->hwcap = cpu_features_curr.hwcap & cpu_features_orig.hwcap;
 155   cpu_features->stfle_bits[0] = cpu_features_curr.stfle_bits[0]
 156     & cpu_features_orig.stfle_bits[0];
 157 }
 158
 159 static inline void
 160 init_cpu_features (struct cpu_features *cpu_features)
 161 {
 162   /* Fill cpu_features as passed by kernel and machine.  */
 163   cpu_features->hwcap = GLRO(dl_hwcap);
 164
 165   /* We want just 1 double word to be returned.  */
 166   if (__glibc_likely ((cpu_features->hwcap & HWCAP_S390_STFLE)
 167                       && (cpu_features->hwcap & HWCAP_S390_ZARCH)
 168                       && (cpu_features->hwcap & HWCAP_S390_HIGH_GPRS)))
 169     {
 170       register unsigned long reg0 __asm__("0") = 0;
 171       __asm__ __volatile__(".machine push"        "\n\t"
 172                            ".machine \"z9-109\""  "\n\t"
 173                            ".machinemode \"zarch_nohighgprs\"\n\t"
 174                            "stfle %0"             "\n\t"
 175                            ".machine pop"         "\n"
 176                            : "=QS" (cpu_features->stfle_bits[0]),
 177                              "+d" (reg0)
 178                            : : "cc");
 179     }
 180   else
 181     {
 182       cpu_features->stfle_bits[0] = 0ULL;
 183     }
 184
 185   TUNABLE_GET (glibc, cpu, hwcaps, tunable_val_t *, TUNABLE_CALLBACK (set_hwcaps));
 186 }