sysdeps/unix/sysv/linux/aarch64/cpu-features.c

   1 /* Initialize CPU feature data.  AArch64 version.
   2    This file is part of the GNU C Library.
   3    Copyright (C) 2017-2018 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    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <cpu-features.h>
  20 #include <sys/auxv.h>
  21 #include <elf/dl-hwcaps.h>
  22
  23 #define DCZID_DZP_MASK (1 << 4)
  24 #define DCZID_BS_MASK (0xf)
  25
  26 #if HAVE_TUNABLES
  27 struct cpu_list
  28 {
  29   const char *name;
  30   uint64_t midr;
  31 };
  32
  33 static struct cpu_list cpu_list[] = {
  34       {"falkor",         0x510FC000},
  35       {"thunderxt88",    0x430F0A10},
  36       {"thunderx2t99",   0x431F0AF0},
  37       {"thunderx2t99p1", 0x420F5160},
  38       {"phecda",         0x680F0000},
  39       {"generic",        0x0}
  40 };
  41
  42 static uint64_t
  43 get_midr_from_mcpu (const char *mcpu)
  44 {
  45   for (int i = 0; i < sizeof (cpu_list) / sizeof (struct cpu_list); i++)
  46     if (strcmp (mcpu, cpu_list[i].name) == 0)
  47       return cpu_list[i].midr;
  48
  49   return UINT64_MAX;
  50 }
  51 #endif
  52
  53 static inline void
  54 init_cpu_features (struct cpu_features *cpu_features)
  55 {
  56   uint64_t hwcap_mask = GET_HWCAP_MASK();
  57   uint64_t hwcap = GLRO (dl_hwcap) & hwcap_mask;
  58
  59   register uint64_t midr = UINT64_MAX;
  60
  61 #if HAVE_TUNABLES
  62   /* Get the tunable override.  */
  63   const char *mcpu = TUNABLE_GET (glibc, tune, cpu, const char *, NULL);
  64   if (mcpu != NULL)
  65     midr = get_midr_from_mcpu (mcpu);
  66 #endif
  67
  68   /* If there was no useful tunable override, query the MIDR if the kernel
  69      allows it.  */
  70   if (midr == UINT64_MAX)
  71     {
  72       if (hwcap & HWCAP_CPUID)
  73         asm volatile ("mrs %0, midr_el1" : "=r"(midr));
  74       else
  75         midr = 0;
  76     }
  77
  78   cpu_features->midr_el1 = midr;
  79
  80   /* Check if ZVA is enabled.  */
  81   unsigned dczid;
  82   asm volatile ("mrs %0, dczid_el0" : "=r"(dczid));
  83
  84   if ((dczid & DCZID_DZP_MASK) == 0)
  85     cpu_features->zva_size = 4 << (dczid & DCZID_BS_MASK);
  86 }