sysdeps/unix/sysv/linux/aarch64/sysconf.c

   1 /* Copyright (C) 2017-2020 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library.  If not, see
  16    <https://www.gnu.org/licenses/>.  */
  17
  18 #include <assert.h>
  19 #include <stdbool.h>
  20 #include <stdlib.h>
  21 #include <unistd.h>
  22
  23
  24 static long int linux_sysconf (int name);
  25
  26 /* Get the value of the system variable NAME.  */
  27 long int
  28 __sysconf (int name)
  29 {
  30   unsigned ctr;
  31
  32   /* Unfortunately, the registers that contain the actual cache info
  33      (CCSIDR_EL1, CLIDR_EL1, and CSSELR_EL1) are protected by the Linux
  34      kernel (though they need not have been).  However, CTR_EL0 contains
  35      the *minimum* linesize in the entire cache hierarchy, and is
  36      accessible to userland, for use in __aarch64_sync_cache_range,
  37      and it is a reasonable assumption that the L1 cache will have that
  38      minimum line size.  */
  39   switch (name)
  40     {
  41     case _SC_LEVEL1_ICACHE_LINESIZE:
  42       asm("mrs\t%0, ctr_el0" : "=r"(ctr));
  43       return 4 << (ctr & 0xf);
  44     case _SC_LEVEL1_DCACHE_LINESIZE:
  45       asm("mrs\t%0, ctr_el0" : "=r"(ctr));
  46       return 4 << ((ctr >> 16) & 0xf);
  47     }
  48
  49   return linux_sysconf (name);
  50 }
  51
  52 /* Now the generic Linux version.  */
  53 #undef __sysconf
  54 #define __sysconf static linux_sysconf
  55 #include <sysdeps/unix/sysv/linux/sysconf.c>