1  /* Copyright (C) 2017-2023 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>