1 /* Copyright (C) 2017-2021 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
__sysconf(int name)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>
56