1/* Initialize cpu feature data. PowerPC version.
2 Copyright (C) 2017-2024 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 <array_length.h>
20#include <stdint.h>
21#include <cpu-features.h>
22#include <elf/dl-tunables.h>
23#include <dl-tunables-parse.h>
24#include <unistd.h>
25#include <string.h>
26
27static void
28TUNABLE_CALLBACK (set_hwcaps) (tunable_val_t *valp)
29{
30 /* The current IFUNC selection is always using the most recent
31 features which are available via AT_HWCAP or AT_HWCAP2. But in
32 some scenarios it is useful to adjust this selection.
33
34 The environment variable:
35
36 GLIBC_TUNABLES=glibc.cpu.hwcaps=-xxx,yyy,....
37
38 Can be used to enable HWCAP/HWCAP2 feature yyy, disable HWCAP/HWCAP2
39 feature xxx, where the feature name is case-sensitive and has to match
40 the ones mentioned in the file{sysdeps/powerpc/dl-procinfo.c}. */
41
42 /* Copy the features from dl_powerpc_cpu_features, which contains the
43 features provided by AT_HWCAP and AT_HWCAP2. */
44 struct cpu_features *cpu_features = &GLRO(dl_powerpc_cpu_features);
45 unsigned long int tcbv_hwcap = cpu_features->hwcap;
46 unsigned long int tcbv_hwcap2 = cpu_features->hwcap2;
47
48 struct tunable_str_comma_state_t ts;
49 tunable_str_comma_init (state: &ts, valp);
50
51 struct tunable_str_comma_t t;
52 while (tunable_str_comma_next (state: &ts, str: &t))
53 {
54 if (t.len == 0)
55 continue;
56
57 size_t offset = 0;
58 for (int i = 0; i < array_length (hwcap_tunables); ++i)
59 {
60 const char *hwcap_name = hwcap_names + offset;
61 size_t hwcap_name_len = strlen (hwcap_name);
62 /* Check the tunable name on the supported list. */
63 if (tunable_str_comma_strcmp (&t, hwcap_name, hwcap_name_len))
64 {
65 /* Update the hwcap and hwcap2 bits. */
66 if (t.disable)
67 {
68 /* Id is 1 for hwcap2 tunable. */
69 if (hwcap_tunables[i].id)
70 cpu_features->hwcap2 &= ~(hwcap_tunables[i].mask);
71 else
72 cpu_features->hwcap &= ~(hwcap_tunables[i].mask);
73 }
74 else
75 {
76 /* Enable the features and also check that no unsupported
77 features were enabled by user. */
78 if (hwcap_tunables[i].id)
79 cpu_features->hwcap2 |= (tcbv_hwcap2 & hwcap_tunables[i].mask);
80 else
81 cpu_features->hwcap |= (tcbv_hwcap & hwcap_tunables[i].mask);
82 }
83 break;
84 }
85 offset += hwcap_name_len + 1;
86 }
87 }
88}
89
90static inline void
91init_cpu_features (struct cpu_features *cpu_features, uint64_t hwcaps[])
92{
93 /* Fill the cpu_features with the supported hwcaps
94 which are set by __tcb_parse_hwcap_and_convert_at_platform. */
95 cpu_features->hwcap = hwcaps[0];
96 cpu_features->hwcap2 = hwcaps[1];
97 cpu_features->hwcap3 = hwcaps[2];
98 cpu_features->hwcap4 = hwcaps[3];
99 /* Default is to use aligned memory access on optimized function unless
100 tunables is enable, since for this case user can explicit disable
101 unaligned optimizations. */
102 int32_t cached_memfunc = TUNABLE_GET (glibc, cpu, cached_memopt, int32_t,
103 NULL);
104 cpu_features->use_cached_memopt = (cached_memfunc > 0);
105 TUNABLE_GET (glibc, cpu, hwcaps, tunable_val_t *,
106 TUNABLE_CALLBACK (set_hwcaps));
107}
108

source code of glibc/sysdeps/unix/sysv/linux/powerpc/cpu-features.c