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/* Initialize cpu feature data. PowerPC version.
Copyright (C) 2017-2025 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include <array_length.h>
#include <stdint.h>
#include <cpu-features.h>
#include <elf/dl-tunables.h>
#include <dl-tunables-parse.h>
#include <dl-hwcap-info.h>
#include <unistd.h>
#include <string.h>
static void set_hwcap_bit (unsigned long int *hwcap, bool disable,
unsigned long int tcb_value, unsigned int value)
{
if (disable)
*hwcap &= ~value;
else
*hwcap |= tcb_value & value;
}
static void
TUNABLE_CALLBACK (set_hwcaps) (tunable_val_t *valp)
{
/* The current IFUNC selection is always using the most recent
features which are available via AT_HWCAP or AT_HWCAP2. But in
some scenarios it is useful to adjust this selection.
The environment variable:
GLIBC_TUNABLES=glibc.cpu.hwcaps=-xxx,yyy,....
Can be used to enable HWCAP/HWCAP2 feature yyy, disable HWCAP/HWCAP2
feature xxx, where the feature name is case-sensitive and has to match
the ones mentioned in the file{sysdeps/powerpc/dl-procinfo.c}. */
/* Copy the features from dl_powerpc_cpu_features, which contains the
features provided by AT_HWCAP and AT_HWCAP2. */
struct cpu_features *cpu_features = &GLRO(dl_powerpc_cpu_features);
unsigned long int tcbv_hwcap = cpu_features->hwcap;
unsigned long int tcbv_hwcap2 = cpu_features->hwcap2;
struct tunable_str_comma_state_t ts;
tunable_str_comma_init (&ts, valp);
struct tunable_str_comma_t t;
while (tunable_str_comma_next (&ts, &t))
{
if (t.len == 0)
continue;
size_t offset = 0;
for (int i = 0; i < __dl_hwcap_info_size; ++i)
{
const char *hwcap_name = __dl_hwcap_names + offset;
size_t hwcap_name_len = strlen (hwcap_name);
/* Check the tunable name on the supported list. */
if (tunable_str_comma_strcmp (&t, hwcap_name, hwcap_name_len))
{
switch (__dl_hwcap_info[i].hwcap)
{
case AT_HWCAP:
set_hwcap_bit (&cpu_features->hwcap, t.disable, tcbv_hwcap,
__dl_hwcap_info[i].value);
break;
case AT_HWCAP2:
set_hwcap_bit (&cpu_features->hwcap2, t.disable, tcbv_hwcap2,
__dl_hwcap_info[i].value);
break;
/* Ignore unknown values. */
}
}
offset += hwcap_name_len + 1;
}
}
}
static inline void
init_cpu_features (struct cpu_features *cpu_features, uint64_t hwcaps[])
{
/* Fill the cpu_features with the supported hwcaps
which are set by __tcb_parse_hwcap_and_convert_at_platform. */
cpu_features->hwcap = hwcaps[0];
cpu_features->hwcap2 = hwcaps[1];
cpu_features->hwcap3 = hwcaps[2];
cpu_features->hwcap4 = hwcaps[3];
/* Default is to use aligned memory access on optimized function unless
tunables is enable, since for this case user can explicit disable
unaligned optimizations. */
int32_t cached_memfunc = TUNABLE_GET (glibc, cpu, cached_memopt, int32_t,
NULL);
cpu_features->use_cached_memopt = (cached_memfunc > 0);
TUNABLE_GET (glibc, cpu, hwcaps, tunable_val_t *,
TUNABLE_CALLBACK (set_hwcaps));
}
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