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3ab9b88e2a
This patch adds a new feature for powerpc. In order to get faster access to the HWCAP3/HWCAP4 masks, similar to HWCAP/HWCAP2 (i.e. for implementing __builtin_cpu_supports() in GCC) without the overhead of reading them from the auxiliary vector, we now reserve space for them in the TCB. This is an ABI change for GLIBC 2.39. Suggested-by: Peter Bergner <bergner@linux.ibm.com> Reviewed-by: Peter Bergner <bergner@linux.ibm.com>
107 lines
3.7 KiB
C
107 lines
3.7 KiB
C
/* Initialize cpu feature data. PowerPC version.
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Copyright (C) 2017-2024 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#include <array_length.h>
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#include <stdint.h>
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#include <cpu-features.h>
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#include <elf/dl-tunables.h>
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#include <dl-tunables-parse.h>
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#include <unistd.h>
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#include <string.h>
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static void
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TUNABLE_CALLBACK (set_hwcaps) (tunable_val_t *valp)
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{
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/* The current IFUNC selection is always using the most recent
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features which are available via AT_HWCAP or AT_HWCAP2. But in
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some scenarios it is useful to adjust this selection.
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The environment variable:
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GLIBC_TUNABLES=glibc.cpu.hwcaps=-xxx,yyy,....
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Can be used to enable HWCAP/HWCAP2 feature yyy, disable HWCAP/HWCAP2
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feature xxx, where the feature name is case-sensitive and has to match
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the ones mentioned in the file{sysdeps/powerpc/dl-procinfo.c}. */
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/* Copy the features from dl_powerpc_cpu_features, which contains the
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features provided by AT_HWCAP and AT_HWCAP2. */
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struct cpu_features *cpu_features = &GLRO(dl_powerpc_cpu_features);
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unsigned long int tcbv_hwcap = cpu_features->hwcap;
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unsigned long int tcbv_hwcap2 = cpu_features->hwcap2;
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struct tunable_str_comma_state_t ts;
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tunable_str_comma_init (&ts, valp);
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struct tunable_str_comma_t t;
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while (tunable_str_comma_next (&ts, &t))
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{
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if (t.len == 0)
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continue;
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size_t offset = 0;
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for (int i = 0; i < array_length (hwcap_tunables); ++i)
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{
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const char *hwcap_name = hwcap_names + offset;
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size_t hwcap_name_len = strlen (hwcap_name);
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/* Check the tunable name on the supported list. */
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if (tunable_str_comma_strcmp (&t, hwcap_name, hwcap_name_len))
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{
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/* Update the hwcap and hwcap2 bits. */
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if (t.disable)
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{
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/* Id is 1 for hwcap2 tunable. */
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if (hwcap_tunables[i].id)
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cpu_features->hwcap2 &= ~(hwcap_tunables[i].mask);
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else
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cpu_features->hwcap &= ~(hwcap_tunables[i].mask);
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}
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else
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{
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/* Enable the features and also check that no unsupported
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features were enabled by user. */
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if (hwcap_tunables[i].id)
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cpu_features->hwcap2 |= (tcbv_hwcap2 & hwcap_tunables[i].mask);
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else
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cpu_features->hwcap |= (tcbv_hwcap & hwcap_tunables[i].mask);
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}
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break;
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}
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offset += hwcap_name_len + 1;
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}
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}
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}
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static inline void
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init_cpu_features (struct cpu_features *cpu_features, uint64_t hwcaps[])
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{
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/* Fill the cpu_features with the supported hwcaps
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which are set by __tcb_parse_hwcap_and_convert_at_platform. */
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cpu_features->hwcap = hwcaps[0];
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cpu_features->hwcap2 = hwcaps[1];
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cpu_features->hwcap3 = hwcaps[2];
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cpu_features->hwcap4 = hwcaps[3];
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/* Default is to use aligned memory access on optimized function unless
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tunables is enable, since for this case user can explicit disable
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unaligned optimizations. */
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int32_t cached_memfunc = TUNABLE_GET (glibc, cpu, cached_memopt, int32_t,
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NULL);
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cpu_features->use_cached_memopt = (cached_memfunc > 0);
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TUNABLE_GET (glibc, cpu, hwcaps, tunable_val_t *,
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TUNABLE_CALLBACK (set_hwcaps));
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}
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