156 lines
5.4 KiB
C
156 lines
5.4 KiB
C
/* Hardware capability support for run-time dynamic loader.
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Copyright (C) 2017-2022 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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#ifndef _DL_HWCAPS_H
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#define _DL_HWCAPS_H
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#include <stdint.h>
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#include <stddef.h>
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#include <elf/dl-tunables.h>
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#if HAVE_TUNABLES
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# define GET_HWCAP_MASK() TUNABLE_GET (glibc, cpu, hwcap_mask, uint64_t, NULL)
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#else
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# ifdef SHARED
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# define GET_HWCAP_MASK() GLRO(dl_hwcap_mask)
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# else
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/* HWCAP_MASK is ignored in static binaries when built without tunables. */
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# define GET_HWCAP_MASK() (0)
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# endif
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#endif
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#define GLIBC_HWCAPS_SUBDIRECTORY "glibc-hwcaps"
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#define GLIBC_HWCAPS_PREFIX GLIBC_HWCAPS_SUBDIRECTORY "/"
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/* Used by _dl_hwcaps_split below, to split strings at ':'
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separators. */
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struct dl_hwcaps_split
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{
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const char *segment; /* Start of the current segment. */
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size_t length; /* Number of bytes until ':' or NUL. */
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};
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/* Prepare *S to parse SUBJECT, for future _dl_hwcaps_split calls. If
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SUBJECT is NULL, it is treated as the empty string. */
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static inline void
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_dl_hwcaps_split_init (struct dl_hwcaps_split *s, const char *subject)
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{
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s->segment = subject;
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/* The initial call to _dl_hwcaps_split will not skip anything. */
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s->length = 0;
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}
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/* Extract the next non-empty string segment, up to ':' or the null
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terminator. Return true if one more segment was found, or false if
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the end of the string was reached. On success, S->segment is the
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start of the segment found, and S->length is its length.
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(Typically, S->segment[S->length] is not null.) */
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_Bool _dl_hwcaps_split (struct dl_hwcaps_split *s) attribute_hidden;
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/* Similar to dl_hwcaps_split, but with bit-based and name-based
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masking. */
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struct dl_hwcaps_split_masked
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{
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struct dl_hwcaps_split split;
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/* For used by the iterator implementation. */
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const char *mask;
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uint32_t bitmask;
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};
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/* Prepare *S for iteration with _dl_hwcaps_split_masked. Only HWCAP
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names in SUBJECT whose bit is set in BITMASK and whose name is in
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MASK will be returned. SUBJECT must not contain empty HWCAP names.
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If MASK is NULL, no name-based masking is applied. Likewise for
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BITMASK if BITMASK is -1 (infinite number of bits). */
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static inline void
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_dl_hwcaps_split_masked_init (struct dl_hwcaps_split_masked *s,
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const char *subject,
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uint32_t bitmask, const char *mask)
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{
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_dl_hwcaps_split_init (&s->split, subject);
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s->bitmask = bitmask;
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s->mask = mask;
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}
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/* Like _dl_hwcaps_split, but apply masking. */
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_Bool _dl_hwcaps_split_masked (struct dl_hwcaps_split_masked *s)
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attribute_hidden;
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/* Returns true if the colon-separated HWCAP list HWCAPS contains the
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capability NAME (with length NAME_LENGTH). If HWCAPS is NULL, the
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function returns true. */
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_Bool _dl_hwcaps_contains (const char *hwcaps, const char *name,
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size_t name_length) attribute_hidden;
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/* Colon-separated string of glibc-hwcaps subdirectories, without the
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"glibc-hwcaps/" prefix. The most preferred subdirectory needs to
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be listed first. Up to 32 subdirectories are supported, limited by
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the width of the uint32_t mask. */
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extern const char _dl_hwcaps_subdirs[] attribute_hidden;
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/* Returns a bitmap of active subdirectories in _dl_hwcaps_subdirs.
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Bit 0 (the LSB) corresponds to the first substring in
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_dl_hwcaps_subdirs, bit 1 to the second substring, and so on.
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There is no direct correspondence between HWCAP bitmasks and this
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bitmask. */
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uint32_t _dl_hwcaps_subdirs_active (void) attribute_hidden;
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/* Returns a bitmask that marks the last ACTIVE subdirectories in a
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_dl_hwcaps_subdirs_active string (containing SUBDIRS directories in
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total) as active. Intended for use in _dl_hwcaps_subdirs_active
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implementations (if a contiguous tail of the list in
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_dl_hwcaps_subdirs is selected). */
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static inline uint32_t
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_dl_hwcaps_subdirs_build_bitmask (int subdirs, int active)
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{
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/* Leading subdirectories that are not active. */
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int inactive = subdirs - active;
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if (inactive == 32)
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return 0;
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uint32_t mask;
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if (subdirs != 32)
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mask = (1U << subdirs) - 1;
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else
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mask = -1;
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return mask ^ ((1U << inactive) - 1);
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}
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/* Pre-computed glibc-hwcaps subdirectory priorities. Used in
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dl-cache.c to quickly find the proprieties for the stored HWCAP
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names. */
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struct dl_hwcaps_priority
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{
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/* The name consists of name_length bytes at name (not necessarily
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null-terminated). */
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const char *name;
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uint32_t name_length;
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/* Priority of this name. A positive number. */
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uint32_t priority;
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};
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/* Pre-computed hwcaps priorities. Set up by
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_dl_important_hwcaps. */
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extern struct dl_hwcaps_priority *_dl_hwcaps_priorities attribute_hidden;
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extern uint32_t _dl_hwcaps_priorities_length attribute_hidden;
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#endif /* _DL_HWCAPS_H */
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