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304221775c
Add the Linux implementation of 'extra TLS' which will allocate space for the rseq area at the end of the TLS blocks in allocation order. Signed-off-by: Michael Jeanson <mjeanson@efficios.com> Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Reviewed-by: Florian Weimer <fweimer@redhat.com>
71 lines
2.4 KiB
C
71 lines
2.4 KiB
C
/* extra tls block utils for the dynamic linker. Linux version.
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Copyright (C) 2025 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_EXTRA_TLS_H
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#define _DL_EXTRA_TLS_H 1
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#include <stddef.h>
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#include <sys/rseq.h>
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#include <rseq-internal.h>
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#include <elf/dl-tunables.h>
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/* Returns the size of the extra TLS block, it must always be a multiple of the
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alignment. */
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static inline size_t
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_dl_extra_tls_get_size (void)
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{
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bool do_rseq = TUNABLE_GET_FULL (glibc, pthread, rseq, int, NULL);
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if (do_rseq)
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{
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/* Make sure the rseq area size is at least the minimum ABI size and a
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multiple of the requested aligment. */
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return roundup (MAX (_rseq_size, RSEQ_AREA_SIZE_INITIAL), _rseq_align);
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}
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/* Even when disabled by tunable, an rseq area will be allocated to allow
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application code to test the registration status with 'rseq->cpu_id >= 0'.
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Default to the rseq ABI minimum size, this will ensure we don't use more
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TLS than necessary. */
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return RSEQ_AREA_SIZE_INITIAL;
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}
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/* Returns the alignment requirements of the extra TLS block. */
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static inline size_t
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_dl_extra_tls_get_align (void)
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{
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bool do_rseq = TUNABLE_GET_FULL (glibc, pthread, rseq, int, NULL);
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if (do_rseq)
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{
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return _rseq_align;
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}
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/* Even when disabled by tunable, an rseq area will be allocated to allow
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application code to test the registration status with 'rseq->cpu_id >= 0'.
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Default to the rseq ABI minimum alignment, this will ensure we don't use
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more TLS than necessary. */
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return RSEQ_MIN_ALIGN;
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}
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/* Record the offset of the extra TLS block from the thread pointer. */
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static inline void
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_dl_extra_tls_set_offset (ptrdiff_t tls_offset)
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{
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_rseq_offset = tls_offset;
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}
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#endif
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