mirror of git://sourceware.org/git/glibc.git
71 lines
2.6 KiB
C
71 lines
2.6 KiB
C
/* Computation of TLS block size and its alignment.
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Copyright (C) 2002-2025 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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/* Compute the size of the TLS block for memory allocation. */
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static size_t
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_dl_tls_block_size_with_pre (void)
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{
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size_t size = GLRO (dl_tls_static_size);
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#if TLS_DTV_AT_TP
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/* Memory layout is:
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[ TLS_PRE_TCB_SIZE ] [ TLS_TCB_SIZE ] [ TLS blocks ]
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^ This should be returned. */
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size += TLS_PRE_TCB_SIZE;
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#endif
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return size;
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}
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/* SIZE must be the value returned by _dl_tls_block_size_with_pre.
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ALLOCATED must point to at least SIZE + GLRO (dl_tls_static_align)
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bytes. */
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static void *
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_dl_tls_block_align (size_t size, void *allocated)
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{
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void *result;
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size_t alignment = GLRO (dl_tls_static_align);
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#if TLS_TCB_AT_TP
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/* The TCB follows the TLS blocks, which determine the alignment.
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(TCB alignment requirements have been taken into account when
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calculating GLRO (dl_tls_static_align).) */
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void *aligned = (void *) roundup ((uintptr_t) allocated, alignment);
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result = aligned + size - TLS_TCB_SIZE;
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/* Clear the TCB data structure. We can't ask the caller (i.e.
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libpthread) to do it, because we will initialize the DTV et al. */
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memset (result, '\0', TLS_TCB_SIZE);
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#elif TLS_DTV_AT_TP
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/* Pre-TCB and TCB come before the TLS blocks. The layout computed
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in _dl_determine_tlsoffset assumes that the TCB is aligned to the
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TLS block alignment, and not just the TLS blocks after it. This
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can leave an unused alignment gap between the TCB and the TLS
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blocks. */
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result = (void *) roundup
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(sizeof (void *) + TLS_PRE_TCB_SIZE + (uintptr_t) allocated,
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alignment);
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/* Clear the TCB data structure and TLS_PRE_TCB_SIZE bytes before
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it. We can't ask the caller (i.e. libpthread) to do it, because
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we will initialize the DTV et al. */
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memset (result - TLS_PRE_TCB_SIZE, '\0', TLS_PRE_TCB_SIZE + TLS_TCB_SIZE);
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#endif
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return result;
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}
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