1106 lines
34 KiB
C
1106 lines
34 KiB
C
/* Thread-local storage handling in the ELF dynamic linker. Generic version.
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Copyright (C) 2002-2022 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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#include <assert.h>
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#include <errno.h>
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#include <libintl.h>
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#include <signal.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <sys/param.h>
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#include <atomic.h>
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#include <tls.h>
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#include <dl-tls.h>
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#include <ldsodefs.h>
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#if PTHREAD_IN_LIBC
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# include <list.h>
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#endif
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#define TUNABLE_NAMESPACE rtld
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#include <dl-tunables.h>
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/* Surplus static TLS, GLRO(dl_tls_static_surplus), is used for
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- IE TLS in libc.so for all dlmopen namespaces except in the initial
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one where libc.so is not loaded dynamically but at startup time,
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- IE TLS in other libraries which may be dynamically loaded even in the
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initial namespace,
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- and optionally for optimizing dynamic TLS access.
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The maximum number of namespaces is DL_NNS, but to support that many
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namespaces correctly the static TLS allocation should be significantly
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increased, which may cause problems with small thread stacks due to the
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way static TLS is accounted (bug 11787).
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So there is a rtld.nns tunable limit on the number of supported namespaces
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that affects the size of the static TLS and by default it's small enough
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not to cause problems with existing applications. The limit is not
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enforced or checked: it is the user's responsibility to increase rtld.nns
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if more dlmopen namespaces are used.
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Audit modules use their own namespaces, they are not included in rtld.nns,
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but come on top when computing the number of namespaces. */
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/* Size of initial-exec TLS in libc.so. This should be the maximum of
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observed PT_GNU_TLS sizes across all architectures. Some
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architectures have lower values due to differences in type sizes
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and link editor capabilities. */
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#define LIBC_IE_TLS 144
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/* Size of initial-exec TLS in libraries other than libc.so.
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This should be large enough to cover runtime libraries of the
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compiler such as libgomp and libraries in libc other than libc.so. */
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#define OTHER_IE_TLS 144
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/* Default number of namespaces. */
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#define DEFAULT_NNS 4
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/* Default for dl_tls_static_optional. */
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#define OPTIONAL_TLS 512
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/* Compute the static TLS surplus based on the namespace count and the
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TLS space that can be used for optimizations. */
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static inline int
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tls_static_surplus (int nns, int opt_tls)
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{
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return (nns - 1) * LIBC_IE_TLS + nns * OTHER_IE_TLS + opt_tls;
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}
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/* This value is chosen so that with default values for the tunables,
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the computation of dl_tls_static_surplus in
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_dl_tls_static_surplus_init yields the historic value 1664, for
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backwards compatibility. */
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#define LEGACY_TLS (1664 - tls_static_surplus (DEFAULT_NNS, OPTIONAL_TLS))
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/* Calculate the size of the static TLS surplus, when the given
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number of audit modules are loaded. Must be called after the
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number of audit modules is known and before static TLS allocation. */
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void
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_dl_tls_static_surplus_init (size_t naudit)
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{
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size_t nns, opt_tls;
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#if HAVE_TUNABLES
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nns = TUNABLE_GET (nns, size_t, NULL);
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opt_tls = TUNABLE_GET (optional_static_tls, size_t, NULL);
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#else
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/* Default values of the tunables. */
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nns = DEFAULT_NNS;
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opt_tls = OPTIONAL_TLS;
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#endif
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if (nns > DL_NNS)
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nns = DL_NNS;
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if (DL_NNS - nns < naudit)
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_dl_fatal_printf ("Failed loading %lu audit modules, %lu are supported.\n",
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(unsigned long) naudit, (unsigned long) (DL_NNS - nns));
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nns += naudit;
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GL(dl_tls_static_optional) = opt_tls;
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assert (LEGACY_TLS >= 0);
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GLRO(dl_tls_static_surplus) = tls_static_surplus (nns, opt_tls) + LEGACY_TLS;
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}
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/* Out-of-memory handler. */
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static void
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__attribute__ ((__noreturn__))
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oom (void)
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{
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_dl_fatal_printf ("cannot allocate memory for thread-local data: ABORT\n");
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}
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void
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_dl_assign_tls_modid (struct link_map *l)
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{
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size_t result;
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if (__builtin_expect (GL(dl_tls_dtv_gaps), false))
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{
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size_t disp = 0;
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struct dtv_slotinfo_list *runp = GL(dl_tls_dtv_slotinfo_list);
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/* Note that this branch will never be executed during program
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start since there are no gaps at that time. Therefore it
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does not matter that the dl_tls_dtv_slotinfo is not allocated
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yet when the function is called for the first times.
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NB: the offset +1 is due to the fact that DTV[0] is used
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for something else. */
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result = GL(dl_tls_static_nelem) + 1;
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if (result <= GL(dl_tls_max_dtv_idx))
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do
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{
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while (result - disp < runp->len)
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{
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if (runp->slotinfo[result - disp].map == NULL)
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break;
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++result;
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assert (result <= GL(dl_tls_max_dtv_idx) + 1);
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}
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if (result - disp < runp->len)
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{
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/* Mark the entry as used, so any dependency see it. */
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atomic_store_relaxed (&runp->slotinfo[result - disp].map, l);
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break;
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}
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disp += runp->len;
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}
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while ((runp = runp->next) != NULL);
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if (result > GL(dl_tls_max_dtv_idx))
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{
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/* The new index must indeed be exactly one higher than the
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previous high. */
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assert (result == GL(dl_tls_max_dtv_idx) + 1);
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/* There is no gap anymore. */
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GL(dl_tls_dtv_gaps) = false;
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goto nogaps;
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}
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}
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else
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{
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/* No gaps, allocate a new entry. */
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nogaps:
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result = GL(dl_tls_max_dtv_idx) + 1;
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/* Can be read concurrently. */
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atomic_store_relaxed (&GL(dl_tls_max_dtv_idx), result);
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}
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l->l_tls_modid = result;
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}
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size_t
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_dl_count_modids (void)
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{
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/* The count is the max unless dlclose or failed dlopen created gaps. */
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if (__glibc_likely (!GL(dl_tls_dtv_gaps)))
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return GL(dl_tls_max_dtv_idx);
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/* We have gaps and are forced to count the non-NULL entries. */
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size_t n = 0;
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struct dtv_slotinfo_list *runp = GL(dl_tls_dtv_slotinfo_list);
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while (runp != NULL)
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{
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for (size_t i = 0; i < runp->len; ++i)
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if (runp->slotinfo[i].map != NULL)
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++n;
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runp = runp->next;
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}
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return n;
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}
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#ifdef SHARED
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void
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_dl_determine_tlsoffset (void)
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{
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size_t max_align = TCB_ALIGNMENT;
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size_t freetop = 0;
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size_t freebottom = 0;
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/* The first element of the dtv slot info list is allocated. */
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assert (GL(dl_tls_dtv_slotinfo_list) != NULL);
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/* There is at this point only one element in the
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dl_tls_dtv_slotinfo_list list. */
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assert (GL(dl_tls_dtv_slotinfo_list)->next == NULL);
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struct dtv_slotinfo *slotinfo = GL(dl_tls_dtv_slotinfo_list)->slotinfo;
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/* Determining the offset of the various parts of the static TLS
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block has several dependencies. In addition we have to work
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around bugs in some toolchains.
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Each TLS block from the objects available at link time has a size
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and an alignment requirement. The GNU ld computes the alignment
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requirements for the data at the positions *in the file*, though.
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I.e, it is not simply possible to allocate a block with the size
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of the TLS program header entry. The data is layed out assuming
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that the first byte of the TLS block fulfills
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p_vaddr mod p_align == &TLS_BLOCK mod p_align
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This means we have to add artificial padding at the beginning of
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the TLS block. These bytes are never used for the TLS data in
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this module but the first byte allocated must be aligned
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according to mod p_align == 0 so that the first byte of the TLS
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block is aligned according to p_vaddr mod p_align. This is ugly
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and the linker can help by computing the offsets in the TLS block
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assuming the first byte of the TLS block is aligned according to
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p_align.
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The extra space which might be allocated before the first byte of
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the TLS block need not go unused. The code below tries to use
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that memory for the next TLS block. This can work if the total
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memory requirement for the next TLS block is smaller than the
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gap. */
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#if TLS_TCB_AT_TP
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/* We simply start with zero. */
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size_t offset = 0;
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for (size_t cnt = 0; slotinfo[cnt].map != NULL; ++cnt)
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{
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assert (cnt < GL(dl_tls_dtv_slotinfo_list)->len);
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size_t firstbyte = (-slotinfo[cnt].map->l_tls_firstbyte_offset
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& (slotinfo[cnt].map->l_tls_align - 1));
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size_t off;
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max_align = MAX (max_align, slotinfo[cnt].map->l_tls_align);
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if (freebottom - freetop >= slotinfo[cnt].map->l_tls_blocksize)
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{
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off = roundup (freetop + slotinfo[cnt].map->l_tls_blocksize
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- firstbyte, slotinfo[cnt].map->l_tls_align)
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+ firstbyte;
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if (off <= freebottom)
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{
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freetop = off;
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/* XXX For some architectures we perhaps should store the
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negative offset. */
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slotinfo[cnt].map->l_tls_offset = off;
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continue;
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}
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}
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off = roundup (offset + slotinfo[cnt].map->l_tls_blocksize - firstbyte,
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slotinfo[cnt].map->l_tls_align) + firstbyte;
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if (off > offset + slotinfo[cnt].map->l_tls_blocksize
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+ (freebottom - freetop))
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{
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freetop = offset;
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freebottom = off - slotinfo[cnt].map->l_tls_blocksize;
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}
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offset = off;
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/* XXX For some architectures we perhaps should store the
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negative offset. */
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slotinfo[cnt].map->l_tls_offset = off;
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}
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GL(dl_tls_static_used) = offset;
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GLRO (dl_tls_static_size) = (roundup (offset + GLRO(dl_tls_static_surplus),
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max_align)
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+ TLS_TCB_SIZE);
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#elif TLS_DTV_AT_TP
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/* The TLS blocks start right after the TCB. */
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size_t offset = TLS_TCB_SIZE;
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for (size_t cnt = 0; slotinfo[cnt].map != NULL; ++cnt)
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{
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assert (cnt < GL(dl_tls_dtv_slotinfo_list)->len);
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size_t firstbyte = (-slotinfo[cnt].map->l_tls_firstbyte_offset
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& (slotinfo[cnt].map->l_tls_align - 1));
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size_t off;
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max_align = MAX (max_align, slotinfo[cnt].map->l_tls_align);
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if (slotinfo[cnt].map->l_tls_blocksize <= freetop - freebottom)
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{
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off = roundup (freebottom, slotinfo[cnt].map->l_tls_align);
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if (off - freebottom < firstbyte)
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off += slotinfo[cnt].map->l_tls_align;
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if (off + slotinfo[cnt].map->l_tls_blocksize - firstbyte <= freetop)
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{
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slotinfo[cnt].map->l_tls_offset = off - firstbyte;
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freebottom = (off + slotinfo[cnt].map->l_tls_blocksize
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- firstbyte);
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continue;
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}
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}
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off = roundup (offset, slotinfo[cnt].map->l_tls_align);
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if (off - offset < firstbyte)
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off += slotinfo[cnt].map->l_tls_align;
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slotinfo[cnt].map->l_tls_offset = off - firstbyte;
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if (off - firstbyte - offset > freetop - freebottom)
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{
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freebottom = offset;
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freetop = off - firstbyte;
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}
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offset = off + slotinfo[cnt].map->l_tls_blocksize - firstbyte;
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}
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GL(dl_tls_static_used) = offset;
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GLRO (dl_tls_static_size) = roundup (offset + GLRO(dl_tls_static_surplus),
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TCB_ALIGNMENT);
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#else
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# error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
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#endif
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/* The alignment requirement for the static TLS block. */
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GLRO (dl_tls_static_align) = max_align;
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}
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#endif /* SHARED */
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static void *
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allocate_dtv (void *result)
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{
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dtv_t *dtv;
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size_t dtv_length;
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/* Relaxed MO, because the dtv size is later rechecked, not relied on. */
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size_t max_modid = atomic_load_relaxed (&GL(dl_tls_max_dtv_idx));
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/* We allocate a few more elements in the dtv than are needed for the
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initial set of modules. This should avoid in most cases expansions
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of the dtv. */
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dtv_length = max_modid + DTV_SURPLUS;
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dtv = calloc (dtv_length + 2, sizeof (dtv_t));
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if (dtv != NULL)
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{
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/* This is the initial length of the dtv. */
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dtv[0].counter = dtv_length;
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/* The rest of the dtv (including the generation counter) is
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Initialize with zero to indicate nothing there. */
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/* Add the dtv to the thread data structures. */
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INSTALL_DTV (result, dtv);
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}
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else
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result = NULL;
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return result;
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}
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/* Get size and alignment requirements of the static TLS block. This
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function is no longer used by glibc itself, but the GCC sanitizers
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use it despite the GLIBC_PRIVATE status. */
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void
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_dl_get_tls_static_info (size_t *sizep, size_t *alignp)
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{
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*sizep = GLRO (dl_tls_static_size);
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*alignp = GLRO (dl_tls_static_align);
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}
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/* Derive the location of the pointer to the start of the original
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allocation (before alignment) from the pointer to the TCB. */
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static inline void **
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tcb_to_pointer_to_free_location (void *tcb)
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{
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#if TLS_TCB_AT_TP
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/* The TCB follows the TLS blocks, and the pointer to the front
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follows the TCB. */
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void **original_pointer_location = tcb + TLS_TCB_SIZE;
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#elif TLS_DTV_AT_TP
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/* The TCB comes first, preceded by the pre-TCB, and the pointer is
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before that. */
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void **original_pointer_location = tcb - TLS_PRE_TCB_SIZE - sizeof (void *);
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#endif
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return original_pointer_location;
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}
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void *
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_dl_allocate_tls_storage (void)
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{
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void *result;
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size_t size = GLRO (dl_tls_static_size);
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|
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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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/* Perform the allocation. Reserve space for the required alignment
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and the pointer to the original allocation. */
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size_t alignment = GLRO (dl_tls_static_align);
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void *allocated = malloc (size + alignment + sizeof (void *));
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if (__glibc_unlikely (allocated == NULL))
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return NULL;
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|
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/* Perform alignment and allocate the DTV. */
|
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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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|
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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
|
|
in _dl_determine_tlsoffset assumes that the TCB is aligned to the
|
|
TLS block alignment, and not just the TLS blocks after it. This
|
|
can leave an unused alignment gap between the TCB and the TLS
|
|
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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|
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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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|
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/* Record the value of the original pointer for later
|
|
deallocation. */
|
|
*tcb_to_pointer_to_free_location (result) = allocated;
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|
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result = allocate_dtv (result);
|
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if (result == NULL)
|
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free (allocated);
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return result;
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}
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|
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|
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#ifndef SHARED
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extern dtv_t _dl_static_dtv[];
|
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# define _dl_initial_dtv (&_dl_static_dtv[1])
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#endif
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|
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static dtv_t *
|
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_dl_resize_dtv (dtv_t *dtv, size_t max_modid)
|
|
{
|
|
/* Resize the dtv. */
|
|
dtv_t *newp;
|
|
size_t newsize = max_modid + DTV_SURPLUS;
|
|
size_t oldsize = dtv[-1].counter;
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|
|
if (dtv == GL(dl_initial_dtv))
|
|
{
|
|
/* This is the initial dtv that was either statically allocated in
|
|
__libc_setup_tls or allocated during rtld startup using the
|
|
dl-minimal.c malloc instead of the real malloc. We can't free
|
|
it, we have to abandon the old storage. */
|
|
|
|
newp = malloc ((2 + newsize) * sizeof (dtv_t));
|
|
if (newp == NULL)
|
|
oom ();
|
|
memcpy (newp, &dtv[-1], (2 + oldsize) * sizeof (dtv_t));
|
|
}
|
|
else
|
|
{
|
|
newp = realloc (&dtv[-1],
|
|
(2 + newsize) * sizeof (dtv_t));
|
|
if (newp == NULL)
|
|
oom ();
|
|
}
|
|
|
|
newp[0].counter = newsize;
|
|
|
|
/* Clear the newly allocated part. */
|
|
memset (newp + 2 + oldsize, '\0',
|
|
(newsize - oldsize) * sizeof (dtv_t));
|
|
|
|
/* Return the generation counter. */
|
|
return &newp[1];
|
|
}
|
|
|
|
|
|
/* Allocate initial TLS. RESULT should be a non-NULL pointer to storage
|
|
for the TLS space. The DTV may be resized, and so this function may
|
|
call malloc to allocate that space. The loader's GL(dl_load_tls_lock)
|
|
is taken when manipulating global TLS-related data in the loader. */
|
|
void *
|
|
_dl_allocate_tls_init (void *result, bool init_tls)
|
|
{
|
|
if (result == NULL)
|
|
/* The memory allocation failed. */
|
|
return NULL;
|
|
|
|
dtv_t *dtv = GET_DTV (result);
|
|
struct dtv_slotinfo_list *listp;
|
|
size_t total = 0;
|
|
size_t maxgen = 0;
|
|
|
|
/* Protects global dynamic TLS related state. */
|
|
__rtld_lock_lock_recursive (GL(dl_load_tls_lock));
|
|
|
|
/* Check if the current dtv is big enough. */
|
|
if (dtv[-1].counter < GL(dl_tls_max_dtv_idx))
|
|
{
|
|
/* Resize the dtv. */
|
|
dtv = _dl_resize_dtv (dtv, GL(dl_tls_max_dtv_idx));
|
|
|
|
/* Install this new dtv in the thread data structures. */
|
|
INSTALL_DTV (result, &dtv[-1]);
|
|
}
|
|
|
|
/* We have to prepare the dtv for all currently loaded modules using
|
|
TLS. For those which are dynamically loaded we add the values
|
|
indicating deferred allocation. */
|
|
listp = GL(dl_tls_dtv_slotinfo_list);
|
|
while (1)
|
|
{
|
|
size_t cnt;
|
|
|
|
for (cnt = total == 0 ? 1 : 0; cnt < listp->len; ++cnt)
|
|
{
|
|
struct link_map *map;
|
|
void *dest;
|
|
|
|
/* Check for the total number of used slots. */
|
|
if (total + cnt > GL(dl_tls_max_dtv_idx))
|
|
break;
|
|
|
|
map = listp->slotinfo[cnt].map;
|
|
if (map == NULL)
|
|
/* Unused entry. */
|
|
continue;
|
|
|
|
/* Keep track of the maximum generation number. This might
|
|
not be the generation counter. */
|
|
assert (listp->slotinfo[cnt].gen <= GL(dl_tls_generation));
|
|
maxgen = MAX (maxgen, listp->slotinfo[cnt].gen);
|
|
|
|
dtv[map->l_tls_modid].pointer.val = TLS_DTV_UNALLOCATED;
|
|
dtv[map->l_tls_modid].pointer.to_free = NULL;
|
|
|
|
if (map->l_tls_offset == NO_TLS_OFFSET
|
|
|| map->l_tls_offset == FORCED_DYNAMIC_TLS_OFFSET)
|
|
continue;
|
|
|
|
assert (map->l_tls_modid == total + cnt);
|
|
assert (map->l_tls_blocksize >= map->l_tls_initimage_size);
|
|
#if TLS_TCB_AT_TP
|
|
assert ((size_t) map->l_tls_offset >= map->l_tls_blocksize);
|
|
dest = (char *) result - map->l_tls_offset;
|
|
#elif TLS_DTV_AT_TP
|
|
dest = (char *) result + map->l_tls_offset;
|
|
#else
|
|
# error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
|
|
#endif
|
|
|
|
/* Set up the DTV entry. The simplified __tls_get_addr that
|
|
some platforms use in static programs requires it. */
|
|
dtv[map->l_tls_modid].pointer.val = dest;
|
|
|
|
/* Copy the initialization image and clear the BSS part. For
|
|
audit modules or dependencies with initial-exec TLS, we can not
|
|
set the initial TLS image on default loader initialization
|
|
because it would already be set by the audit setup. However,
|
|
subsequent thread creation would need to follow the default
|
|
behaviour. */
|
|
if (map->l_ns != LM_ID_BASE && !init_tls)
|
|
continue;
|
|
memset (__mempcpy (dest, map->l_tls_initimage,
|
|
map->l_tls_initimage_size), '\0',
|
|
map->l_tls_blocksize - map->l_tls_initimage_size);
|
|
}
|
|
|
|
total += cnt;
|
|
if (total > GL(dl_tls_max_dtv_idx))
|
|
break;
|
|
|
|
listp = listp->next;
|
|
assert (listp != NULL);
|
|
}
|
|
__rtld_lock_unlock_recursive (GL(dl_load_tls_lock));
|
|
|
|
/* The DTV version is up-to-date now. */
|
|
dtv[0].counter = maxgen;
|
|
|
|
return result;
|
|
}
|
|
rtld_hidden_def (_dl_allocate_tls_init)
|
|
|
|
void *
|
|
_dl_allocate_tls (void *mem)
|
|
{
|
|
return _dl_allocate_tls_init (mem == NULL
|
|
? _dl_allocate_tls_storage ()
|
|
: allocate_dtv (mem), true);
|
|
}
|
|
rtld_hidden_def (_dl_allocate_tls)
|
|
|
|
|
|
void
|
|
_dl_deallocate_tls (void *tcb, bool dealloc_tcb)
|
|
{
|
|
dtv_t *dtv = GET_DTV (tcb);
|
|
|
|
/* We need to free the memory allocated for non-static TLS. */
|
|
for (size_t cnt = 0; cnt < dtv[-1].counter; ++cnt)
|
|
free (dtv[1 + cnt].pointer.to_free);
|
|
|
|
/* The array starts with dtv[-1]. */
|
|
if (dtv != GL(dl_initial_dtv))
|
|
free (dtv - 1);
|
|
|
|
if (dealloc_tcb)
|
|
free (*tcb_to_pointer_to_free_location (tcb));
|
|
}
|
|
rtld_hidden_def (_dl_deallocate_tls)
|
|
|
|
|
|
#ifdef SHARED
|
|
/* The __tls_get_addr function has two basic forms which differ in the
|
|
arguments. The IA-64 form takes two parameters, the module ID and
|
|
offset. The form used, among others, on IA-32 takes a reference to
|
|
a special structure which contain the same information. The second
|
|
form seems to be more often used (in the moment) so we default to
|
|
it. Users of the IA-64 form have to provide adequate definitions
|
|
of the following macros. */
|
|
# ifndef GET_ADDR_ARGS
|
|
# define GET_ADDR_ARGS tls_index *ti
|
|
# define GET_ADDR_PARAM ti
|
|
# endif
|
|
# ifndef GET_ADDR_MODULE
|
|
# define GET_ADDR_MODULE ti->ti_module
|
|
# endif
|
|
# ifndef GET_ADDR_OFFSET
|
|
# define GET_ADDR_OFFSET ti->ti_offset
|
|
# endif
|
|
|
|
/* Allocate one DTV entry. */
|
|
static struct dtv_pointer
|
|
allocate_dtv_entry (size_t alignment, size_t size)
|
|
{
|
|
if (powerof2 (alignment) && alignment <= _Alignof (max_align_t))
|
|
{
|
|
/* The alignment is supported by malloc. */
|
|
void *ptr = malloc (size);
|
|
return (struct dtv_pointer) { ptr, ptr };
|
|
}
|
|
|
|
/* Emulate memalign to by manually aligning a pointer returned by
|
|
malloc. First compute the size with an overflow check. */
|
|
size_t alloc_size = size + alignment;
|
|
if (alloc_size < size)
|
|
return (struct dtv_pointer) {};
|
|
|
|
/* Perform the allocation. This is the pointer we need to free
|
|
later. */
|
|
void *start = malloc (alloc_size);
|
|
if (start == NULL)
|
|
return (struct dtv_pointer) {};
|
|
|
|
/* Find the aligned position within the larger allocation. */
|
|
void *aligned = (void *) roundup ((uintptr_t) start, alignment);
|
|
|
|
return (struct dtv_pointer) { .val = aligned, .to_free = start };
|
|
}
|
|
|
|
static struct dtv_pointer
|
|
allocate_and_init (struct link_map *map)
|
|
{
|
|
struct dtv_pointer result = allocate_dtv_entry
|
|
(map->l_tls_align, map->l_tls_blocksize);
|
|
if (result.val == NULL)
|
|
oom ();
|
|
|
|
/* Initialize the memory. */
|
|
memset (__mempcpy (result.val, map->l_tls_initimage,
|
|
map->l_tls_initimage_size),
|
|
'\0', map->l_tls_blocksize - map->l_tls_initimage_size);
|
|
|
|
return result;
|
|
}
|
|
|
|
|
|
struct link_map *
|
|
_dl_update_slotinfo (unsigned long int req_modid)
|
|
{
|
|
struct link_map *the_map = NULL;
|
|
dtv_t *dtv = THREAD_DTV ();
|
|
|
|
/* The global dl_tls_dtv_slotinfo array contains for each module
|
|
index the generation counter current when the entry was created.
|
|
This array never shrinks so that all module indices which were
|
|
valid at some time can be used to access it. Before the first
|
|
use of a new module index in this function the array was extended
|
|
appropriately. Access also does not have to be guarded against
|
|
modifications of the array. It is assumed that pointer-size
|
|
values can be read atomically even in SMP environments. It is
|
|
possible that other threads at the same time dynamically load
|
|
code and therefore add to the slotinfo list. This is a problem
|
|
since we must not pick up any information about incomplete work.
|
|
The solution to this is to ignore all dtv slots which were
|
|
created after the one we are currently interested. We know that
|
|
dynamic loading for this module is completed and this is the last
|
|
load operation we know finished. */
|
|
unsigned long int idx = req_modid;
|
|
struct dtv_slotinfo_list *listp = GL(dl_tls_dtv_slotinfo_list);
|
|
|
|
while (idx >= listp->len)
|
|
{
|
|
idx -= listp->len;
|
|
listp = listp->next;
|
|
}
|
|
|
|
if (dtv[0].counter < listp->slotinfo[idx].gen)
|
|
{
|
|
/* CONCURRENCY NOTES:
|
|
|
|
Here the dtv needs to be updated to new_gen generation count.
|
|
|
|
This code may be called during TLS access when GL(dl_load_tls_lock)
|
|
is not held. In that case the user code has to synchronize with
|
|
dlopen and dlclose calls of relevant modules. A module m is
|
|
relevant if the generation of m <= new_gen and dlclose of m is
|
|
synchronized: a memory access here happens after the dlopen and
|
|
before the dlclose of relevant modules. The dtv entries for
|
|
relevant modules need to be updated, other entries can be
|
|
arbitrary.
|
|
|
|
This e.g. means that the first part of the slotinfo list can be
|
|
accessed race free, but the tail may be concurrently extended.
|
|
Similarly relevant slotinfo entries can be read race free, but
|
|
other entries are racy. However updating a non-relevant dtv
|
|
entry does not affect correctness. For a relevant module m,
|
|
max_modid >= modid of m. */
|
|
size_t new_gen = listp->slotinfo[idx].gen;
|
|
size_t total = 0;
|
|
size_t max_modid = atomic_load_relaxed (&GL(dl_tls_max_dtv_idx));
|
|
assert (max_modid >= req_modid);
|
|
|
|
/* We have to look through the entire dtv slotinfo list. */
|
|
listp = GL(dl_tls_dtv_slotinfo_list);
|
|
do
|
|
{
|
|
for (size_t cnt = total == 0 ? 1 : 0; cnt < listp->len; ++cnt)
|
|
{
|
|
size_t modid = total + cnt;
|
|
|
|
/* Later entries are not relevant. */
|
|
if (modid > max_modid)
|
|
break;
|
|
|
|
size_t gen = atomic_load_relaxed (&listp->slotinfo[cnt].gen);
|
|
|
|
if (gen > new_gen)
|
|
/* Not relevant. */
|
|
continue;
|
|
|
|
/* If the entry is older than the current dtv layout we
|
|
know we don't have to handle it. */
|
|
if (gen <= dtv[0].counter)
|
|
continue;
|
|
|
|
/* If there is no map this means the entry is empty. */
|
|
struct link_map *map
|
|
= atomic_load_relaxed (&listp->slotinfo[cnt].map);
|
|
/* Check whether the current dtv array is large enough. */
|
|
if (dtv[-1].counter < modid)
|
|
{
|
|
if (map == NULL)
|
|
continue;
|
|
|
|
/* Resize the dtv. */
|
|
dtv = _dl_resize_dtv (dtv, max_modid);
|
|
|
|
assert (modid <= dtv[-1].counter);
|
|
|
|
/* Install this new dtv in the thread data
|
|
structures. */
|
|
INSTALL_NEW_DTV (dtv);
|
|
}
|
|
|
|
/* If there is currently memory allocate for this
|
|
dtv entry free it. */
|
|
/* XXX Ideally we will at some point create a memory
|
|
pool. */
|
|
free (dtv[modid].pointer.to_free);
|
|
dtv[modid].pointer.val = TLS_DTV_UNALLOCATED;
|
|
dtv[modid].pointer.to_free = NULL;
|
|
|
|
if (modid == req_modid)
|
|
the_map = map;
|
|
}
|
|
|
|
total += listp->len;
|
|
if (total > max_modid)
|
|
break;
|
|
|
|
/* Synchronize with _dl_add_to_slotinfo. Ideally this would
|
|
be consume MO since we only need to order the accesses to
|
|
the next node after the read of the address and on most
|
|
hardware (other than alpha) a normal load would do that
|
|
because of the address dependency. */
|
|
listp = atomic_load_acquire (&listp->next);
|
|
}
|
|
while (listp != NULL);
|
|
|
|
/* This will be the new maximum generation counter. */
|
|
dtv[0].counter = new_gen;
|
|
}
|
|
|
|
return the_map;
|
|
}
|
|
|
|
|
|
static void *
|
|
__attribute_noinline__
|
|
tls_get_addr_tail (GET_ADDR_ARGS, dtv_t *dtv, struct link_map *the_map)
|
|
{
|
|
/* The allocation was deferred. Do it now. */
|
|
if (the_map == NULL)
|
|
{
|
|
/* Find the link map for this module. */
|
|
size_t idx = GET_ADDR_MODULE;
|
|
struct dtv_slotinfo_list *listp = GL(dl_tls_dtv_slotinfo_list);
|
|
|
|
while (idx >= listp->len)
|
|
{
|
|
idx -= listp->len;
|
|
listp = listp->next;
|
|
}
|
|
|
|
the_map = listp->slotinfo[idx].map;
|
|
}
|
|
|
|
/* Make sure that, if a dlopen running in parallel forces the
|
|
variable into static storage, we'll wait until the address in the
|
|
static TLS block is set up, and use that. If we're undecided
|
|
yet, make sure we make the decision holding the lock as well. */
|
|
if (__glibc_unlikely (the_map->l_tls_offset
|
|
!= FORCED_DYNAMIC_TLS_OFFSET))
|
|
{
|
|
__rtld_lock_lock_recursive (GL(dl_load_tls_lock));
|
|
if (__glibc_likely (the_map->l_tls_offset == NO_TLS_OFFSET))
|
|
{
|
|
the_map->l_tls_offset = FORCED_DYNAMIC_TLS_OFFSET;
|
|
__rtld_lock_unlock_recursive (GL(dl_load_tls_lock));
|
|
}
|
|
else if (__glibc_likely (the_map->l_tls_offset
|
|
!= FORCED_DYNAMIC_TLS_OFFSET))
|
|
{
|
|
#if TLS_TCB_AT_TP
|
|
void *p = (char *) THREAD_SELF - the_map->l_tls_offset;
|
|
#elif TLS_DTV_AT_TP
|
|
void *p = (char *) THREAD_SELF + the_map->l_tls_offset + TLS_PRE_TCB_SIZE;
|
|
#else
|
|
# error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
|
|
#endif
|
|
__rtld_lock_unlock_recursive (GL(dl_load_tls_lock));
|
|
|
|
dtv[GET_ADDR_MODULE].pointer.to_free = NULL;
|
|
dtv[GET_ADDR_MODULE].pointer.val = p;
|
|
|
|
return (char *) p + GET_ADDR_OFFSET;
|
|
}
|
|
else
|
|
__rtld_lock_unlock_recursive (GL(dl_load_tls_lock));
|
|
}
|
|
struct dtv_pointer result = allocate_and_init (the_map);
|
|
dtv[GET_ADDR_MODULE].pointer = result;
|
|
assert (result.to_free != NULL);
|
|
|
|
return (char *) result.val + GET_ADDR_OFFSET;
|
|
}
|
|
|
|
|
|
static struct link_map *
|
|
__attribute_noinline__
|
|
update_get_addr (GET_ADDR_ARGS)
|
|
{
|
|
struct link_map *the_map = _dl_update_slotinfo (GET_ADDR_MODULE);
|
|
dtv_t *dtv = THREAD_DTV ();
|
|
|
|
void *p = dtv[GET_ADDR_MODULE].pointer.val;
|
|
|
|
if (__glibc_unlikely (p == TLS_DTV_UNALLOCATED))
|
|
return tls_get_addr_tail (GET_ADDR_PARAM, dtv, the_map);
|
|
|
|
return (void *) p + GET_ADDR_OFFSET;
|
|
}
|
|
|
|
/* For all machines that have a non-macro version of __tls_get_addr, we
|
|
want to use rtld_hidden_proto/rtld_hidden_def in order to call the
|
|
internal alias for __tls_get_addr from ld.so. This avoids a PLT entry
|
|
in ld.so for __tls_get_addr. */
|
|
|
|
#ifndef __tls_get_addr
|
|
extern void * __tls_get_addr (GET_ADDR_ARGS);
|
|
rtld_hidden_proto (__tls_get_addr)
|
|
rtld_hidden_def (__tls_get_addr)
|
|
#endif
|
|
|
|
/* The generic dynamic and local dynamic model cannot be used in
|
|
statically linked applications. */
|
|
void *
|
|
__tls_get_addr (GET_ADDR_ARGS)
|
|
{
|
|
dtv_t *dtv = THREAD_DTV ();
|
|
|
|
/* Update is needed if dtv[0].counter < the generation of the accessed
|
|
module. The global generation counter is used here as it is easier
|
|
to check. Synchronization for the relaxed MO access is guaranteed
|
|
by user code, see CONCURRENCY NOTES in _dl_update_slotinfo. */
|
|
size_t gen = atomic_load_relaxed (&GL(dl_tls_generation));
|
|
if (__glibc_unlikely (dtv[0].counter != gen))
|
|
return update_get_addr (GET_ADDR_PARAM);
|
|
|
|
void *p = dtv[GET_ADDR_MODULE].pointer.val;
|
|
|
|
if (__glibc_unlikely (p == TLS_DTV_UNALLOCATED))
|
|
return tls_get_addr_tail (GET_ADDR_PARAM, dtv, NULL);
|
|
|
|
return (char *) p + GET_ADDR_OFFSET;
|
|
}
|
|
#endif
|
|
|
|
|
|
/* Look up the module's TLS block as for __tls_get_addr,
|
|
but never touch anything. Return null if it's not allocated yet. */
|
|
void *
|
|
_dl_tls_get_addr_soft (struct link_map *l)
|
|
{
|
|
if (__glibc_unlikely (l->l_tls_modid == 0))
|
|
/* This module has no TLS segment. */
|
|
return NULL;
|
|
|
|
dtv_t *dtv = THREAD_DTV ();
|
|
/* This may be called without holding the GL(dl_load_tls_lock). Reading
|
|
arbitrary gen value is fine since this is best effort code. */
|
|
size_t gen = atomic_load_relaxed (&GL(dl_tls_generation));
|
|
if (__glibc_unlikely (dtv[0].counter != gen))
|
|
{
|
|
/* This thread's DTV is not completely current,
|
|
but it might already cover this module. */
|
|
|
|
if (l->l_tls_modid >= dtv[-1].counter)
|
|
/* Nope. */
|
|
return NULL;
|
|
|
|
size_t idx = l->l_tls_modid;
|
|
struct dtv_slotinfo_list *listp = GL(dl_tls_dtv_slotinfo_list);
|
|
while (idx >= listp->len)
|
|
{
|
|
idx -= listp->len;
|
|
listp = listp->next;
|
|
}
|
|
|
|
/* We've reached the slot for this module.
|
|
If its generation counter is higher than the DTV's,
|
|
this thread does not know about this module yet. */
|
|
if (dtv[0].counter < listp->slotinfo[idx].gen)
|
|
return NULL;
|
|
}
|
|
|
|
void *data = dtv[l->l_tls_modid].pointer.val;
|
|
if (__glibc_unlikely (data == TLS_DTV_UNALLOCATED))
|
|
/* The DTV is current, but this thread has not yet needed
|
|
to allocate this module's segment. */
|
|
data = NULL;
|
|
|
|
return data;
|
|
}
|
|
|
|
|
|
void
|
|
_dl_add_to_slotinfo (struct link_map *l, bool do_add)
|
|
{
|
|
/* Now that we know the object is loaded successfully add
|
|
modules containing TLS data to the dtv info table. We
|
|
might have to increase its size. */
|
|
struct dtv_slotinfo_list *listp;
|
|
struct dtv_slotinfo_list *prevp;
|
|
size_t idx = l->l_tls_modid;
|
|
|
|
/* Find the place in the dtv slotinfo list. */
|
|
listp = GL(dl_tls_dtv_slotinfo_list);
|
|
prevp = NULL; /* Needed to shut up gcc. */
|
|
do
|
|
{
|
|
/* Does it fit in the array of this list element? */
|
|
if (idx < listp->len)
|
|
break;
|
|
idx -= listp->len;
|
|
prevp = listp;
|
|
listp = listp->next;
|
|
}
|
|
while (listp != NULL);
|
|
|
|
if (listp == NULL)
|
|
{
|
|
/* When we come here it means we have to add a new element
|
|
to the slotinfo list. And the new module must be in
|
|
the first slot. */
|
|
assert (idx == 0);
|
|
|
|
listp = (struct dtv_slotinfo_list *)
|
|
malloc (sizeof (struct dtv_slotinfo_list)
|
|
+ TLS_SLOTINFO_SURPLUS * sizeof (struct dtv_slotinfo));
|
|
if (listp == NULL)
|
|
{
|
|
/* We ran out of memory while resizing the dtv slotinfo list. */
|
|
_dl_signal_error (ENOMEM, "dlopen", NULL, N_("\
|
|
cannot create TLS data structures"));
|
|
}
|
|
|
|
listp->len = TLS_SLOTINFO_SURPLUS;
|
|
listp->next = NULL;
|
|
memset (listp->slotinfo, '\0',
|
|
TLS_SLOTINFO_SURPLUS * sizeof (struct dtv_slotinfo));
|
|
/* Synchronize with _dl_update_slotinfo. */
|
|
atomic_store_release (&prevp->next, listp);
|
|
}
|
|
|
|
/* Add the information into the slotinfo data structure. */
|
|
if (do_add)
|
|
{
|
|
/* Can be read concurrently. See _dl_update_slotinfo. */
|
|
atomic_store_relaxed (&listp->slotinfo[idx].map, l);
|
|
atomic_store_relaxed (&listp->slotinfo[idx].gen,
|
|
GL(dl_tls_generation) + 1);
|
|
}
|
|
}
|
|
|
|
#if PTHREAD_IN_LIBC
|
|
static inline void __attribute__((always_inline))
|
|
init_one_static_tls (struct pthread *curp, struct link_map *map)
|
|
{
|
|
# if TLS_TCB_AT_TP
|
|
void *dest = (char *) curp - map->l_tls_offset;
|
|
# elif TLS_DTV_AT_TP
|
|
void *dest = (char *) curp + map->l_tls_offset + TLS_PRE_TCB_SIZE;
|
|
# else
|
|
# error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
|
|
# endif
|
|
|
|
/* Initialize the memory. */
|
|
memset (__mempcpy (dest, map->l_tls_initimage, map->l_tls_initimage_size),
|
|
'\0', map->l_tls_blocksize - map->l_tls_initimage_size);
|
|
}
|
|
|
|
void
|
|
_dl_init_static_tls (struct link_map *map)
|
|
{
|
|
lll_lock (GL (dl_stack_cache_lock), LLL_PRIVATE);
|
|
|
|
/* Iterate over the list with system-allocated threads first. */
|
|
list_t *runp;
|
|
list_for_each (runp, &GL (dl_stack_used))
|
|
init_one_static_tls (list_entry (runp, struct pthread, list), map);
|
|
|
|
/* Now the list with threads using user-allocated stacks. */
|
|
list_for_each (runp, &GL (dl_stack_user))
|
|
init_one_static_tls (list_entry (runp, struct pthread, list), map);
|
|
|
|
lll_unlock (GL (dl_stack_cache_lock), LLL_PRIVATE);
|
|
}
|
|
#endif /* PTHREAD_IN_LIBC */
|