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254d3d5aef
For audit modules and 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. This patch fixes it by setting l_auditing link_map field not only for the audit modules, but also for all its dependencies. This is used on _dl_allocate_tls_init to avoid the static TLS initialization at load time. Checked on x86_64-linux-gnu, i686-linux-gnu, and aarch64-linux-gnu. Reviewed-by: Carlos O'Donell <carlos@redhat.com> Tested-by: Carlos O'Donell <carlos@redhat.com>
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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#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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/* 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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/* 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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/* Record the value of the original pointer for later
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deallocation. */
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*tcb_to_pointer_to_free_location (result) = allocated;
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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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#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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static dtv_t *
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_dl_resize_dtv (dtv_t *dtv, size_t max_modid)
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{
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/* Resize the dtv. */
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dtv_t *newp;
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size_t newsize = max_modid + DTV_SURPLUS;
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size_t oldsize = dtv[-1].counter;
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if (dtv == GL(dl_initial_dtv))
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{
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/* This is the initial dtv that was either statically allocated in
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__libc_setup_tls or allocated during rtld startup using the
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dl-minimal.c malloc instead of the real malloc. We can't free
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it, we have to abandon the old storage. */
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newp = malloc ((2 + newsize) * sizeof (dtv_t));
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if (newp == NULL)
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oom ();
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memcpy (newp, &dtv[-1], (2 + oldsize) * sizeof (dtv_t));
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}
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else
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{
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newp = realloc (&dtv[-1],
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(2 + newsize) * sizeof (dtv_t));
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if (newp == NULL)
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oom ();
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}
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newp[0].counter = newsize;
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/* Clear the newly allocated part. */
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memset (newp + 2 + oldsize, '\0',
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(newsize - oldsize) * sizeof (dtv_t));
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/* Return the generation counter. */
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return &newp[1];
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}
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/* Allocate initial TLS. RESULT should be a non-NULL pointer to storage
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for the TLS space. The DTV may be resized, and so this function may
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call malloc to allocate that space. The loader's GL(dl_load_tls_lock)
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is taken when manipulating global TLS-related data in the loader. */
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void *
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_dl_allocate_tls_init (void *result, bool init_tls)
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{
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if (result == NULL)
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/* The memory allocation failed. */
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return NULL;
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dtv_t *dtv = GET_DTV (result);
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struct dtv_slotinfo_list *listp;
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size_t total = 0;
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size_t maxgen = 0;
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/* Protects global dynamic TLS related state. */
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__rtld_lock_lock_recursive (GL(dl_load_tls_lock));
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/* Check if the current dtv is big enough. */
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if (dtv[-1].counter < GL(dl_tls_max_dtv_idx))
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{
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/* Resize the dtv. */
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dtv = _dl_resize_dtv (dtv, GL(dl_tls_max_dtv_idx));
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/* Install this new dtv in the thread data structures. */
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INSTALL_DTV (result, &dtv[-1]);
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}
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/* We have to prepare the dtv for all currently loaded modules using
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TLS. For those which are dynamically loaded we add the values
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indicating deferred allocation. */
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listp = GL(dl_tls_dtv_slotinfo_list);
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while (1)
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{
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size_t cnt;
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for (cnt = total == 0 ? 1 : 0; cnt < listp->len; ++cnt)
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{
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struct link_map *map;
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void *dest;
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/* Check for the total number of used slots. */
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if (total + cnt > GL(dl_tls_max_dtv_idx))
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break;
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map = listp->slotinfo[cnt].map;
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if (map == NULL)
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/* Unused entry. */
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continue;
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/* Keep track of the maximum generation number. This might
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not be the generation counter. */
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assert (listp->slotinfo[cnt].gen <= GL(dl_tls_generation));
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maxgen = MAX (maxgen, listp->slotinfo[cnt].gen);
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dtv[map->l_tls_modid].pointer.val = TLS_DTV_UNALLOCATED;
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dtv[map->l_tls_modid].pointer.to_free = NULL;
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if (map->l_tls_offset == NO_TLS_OFFSET
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|| map->l_tls_offset == FORCED_DYNAMIC_TLS_OFFSET)
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continue;
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assert (map->l_tls_modid == total + cnt);
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assert (map->l_tls_blocksize >= map->l_tls_initimage_size);
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#if TLS_TCB_AT_TP
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assert ((size_t) map->l_tls_offset >= map->l_tls_blocksize);
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dest = (char *) result - map->l_tls_offset;
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#elif TLS_DTV_AT_TP
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dest = (char *) result + map->l_tls_offset;
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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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/* Set up the DTV entry. The simplified __tls_get_addr that
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some platforms use in static programs requires it. */
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dtv[map->l_tls_modid].pointer.val = dest;
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/* Copy the initialization image and clear the BSS part. For
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audit modules or dependencies with initial-exec TLS, we can not
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set the initial TLS image on default loader initialization
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because it would already be set by the audit setup. However,
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subsequent thread creation would need to follow the default
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behaviour. */
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if (map->l_ns != LM_ID_BASE && !init_tls)
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continue;
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memset (__mempcpy (dest, map->l_tls_initimage,
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map->l_tls_initimage_size), '\0',
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map->l_tls_blocksize - map->l_tls_initimage_size);
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}
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total += cnt;
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if (total > GL(dl_tls_max_dtv_idx))
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break;
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listp = listp->next;
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assert (listp != NULL);
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}
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__rtld_lock_unlock_recursive (GL(dl_load_tls_lock));
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/* The DTV version is up-to-date now. */
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dtv[0].counter = maxgen;
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return result;
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}
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rtld_hidden_def (_dl_allocate_tls_init)
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void *
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_dl_allocate_tls (void *mem)
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{
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return _dl_allocate_tls_init (mem == NULL
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? _dl_allocate_tls_storage ()
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: allocate_dtv (mem), true);
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}
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rtld_hidden_def (_dl_allocate_tls)
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void
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_dl_deallocate_tls (void *tcb, bool dealloc_tcb)
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{
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dtv_t *dtv = GET_DTV (tcb);
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/* We need to free the memory allocated for non-static TLS. */
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for (size_t cnt = 0; cnt < dtv[-1].counter; ++cnt)
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free (dtv[1 + cnt].pointer.to_free);
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/* The array starts with dtv[-1]. */
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if (dtv != GL(dl_initial_dtv))
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free (dtv - 1);
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if (dealloc_tcb)
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free (*tcb_to_pointer_to_free_location (tcb));
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}
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rtld_hidden_def (_dl_deallocate_tls)
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#ifdef SHARED
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/* The __tls_get_addr function has two basic forms which differ in the
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arguments. The IA-64 form takes two parameters, the module ID and
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offset. The form used, among others, on IA-32 takes a reference to
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a special structure which contain the same information. The second
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form seems to be more often used (in the moment) so we default to
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it. Users of the IA-64 form have to provide adequate definitions
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of the following macros. */
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# ifndef GET_ADDR_ARGS
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# define GET_ADDR_ARGS tls_index *ti
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# define GET_ADDR_PARAM ti
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# endif
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# ifndef GET_ADDR_MODULE
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# define GET_ADDR_MODULE ti->ti_module
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# endif
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# ifndef GET_ADDR_OFFSET
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# define GET_ADDR_OFFSET ti->ti_offset
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# endif
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/* Allocate one DTV entry. */
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static struct dtv_pointer
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allocate_dtv_entry (size_t alignment, size_t size)
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{
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if (powerof2 (alignment) && alignment <= _Alignof (max_align_t))
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{
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/* The alignment is supported by malloc. */
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void *ptr = malloc (size);
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return (struct dtv_pointer) { ptr, ptr };
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}
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/* Emulate memalign to by manually aligning a pointer returned by
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malloc. First compute the size with an overflow check. */
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size_t alloc_size = size + alignment;
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if (alloc_size < size)
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return (struct dtv_pointer) {};
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/* Perform the allocation. This is the pointer we need to free
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later. */
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void *start = malloc (alloc_size);
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if (start == NULL)
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return (struct dtv_pointer) {};
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/* Find the aligned position within the larger allocation. */
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void *aligned = (void *) roundup ((uintptr_t) start, alignment);
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return (struct dtv_pointer) { .val = aligned, .to_free = start };
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}
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static struct dtv_pointer
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allocate_and_init (struct link_map *map)
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{
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struct dtv_pointer result = allocate_dtv_entry
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(map->l_tls_align, map->l_tls_blocksize);
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if (result.val == NULL)
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oom ();
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/* Initialize the memory. */
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memset (__mempcpy (result.val, map->l_tls_initimage,
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map->l_tls_initimage_size),
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'\0', map->l_tls_blocksize - map->l_tls_initimage_size);
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return result;
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}
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struct link_map *
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_dl_update_slotinfo (unsigned long int req_modid)
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{
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struct link_map *the_map = NULL;
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dtv_t *dtv = THREAD_DTV ();
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/* The global dl_tls_dtv_slotinfo array contains for each module
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index the generation counter current when the entry was created.
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This array never shrinks so that all module indices which were
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valid at some time can be used to access it. Before the first
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use of a new module index in this function the array was extended
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appropriately. Access also does not have to be guarded against
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modifications of the array. It is assumed that pointer-size
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values can be read atomically even in SMP environments. It is
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possible that other threads at the same time dynamically load
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code and therefore add to the slotinfo list. This is a problem
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since we must not pick up any information about incomplete work.
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The solution to this is to ignore all dtv slots which were
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created after the one we are currently interested. We know that
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dynamic loading for this module is completed and this is the last
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load operation we know finished. */
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|
unsigned long int idx = req_modid;
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struct dtv_slotinfo_list *listp = GL(dl_tls_dtv_slotinfo_list);
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while (idx >= listp->len)
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{
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idx -= listp->len;
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listp = listp->next;
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}
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if (dtv[0].counter < listp->slotinfo[idx].gen)
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{
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|
/* CONCURRENCY NOTES:
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|
Here the dtv needs to be updated to new_gen generation count.
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|
|
|
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.
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|
|
|
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. */
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|
size_t new_gen = listp->slotinfo[idx].gen;
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|
size_t total = 0;
|
|
size_t max_modid = atomic_load_relaxed (&GL(dl_tls_max_dtv_idx));
|
|
assert (max_modid >= req_modid);
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|
|
|
/* We have to look through the entire dtv slotinfo list. */
|
|
listp = GL(dl_tls_dtv_slotinfo_list);
|
|
do
|
|
{
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|
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;
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|
|
|
/* 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;
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|
|
|
/* 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 */
|