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41560a9312
In permissive mode, don't disable IBT nor SHSTK when dlopening a legacy shared library if not single threaded since IBT and SHSTK may be still enabled in other threads. Other threads with IBT or SHSTK enabled will crash when calling functions in the legacy shared library. Instead, an error will be issued.
366 lines
11 KiB
C
366 lines
11 KiB
C
/* x86 CET initializers function.
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Copyright (C) 2018-2023 Free Software Foundation, Inc.
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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 <unistd.h>
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#include <errno.h>
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#include <libintl.h>
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#include <ldsodefs.h>
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#include <dl-cet.h>
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#include <sys/single_threaded.h>
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/* GNU_PROPERTY_X86_FEATURE_1_IBT and GNU_PROPERTY_X86_FEATURE_1_SHSTK
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are defined in <elf.h>, which are only available for C sources.
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X86_FEATURE_1_IBT and X86_FEATURE_1_SHSTK are defined in <sysdep.h>
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which are available for both C and asm sources. They must match. */
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#if GNU_PROPERTY_X86_FEATURE_1_IBT != X86_FEATURE_1_IBT
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# error GNU_PROPERTY_X86_FEATURE_1_IBT != X86_FEATURE_1_IBT
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#endif
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#if GNU_PROPERTY_X86_FEATURE_1_SHSTK != X86_FEATURE_1_SHSTK
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# error GNU_PROPERTY_X86_FEATURE_1_SHSTK != X86_FEATURE_1_SHSTK
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#endif
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struct dl_cet_info
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{
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const char *program;
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/* Check how IBT and SHSTK should be enabled. */
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enum dl_x86_cet_control enable_ibt_type;
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enum dl_x86_cet_control enable_shstk_type;
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/* If IBT and SHSTK were previously enabled. */
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unsigned int feature_1_enabled;
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/* If IBT and SHSTK should be enabled. */
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unsigned int enable_feature_1;
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/* If there are any legacy shared object. */
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unsigned int feature_1_legacy;
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/* Which shared object is the first legacy shared object. */
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unsigned int feature_1_legacy_ibt;
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unsigned int feature_1_legacy_shstk;
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};
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/* Check if the object M and its dependencies are legacy object. */
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static void
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dl_check_legacy_object (struct link_map *m,
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struct dl_cet_info *info)
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{
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unsigned int i;
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struct link_map *l = NULL;
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i = m->l_searchlist.r_nlist;
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while (i-- > 0)
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{
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/* Check each shared object to see if IBT and SHSTK are enabled. */
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l = m->l_initfini[i];
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if (l->l_init_called)
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continue;
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#ifdef SHARED
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/* Skip check for ld.so since it has the features enabled. The
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features will be disabled later if they are not enabled in
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executable. */
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if (l == &GL(dl_rtld_map)
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|| l->l_real == &GL(dl_rtld_map)
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|| (info->program != NULL && l == m))
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continue;
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#endif
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/* IBT and SHSTK set only if enabled in executable and all DSOs.
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NB: cet_always_on is handled outside of the loop. */
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info->enable_feature_1 &= ((l->l_x86_feature_1_and
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& (GNU_PROPERTY_X86_FEATURE_1_IBT
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| GNU_PROPERTY_X86_FEATURE_1_SHSTK))
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| ~(GNU_PROPERTY_X86_FEATURE_1_IBT
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| GNU_PROPERTY_X86_FEATURE_1_SHSTK));
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if ((info->feature_1_legacy
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& GNU_PROPERTY_X86_FEATURE_1_IBT) == 0
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&& ((info->enable_feature_1
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& GNU_PROPERTY_X86_FEATURE_1_IBT)
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!= (info->feature_1_enabled
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& GNU_PROPERTY_X86_FEATURE_1_IBT)))
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{
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info->feature_1_legacy_ibt = i;
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info->feature_1_legacy |= GNU_PROPERTY_X86_FEATURE_1_IBT;
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}
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if ((info->feature_1_legacy
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& GNU_PROPERTY_X86_FEATURE_1_SHSTK) == 0
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&& ((info->enable_feature_1
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& GNU_PROPERTY_X86_FEATURE_1_SHSTK)
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!= (info->feature_1_enabled
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& GNU_PROPERTY_X86_FEATURE_1_SHSTK)))
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{
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info->feature_1_legacy_shstk = i;
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info->feature_1_legacy |= GNU_PROPERTY_X86_FEATURE_1_SHSTK;
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}
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}
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/* Handle cet_always_on. */
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if ((info->feature_1_enabled
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& GNU_PROPERTY_X86_FEATURE_1_IBT) != 0
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&& info->enable_ibt_type == cet_always_on)
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{
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info->feature_1_legacy &= ~GNU_PROPERTY_X86_FEATURE_1_IBT;
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info->enable_feature_1 |= GNU_PROPERTY_X86_FEATURE_1_IBT;
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}
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if ((info->feature_1_enabled
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& GNU_PROPERTY_X86_FEATURE_1_SHSTK) != 0
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&& info->enable_shstk_type == cet_always_on)
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{
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info->feature_1_legacy &= ~GNU_PROPERTY_X86_FEATURE_1_SHSTK;
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info->enable_feature_1 |= GNU_PROPERTY_X86_FEATURE_1_SHSTK;
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}
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}
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#ifdef SHARED
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/* Enable IBT and SHSTK only if they are enabled in executable. Set
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feature bits properly at the start of the program. */
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static void
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dl_cet_check_startup (struct link_map *m, struct dl_cet_info *info)
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{
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/* NB: IBT and SHSTK may be disabled by environment variable:
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GLIBC_TUNABLES=glibc.cpu.hwcaps=-IBT,-SHSTK.
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*/
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if (CPU_FEATURE_USABLE (IBT))
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{
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if (info->enable_ibt_type == cet_always_on)
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info->enable_feature_1 |= GNU_PROPERTY_X86_FEATURE_1_IBT;
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else
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info->enable_feature_1 &= ((m->l_x86_feature_1_and
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& GNU_PROPERTY_X86_FEATURE_1_IBT)
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| ~GNU_PROPERTY_X86_FEATURE_1_IBT);
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}
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else
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info->enable_feature_1 &= ~GNU_PROPERTY_X86_FEATURE_1_IBT;
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if (CPU_FEATURE_USABLE (SHSTK))
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{
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if (info->enable_shstk_type == cet_always_on)
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info->enable_feature_1 |= GNU_PROPERTY_X86_FEATURE_1_SHSTK;
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else
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info->enable_feature_1 &= ((m->l_x86_feature_1_and
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& GNU_PROPERTY_X86_FEATURE_1_SHSTK)
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| ~GNU_PROPERTY_X86_FEATURE_1_SHSTK);
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}
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else
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info->enable_feature_1 &= ~GNU_PROPERTY_X86_FEATURE_1_SHSTK;
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if (info->enable_feature_1 != 0)
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dl_check_legacy_object (m, info);
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unsigned int disable_feature_1
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= info->enable_feature_1 ^ info->feature_1_enabled;
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if (disable_feature_1 != 0)
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{
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/* Disable features in the kernel because of legacy objects or
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cet_always_off. */
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if (dl_cet_disable_cet (disable_feature_1) != 0)
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_dl_fatal_printf ("%s: can't disable x86 Features\n",
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info->program);
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/* Clear the disabled bits. Sync dl_x86_feature_1 and
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info->feature_1_enabled with info->enable_feature_1. */
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info->feature_1_enabled = info->enable_feature_1;
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GL(dl_x86_feature_1) = info->enable_feature_1;
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}
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if (HAS_CPU_FEATURE (IBT) || HAS_CPU_FEATURE (SHSTK))
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{
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/* Lock CET features only if IBT or SHSTK are enabled and are not
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enabled permissively. */
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unsigned int feature_1_lock = 0;
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if (((info->feature_1_enabled & GNU_PROPERTY_X86_FEATURE_1_IBT)
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!= 0)
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&& info->enable_ibt_type != cet_permissive)
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feature_1_lock |= GNU_PROPERTY_X86_FEATURE_1_IBT;
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if (((info->feature_1_enabled & GNU_PROPERTY_X86_FEATURE_1_SHSTK)
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!= 0)
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&& info->enable_shstk_type != cet_permissive)
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feature_1_lock |= GNU_PROPERTY_X86_FEATURE_1_SHSTK;
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if (feature_1_lock != 0
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&& dl_cet_lock_cet () != 0)
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_dl_fatal_printf ("%s: can't lock CET\n", info->program);
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}
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THREAD_SETMEM (THREAD_SELF, header.feature_1, GL(dl_x86_feature_1));
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}
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#endif
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/* Check feature bits when dlopening the shared object M. */
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static void
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dl_cet_check_dlopen (struct link_map *m, struct dl_cet_info *info)
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{
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/* Check if there are any legacy objects loaded. */
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if (info->enable_feature_1 != 0)
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{
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dl_check_legacy_object (m, info);
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/* Skip if there are no legacy shared objects loaded. */
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if (info->feature_1_legacy == 0)
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return;
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}
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unsigned int disable_feature_1 = 0;
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unsigned int legacy_obj = 0;
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const char *msg = NULL;
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if ((info->feature_1_enabled
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& GNU_PROPERTY_X86_FEATURE_1_IBT) != 0
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&& (info->feature_1_legacy
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& GNU_PROPERTY_X86_FEATURE_1_IBT) != 0)
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{
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/* Don't disable IBT if not single threaded since IBT may be still
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enabled in other threads. */
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if (info->enable_ibt_type != cet_permissive
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|| !SINGLE_THREAD_P)
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{
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legacy_obj = info->feature_1_legacy_ibt;
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msg = N_("rebuild shared object with IBT support enabled");
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}
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else
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disable_feature_1 |= GNU_PROPERTY_X86_FEATURE_1_IBT;
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}
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/* Check the next feature only if there is no error. */
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if (msg == NULL
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&& (info->feature_1_enabled
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& GNU_PROPERTY_X86_FEATURE_1_SHSTK) != 0
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&& (info->feature_1_legacy
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& GNU_PROPERTY_X86_FEATURE_1_SHSTK) != 0)
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{
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/* Don't disable SHSTK if not single threaded since SHSTK may be
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still enabled in other threads. */
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if (info->enable_shstk_type != cet_permissive
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|| !SINGLE_THREAD_P)
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{
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legacy_obj = info->feature_1_legacy_shstk;
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msg = N_("rebuild shared object with SHSTK support enabled");
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}
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else
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disable_feature_1 |= GNU_PROPERTY_X86_FEATURE_1_SHSTK;
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}
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/* If there is an error, long jump back to the caller. */
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if (msg != NULL)
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_dl_signal_error (0, m->l_initfini[legacy_obj]->l_name, "dlopen",
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msg);
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if (disable_feature_1 != 0)
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{
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int res = dl_cet_disable_cet (disable_feature_1);
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if (res)
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{
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if ((disable_feature_1
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& GNU_PROPERTY_X86_FEATURE_1_IBT) != 0)
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msg = N_("can't disable IBT");
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else
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msg = N_("can't disable SHSTK");
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/* Long jump back to the caller on error. */
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_dl_signal_error (-res, m->l_initfini[legacy_obj]->l_name,
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"dlopen", msg);
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}
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/* Clear the disabled bits in dl_x86_feature_1. */
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GL(dl_x86_feature_1) &= ~disable_feature_1;
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THREAD_SETMEM (THREAD_SELF, header.feature_1,
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GL(dl_x86_feature_1));
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}
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}
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static void
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dl_cet_check (struct link_map *m, const char *program)
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{
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struct dl_cet_info info;
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/* Check how IBT and SHSTK should be enabled. */
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info.enable_ibt_type = GL(dl_x86_feature_control).ibt;
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info.enable_shstk_type = GL(dl_x86_feature_control).shstk;
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info.feature_1_enabled = GL(dl_x86_feature_1);
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/* No legacy object check if IBT and SHSTK are always on. */
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if (info.enable_ibt_type == cet_always_on
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&& info.enable_shstk_type == cet_always_on)
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{
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#ifdef SHARED
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/* Set it only during startup. */
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if (program != NULL)
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THREAD_SETMEM (THREAD_SELF, header.feature_1,
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info.feature_1_enabled);
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#endif
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return;
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}
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/* Check if IBT and SHSTK were enabled by kernel. */
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if (info.feature_1_enabled == 0)
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return;
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info.program = program;
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/* Check which features should be enabled. */
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info.enable_feature_1 = 0;
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if (info.enable_ibt_type != cet_always_off)
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info.enable_feature_1 |= (info.feature_1_enabled
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& GNU_PROPERTY_X86_FEATURE_1_IBT);
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if (info.enable_shstk_type != cet_always_off)
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info.enable_feature_1 |= (info.feature_1_enabled
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& GNU_PROPERTY_X86_FEATURE_1_SHSTK);
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/* Start with no legacy objects. */
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info.feature_1_legacy = 0;
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info.feature_1_legacy_ibt = 0;
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info.feature_1_legacy_shstk = 0;
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#ifdef SHARED
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if (program)
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dl_cet_check_startup (m, &info);
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else
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#endif
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dl_cet_check_dlopen (m, &info);
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}
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void
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_dl_cet_open_check (struct link_map *l)
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{
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dl_cet_check (l, NULL);
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}
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#ifdef SHARED
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# ifndef LINKAGE
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# define LINKAGE
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# endif
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LINKAGE
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void
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_dl_cet_check (struct link_map *main_map, const char *program)
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{
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dl_cet_check (main_map, program);
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}
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#endif /* SHARED */
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