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a1bbee9fd1
Since CET is only enabled for x86-64, move dl-cet.[ch] to x86_64 directories. Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
365 lines
11 KiB
C
365 lines
11 KiB
C
/* x86-64 CET initializers function.
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Copyright (C) 2018-2024 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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/* 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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}
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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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/* CET is enabled only if RTLD_START_ENABLE_X86_FEATURES is defined. */
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#if defined SHARED && defined RTLD_START_ENABLE_X86_FEATURES
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/* Set dl_x86_feature_1 to features enabled in the executable. */
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if (program != NULL)
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GL(dl_x86_feature_1) = (m->l_x86_feature_1_and
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& (X86_FEATURE_1_IBT
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| X86_FEATURE_1_SHSTK));
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#endif
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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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return;
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/* Check if IBT and SHSTK were enabled. */
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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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/* Set GL(dl_x86_feature_1) to the enabled features and clear the
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active bits of the disabled features. */
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attribute_hidden void
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_dl_cet_setup_features (unsigned int cet_feature)
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{
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/* NB: cet_feature == GL(dl_x86_feature_1) which is set to features
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enabled from executable, not necessarily supported by kernel. */
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if (cet_feature != 0)
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{
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cet_feature = dl_cet_get_cet_status ();
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if (cet_feature != 0)
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{
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THREAD_SETMEM (THREAD_SELF, header.feature_1, cet_feature);
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/* Lock CET if IBT or SHSTK is enabled in executable. Don't
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lock CET if IBT or SHSTK is enabled permissively. */
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if (GL(dl_x86_feature_control).ibt != cet_permissive
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&& (GL(dl_x86_feature_control).shstk != cet_permissive))
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dl_cet_lock_cet (cet_feature);
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}
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/* Sync GL(dl_x86_feature_1) with kernel. */
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GL(dl_x86_feature_1) = cet_feature;
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}
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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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