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/* X86 definitions for libc main startup.
Copyright (C) 2018-2024 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#ifndef SHARED
# define ARCH_SETUP_IREL() apply_irel ()
# define ARCH_APPLY_IREL()
# ifdef __CET__
/* Get CET features enabled in the static executable. */
static inline unsigned int
get_cet_feature (void)
{
/* Check if CET is supported and not disabled by tunables. */
const struct cpu_features *cpu_features = __get_cpu_features ();
unsigned int cet_feature = 0;
if (CPU_FEATURE_USABLE_P (cpu_features, IBT))
cet_feature |= GNU_PROPERTY_X86_FEATURE_1_IBT;
if (CPU_FEATURE_USABLE_P (cpu_features, SHSTK))
cet_feature |= GNU_PROPERTY_X86_FEATURE_1_SHSTK;
if (!cet_feature)
return cet_feature;
struct link_map *main_map = _dl_get_dl_main_map ();
/* Scan program headers backward to check PT_GNU_PROPERTY early for
x86 feature bits on static executable. */
const ElfW(Phdr) *phdr = GL(dl_phdr);
const ElfW(Phdr) *ph;
for (ph = phdr + GL(dl_phnum); ph != phdr; ph--)
if (ph[-1].p_type == PT_GNU_PROPERTY)
{
_dl_process_pt_gnu_property (main_map, -1, &ph[-1]);
/* Enable IBT and SHSTK only if they are enabled on static
executable. */
cet_feature &= (main_map->l_x86_feature_1_and
& (GNU_PROPERTY_X86_FEATURE_1_IBT
| GNU_PROPERTY_X86_FEATURE_1_SHSTK));
/* Set GL(dl_x86_feature_1) to the enabled CET features. */
GL(dl_x86_feature_1) = cet_feature;
break;
}
return cet_feature;
}
/* The function using this macro to enable shadow stack must not return
to avoid shadow stack underflow. */
# define ARCH_SETUP_TLS() \
{ \
__libc_setup_tls (); \
\
unsigned int cet_feature = get_cet_feature (); \
ENABLE_X86_CET (cet_feature); \
_dl_cet_setup_features (cet_feature); \
}
# else
# define ARCH_SETUP_TLS() __libc_setup_tls ()
# endif
#endif /* !SHARED */
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