| 1 | /* x86-64 definitions for libc main startup. |
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| 2 | Copyright (C) 2018-2024 Free Software Foundation, Inc. |
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| 3 | This file is part of the GNU C Library. |
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| 4 | |
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| 5 | The GNU C Library is free software; you can redistribute it and/or |
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| 6 | modify it under the terms of the GNU Lesser General Public |
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| 7 | License as published by the Free Software Foundation; either |
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| 8 | version 2.1 of the License, or (at your option) any later version. |
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| 9 | |
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| 10 | The GNU C Library is distributed in the hope that it will be useful, |
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| 11 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
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| 12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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| 13 | Lesser General Public License for more details. |
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| 14 | |
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| 15 | You should have received a copy of the GNU Lesser General Public |
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| 16 | License along with the GNU C Library; if not, see |
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| 17 | <https://www.gnu.org/licenses/>. */ |
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| 18 | |
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| 19 | #ifndef SHARED |
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| 20 | # define ARCH_SETUP_IREL() apply_irel () |
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| 21 | # define ARCH_APPLY_IREL() |
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| 22 | # ifdef __CET__ |
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| 23 | /* Get CET features enabled in the static executable. */ |
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| 24 | |
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| 25 | static inline unsigned int |
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| 26 | get_cet_feature (void) |
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| 27 | { |
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| 28 | /* Check if CET is supported and not disabled by tunables. */ |
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| 29 | const struct cpu_features *cpu_features = __get_cpu_features (); |
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| 30 | unsigned int cet_feature = 0; |
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| 31 | if (CPU_FEATURE_USABLE_P (cpu_features, IBT)) |
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| 32 | cet_feature |= GNU_PROPERTY_X86_FEATURE_1_IBT; |
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| 33 | if (CPU_FEATURE_USABLE_P (cpu_features, SHSTK)) |
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| 34 | cet_feature |= GNU_PROPERTY_X86_FEATURE_1_SHSTK; |
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| 35 | if (!cet_feature) |
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| 36 | return cet_feature; |
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| 37 | |
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| 38 | struct link_map *main_map = _dl_get_dl_main_map (); |
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| 39 | |
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| 40 | /* Scan program headers backward to check PT_GNU_PROPERTY early for |
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| 41 | x86 feature bits on static executable. */ |
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| 42 | const ElfW(Phdr) *phdr = GL(dl_phdr); |
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| 43 | const ElfW(Phdr) *ph; |
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| 44 | for (ph = phdr + GL(dl_phnum); ph != phdr; ph--) |
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| 45 | if (ph[-1].p_type == PT_GNU_PROPERTY) |
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| 46 | { |
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| 47 | _dl_process_pt_gnu_property (l: main_map, fd: -1, ph: &ph[-1]); |
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| 48 | /* Enable IBT and SHSTK only if they are enabled on static |
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| 49 | executable. */ |
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| 50 | cet_feature &= (main_map->l_x86_feature_1_and |
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| 51 | & (GNU_PROPERTY_X86_FEATURE_1_IBT |
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| 52 | | GNU_PROPERTY_X86_FEATURE_1_SHSTK)); |
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| 53 | /* Set GL(dl_x86_feature_1) to the enabled CET features. */ |
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| 54 | GL(dl_x86_feature_1) = cet_feature; |
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| 55 | break; |
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| 56 | } |
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| 57 | |
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| 58 | return cet_feature; |
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| 59 | } |
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| 60 | |
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| 61 | /* The function using this macro to enable shadow stack must not return |
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| 62 | to avoid shadow stack underflow. */ |
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| 63 | # define ARCH_SETUP_TLS() \ |
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| 64 | { \ |
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| 65 | __libc_setup_tls (); \ |
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| 66 | \ |
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| 67 | unsigned int cet_feature = get_cet_feature (); \ |
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| 68 | ENABLE_X86_CET (cet_feature); \ |
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| 69 | _dl_cet_setup_features (cet_feature); \ |
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| 70 | } |
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| 71 | # else |
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| 72 | # define ARCH_SETUP_TLS() __libc_setup_tls () |
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| 73 | # endif |
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| 74 | #endif /* !SHARED */ |
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| 75 | |
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