diff options
| -rw-r--r-- | sysdeps/unix/sysv/linux/x86/cpu-features.c | 49 | ||||
| -rw-r--r-- | sysdeps/unix/sysv/linux/x86/dl-cet.h | 27 | ||||
| -rw-r--r-- | sysdeps/unix/sysv/linux/x86_64/dl-cet.h | 47 | ||||
| -rw-r--r-- | sysdeps/x86/cpu-features-offsets.sym | 1 | ||||
| -rw-r--r-- | sysdeps/x86/cpu-features.c | 51 | ||||
| -rw-r--r-- | sysdeps/x86/dl-cet.c | 76 | ||||
| -rw-r--r-- | sysdeps/x86/get-cpuid-feature-leaf.c | 2 | ||||
| -rw-r--r-- | sysdeps/x86/include/cpu-features.h | 3 | ||||
| -rw-r--r-- | sysdeps/x86/libc-start.h | 53 | ||||
| -rw-r--r-- | sysdeps/x86_64/dl-machine.h | 12 |
10 files changed, 175 insertions, 146 deletions
diff --git a/sysdeps/unix/sysv/linux/x86/cpu-features.c b/sysdeps/unix/sysv/linux/x86/cpu-features.c deleted file mode 100644 index 0e6e2bf..0000000 --- a/sysdeps/unix/sysv/linux/x86/cpu-features.c +++ /dev/null @@ -1,49 +0,0 @@ -/* Initialize CPU feature data for Linux/x86. - This file is part of the GNU C Library. - Copyright (C) 2018-2023 Free Software Foundation, Inc. - - 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/>. */ - -#if CET_ENABLED -# include <sys/prctl.h> -# include <asm/prctl.h> - -static inline int __attribute__ ((always_inline)) -get_cet_status (void) -{ - unsigned long long kernel_feature; - unsigned int status = 0; - if (INTERNAL_SYSCALL_CALL (arch_prctl, ARCH_SHSTK_STATUS, - &kernel_feature) == 0) - { - if ((kernel_feature & ARCH_SHSTK_SHSTK) != 0) - status = GNU_PROPERTY_X86_FEATURE_1_SHSTK; - } - return status; -} - -# ifndef SHARED -static inline void -x86_setup_tls (void) -{ - __libc_setup_tls (); - THREAD_SETMEM (THREAD_SELF, header.feature_1, GL(dl_x86_feature_1)); -} - -# define ARCH_SETUP_TLS() x86_setup_tls () -# endif -#endif - -#include <sysdeps/x86/cpu-features.c> diff --git a/sysdeps/unix/sysv/linux/x86/dl-cet.h b/sysdeps/unix/sysv/linux/x86/dl-cet.h index da220ac..6ad5e03 100644 --- a/sysdeps/unix/sysv/linux/x86/dl-cet.h +++ b/sysdeps/unix/sysv/linux/x86/dl-cet.h @@ -18,7 +18,7 @@ #include <sys/prctl.h> #include <asm/prctl.h> -static inline int __attribute__ ((always_inline)) +static __always_inline int dl_cet_disable_cet (unsigned int cet_feature) { if (cet_feature != GNU_PROPERTY_X86_FEATURE_1_SHSTK) @@ -28,7 +28,7 @@ dl_cet_disable_cet (unsigned int cet_feature) kernel_feature); } -static inline int __attribute__ ((always_inline)) +static __always_inline int dl_cet_lock_cet (unsigned int cet_feature) { if (cet_feature != GNU_PROPERTY_X86_FEATURE_1_SHSTK) @@ -38,3 +38,26 @@ dl_cet_lock_cet (unsigned int cet_feature) return (int) INTERNAL_SYSCALL_CALL (arch_prctl, ARCH_SHSTK_LOCK, kernel_feature); } + +static __always_inline unsigned int +dl_cet_get_cet_status (void) +{ + unsigned long long kernel_feature; + unsigned int status = 0; + if (INTERNAL_SYSCALL_CALL (arch_prctl, ARCH_SHSTK_STATUS, + &kernel_feature) == 0) + { + if ((kernel_feature & ARCH_SHSTK_SHSTK) != 0) + status = GNU_PROPERTY_X86_FEATURE_1_SHSTK; + } + return status; +} + +/* Enable shadow stack with a macro to avoid shadow stack underflow. */ +#define ENABLE_X86_CET(cet_feature) \ + if ((cet_feature & GNU_PROPERTY_X86_FEATURE_1_SHSTK)) \ + { \ + long long int kernel_feature = ARCH_SHSTK_SHSTK; \ + INTERNAL_SYSCALL_CALL (arch_prctl, ARCH_SHSTK_ENABLE, \ + kernel_feature); \ + } diff --git a/sysdeps/unix/sysv/linux/x86_64/dl-cet.h b/sysdeps/unix/sysv/linux/x86_64/dl-cet.h new file mode 100644 index 0000000..e23e05c6 --- /dev/null +++ b/sysdeps/unix/sysv/linux/x86_64/dl-cet.h @@ -0,0 +1,47 @@ +/* Linux/x86-64 CET initializers function. + Copyright (C) 2023 Free Software Foundation, Inc. + + 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/>. */ + +#include <cpu-features-offsets.h> +#include_next <dl-cet.h> + +#define X86_STRINGIFY_1(x) #x +#define X86_STRINGIFY(x) X86_STRINGIFY_1 (x) + +/* Enable shadow stack before calling _dl_init if it is enabled in + GL(dl_x86_feature_1). Call _dl_setup_x86_features to setup shadow + stack. */ +#define RTLD_START_ENABLE_X86_FEATURES \ +"\ + # Check if shadow stack is enabled in GL(dl_x86_feature_1).\n\ + movl _rtld_local+" X86_STRINGIFY (RTLD_GLOBAL_DL_X86_FEATURE_1_OFFSET) "(%rip), %edx\n\ + testl $" X86_STRINGIFY (X86_FEATURE_1_SHSTK) ", %edx\n\ + jz 1f\n\ + # Enable shadow stack if enabled in GL(dl_x86_feature_1).\n\ + movl $" X86_STRINGIFY (ARCH_SHSTK_SHSTK) ", %esi\n\ + movl $" X86_STRINGIFY (ARCH_SHSTK_ENABLE) ", %edi\n\ + movl $" X86_STRINGIFY (__NR_arch_prctl) ", %eax\n\ + syscall\n\ +1:\n\ + # Pass GL(dl_x86_feature_1) to _dl_cet_setup_features.\n\ + movl %edx, %edi\n\ + # Align stack for the _dl_cet_setup_features call.\n\ + andq $-16, %rsp\n\ + call _dl_cet_setup_features\n\ + # Restore %rax and %rsp from %r12 and %r13.\n\ + movq %r12, %rax\n\ + movq %r13, %rsp\n\ +" diff --git a/sysdeps/x86/cpu-features-offsets.sym b/sysdeps/x86/cpu-features-offsets.sym index 6d03cea..5429f60 100644 --- a/sysdeps/x86/cpu-features-offsets.sym +++ b/sysdeps/x86/cpu-features-offsets.sym @@ -4,3 +4,4 @@ RTLD_GLOBAL_RO_DL_X86_CPU_FEATURES_OFFSET offsetof (struct rtld_global_ro, _dl_x86_cpu_features) XSAVE_STATE_SIZE_OFFSET offsetof (struct cpu_features, xsave_state_size) +RTLD_GLOBAL_DL_X86_FEATURE_1_OFFSET offsetof (struct rtld_global, _dl_x86_feature_1) diff --git a/sysdeps/x86/cpu-features.c b/sysdeps/x86/cpu-features.c index f180f0d..097868c 100644 --- a/sysdeps/x86/cpu-features.c +++ b/sysdeps/x86/cpu-features.c @@ -1106,57 +1106,6 @@ no_cpuid: TUNABLE_CALLBACK (set_x86_ibt)); TUNABLE_GET (x86_shstk, tunable_val_t *, TUNABLE_CALLBACK (set_x86_shstk)); - - /* Check CET status. */ - unsigned int cet_status = get_cet_status (); - - if ((cet_status & GNU_PROPERTY_X86_FEATURE_1_IBT) == 0) - CPU_FEATURE_UNSET (cpu_features, IBT) - if ((cet_status & GNU_PROPERTY_X86_FEATURE_1_SHSTK) == 0) - CPU_FEATURE_UNSET (cpu_features, SHSTK) - - if (cet_status) - { - GL(dl_x86_feature_1) = cet_status; - -# ifndef SHARED - /* Check if IBT and SHSTK are enabled by kernel. */ - if ((cet_status - & (GNU_PROPERTY_X86_FEATURE_1_IBT - | GNU_PROPERTY_X86_FEATURE_1_SHSTK))) - { - /* Disable IBT and/or SHSTK if they are enabled by kernel, but - disabled by environment variable: - - GLIBC_TUNABLES=glibc.cpu.hwcaps=-IBT,-SHSTK - */ - unsigned int cet_feature = 0; - if (!CPU_FEATURE_USABLE (IBT)) - cet_feature |= (cet_status - & GNU_PROPERTY_X86_FEATURE_1_IBT); - if (!CPU_FEATURE_USABLE (SHSTK)) - cet_feature |= (cet_status - & GNU_PROPERTY_X86_FEATURE_1_SHSTK); - - if (cet_feature) - { - int res = dl_cet_disable_cet (cet_feature); - - /* Clear the disabled bits in dl_x86_feature_1. */ - if (res == 0) - GL(dl_x86_feature_1) &= ~cet_feature; - } - - /* Lock CET if IBT or SHSTK is enabled in executable. Don't - lock CET if IBT or SHSTK is enabled permissively. */ - if (GL(dl_x86_feature_control).ibt != cet_permissive - && GL(dl_x86_feature_control).shstk != cet_permissive) - dl_cet_lock_cet (GL(dl_x86_feature_1) - & (GNU_PROPERTY_X86_FEATURE_1_IBT - | GNU_PROPERTY_X86_FEATURE_1_SHSTK)); - } -# endif - } #endif #ifndef SHARED diff --git a/sysdeps/x86/dl-cet.c b/sysdeps/x86/dl-cet.c index 66a7824..82167eb 100644 --- a/sysdeps/x86/dl-cet.c +++ b/sysdeps/x86/dl-cet.c @@ -173,40 +173,11 @@ dl_cet_check_startup (struct link_map *m, struct dl_cet_info *info) = info->enable_feature_1 ^ info->feature_1_enabled; if (disable_feature_1 != 0) { - /* Disable features in the kernel because of legacy objects or - cet_always_off. */ - if (dl_cet_disable_cet (disable_feature_1) != 0) - _dl_fatal_printf ("%s: can't disable x86 Features\n", - info->program); - /* Clear the disabled bits. Sync dl_x86_feature_1 and info->feature_1_enabled with info->enable_feature_1. */ info->feature_1_enabled = info->enable_feature_1; GL(dl_x86_feature_1) = info->enable_feature_1; } - - if (HAS_CPU_FEATURE (IBT) || HAS_CPU_FEATURE (SHSTK)) - { - /* Lock CET features only if IBT or SHSTK are enabled and are not - enabled permissively. */ - unsigned int feature_1_lock = 0; - - if (((info->feature_1_enabled & GNU_PROPERTY_X86_FEATURE_1_IBT) - != 0) - && info->enable_ibt_type != cet_permissive) - feature_1_lock |= GNU_PROPERTY_X86_FEATURE_1_IBT; - - if (((info->feature_1_enabled & GNU_PROPERTY_X86_FEATURE_1_SHSTK) - != 0) - && info->enable_shstk_type != cet_permissive) - feature_1_lock |= GNU_PROPERTY_X86_FEATURE_1_SHSTK; - - if (feature_1_lock != 0 - && dl_cet_lock_cet (feature_1_lock) != 0) - _dl_fatal_printf ("%s: can't lock CET\n", info->program); - } - - THREAD_SETMEM (THREAD_SELF, header.feature_1, GL(dl_x86_feature_1)); } #endif @@ -298,6 +269,15 @@ dl_cet_check (struct link_map *m, const char *program) { struct dl_cet_info info; + /* CET is enabled only if RTLD_START_ENABLE_X86_FEATURES is defined. */ +#if defined SHARED && defined RTLD_START_ENABLE_X86_FEATURES + /* Set dl_x86_feature_1 to features enabled in the executable. */ + if (program != NULL) + GL(dl_x86_feature_1) = (m->l_x86_feature_1_and + & (X86_FEATURE_1_IBT + | X86_FEATURE_1_SHSTK)); +#endif + /* Check how IBT and SHSTK should be enabled. */ info.enable_ibt_type = GL(dl_x86_feature_control).ibt; info.enable_shstk_type = GL(dl_x86_feature_control).shstk; @@ -307,17 +287,9 @@ dl_cet_check (struct link_map *m, const char *program) /* No legacy object check if IBT and SHSTK are always on. */ if (info.enable_ibt_type == cet_always_on && info.enable_shstk_type == cet_always_on) - { -#ifdef SHARED - /* Set it only during startup. */ - if (program != NULL) - THREAD_SETMEM (THREAD_SELF, header.feature_1, - info.feature_1_enabled); -#endif - return; - } + return; - /* Check if IBT and SHSTK were enabled by kernel. */ + /* Check if IBT and SHSTK were enabled. */ if (info.feature_1_enabled == 0) return; @@ -351,6 +323,32 @@ _dl_cet_open_check (struct link_map *l) dl_cet_check (l, NULL); } +/* Set GL(dl_x86_feature_1) to the enabled features and clear the + active bits of the disabled features. */ + +attribute_hidden void +_dl_cet_setup_features (unsigned int cet_feature) +{ + /* NB: cet_feature == GL(dl_x86_feature_1) which is set to features + enabled from executable, not necessarily supported by kernel. */ + if (cet_feature != 0) + { + cet_feature = dl_cet_get_cet_status (); + if (cet_feature != 0) + { + THREAD_SETMEM (THREAD_SELF, header.feature_1, cet_feature); + + /* Lock CET if IBT or SHSTK is enabled in executable. Don't + lock CET if IBT or SHSTK is enabled permissively. */ + if (GL(dl_x86_feature_control).ibt != cet_permissive + && (GL(dl_x86_feature_control).shstk != cet_permissive)) + dl_cet_lock_cet (cet_feature); + } + /* Sync GL(dl_x86_feature_1) with kernel. */ + GL(dl_x86_feature_1) = cet_feature; + } +} + #ifdef SHARED # ifndef LINKAGE diff --git a/sysdeps/x86/get-cpuid-feature-leaf.c b/sysdeps/x86/get-cpuid-feature-leaf.c index 40a46cc..9317a6b 100644 --- a/sysdeps/x86/get-cpuid-feature-leaf.c +++ b/sysdeps/x86/get-cpuid-feature-leaf.c @@ -24,7 +24,7 @@ __x86_get_cpuid_feature_leaf (unsigned int leaf) static const struct cpuid_feature feature = {}; if (leaf < CPUID_INDEX_MAX) return ((const struct cpuid_feature *) - &GLRO(dl_x86_cpu_features).features[leaf]); + &GLRO(dl_x86_cpu_features).features[leaf]); else return &feature; } diff --git a/sysdeps/x86/include/cpu-features.h b/sysdeps/x86/include/cpu-features.h index 2d7427a..23bd814 100644 --- a/sysdeps/x86/include/cpu-features.h +++ b/sysdeps/x86/include/cpu-features.h @@ -990,6 +990,9 @@ extern const struct cpu_features *_dl_x86_get_cpu_features (void) # define INIT_ARCH() # define _dl_x86_get_cpu_features() (&GLRO(dl_x86_cpu_features)) extern void _dl_x86_init_cpu_features (void) attribute_hidden; + +extern void _dl_cet_setup_features (unsigned int) + attribute_hidden; #endif #ifdef __x86_64__ diff --git a/sysdeps/x86/libc-start.h b/sysdeps/x86/libc-start.h index e93da6e..7a91dd1 100644 --- a/sysdeps/x86/libc-start.h +++ b/sysdeps/x86/libc-start.h @@ -19,7 +19,56 @@ #ifndef SHARED # define ARCH_SETUP_IREL() apply_irel () # define ARCH_APPLY_IREL() -# ifndef ARCH_SETUP_TLS -# define ARCH_SETUP_TLS() __libc_setup_tls () +# 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 */ diff --git a/sysdeps/x86_64/dl-machine.h b/sysdeps/x86_64/dl-machine.h index 581a2f1..faeae72 100644 --- a/sysdeps/x86_64/dl-machine.h +++ b/sysdeps/x86_64/dl-machine.h @@ -29,6 +29,11 @@ #include <dl-static-tls.h> #include <dl-machine-rel.h> #include <isa-level.h> +#ifdef __CET__ +# include <dl-cet.h> +#else +# define RTLD_START_ENABLE_X86_FEATURES +#endif /* Return nonzero iff ELF header is compatible with the running host. */ static inline int __attribute__ ((unused)) @@ -146,13 +151,16 @@ _start:\n\ _dl_start_user:\n\ # Save the user entry point address in %r12.\n\ movq %rax, %r12\n\ + # Save %rsp value in %r13.\n\ + movq %rsp, %r13\n\ +"\ + RTLD_START_ENABLE_X86_FEATURES \ +"\ # Read the original argument count.\n\ movq (%rsp), %rdx\n\ # Call _dl_init (struct link_map *main_map, int argc, char **argv, char **env)\n\ # argc -> rsi\n\ movq %rdx, %rsi\n\ - # Save %rsp value in %r13.\n\ - movq %rsp, %r13\n\ # And align stack for the _dl_init call. \n\ andq $-16, %rsp\n\ # _dl_loaded -> rdi\n\ |