deleted file mode 100644
@@ -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>
@@ -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); \
+ }
new file mode 100644
@@ -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\
+"
@@ -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)
@@ -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
@@ -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
@@ -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;
}
@@ -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__
@@ -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 */
@@ -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\