x86: Move CET control to _dl_x86_feature_control [BZ #25887]

1. Include <dl-procruntime.c> to get architecture specific initializer in
rtld_global.
2. Change _dl_x86_feature_1[2] to _dl_x86_feature_1.
3. Add _dl_x86_feature_control after _dl_x86_feature_1, which is a
struct of 2 bitfields for IBT and SHSTK control

This fixes [BZ #25887].

diff --git a/elf/rtld.c b/elf/rtld.c
index 5ccc3c2..882b070 100644 (file)
--- a/elf/rtld.c
+++ b/elf/rtld.c
@@ -315,6 +315,8 @@ rtld_hidden_def (_dl_starting_up)
    (except those which cannot be added for some reason).  */
 struct rtld_global _rtld_global =
   {
+    /* Get architecture specific initializer.  */
+#include <dl-procruntime.c>
     /* Generally the default presumption without further information is an
      * executable stack but this is not true for all platforms.  */
     ._dl_stack_flags = DEFAULT_STACK_PERMS,

diff --git a/sysdeps/i386/dl-machine.h b/sysdeps/i386/dl-machine.h
index 8af0789..0f08079 100644 (file)
--- a/sysdeps/i386/dl-machine.h
+++ b/sysdeps/i386/dl-machine.h
@@ -71,7 +71,7 @@ elf_machine_runtime_setup (struct link_map *l, int lazy, int profile)
   extern void _dl_runtime_profile_shstk (Elf32_Word) attribute_hidden;
   /* Check if SHSTK is enabled by kernel.  */
   bool shstk_enabled
-    = (GL(dl_x86_feature_1)[0] & GNU_PROPERTY_X86_FEATURE_1_SHSTK) != 0;
+    = (GL(dl_x86_feature_1) & GNU_PROPERTY_X86_FEATURE_1_SHSTK) != 0;
 
   if (l->l_info[DT_JMPREL] && lazy)
     {

diff --git a/sysdeps/unix/sysv/linux/x86/cpu-features.c b/sysdeps/unix/sysv/linux/x86/cpu-features.c
index d67b300..fc0e328 100644 (file)
--- a/sysdeps/unix/sysv/linux/x86/cpu-features.c
+++ b/sysdeps/unix/sysv/linux/x86/cpu-features.c
@@ -34,7 +34,7 @@ static inline void
 x86_setup_tls (void)
 {
   __libc_setup_tls ();
-  THREAD_SETMEM (THREAD_SELF, header.feature_1, GL(dl_x86_feature_1)[0]);
+  THREAD_SETMEM (THREAD_SELF, header.feature_1, GL(dl_x86_feature_1));
 }
 
 #  define ARCH_SETUP_TLS() x86_setup_tls ()

diff --git a/sysdeps/x86/cet-tunables.h b/sysdeps/x86/cet-control.h
similarity index 60%
rename from sysdeps/x86/cet-tunables.h
rename to sysdeps/x86/cet-control.h
index 5e1e42d..e163a7f 100644 (file)
--- a/sysdeps/x86/cet-tunables.h
+++ b/sysdeps/x86/cet-control.h
@@ -16,14 +16,26 @@
    License along with the GNU C Library; if not, see
    <https://www.gnu.org/licenses/>.  */
 
-/* Valid control values:
-   0: Enable CET features based on ELF property note.
-   1: Always disable CET features.
-   2: Always enable CET features.
-   3: Enable CET features permissively.
- */
-#define CET_ELF_PROPERTY       0
-#define CET_ALWAYS_OFF         1
-#define CET_ALWAYS_ON          2
-#define CET_PERMISSIVE         3
-#define CET_MAX                        CET_PERMISSIVE
+#ifndef _CET_CONTROL_H
+#define _CET_CONTROL_H
+
+/* For each CET feature, IBT and SHSTK, valid control values.  */
+enum dl_x86_cet_control
+{
+  /* Enable CET features based on ELF property note.  */
+  cet_elf_property = 0,
+  /* Always enable CET features.  */
+  cet_always_on,
+  /* Always disable CET features.  */
+  cet_always_off,
+  /* Enable CET features permissively.  */
+  cet_permissive
+};
+
+struct dl_x86_feature_control
+{
+  enum dl_x86_cet_control ibt : 2;
+  enum dl_x86_cet_control shstk : 2;
+};
+
+#endif /* cet-control.h */

diff --git a/sysdeps/x86/cpu-features.c b/sysdeps/x86/cpu-features.c
index bfb415f..b6d5d9d 100644 (file)
--- a/sysdeps/x86/cpu-features.c
+++ b/sysdeps/x86/cpu-features.c
@@ -39,7 +39,6 @@ extern void TUNABLE_CALLBACK (set_x86_shstk) (tunable_val_t *)
 
 #if CET_ENABLED
 # include <dl-cet.h>
-# include <cet-tunables.h>
 #endif
 
 static void
@@ -620,7 +619,7 @@ no_cpuid:
 
   if (cet_status)
     {
-      GL(dl_x86_feature_1)[0] = cet_status;
+      GL(dl_x86_feature_1) = cet_status;
 
 # ifndef SHARED
       /* Check if IBT and SHSTK are enabled by kernel.  */
@@ -644,14 +643,13 @@ no_cpuid:
 
              /* Clear the disabled bits in dl_x86_feature_1.  */
              if (res == 0)
-               GL(dl_x86_feature_1)[0] &= ~cet_feature;
+               GL(dl_x86_feature_1) &= ~cet_feature;
            }
 
          /* Lock CET if IBT or SHSTK is enabled in executable.  Don't
-            lock CET if SHSTK is enabled permissively.  */
-         if (((GL(dl_x86_feature_1)[1] >> CET_MAX)
-              & ((1 << CET_MAX) - 1))
-              != CET_PERMISSIVE)
+            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 ();
        }
 # endif

diff --git a/sysdeps/x86/cpu-tunables.c b/sysdeps/x86/cpu-tunables.c
index 861bd7b..38ad2c2 100644 (file)
--- a/sysdeps/x86/cpu-tunables.c
+++ b/sysdeps/x86/cpu-tunables.c
@@ -336,28 +336,18 @@ TUNABLE_CALLBACK (set_hwcaps) (tunable_val_t *valp)
 }
 
 # if CET_ENABLED
-#  include <cet-tunables.h>
 
 attribute_hidden
 void
 TUNABLE_CALLBACK (set_x86_ibt) (tunable_val_t *valp)
 {
   if (DEFAULT_MEMCMP (valp->strval, "on", sizeof ("on")) == 0)
-    {
-      GL(dl_x86_feature_1)[1] &= ~((1 << CET_MAX) - 1);
-      GL(dl_x86_feature_1)[1] |= CET_ALWAYS_ON;
-    }
+    GL(dl_x86_feature_control).ibt = cet_always_on;
   else if (DEFAULT_MEMCMP (valp->strval, "off", sizeof ("off")) == 0)
-    {
-      GL(dl_x86_feature_1)[1] &= ~((1 << CET_MAX) - 1);
-      GL(dl_x86_feature_1)[1] |= CET_ALWAYS_OFF;
-    }
+    GL(dl_x86_feature_control).ibt = cet_always_off;
   else if (DEFAULT_MEMCMP (valp->strval, "permissive",
                           sizeof ("permissive")) == 0)
-    {
-      GL(dl_x86_feature_1)[1] &= ~((1 << CET_MAX) - 1);
-      GL(dl_x86_feature_1)[1] |= CET_PERMISSIVE;
-    }
+    GL(dl_x86_feature_control).ibt = cet_permissive;
 }
 
 attribute_hidden
@@ -365,21 +355,12 @@ void
 TUNABLE_CALLBACK (set_x86_shstk) (tunable_val_t *valp)
 {
   if (DEFAULT_MEMCMP (valp->strval, "on", sizeof ("on")) == 0)
-    {
-      GL(dl_x86_feature_1)[1] &= ~(((1 << CET_MAX) - 1) << CET_MAX);
-      GL(dl_x86_feature_1)[1] |= (CET_ALWAYS_ON << CET_MAX);
-    }
+    GL(dl_x86_feature_control).shstk = cet_always_on;
   else if (DEFAULT_MEMCMP (valp->strval, "off", sizeof ("off")) == 0)
-    {
-      GL(dl_x86_feature_1)[1] &= ~(((1 << CET_MAX) - 1) << CET_MAX);
-      GL(dl_x86_feature_1)[1] |= (CET_ALWAYS_OFF << CET_MAX);
-    }
+    GL(dl_x86_feature_control).shstk = cet_always_off;
   else if (DEFAULT_MEMCMP (valp->strval, "permissive",
                           sizeof ("permissive")) == 0)
-    {
-      GL(dl_x86_feature_1)[1] &= ~(((1 << CET_MAX) - 1) << CET_MAX);
-      GL(dl_x86_feature_1)[1] |= (CET_PERMISSIVE << CET_MAX);
-    }
+    GL(dl_x86_feature_control).shstk = cet_permissive;
 }
 # endif
 #endif

diff --git a/sysdeps/x86/dl-cet.c b/sysdeps/x86/dl-cet.c
index c7029f1..5524b66 100644 (file)
--- a/sysdeps/x86/dl-cet.c
+++ b/sysdeps/x86/dl-cet.c
@@ -20,7 +20,6 @@
 #include <libintl.h>
 #include <ldsodefs.h>
 #include <dl-cet.h>
-#include <cet-tunables.h>
 
 /* GNU_PROPERTY_X86_FEATURE_1_IBT and GNU_PROPERTY_X86_FEATURE_1_SHSTK
    are defined in <elf.h>, which are only available for C sources.
@@ -39,23 +38,23 @@ static void
 dl_cet_check (struct link_map *m, const char *program)
 {
   /* Check how IBT should be enabled.  */
-  unsigned int enable_ibt_type
-    = GL(dl_x86_feature_1)[1] & ((1 << CET_MAX) - 1);
+  enum dl_x86_cet_control enable_ibt_type
+    = GL(dl_x86_feature_control).ibt;
   /* Check how SHSTK should be enabled.  */
-  unsigned int enable_shstk_type
-    = ((GL(dl_x86_feature_1)[1] >> CET_MAX) & ((1 << CET_MAX) - 1));
+  enum dl_x86_cet_control enable_shstk_type
+    = GL(dl_x86_feature_control).shstk;
 
   /* No legacy object check if both IBT and SHSTK are always on.  */
-  if (enable_ibt_type == CET_ALWAYS_ON
-      && enable_shstk_type == CET_ALWAYS_ON)
+  if (enable_ibt_type == cet_always_on
+      && enable_shstk_type == cet_always_on)
     return;
 
   /* Check if IBT is enabled by kernel.  */
   bool ibt_enabled
-    = (GL(dl_x86_feature_1)[0] & GNU_PROPERTY_X86_FEATURE_1_IBT) != 0;
+    = (GL(dl_x86_feature_1) & GNU_PROPERTY_X86_FEATURE_1_IBT) != 0;
   /* Check if SHSTK is enabled by kernel.  */
   bool shstk_enabled
-    = (GL(dl_x86_feature_1)[0] & GNU_PROPERTY_X86_FEATURE_1_SHSTK) != 0;
+    = (GL(dl_x86_feature_1) & GNU_PROPERTY_X86_FEATURE_1_SHSTK) != 0;
 
   if (ibt_enabled || shstk_enabled)
     {
@@ -65,9 +64,9 @@ dl_cet_check (struct link_map *m, const char *program)
 
       /* Check if IBT and SHSTK are enabled in object.  */
       bool enable_ibt = (ibt_enabled
-                        && enable_ibt_type != CET_ALWAYS_OFF);
+                        && enable_ibt_type != cet_always_off);
       bool enable_shstk = (shstk_enabled
-                          && enable_shstk_type != CET_ALWAYS_OFF);
+                          && enable_shstk_type != cet_always_off);
       if (program)
        {
          /* Enable IBT and SHSTK only if they are enabled in executable.
@@ -76,10 +75,10 @@ dl_cet_check (struct link_map *m, const char *program)
             GLIBC_TUNABLES=glibc.cpu.hwcaps=-IBT,-SHSTK
           */
          enable_ibt &= (HAS_CPU_FEATURE (IBT)
-                        && (enable_ibt_type == CET_ALWAYS_ON
+                        && (enable_ibt_type == cet_always_on
                             || (m->l_cet & lc_ibt) != 0));
          enable_shstk &= (HAS_CPU_FEATURE (SHSTK)
-                          && (enable_shstk_type == CET_ALWAYS_ON
+                          && (enable_shstk_type == cet_always_on
                               || (m->l_cet & lc_shstk) != 0));
        }
 
@@ -111,7 +110,7 @@ dl_cet_check (struct link_map *m, const char *program)
 
              /* IBT is enabled only if it is enabled in executable as
                 well as all shared objects.  */
-             enable_ibt &= (enable_ibt_type == CET_ALWAYS_ON
+             enable_ibt &= (enable_ibt_type == cet_always_on
                             || (l->l_cet & lc_ibt) != 0);
              if (!found_ibt_legacy && enable_ibt != ibt_enabled)
                {
@@ -121,7 +120,7 @@ dl_cet_check (struct link_map *m, const char *program)
 
              /* SHSTK is enabled only if it is enabled in executable as
                 well as all shared objects.  */
-             enable_shstk &= (enable_shstk_type == CET_ALWAYS_ON
+             enable_shstk &= (enable_shstk_type == cet_always_on
                               || (l->l_cet & lc_shstk) != 0);
              if (enable_shstk != shstk_enabled)
                {
@@ -137,7 +136,7 @@ dl_cet_check (struct link_map *m, const char *program)
        {
          if (!program)
            {
-             if (enable_ibt_type != CET_PERMISSIVE)
+             if (enable_ibt_type != cet_permissive)
                {
                  /* When IBT is enabled, we cannot dlopen a shared
                     object without IBT.  */
@@ -148,7 +147,7 @@ dl_cet_check (struct link_map *m, const char *program)
                                      N_("rebuild shared object with IBT support enabled"));
                }
 
-             if (enable_shstk_type != CET_PERMISSIVE)
+             if (enable_shstk_type != cet_permissive)
                {
                  /* When SHSTK is enabled, we cannot dlopen a shared
                     object without SHSTK.  */
@@ -159,8 +158,8 @@ dl_cet_check (struct link_map *m, const char *program)
                                      N_("rebuild shared object with SHSTK support enabled"));
                }
 
-             if (enable_ibt_type != CET_PERMISSIVE
-                 && enable_shstk_type != CET_PERMISSIVE)
+             if (enable_ibt_type != cet_permissive
+                 && enable_shstk_type != cet_permissive)
                return;
            }
 
@@ -190,7 +189,7 @@ dl_cet_check (struct link_map *m, const char *program)
            }
 
          /* Clear the disabled bits in dl_x86_feature_1.  */
-         GL(dl_x86_feature_1)[0] &= ~cet_feature;
+         GL(dl_x86_feature_1) &= ~cet_feature;
 
          cet_feature_changed = true;
        }
@@ -199,9 +198,9 @@ dl_cet_check (struct link_map *m, const char *program)
       if (program && (ibt_enabled || shstk_enabled))
        {
          if ((!ibt_enabled
-              || enable_ibt_type != CET_PERMISSIVE)
+              || enable_ibt_type != cet_permissive)
              && (!shstk_enabled
-                 || enable_shstk_type != CET_PERMISSIVE))
+                 || enable_shstk_type != cet_permissive))
            {
              /* Lock CET if IBT or SHSTK is enabled in executable unless
                 IBT or SHSTK is enabled permissively.  */

diff --git a/sysdeps/x86/dl-procruntime.c b/sysdeps/x86/dl-procruntime.c
index 5e39a38..2c3e979 100644 (file)
--- a/sysdeps/x86/dl-procruntime.c
+++ b/sysdeps/x86/dl-procruntime.c
@@ -47,7 +47,27 @@
 # if !defined PROCINFO_DECL && defined SHARED
   ._dl_x86_feature_1
 # else
-PROCINFO_CLASS unsigned int _dl_x86_feature_1[2]
+PROCINFO_CLASS unsigned int _dl_x86_feature_1
+# endif
+# ifndef PROCINFO_DECL
+= 0
+# endif
+# if !defined SHARED || defined PROCINFO_DECL
+;
+# else
+,
+# endif
+
+# if !defined PROCINFO_DECL && defined SHARED
+  ._dl_x86_feature_control
+# else
+PROCINFO_CLASS struct dl_x86_feature_control _dl_x86_feature_control
+# endif
+# ifndef PROCINFO_DECL
+= {
+    .ibt = cet_elf_property,
+    .shstk = cet_elf_property
+  }
 # endif
 # if !defined SHARED || defined PROCINFO_DECL
 ;

diff --git a/sysdeps/x86/ldsodefs.h b/sysdeps/x86/ldsodefs.h
index 072f826..5b1b09d 100644 (file)
--- a/sysdeps/x86/ldsodefs.h
+++ b/sysdeps/x86/ldsodefs.h
@@ -61,6 +61,7 @@ struct La_x32_retval;
                                     struct La_x86_64_retval *,         \
                                     const char *)
 
+#include <cet-control.h>
 #include_next <ldsodefs.h>
 
 #endif