x86-64/cet: Move dl-cet.[ch] to x86_64 directories

Since CET is only enabled for x86-64, move dl-cet.[ch] to x86_64
directories.
Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

1 files changed, 364 insertions, 0 deletions

diff --git a/sysdeps/x86_64/dl-cet.c b/sysdeps/x86_64/dl-cet.c
new file mode 100644
index 0000000000..1297c09f84
--- /dev/null
+++ b/sysdeps/x86_64/dl-cet.c
@@ -0,0 +1,364 @@
+/* x86-64 CET initializers function.
+   Copyright (C) 2018-2024 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 <unistd.h>
+#include <errno.h>
+#include <libintl.h>
+#include <ldsodefs.h>
+#include <dl-cet.h>
+#include <sys/single_threaded.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.
+   X86_FEATURE_1_IBT and X86_FEATURE_1_SHSTK are defined in <sysdep.h>
+   which are available for both C and asm sources.  They must match.   */
+#if GNU_PROPERTY_X86_FEATURE_1_IBT != X86_FEATURE_1_IBT
+# error GNU_PROPERTY_X86_FEATURE_1_IBT != X86_FEATURE_1_IBT
+#endif
+#if GNU_PROPERTY_X86_FEATURE_1_SHSTK != X86_FEATURE_1_SHSTK
+# error GNU_PROPERTY_X86_FEATURE_1_SHSTK != X86_FEATURE_1_SHSTK
+#endif
+
+struct dl_cet_info
+{
+  const char *program;
+
+  /* Check how IBT and SHSTK should be enabled.  */
+  enum dl_x86_cet_control enable_ibt_type;
+  enum dl_x86_cet_control enable_shstk_type;
+
+  /* If IBT and SHSTK were previously enabled.  */
+  unsigned int feature_1_enabled;
+
+  /* If IBT and SHSTK should be enabled.  */
+  unsigned int enable_feature_1;
+
+  /* If there are any legacy shared object.  */
+  unsigned int feature_1_legacy;
+
+  /* Which shared object is the first legacy shared object.  */
+  unsigned int feature_1_legacy_ibt;
+  unsigned int feature_1_legacy_shstk;
+};
+
+/* Check if the object M and its dependencies are legacy object.  */
+
+static void
+dl_check_legacy_object (struct link_map *m,
+			struct dl_cet_info *info)
+{
+  unsigned int i;
+  struct link_map *l = NULL;
+
+  i = m->l_searchlist.r_nlist;
+  while (i-- > 0)
+    {
+      /* Check each shared object to see if IBT and SHSTK are enabled.  */
+      l = m->l_initfini[i];
+
+      if (l->l_init_called)
+        continue;
+
+#ifdef SHARED
+      /* Skip check for ld.so since it has the features enabled.  The
+         features will be disabled later if they are not enabled in
+	 executable.  */
+      if (l == &GL(dl_rtld_map)
+          || l->l_real == &GL(dl_rtld_map)
+          || (info->program != NULL && l == m))
+         continue;
+#endif
+
+      /* IBT and SHSTK set only if enabled in executable and all DSOs.
+	 NB: cet_always_on is handled outside of the loop.  */
+      info->enable_feature_1 &= ((l->l_x86_feature_1_and
+				  & (GNU_PROPERTY_X86_FEATURE_1_IBT
+				     | GNU_PROPERTY_X86_FEATURE_1_SHSTK))
+				 | ~(GNU_PROPERTY_X86_FEATURE_1_IBT
+				     | GNU_PROPERTY_X86_FEATURE_1_SHSTK));
+      if ((info->feature_1_legacy
+	   & GNU_PROPERTY_X86_FEATURE_1_IBT) == 0
+	  && ((info->enable_feature_1
+	       & GNU_PROPERTY_X86_FEATURE_1_IBT)
+	      != (info->feature_1_enabled
+		  & GNU_PROPERTY_X86_FEATURE_1_IBT)))
+	{
+	  info->feature_1_legacy_ibt = i;
+	  info->feature_1_legacy |= GNU_PROPERTY_X86_FEATURE_1_IBT;
+	}
+
+      if ((info->feature_1_legacy
+	   & GNU_PROPERTY_X86_FEATURE_1_SHSTK) == 0
+	  && ((info->enable_feature_1
+	       & GNU_PROPERTY_X86_FEATURE_1_SHSTK)
+	      != (info->feature_1_enabled
+		  & GNU_PROPERTY_X86_FEATURE_1_SHSTK)))
+        {
+	  info->feature_1_legacy_shstk = i;
+	  info->feature_1_legacy |= GNU_PROPERTY_X86_FEATURE_1_SHSTK;
+        }
+    }
+
+  /* Handle cet_always_on.  */
+  if ((info->feature_1_enabled
+       & GNU_PROPERTY_X86_FEATURE_1_IBT) != 0
+      && info->enable_ibt_type == cet_always_on)
+    {
+      info->feature_1_legacy &= ~GNU_PROPERTY_X86_FEATURE_1_IBT;
+      info->enable_feature_1 |= GNU_PROPERTY_X86_FEATURE_1_IBT;
+    }
+
+  if ((info->feature_1_enabled
+       & GNU_PROPERTY_X86_FEATURE_1_SHSTK) != 0
+      && info->enable_shstk_type == cet_always_on)
+    {
+      info->feature_1_legacy &= ~GNU_PROPERTY_X86_FEATURE_1_SHSTK;
+      info->enable_feature_1 |= GNU_PROPERTY_X86_FEATURE_1_SHSTK;
+    }
+}
+
+#ifdef SHARED
+/* Enable IBT and SHSTK only if they are enabled in executable.  Set
+   feature bits properly at the start of the program.  */
+
+static void
+dl_cet_check_startup (struct link_map *m, struct dl_cet_info *info)
+{
+  /* NB: IBT and SHSTK may be disabled by environment variable:
+
+     GLIBC_TUNABLES=glibc.cpu.hwcaps=-IBT,-SHSTK.
+   */
+  if (CPU_FEATURE_USABLE (IBT))
+    {
+      if (info->enable_ibt_type == cet_always_on)
+	info->enable_feature_1 |= GNU_PROPERTY_X86_FEATURE_1_IBT;
+      else
+	info->enable_feature_1 &= ((m->l_x86_feature_1_and
+				    & GNU_PROPERTY_X86_FEATURE_1_IBT)
+				   | ~GNU_PROPERTY_X86_FEATURE_1_IBT);
+    }
+  else
+    info->enable_feature_1 &= ~GNU_PROPERTY_X86_FEATURE_1_IBT;
+
+  if (CPU_FEATURE_USABLE (SHSTK))
+    {
+      if (info->enable_shstk_type == cet_always_on)
+	info->enable_feature_1 |= GNU_PROPERTY_X86_FEATURE_1_SHSTK;
+      else
+	info->enable_feature_1 &= ((m->l_x86_feature_1_and
+				    & GNU_PROPERTY_X86_FEATURE_1_SHSTK)
+				   | ~GNU_PROPERTY_X86_FEATURE_1_SHSTK);
+    }
+  else
+    info->enable_feature_1 &= ~GNU_PROPERTY_X86_FEATURE_1_SHSTK;
+
+  if (info->enable_feature_1 != 0)
+    dl_check_legacy_object (m, info);
+
+  unsigned int disable_feature_1
+    = info->enable_feature_1 ^ info->feature_1_enabled;
+  if (disable_feature_1 != 0)
+    {
+      /* 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;
+    }
+}
+#endif
+
+/* Check feature bits when dlopening the shared object M.  */
+
+static void
+dl_cet_check_dlopen (struct link_map *m, struct dl_cet_info *info)
+{
+  /* Check if there are any legacy objects loaded.  */
+  if (info->enable_feature_1 != 0)
+    {
+      dl_check_legacy_object (m, info);
+
+      /* Skip if there are no legacy shared objects loaded.  */
+      if (info->feature_1_legacy == 0)
+	return;
+    }
+
+  unsigned int disable_feature_1 = 0;
+  unsigned int legacy_obj = 0;
+  const char *msg = NULL;
+
+  if ((info->feature_1_enabled
+       & GNU_PROPERTY_X86_FEATURE_1_IBT) != 0
+      && (info->feature_1_legacy
+	  & GNU_PROPERTY_X86_FEATURE_1_IBT) != 0)
+    {
+      /* Don't disable IBT if not single threaded since IBT may be still
+	 enabled in other threads.  */
+      if (info->enable_ibt_type != cet_permissive
+	  || !SINGLE_THREAD_P)
+	{
+	  legacy_obj = info->feature_1_legacy_ibt;
+	  msg = N_("rebuild shared object with IBT support enabled");
+	}
+      else
+        disable_feature_1 |= GNU_PROPERTY_X86_FEATURE_1_IBT;
+    }
+
+  /* Check the next feature only if there is no error.  */
+  if (msg == NULL
+      && (info->feature_1_enabled
+	  & GNU_PROPERTY_X86_FEATURE_1_SHSTK) != 0
+      && (info->feature_1_legacy
+	  & GNU_PROPERTY_X86_FEATURE_1_SHSTK) != 0)
+    {
+      /* Don't disable SHSTK if not single threaded since SHSTK may be
+         still enabled in other threads.  */
+      if (info->enable_shstk_type != cet_permissive
+	  || !SINGLE_THREAD_P)
+	{
+	  legacy_obj = info->feature_1_legacy_shstk;
+	  msg = N_("rebuild shared object with SHSTK support enabled");
+	}
+      else
+        disable_feature_1 |= GNU_PROPERTY_X86_FEATURE_1_SHSTK;
+    }
+
+  /* If there is an error, long jump back to the caller.  */
+  if (msg != NULL)
+    _dl_signal_error (0, m->l_initfini[legacy_obj]->l_name, "dlopen",
+		      msg);
+
+  if (disable_feature_1 != 0)
+    {
+      int res = dl_cet_disable_cet (disable_feature_1);
+      if (res)
+        {
+	  if ((disable_feature_1
+	       & GNU_PROPERTY_X86_FEATURE_1_IBT) != 0)
+	    msg = N_("can't disable IBT");
+	  else
+	    msg = N_("can't disable SHSTK");
+	  /* Long jump back to the caller on error.  */
+	  _dl_signal_error (-res, m->l_initfini[legacy_obj]->l_name,
+			    "dlopen", msg);
+       }
+
+      /* Clear the disabled bits in dl_x86_feature_1.  */
+      GL(dl_x86_feature_1) &= ~disable_feature_1;
+
+      THREAD_SETMEM (THREAD_SELF, header.feature_1,
+		     GL(dl_x86_feature_1));
+    }
+}
+
+static void
+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;
+
+  info.feature_1_enabled = GL(dl_x86_feature_1);
+
+  /* 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)
+    return;
+
+  /* Check if IBT and SHSTK were enabled.  */
+  if (info.feature_1_enabled == 0)
+    return;
+
+  info.program = program;
+
+  /* Check which features should be enabled.  */
+  info.enable_feature_1 = 0;
+  if (info.enable_ibt_type != cet_always_off)
+    info.enable_feature_1 |= (info.feature_1_enabled
+			      & GNU_PROPERTY_X86_FEATURE_1_IBT);
+  if (info.enable_shstk_type != cet_always_off)
+    info.enable_feature_1 |= (info.feature_1_enabled
+			      & GNU_PROPERTY_X86_FEATURE_1_SHSTK);
+
+  /* Start with no legacy objects.  */
+  info.feature_1_legacy = 0;
+  info.feature_1_legacy_ibt = 0;
+  info.feature_1_legacy_shstk = 0;
+
+#ifdef SHARED
+  if (program)
+    dl_cet_check_startup (m, &info);
+  else
+#endif
+    dl_cet_check_dlopen (m, &info);
+}
+
+void
+_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
+#  define LINKAGE
+# endif
+
+LINKAGE
+void
+_dl_cet_check (struct link_map *main_map, const char *program)
+{
+  dl_cet_check (main_map, program);
+}
+#endif /* SHARED */