[PATCH v8 15/20] aarch64: Handle GCS marking

[Yury Khrustalev]

From: Szabolcs Nagy <szabolcs.nagy@arm.com>

 - Handle GCS marking
 - Use l_searchlist.r_list for gcs (allows using the
   same function for static exe)
---
 sysdeps/aarch64/dl-gcs.c  | 53 +++++++++++++++++++++++++++++++++++++++
 sysdeps/aarch64/dl-prop.h | 15 +++++++----
 sysdeps/aarch64/linkmap.h |  1 +
 3 files changed, 64 insertions(+), 5 deletions(-)

diff --git a/sysdeps/aarch64/dl-gcs.c b/sysdeps/aarch64/dl-gcs.c
index 870336f2bb..97146fb4bc 100644
--- a/sysdeps/aarch64/dl-gcs.c
+++ b/sysdeps/aarch64/dl-gcs.c
@@ -15,8 +15,61 @@
    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>
 
+static void
+fail (struct link_map *l, const char *program)
+{
+  if (program && program[0])
+    _dl_fatal_printf ("%s: %s: %s\n", program, l->l_name, "not GCS compatible");
+  else if (program)
+    _dl_fatal_printf ("%s\n", "not GCS compatible");
+  else
+    _dl_signal_error (0, l->l_name, "dlopen", "not GCS compatible");
+}
+
+static void
+unsupported (void)
+{
+  _dl_fatal_printf ("%s\n", "unsupported GCS policy");
+}
+
+static void
+check_gcs (struct link_map *l, const char *program)
+{
+  bool for_dlopen = program == NULL;
+  if (!l->l_mach.gcs)
+    {
+      if (GLRO(dl_aarch64_gcs_policy) == 2 || for_dlopen)
+	fail (l, program);
+      if (GLRO(dl_aarch64_gcs_policy) == 1)
+	GL(dl_aarch64_gcs) = 0;
+      else
+	unsupported ();
+    }
+}
+
+/* Apply GCS policy for L and its dependencies.
+   PROGRAM is NULL when this check is invoked for dl_open.  */
+
+void
+_dl_gcs_check (struct link_map *l, const char *program)
+{
+  /* GCS is disabled.  */
+  if (GL(dl_aarch64_gcs) == 0)
+    return;
+  /* GCS marking is ignored.  */
+  if (GLRO(dl_aarch64_gcs_policy) == 0)
+    return;
+
+  check_gcs (l, program);
+  for (unsigned int i = 0; i < l->l_searchlist.r_nlist; i++)
+    check_gcs (l->l_searchlist.r_list[i], program);
+}
+
 /* Used to report error when prctl system call to enabled GCS fails.  */
 
 void _dl_gcs_enable_failed (int code)
diff --git a/sysdeps/aarch64/dl-prop.h b/sysdeps/aarch64/dl-prop.h
index 361fc593da..abca2be7fa 100644
--- a/sysdeps/aarch64/dl-prop.h
+++ b/sysdeps/aarch64/dl-prop.h
@@ -24,16 +24,21 @@ extern void _dl_bti_protect (struct link_map *, int) attribute_hidden;
 extern void _dl_bti_check (struct link_map *, const char *)
     attribute_hidden;
 
+extern void _dl_gcs_check (struct link_map *, const char *)
+    attribute_hidden;
+
 static inline void __attribute__ ((always_inline))
 _rtld_main_check (struct link_map *m, const char *program)
 {
   _dl_bti_check (m, program);
+  _dl_gcs_check (m, program);
 }
 
 static inline void __attribute__ ((always_inline))
 _dl_open_check (struct link_map *m)
 {
   _dl_bti_check (m, NULL);
+  _dl_gcs_check (m, NULL);
 }
 
 static inline void __attribute__ ((always_inline))
@@ -45,10 +50,6 @@ static inline int
 _dl_process_gnu_property (struct link_map *l, int fd, uint32_t type,
 			  uint32_t datasz, void *data)
 {
-  if (!GLRO(dl_aarch64_cpu_features).bti)
-    /* Skip note processing.  */
-    return 0;
-
   if (type == GNU_PROPERTY_AARCH64_FEATURE_1_AND)
     {
       /* Stop if the property note is ill-formed.  */
@@ -57,7 +58,11 @@ _dl_process_gnu_property (struct link_map *l, int fd, uint32_t type,
 
       unsigned int feature_1 = *(unsigned int *) data;
       if (feature_1 & GNU_PROPERTY_AARCH64_FEATURE_1_BTI)
-	_dl_bti_protect (l, fd);
+	if (GLRO(dl_aarch64_cpu_features).bti)
+	  _dl_bti_protect (l, fd);
+
+      if (feature_1 & GNU_PROPERTY_AARCH64_FEATURE_1_GCS)
+	l->l_mach.gcs = 1;
 
       /* Stop if we processed the property note.  */
       return 0;
diff --git a/sysdeps/aarch64/linkmap.h b/sysdeps/aarch64/linkmap.h
index df6d3c66e8..e56c890aea 100644
--- a/sysdeps/aarch64/linkmap.h
+++ b/sysdeps/aarch64/linkmap.h
@@ -23,4 +23,5 @@ struct link_map_machine
   ElfW(Addr) plt;	  /* Address of .plt */
   void *tlsdesc_table;	  /* Address of TLS descriptor hash table.  */
   bool bti_fail;	  /* Failed to enable Branch Target Identification.  */
+  bool gcs;		  /* Guarded Control Stack marking.  */
 };
-- 
2.39.5