nptl: Move changing of stack permissions into ld.so

All the stack lists are now in _rtld_global, so it is possible
to change stack permissions directly from there, instead of
calling into libpthread to do the change.

Tested-by: Carlos O'Donell <carlos@redhat.com>
Reviewed-by: Carlos O'Donell <carlos@redhat.com>

3 files changed, 84 insertions, 9 deletions

diff --git a/sysdeps/generic/ldsodefs.h b/sysdeps/generic/ldsodefs.h
index 81cce2e4d5..8426b5cbd8 100644
--- a/sysdeps/generic/ldsodefs.h
+++ b/sysdeps/generic/ldsodefs.h
@@ -416,10 +416,12 @@ struct rtld_global
 #endif
 #include <dl-procruntime.c>
 
+#if !PTHREAD_IN_LIBC
   /* If loading a shared object requires that we make the stack executable
      when it was not, we do it by calling this function.
      It returns an errno code or zero on success.  */
   EXTERN int (*_dl_make_stack_executable_hook) (void **);
+#endif
 
   /* Prevailing state of the stack, PF_X indicating it's executable.  */
   EXTERN ElfW(Word) _dl_stack_flags;
@@ -717,10 +719,17 @@ extern const ElfW(Phdr) *_dl_phdr;
 extern size_t _dl_phnum;
 #endif
 
+#if PTHREAD_IN_LIBC
+/* This function changes the permissions of all stacks (not just those
+   of the main stack).  */
+int _dl_make_stacks_executable (void **stack_endp) attribute_hidden;
+#else
 /* This is the initial value of GL(dl_make_stack_executable_hook).
-   A threads library can change it.  */
+   A threads library can change it.  The ld.so implementation changes
+   the permissions of the main stack only.  */
 extern int _dl_make_stack_executable (void **stack_endp);
 rtld_hidden_proto (_dl_make_stack_executable)
+#endif
 
 /* Variable pointing to the end of the stack (or close to it).  This value
    must be constant over the runtime of the application.  Some programs
diff --git a/sysdeps/unix/sysv/linux/Versions b/sysdeps/unix/sysv/linux/Versions
index c35f783e2a..220bb2dffe 100644
--- a/sysdeps/unix/sysv/linux/Versions
+++ b/sysdeps/unix/sysv/linux/Versions
@@ -181,3 +181,9 @@ libc {
     __netlink_assert_response;
   }
 }
+
+ld {
+  GLIBC_PRIVATE {
+    __nptl_change_stack_perm;
+  }
+}
diff --git a/sysdeps/unix/sysv/linux/dl-execstack.c b/sysdeps/unix/sysv/linux/dl-execstack.c
index 3339138c42..e2449d1890 100644
--- a/sysdeps/unix/sysv/linux/dl-execstack.c
+++ b/sysdeps/unix/sysv/linux/dl-execstack.c
@@ -16,20 +16,21 @@
    License along with the GNU C Library; if not, see
    <https://www.gnu.org/licenses/>.  */
 
-#include <ldsodefs.h>
-#include <sys/mman.h>
 #include <errno.h>
+#include <ldsodefs.h>
 #include <libintl.h>
-#include <stdbool.h>
+#include <list.h>
+#include <nptl/pthreadP.h>
 #include <stackinfo.h>
+#include <stdbool.h>
+#include <sys/mman.h>
 #include <sysdep.h>
-
+#include <unistd.h>
 
 extern int __stack_prot attribute_relro attribute_hidden;
 
-
-int
-_dl_make_stack_executable (void **stack_endp)
+static int
+make_main_stack_executable (void **stack_endp)
 {
   /* This gives us the highest/lowest page that needs to be changed.  */
   uintptr_t page = ((uintptr_t) *stack_endp
@@ -56,4 +57,63 @@ _dl_make_stack_executable (void **stack_endp)
 
   return result;
 }
-rtld_hidden_def (_dl_make_stack_executable)
+
+int
+_dl_make_stacks_executable (void **stack_endp)
+{
+  /* First the main thread's stack.  */
+  int err = make_main_stack_executable (stack_endp);
+  if (err != 0)
+    return err;
+
+  lll_lock (GL (dl_stack_cache_lock), LLL_PRIVATE);
+
+  list_t *runp;
+  list_for_each (runp, &GL (dl_stack_used))
+    {
+      err = __nptl_change_stack_perm (list_entry (runp, struct pthread, list));
+      if (err != 0)
+	break;
+    }
+
+  /* Also change the permission for the currently unused stacks.  This
+     might be wasted time but better spend it here than adding a check
+     in the fast path.  */
+  if (err == 0)
+    list_for_each (runp, &GL (dl_stack_cache))
+      {
+	err = __nptl_change_stack_perm (list_entry (runp, struct pthread,
+						    list));
+	if (err != 0)
+	  break;
+      }
+
+  lll_unlock (GL (dl_stack_cache_lock), LLL_PRIVATE);
+
+  return err;
+}
+
+int
+__nptl_change_stack_perm (struct pthread *pd)
+{
+#ifdef NEED_SEPARATE_REGISTER_STACK
+  size_t pagemask = __getpagesize () - 1;
+  void *stack = (pd->stackblock
+		 + (((((pd->stackblock_size - pd->guardsize) / 2)
+		      & pagemask) + pd->guardsize) & pagemask));
+  size_t len = pd->stackblock + pd->stackblock_size - stack;
+#elif _STACK_GROWS_DOWN
+  void *stack = pd->stackblock + pd->guardsize;
+  size_t len = pd->stackblock_size - pd->guardsize;
+#elif _STACK_GROWS_UP
+  void *stack = pd->stackblock;
+  size_t len = (uintptr_t) pd - pd->guardsize - (uintptr_t) pd->stackblock;
+#else
+# error "Define either _STACK_GROWS_DOWN or _STACK_GROWS_UP"
+#endif
+  if (__mprotect (stack, len, PROT_READ | PROT_WRITE | PROT_EXEC) != 0)
+    return errno;
+
+  return 0;
+}
+rtld_hidden_def (__nptl_change_stack_perm)