linux: Remove __stack_prot

The __stack_prot is used by Linux to make the stack executable if
a modules requires it.  It is also marked as RELRO, which requires
to change the segment permission to RW to update it.

Also, there is no need to keep track of the flags: either the stack
will have the default permission of the ABI or should be change to
PROT_READ | PROT_WRITE | PROT_EXEC.  The only additional flag,
PROT_GROWSDOWN or PROT_GROWSUP, is Linux only and can be deducted
from _STACK_GROWS_DOWN/_STACK_GROWS_UP.

Also, the check_consistency function was already removed some time
ago.

Checked on x86_64-linux-gnu and i686-linux-gnu.
Reviewed-by: Florian Weimer <fweimer@redhat.com>

1 files changed, 10 insertions, 15 deletions

diff --git a/sysdeps/unix/sysv/linux/dl-execstack.c b/sysdeps/unix/sysv/linux/dl-execstack.c
index 3d8f3938da..b986898598 100644
--- a/sysdeps/unix/sysv/linux/dl-execstack.c
+++ b/sysdeps/unix/sysv/linux/dl-execstack.c
@@ -27,35 +27,30 @@
 #include <sysdep.h>
 #include <unistd.h>
 
-extern int __stack_prot attribute_relro attribute_hidden;
-
 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
 		    & -(intptr_t) GLRO(dl_pagesize));
-  int result = 0;
 
-  if (__builtin_expect (__mprotect ((void *) page, GLRO(dl_pagesize),
-				    __stack_prot) == 0, 1))
-    goto return_success;
-  result = errno;
-  goto out;
+  if (__mprotect ((void *) page, GLRO(dl_pagesize),
+		  PROT_READ | PROT_WRITE | PROT_EXEC
+#if _STACK_GROWS_DOWN
+		  | PROT_GROWSDOWN
+#elif _STACK_GROWS_UP
+		  | PROT_GROWSUP
+#endif
+		  ) != 0)
+    return errno;
 
- return_success:
   /* Clear the address.  */
   *stack_endp = NULL;
 
   /* Remember that we changed the permission.  */
   GL(dl_stack_flags) |= PF_X;
 
- out:
-#ifdef check_consistency
-  check_consistency ();
-#endif
-
-  return result;
+  return 0;
 }
 
 int