exec: make prepare_bprm_creds static

prepare_bprm_creds is not used outside exec.c, so there's no reason for it
to have external linkage.
Signed-off-by: Chanho Min <chanho.min@lge.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/exec.c

@@ -1399,7 +1399,7 @@ EXPORT_SYMBOL(finalize_exec);
  * Or, if exec fails before, free_bprm() should release ->cred and
  * and unlock.
  */
-int prepare_bprm_creds(struct linux_binprm *bprm)
+static int prepare_bprm_creds(struct linux_binprm *bprm)
 {
 	if (mutex_lock_interruptible(&current->signal->cred_guard_mutex))
 		return -ERESTARTNOINTR;

include/linux/binfmts.h

@@ -138,7 +138,6 @@ extern int transfer_args_to_stack(struct linux_binprm *bprm,
 extern int bprm_change_interp(const char *interp, struct linux_binprm *bprm);
 extern int copy_strings_kernel(int argc, const char *const *argv,
 			       struct linux_binprm *bprm);
-extern int prepare_bprm_creds(struct linux_binprm *bprm);
 extern void install_exec_creds(struct linux_binprm *bprm);
 extern void set_binfmt(struct linux_binfmt *new);
 extern ssize_t read_code(struct file *, unsigned long, loff_t, size_t);