[PATCH mm-unstable] kernel/pid_sysctl.h: Add missing definitions for specific config

[SeongJae Park <sj@kernel.org>]

Commit bdb6231e88a3 ("mm/memfd: add MFD_NOEXEC_SEAL and MFD_EXEC") on
mm-unstable when CONFIG_SYSCTL or CONFIG_MEMFD_CRETE not defined, as
below, because initialize_memfd_noexec_scope() and
register_pid_ns_sysctl_table_vm(), which defined by the commit, is not
defined for the config case.

    ERROR:root:/kernel/pid_namespace.c: In function ‘create_pid_namespace’:
    /kernel/pid_namespace.c:114:2: error: implicit declaration of function ‘initialize_memfd_noexec_scope’; did you mean ‘set_memfd_noexec_scope’? [-Werror=implicit-function-declaration]
      114 |  initialize_memfd_noexec_scope(ns);
          |  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
          |  set_memfd_noexec_scope
    /kernel/pid_namespace.c: In function ‘pid_namespaces_init’:
    /kernel/pid_namespace.c:462:2: error: implicit declaration of function ‘register_pid_ns_sysctl_table_vm’; did you mean ‘register_pid_ns_ctl_table_vm’? [-Werror=implicit-function-declaration]
      462 |  register_pid_ns_sysctl_table_vm();
          |  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
          |  register_pid_ns_ctl_table_vm
    cc1: some warnings being treated as errors
    make[3]: *** [/scripts/Makefile.build:250: kernel/pid_namespace.o] Error 1

Fix the commit by defining the functions for the configuration.

Fixes: bdb6231e88a3 ("mm/memfd: add MFD_NOEXEC_SEAL and MFD_EXEC") on mm-unstable
Signed-off-by: SeongJae Park <sj@kernel.org>
---
 kernel/pid_sysctl.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/pid_sysctl.h b/kernel/pid_sysctl.h
index 90a93161a122..770c060a0d33 100644
--- a/kernel/pid_sysctl.h
+++ b/kernel/pid_sysctl.h
@@ -52,8 +52,10 @@ static inline void register_pid_ns_sysctl_table_vm(void)
 	register_sysctl_paths(vm_path, pid_ns_ctl_table_vm);
 }
 #else
+static inline void initialize_memfd_noexec_scope(struct pid_namespace *ns) {}
 static inline void set_memfd_noexec_scope(struct pid_namespace *ns) {}
 static inline void register_pid_ns_ctl_table_vm(void) {}
+static inline void register_pid_ns_sysctl_table_vm(void) {}
 #endif
 
 #endif /* LINUX_PID_SYSCTL_H */
-- 
2.25.1