Without attached patch against current -git I get following with
!PROC_SYSCTL (with EMBEDDED and PROC_FS set):

    CC      init/version.o
    LD      init/built-in.o
    LD      vmlinux
  fs/built-in.o: In function `do_proc_sys_lookup':
  proc_sysctl.c:(.text+0x26583): undefined reference to `sysctl_head_next'
  fs/built-in.o: In function `proc_sys_revalidate':
  proc_sysctl.c:(.text+0x265bb): undefined reference to `sysctl_head_finish'
  fs/built-in.o: In function `proc_sys_readdir':
  proc_sysctl.c:(.text+0x26720): undefined reference to `sysctl_head_next'
  proc_sysctl.c:(.text+0x267d8): undefined reference to `sysctl_head_finish'
  proc_sysctl.c:(.text+0x268e7): undefined reference to `sysctl_head_next'
  proc_sysctl.c:(.text+0x26910): undefined reference to `sysctl_head_finish'
  fs/built-in.o: In function `proc_sys_write':
  proc_sysctl.c:(.text+0x2695d): undefined reference to `sysctl_perm'
  proc_sysctl.c:(.text+0x2699c): undefined reference to `sysctl_head_finish'
  fs/built-in.o: In function `proc_sys_read':
  proc_sysctl.c:(.text+0x269e9): undefined reference to `sysctl_perm'
  proc_sysctl.c:(.text+0x26a25): undefined reference to `sysctl_head_finish'
  fs/built-in.o: In function `proc_sys_permission':
  proc_sysctl.c:(.text+0x26ad1): undefined reference to `sysctl_perm'
  proc_sysctl.c:(.text+0x26adb): undefined reference to `sysctl_head_finish'
  fs/built-in.o: In function `proc_sys_lookup':
  proc_sysctl.c:(.text+0x26b39): undefined reference to `sysctl_head_finish'
  make: *** [vmlinux] Virhe 1

All those functions are in fs/proc/proc_sysctl.c, which has no CONFIG_
#define's in it, so the patch makes the compilation of that file to depend
on CONFIG_PROC_SYSCTL (the simplest choice).
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>