mm/pkeys: generate pkey system call code only if ARCH_HAS_PKEYS is se…

…lected

Having code for the pkey_mprotect, pkey_alloc and pkey_free system calls
makes only sense if ARCH_HAS_PKEYS is selected.  If not selected these
system calls will always return -ENOSPC or -EINVAL.

To simplify things and have less code generate the pkey system call code
only if ARCH_HAS_PKEYS is selected.

For architectures which have already wired up the system calls, but do
not select ARCH_HAS_PKEYS this will result in less generated code and a
different return code: the three system calls will now always return
-ENOSYS, using the cond_syscall mechanism.

For architectures which have not wired up the system calls less
unreachable code will be generated.

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Heiko Carstens <[email protected]>
Acked-by: Dave Hansen <[email protected]>
Cc: Mark Rutland <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

mm/mprotect.c

@@ -497,6 +497,8 @@ SYSCALL_DEFINE3(mprotect, unsigned long, start, size_t, len,
 	return do_mprotect_pkey(start, len, prot, -1);
 }
 
+#ifdef CONFIG_ARCH_HAS_PKEYS
+
 SYSCALL_DEFINE4(pkey_mprotect, unsigned long, start, size_t, len,
 		unsigned long, prot, int, pkey)
 {
@@ -547,3 +549,5 @@ SYSCALL_DEFINE1(pkey_free, int, pkey)
 	 */
 	return ret;
 }
+
+#endif /* CONFIG_ARCH_HAS_PKEYS */