linux-kernel - [PATCH] mm/pkeys: generate pkey system call code only if ARCH_HAS

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Date:   Mon, 14 Nov 2016 12:12:51 +0100
From:   Heiko Carstens <heiko.carstens@...ibm.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, Dave Hansen <dave.hansen@...ux.intel.com>,
        Mark Rutland <mark.rutland@....com>
Subject: [PATCH] mm/pkeys: generate pkey system call code only if ARCH_HAS_PKEYS is selected

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.

Signed-off-by: Heiko Carstens <heiko.carstens@...ibm.com>
---
 mm/mprotect.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/mm/mprotect.c b/mm/mprotect.c
index 11936526b08b..a06e91c4de29 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -484,6 +484,8 @@ 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)
 {
@@ -534,3 +536,5 @@ SYSCALL_DEFINE1(pkey_free, int, pkey)
 	 */
 	return ret;
 }
+
+#endif /* CONFIG_ARCH_HAS_PKEYS */
-- 
2.8.4