KEYS: Extend TIF_NOTIFY_RESUME to (almost) all architectures [try #6]

Implement TIF_NOTIFY_RESUME for most of those architectures in which isn't yet
available, and, whilst we're at it, have it call the appropriate tracehook.

After this patch, blackfin, m68k* and xtensa still lack support and need
alteration of assembly code to make it work.

Resume notification can then be used (by a later patch) to install a new
session keyring on the parent of a process.

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Russell King <rmk+kernel@arm.linux.org.uk>

cc: linux-arch@vger.kernel.org
Signed-off-by: James Morris <jmorris@namei.org>
diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S
index 8c3de1a..7813ab7 100644
--- a/arch/arm/kernel/entry-common.S
+++ b/arch/arm/kernel/entry-common.S
@@ -51,7 +51,7 @@
 work_pending:
 	tst	r1, #_TIF_NEED_RESCHED
 	bne	work_resched
-	tst	r1, #_TIF_SIGPENDING
+	tst	r1, #_TIF_SIGPENDING|_TIF_NOTIFY_RESUME
 	beq	no_work_pending
 	mov	r0, sp				@ 'regs'
 	mov	r2, why				@ 'syscall'
diff --git a/arch/arm/kernel/signal.c b/arch/arm/kernel/signal.c
index f6bc5d4..13dec27 100644
--- a/arch/arm/kernel/signal.c
+++ b/arch/arm/kernel/signal.c
@@ -707,4 +707,9 @@
 {
 	if (thread_flags & _TIF_SIGPENDING)
 		do_signal(&current->blocked, regs, syscall);
+
+	if (thread_flags & _TIF_NOTIFY_RESUME) {
+		clear_thread_flag(TIF_NOTIFY_RESUME);
+		tracehook_notify_resume(regs);
+	}
 }