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>

3 files changed, 9 insertions, 1 deletions

diff --git a/arch/arm/include/asm/thread_info.h b/arch/arm/include/asm/thread_info.h
index 73394e50cbca..d3a39b1e6c0f 100644
--- a/arch/arm/include/asm/thread_info.h
+++ b/arch/arm/include/asm/thread_info.h
@@ -130,11 +130,13 @@ extern void vfp_sync_state(struct thread_info *thread);
  *  TIF_SYSCALL_TRACE   - syscall trace active
  *  TIF_SIGPENDING      - signal pending
  *  TIF_NEED_RESCHED    - rescheduling necessary
+ *  TIF_NOTIFY_RESUME   - callback before returning to user
  *  TIF_USEDFPU         - FPU was used by this task this quantum (SMP)
  *  TIF_POLLING_NRFLAG  - true if poll_idle() is polling TIF_NEED_RESCHED
  */
 #define TIF_SIGPENDING          0
 #define TIF_NEED_RESCHED        1
+#define TIF_NOTIFY_RESUME       2       /* callback before returning to user */
 #define TIF_SYSCALL_TRACE       8
 #define TIF_POLLING_NRFLAG      16
 #define TIF_USING_IWMMXT        17
@@ -143,6 +145,7 @@ extern void vfp_sync_state(struct thread_info *thread);
 
 #define _TIF_SIGPENDING         (1 << TIF_SIGPENDING)
 #define _TIF_NEED_RESCHED       (1 << TIF_NEED_RESCHED)
+#define _TIF_NOTIFY_RESUME      (1 << TIF_NOTIFY_RESUME)
 #define _TIF_SYSCALL_TRACE      (1 << TIF_SYSCALL_TRACE)
 #define _TIF_POLLING_NRFLAG     (1 << TIF_POLLING_NRFLAG)
 #define _TIF_USING_IWMMXT       (1 << TIF_USING_IWMMXT)
diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S
index 8c3de1a350b5..7813ab782fda 100644
--- a/arch/arm/kernel/entry-common.S
+++ b/arch/arm/kernel/entry-common.S
@@ -51,7 +51,7 @@ fast_work_pending:
 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 f6bc5d442782..13dec276927a 100644
--- a/arch/arm/kernel/signal.c
+++ b/arch/arm/kernel/signal.c
@@ -707,4 +707,9 @@ do_notify_resume(struct pt_regs *regs, unsigned int thread_flags, int syscall)
 {
         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);
+        }
 }