[PATCH] arm: add support for TIF_NOTIFY_SIGNAL

[Jens Axboe <axboe@kernel.dk>]

Wire up TIF_NOTIFY_SIGNAL handling for arm.

Cc: linux-arm-kernel@lists.infradead.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---

5.11 has support queued up for TIF_NOTIFY_SIGNAL, see this posting
for details:

https://lore.kernel.org/io-uring/20201026203230.386348-1-axboe@kernel.dk/

As part of that work, I'm adding TIF_NOTIFY_SIGNAL support to all archs,
as that will enable a set of cleanups once all of them support it.

This needs a bit of asm help, immediate doesn't like anything outside
of 1 byte, it seems. Any clues?

 arch/arm/include/asm/thread_info.h | 5 ++++-
 arch/arm/kernel/entry-common.S     | 9 ++++++---
 arch/arm/kernel/signal.c           | 2 +-
 3 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/arch/arm/include/asm/thread_info.h b/arch/arm/include/asm/thread_info.h
index 536b6b979f63..fec16d770180 100644
--- a/arch/arm/include/asm/thread_info.h
+++ b/arch/arm/include/asm/thread_info.h
@@ -135,6 +135,7 @@ extern int vfp_restore_user_hwstate(struct user_vfp *,
 #define TIF_SYSCALL_AUDIT	5	/* syscall auditing active */
 #define TIF_SYSCALL_TRACEPOINT	6	/* syscall tracepoint instrumentation */
 #define TIF_SECCOMP		7	/* seccomp syscall filtering active */
+#define TIF_NOTIFY_SIGNAL	8	/* signal notifications exist */
 
 #define TIF_USING_IWMMXT	17
 #define TIF_MEMDIE		18	/* is terminating due to OOM killer */
@@ -148,6 +149,7 @@ extern int vfp_restore_user_hwstate(struct user_vfp *,
 #define _TIF_SYSCALL_AUDIT	(1 << TIF_SYSCALL_AUDIT)
 #define _TIF_SYSCALL_TRACEPOINT	(1 << TIF_SYSCALL_TRACEPOINT)
 #define _TIF_SECCOMP		(1 << TIF_SECCOMP)
+#define _TIF_NOTIFY_SIGNAL	(1 << TIF_NOTIFY_SIGNAL)
 #define _TIF_USING_IWMMXT	(1 << TIF_USING_IWMMXT)
 
 /* Checks for any syscall work in entry-common.S */
@@ -158,7 +160,8 @@ extern int vfp_restore_user_hwstate(struct user_vfp *,
  * Change these and you break ASM code in entry-common.S
  */
 #define _TIF_WORK_MASK		(_TIF_NEED_RESCHED | _TIF_SIGPENDING | \
-				 _TIF_NOTIFY_RESUME | _TIF_UPROBE)
+				 _TIF_NOTIFY_RESUME | _TIF_UPROBE | \
+				 _TIF_NOTIFY_SIGNAL)
 
 #endif /* __KERNEL__ */
 #endif /* __ASM_ARM_THREAD_INFO_H */
diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S
index 271cb8a1eba1..7485b58673b4 100644
--- a/arch/arm/kernel/entry-common.S
+++ b/arch/arm/kernel/entry-common.S
@@ -53,7 +53,8 @@ __ret_fast_syscall:
 	cmp	r2, #TASK_SIZE
 	blne	addr_limit_check_failed
 	ldr	r1, [tsk, #TI_FLAGS]		@ re-check for syscall tracing
-	tst	r1, #_TIF_SYSCALL_WORK | _TIF_WORK_MASK
+	ldr	r2, =#_TIF_SYSCALL_WORK | _TIF_WORK_MASK
+	tst	r1, r2
 	bne	fast_work_pending
 
 
@@ -90,7 +91,8 @@ __ret_fast_syscall:
 	cmp	r2, #TASK_SIZE
 	blne	addr_limit_check_failed
 	ldr	r1, [tsk, #TI_FLAGS]		@ re-check for syscall tracing
-	tst	r1, #_TIF_SYSCALL_WORK | _TIF_WORK_MASK
+	ldr	r2, =#_TIF_SYSCALL_WORK | _TIF_WORK_MASK
+	tst	r1, r2
 	beq	no_work_pending
  UNWIND(.fnend		)
 ENDPROC(ret_fast_syscall)
@@ -131,7 +133,8 @@ ENTRY(ret_to_user_from_irq)
 	cmp	r2, #TASK_SIZE
 	blne	addr_limit_check_failed
 	ldr	r1, [tsk, #TI_FLAGS]
-	tst	r1, #_TIF_WORK_MASK
+	ldr	r2, =#_TIF_WORK_MASK
+	tst	r1, r2
 	bne	slow_work_pending
 no_work_pending:
 	asm_trace_hardirqs_on save = 0
diff --git a/arch/arm/kernel/signal.c b/arch/arm/kernel/signal.c
index 585edbfccf6d..9d2e916121be 100644
--- a/arch/arm/kernel/signal.c
+++ b/arch/arm/kernel/signal.c
@@ -655,7 +655,7 @@ do_work_pending(struct pt_regs *regs, unsigned int thread_flags, int syscall)
 			if (unlikely(!user_mode(regs)))
 				return 0;
 			local_irq_enable();
-			if (thread_flags & _TIF_SIGPENDING) {
+			if (thread_flags & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL)) {
 				int restart = do_signal(regs, syscall);
 				if (unlikely(restart)) {
 					/*
-- 
2.29.0

-- 
Jens Axboe


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