Re: [PATCH] arm: add support for TIF_NOTIFY_SIGNAL

[Russell King - ARM Linux admin <linux@armlinux.org.uk>]

On Thu, Oct 29, 2020 at 11:15:37AM -0600, Jens Axboe wrote:
> How about this?
> 
> commit c03932936d8f99ff7c1c6c7d984e7a457284396c
> Author: Jens Axboe <axboe@kernel.dk>
> Date:   Fri Oct 9 16:00:49 2020 -0600
> 
>     arm: add support for TIF_NOTIFY_SIGNAL
>     
>     Wire up TIF_NOTIFY_SIGNAL handling for arm.
>     
>     Cc: linux-arm-kernel@lists.infradead.org
>     Signed-off-by: Jens Axboe <axboe@kernel.dk>
> 
> diff --git a/arch/arm/include/asm/thread_info.h b/arch/arm/include/asm/thread_info.h
> index 536b6b979f63..eb7ce2747eb0 100644
> --- a/arch/arm/include/asm/thread_info.h
> +++ b/arch/arm/include/asm/thread_info.h
> @@ -126,6 +126,8 @@ extern int vfp_restore_user_hwstate(struct user_vfp *,
>   * thread information flags:
>   *  TIF_USEDFPU		- FPU was used by this task this quantum (SMP)
>   *  TIF_POLLING_NRFLAG	- true if poll_idle() is polling TIF_NEED_RESCHED
> + *
> + * Any bit in the range of 0..15 will cause do_work_pending() to be invoked.
>   */
>  #define TIF_SIGPENDING		0	/* signal pending */
>  #define TIF_NEED_RESCHED	1	/* rescheduling necessary */
> @@ -135,6 +137,7 @@ 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 +151,7 @@ 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 +162,8 @@ 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..77d16390a524 100644
> --- a/arch/arm/kernel/entry-common.S
> +++ b/arch/arm/kernel/entry-common.S
> @@ -53,7 +53,7 @@ __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
> +	movs	r1, r1, lsl #16
>  	bne	fast_work_pending
>  
>  
> @@ -90,7 +90,7 @@ __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
> +	movs	r1, r1, lsl #16
>  	beq	no_work_pending
>   UNWIND(.fnend		)
>  ENDPROC(ret_fast_syscall)
> @@ -131,7 +131,7 @@ 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
> +	movs	r1, r1, lsl #16
>  	bne	slow_work_pending
>  no_work_pending:
>  	asm_trace_hardirqs_on save = 0
> diff --git a/arch/arm/kernel/entry-v7m.S b/arch/arm/kernel/entry-v7m.S
> index de1f20624be1..d0e898608d30 100644
> --- a/arch/arm/kernel/entry-v7m.S
> +++ b/arch/arm/kernel/entry-v7m.S
> @@ -59,7 +59,7 @@ __irq_entry:
>  
>  	get_thread_info tsk
>  	ldr	r2, [tsk, #TI_FLAGS]
> -	tst	r2, #_TIF_WORK_MASK
> +	movs	r2, r2, lsl #16
>  	beq	2f			@ no work pending
>  	mov	r0, #V7M_SCB_ICSR_PENDSVSET
>  	str	r0, [r1, V7M_SCB_ICSR]	@ raise PendSV
> 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)) {
>  					/*
> 

Looks perfect to me, thanks! I assume the pre-requisits for this are
already in mainline or linux-next?

-- 
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