[PATCH] arm: add support for TIF_NOTIFY_SIGNAL

Tue Nov 3 10:11:49 EST 2020

On 10/29/20 11:42 AM, Russell King - ARM Linux admin wrote:
> On Thu, Oct 29, 2020 at 11:20:07AM -0600, Jens Axboe wrote:
>> On 10/29/20 11:17 AM, Russell King - ARM Linux admin wrote:
>>> On Thu, Oct 29, 2020 at 11:15:37AM -0600, Jens Axboe wrote:
>>>> How about this?
>>>>
>>>> commit c03932936d8f99ff7c1c6c7d984e7a457284396c
>>>> Author: Jens Axboe <axboe at 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 at lists.infradead.org
>>>>     Signed-off-by: Jens Axboe <axboe at 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?
>>
>> Great! Thanks for your expedient attention and help.
>>
>> The bits using this are queued in tip for 5.11, so not in mainline yet,
>> but should be in linux-next tomorrow I guess. But it was done such that
>> arch patches could be queued up independently, so we didn't have weird
>> cross dependencies.
> 
> Okay, I'll wait a few days and see about temporarily dumping it in
> my for-next branch so it gets a spin through kernelci next week.
> I'm not anticipating any breakage, so (if I remember) I'll give you
> a reviewed-by next week once it seems good. As I say, if I remember.

Russell, did you have a chance to run it through the machinery?

-- 
Jens Axboe