Re: [PATCH] arm: add support for TIF_NOTIFY_SIGNAL

[Jens Axboe <axboe@kernel.dk>]

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@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?

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.

-- 
Jens Axboe


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