Re: [PATCH] arm: add support for TIF_NOTIFY_SIGNAL

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

On Thu, Oct 29, 2020 at 11:20:07AM -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@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.

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.

Thanks.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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