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Received: from shell.armlinux.org.uk ([fd8f:7570:feb6:1:5054:ff:fe00:4ec]:52532) by pandora.armlinux.org.uk with esmtpsa (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1kYAnv-0004eC-8d; Thu, 29 Oct 2020 16:29:35 +0000 Received: from linux by shell.armlinux.org.uk with local (Exim 4.92) (envelope-from ) id 1kYAnu-0006HL-Px; Thu, 29 Oct 2020 16:29:34 +0000 Date: Thu, 29 Oct 2020 16:29:34 +0000 From: Russell King - ARM Linux admin To: Jens Axboe Subject: Re: [PATCH] arm: add support for TIF_NOTIFY_SIGNAL Message-ID: <20201029162934.GX1551@shell.armlinux.org.uk> References: <3c1ebfa5-38d9-e6b2-fcf7-d8b17c0fa515@kernel.dk> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <3c1ebfa5-38d9-e6b2-fcf7-d8b17c0fa515@kernel.dk> User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201029_122937_581566_421FE221 X-CRM114-Status: GOOD ( 24.33 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "linux-arm-kernel@lists.infradead.org" Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, Oct 29, 2020 at 10:11:07AM -0600, Jens Axboe wrote: > Wire up TIF_NOTIFY_SIGNAL handling for arm. > > Cc: linux-arm-kernel@lists.infradead.org > Signed-off-by: Jens Axboe > --- > > 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? Correct - immediates take an 8 bit value shifted by an even number of bits. I'm tempted to suggest that we simplify things by making TIF bits 0..15 invoke do_work_pending() no matter what - which will require a comment in thread_info.h that all those bits will have that effect. The resulting assembly would be: ldr r1, [tsk, #TI_FLAGS] @ re-check for syscall tracing - tst r1, #_TIF_SYSCALL_WORK | _TIF_WORK_MASK + movs r1, r1, lsl #16 which avoids the additional load caused by "ldr r2, =..." It's not like we're desperate for bits here. Further comments below if we don't decide on that approach... > > 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 No # required. > + 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 Ditto. > + 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 Ditto. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 40Mbps down 10Mbps up. 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