From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id BB162CD3427 for ; Mon, 11 May 2026 03:18:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:CC:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=XCvSTEjCOYEmY0eytTTIRnXZbs/A9bXSVn9+vYOCfiM=; b=SbfZx65eB6o35LXBP15K0X4muh DVrkwDCxdN+JnYX4j8dgVwKbUQo7hlOkNPf69mjmZdvcwifqFTpTA1EJTYdBUESOavQ1c3k81xcBZ kUjvRQ7SSJK6X5orsoEs5duBwOdwVEI+C7TjSGVy2ZPpocWG65aHsrBD0n43iHE6bOUGVaNmkg98p XzwUMUOFeMtGdbc6/ZVv3DoplBHR/ukPvMshYOrG4F8MezxP72yC6+vRxbYqjjyoRS22At6Roc9D3 6bFmZYFRowD9B4ClwJLnMgSPYwu3RPSXQXCa/sCD7N2TjbgLkK/2+opgRv89WVmQRWjIJa5mvadAx n6mXWt5Q==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wMHAH-0000000C9fZ-2t63; Mon, 11 May 2026 03:18:41 +0000 Received: from canpmsgout04.his.huawei.com ([113.46.200.219]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1wMHAE-0000000C9df-1KOV for linux-arm-kernel@lists.infradead.org; Mon, 11 May 2026 03:18:40 +0000 dkim-signature: v=1; a=rsa-sha256; d=huawei.com; s=dkim; c=relaxed/relaxed; q=dns/txt; h=From; bh=XCvSTEjCOYEmY0eytTTIRnXZbs/A9bXSVn9+vYOCfiM=; b=OD3Pg+lveGRtHLEsb8h+RiK9poIiBwxtrSBg3CeRa2T3mhjkdWiVgqEEpfkPcxJJ5//1KbwYD DtPusXqr3365LHD7UmIuUEuFGCMvE8FB1ZBgy49Pr2WdzVeQ9IA2wYoNTxaArfhNL3lvCo973sj P96qW5N3W7rX5JxLSwtOiPg= Received: from mail.maildlp.com (unknown [172.19.163.0]) by canpmsgout04.his.huawei.com (SkyGuard) with ESMTPS id 4gDPqx5L5gz1prxP; Mon, 11 May 2026 11:10:53 +0800 (CST) Received: from dggpemf500011.china.huawei.com (unknown [7.185.36.131]) by mail.maildlp.com (Postfix) with ESMTPS id 0627A40537; Mon, 11 May 2026 11:18:32 +0800 (CST) Received: from [10.67.109.254] (10.67.109.254) by dggpemf500011.china.huawei.com (7.185.36.131) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Mon, 11 May 2026 11:18:31 +0800 Message-ID: <54ffcf73-dfc5-417c-b9d5-6dee551f8d39@huawei.com> Date: Mon, 11 May 2026 11:18:31 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCHv2] arm64/entry: Fix arm64-specific rseq brokenness To: Mark Rutland , , Catalin Marinas , Peter Zijlstra , Thomas Gleixner , Will Deacon CC: , , , , References: <20260508142023.3268622-1-mark.rutland@arm.com> From: Jinjie Ruan In-Reply-To: <20260508142023.3268622-1-mark.rutland@arm.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.67.109.254] X-ClientProxiedBy: kwepems100001.china.huawei.com (7.221.188.238) To dggpemf500011.china.huawei.com (7.185.36.131) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260510_201838_674105_B7DD22B7 X-CRM114-Status: GOOD ( 40.92 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 5/8/2026 10:20 PM, Mark Rutland wrote: > Hi, > > In all the confusion with the rseq fixes, it looks like the arm64 patch > didn't get picked up into the tip tree. That was queued up in Thomas's > devel/core/rseq branch, but it didn't get reposted and picked up into > tip. > > Thomas, Peter, are you happy to pick the below into the tip sched/urgent > branch? It's the same as what what in Thomas's devel/core/rseq branch: > > https://git.kernel.org/pub/scm/linux/kernel/git/tglx/devel.git/commit/?h=core/rseq&id=04db289d5633dad546a0778537f0f0e52ebfc88b > > ... which was taken from my arm64/rseq branch: > > https://git.kernel.org/pub/scm/linux/kernel/git/mark/linux.git/commit/?h=arm64/rseq&id=05bce437d4f2fd14a7be4706c684a618e2fcc82f > > It applies cleanly and passes all tests. > > Catalin, Will, you both mentioned off-list that you were happy for this > to go via tip with the rest of the rseq fixes. Can either of you please > confirm with an ack? > > Mark. > > ---->8---- > Mathias Stearn reports that since v6.19, there are two big issues > affecting rseq: > > (1) On arm64 specifically, rseq critical sections aren't aborted when > they should be. > > (2) The 'cpu_id_start' field is no longer written by the kernel in all > cases it used to be, including some cases where TCMalloc depends on > the kernel clobbering the field. > > This patch fixes issue #1. This patch DOES NOT fix issue #2, which will > need to be addressed by other patches. > > The arm64-specific brokenness is a result of commits: > > 2fc0e4b4126c ("rseq: Record interrupt from user space") > 39a167560a61 ("rseq: Optimize event setting") > > The first commit failed to add a call to rseq_note_user_irq_entry() on > arm64. Thus arm64 never sets rseq_event::user_irq to record that it may > be necessary to abort an active rseq critical section upon return to > userspace. On its own, this commit had no functional impact as the value > of rseq_event::user_irq was not consumed. > > The second commit relied upon rseq_event::user_irq to determine whether > or not to bother to perform rseq work when returning to userspace. As > rseq_event::user_irq wasn't set on arm64, this work would be skipped, > and consequently an active rseq critical section would not be aborted. > > Fix this by giving arm64 syscall-specific entry/exit paths, and > performing the relevant logic in syscall and non-syscall paths, > including calling rseq_note_user_irq_entry() for non-syscall entry. > > Currently arm64 cannot use syscall_enter_from_user_mode(), > syscall_exit_to_user_mode(), and irqentry_exit_to_user_mode(), due to > ordering constraints with exception masking, and risk of ABI breakage > for syscall tracing/audit/etc. For the moment the entry/exit logic is > left as arm64-specific, directly using enter_from_user_mode() and > exit_to_user_mode(), but mirroring the generic code. > > I intend to follow up with refactoring/cleanup, as we did for kernel > mode entry paths in commit: > > 041aa7a85390 ("entry: Split preemption from irqentry_exit_to_kernel_mode()") > > ... which will allow arm64 to use the GENERIC_IRQ_ENTRY functions directly. > > Fixes: 39a167560a61 ("rseq: Optimize event setting") > Reported-by: Mathias Stearn > Link: https://lore.kernel.org/regressions/CAHnCjA25b+nO2n5CeifknSKHssJpPrjnf+dtr7UgzRw4Zgu=oA@mail.gmail.com/ > Signed-off-by: Mark Rutland > Cc: Catalin Marinas > Cc: Chris Kennelly > Cc: Dmitry Vyukov > Cc: Jinjie Ruan > Cc: Mathieu Desnoyers > Cc: Peter Zijlstra > Cc: Thomas Gleixner > Cc: Will Deacon > --- > arch/arm64/kernel/entry-common.c | 31 ++++++++++++++++++++++++------- > include/linux/irq-entry-common.h | 8 -------- > include/linux/rseq_entry.h | 19 ------------------- > 3 files changed, 24 insertions(+), 34 deletions(-) > > Since v1 [1]: > * Restore sme_{enter_from,exit_to}_user_mode() > * Describe use of enter_from_user_mode() in commit message Reviewed-by: Jinjie Ruan > > [1] https://lore.kernel.org/linux-arm-kernel/aeueE1I1OuVkOcEZ@J2N7QTR9R3/ > > diff --git a/arch/arm64/kernel/entry-common.c b/arch/arm64/kernel/entry-common.c > index cb54335465f66..c7a23f7c22122 100644 > --- a/arch/arm64/kernel/entry-common.c > +++ b/arch/arm64/kernel/entry-common.c > @@ -62,6 +62,13 @@ static void noinstr arm64_exit_to_kernel_mode(struct pt_regs *regs, > irqentry_exit_to_kernel_mode_after_preempt(regs, state); > } > > +static __always_inline void arm64_syscall_enter_from_user_mode(struct pt_regs *regs) > +{ > + enter_from_user_mode(regs); > + mte_disable_tco_entry(current); > + sme_enter_from_user_mode(); > +} > + > /* > * Handle IRQ/context state management when entering from user mode. > * Before this function is called it is not safe to call regular kernel code, > @@ -70,20 +77,30 @@ static void noinstr arm64_exit_to_kernel_mode(struct pt_regs *regs, > static __always_inline void arm64_enter_from_user_mode(struct pt_regs *regs) > { > enter_from_user_mode(regs); > + rseq_note_user_irq_entry(); > mte_disable_tco_entry(current); > sme_enter_from_user_mode(); > } > > +static __always_inline void arm64_syscall_exit_to_user_mode(struct pt_regs *regs) > +{ > + local_irq_disable(); > + syscall_exit_to_user_mode_prepare(regs); > + local_daif_mask(); > + sme_exit_to_user_mode(); > + mte_check_tfsr_exit(); > + exit_to_user_mode(); > +} > + > /* > * Handle IRQ/context state management when exiting to user mode. > * After this function returns it is not safe to call regular kernel code, > * instrumentable code, or any code which may trigger an exception. > */ > - > static __always_inline void arm64_exit_to_user_mode(struct pt_regs *regs) > { > local_irq_disable(); > - exit_to_user_mode_prepare_legacy(regs); > + irqentry_exit_to_user_mode_prepare(regs); > local_daif_mask(); > sme_exit_to_user_mode(); > mte_check_tfsr_exit(); > @@ -92,7 +109,7 @@ static __always_inline void arm64_exit_to_user_mode(struct pt_regs *regs) > > asmlinkage void noinstr asm_exit_to_user_mode(struct pt_regs *regs) > { > - arm64_exit_to_user_mode(regs); > + arm64_syscall_exit_to_user_mode(regs); > } > > /* > @@ -716,12 +733,12 @@ static void noinstr el0_brk64(struct pt_regs *regs, unsigned long esr) > > static void noinstr el0_svc(struct pt_regs *regs) > { > - arm64_enter_from_user_mode(regs); > + arm64_syscall_enter_from_user_mode(regs); > cortex_a76_erratum_1463225_svc_handler(); > fpsimd_syscall_enter(); > local_daif_restore(DAIF_PROCCTX); > do_el0_svc(regs); > - arm64_exit_to_user_mode(regs); > + arm64_syscall_exit_to_user_mode(regs); > fpsimd_syscall_exit(); > } > > @@ -868,11 +885,11 @@ static void noinstr el0_cp15(struct pt_regs *regs, unsigned long esr) > > static void noinstr el0_svc_compat(struct pt_regs *regs) > { > - arm64_enter_from_user_mode(regs); > + arm64_syscall_enter_from_user_mode(regs); > cortex_a76_erratum_1463225_svc_handler(); > local_daif_restore(DAIF_PROCCTX); > do_el0_svc_compat(regs); > - arm64_exit_to_user_mode(regs); > + arm64_syscall_exit_to_user_mode(regs); > } > > static void noinstr el0_bkpt32(struct pt_regs *regs, unsigned long esr) > diff --git a/include/linux/irq-entry-common.h b/include/linux/irq-entry-common.h > index 167fba7dbf043..1fabf0f5ea8e7 100644 > --- a/include/linux/irq-entry-common.h > +++ b/include/linux/irq-entry-common.h > @@ -218,14 +218,6 @@ static __always_inline void __exit_to_user_mode_validate(void) > lockdep_sys_exit(); > } > > -/* Temporary workaround to keep ARM64 alive */ > -static __always_inline void exit_to_user_mode_prepare_legacy(struct pt_regs *regs) > -{ > - __exit_to_user_mode_prepare(regs, EXIT_TO_USER_MODE_WORK); > - rseq_exit_to_user_mode_legacy(); > - __exit_to_user_mode_validate(); > -} > - > /** > * syscall_exit_to_user_mode_prepare - call exit_to_user_mode_loop() if required > * @regs: Pointer to pt_regs on entry stack > diff --git a/include/linux/rseq_entry.h b/include/linux/rseq_entry.h > index 2d0295df5107c..63bc72086e75b 100644 > --- a/include/linux/rseq_entry.h > +++ b/include/linux/rseq_entry.h > @@ -749,24 +749,6 @@ static __always_inline void rseq_irqentry_exit_to_user_mode(void) > ev->events = 0; > } > > -/* Required to keep ARM64 working */ > -static __always_inline void rseq_exit_to_user_mode_legacy(void) > -{ > - struct rseq_event *ev = ¤t->rseq.event; > - > - rseq_stat_inc(rseq_stats.exit); > - > - if (static_branch_unlikely(&rseq_debug_enabled)) > - WARN_ON_ONCE(ev->sched_switch); > - > - /* > - * Ensure that event (especially user_irq) is cleared when the > - * interrupt did not result in a schedule and therefore the > - * rseq processing did not clear it. > - */ > - ev->events = 0; > -} > - > void __rseq_debug_syscall_return(struct pt_regs *regs); > > static __always_inline void rseq_debug_syscall_return(struct pt_regs *regs) > @@ -782,7 +764,6 @@ static inline bool rseq_exit_to_user_mode_restart(struct pt_regs *regs, unsigned > } > static inline void rseq_syscall_exit_to_user_mode(void) { } > static inline void rseq_irqentry_exit_to_user_mode(void) { } > -static inline void rseq_exit_to_user_mode_legacy(void) { } > static inline void rseq_debug_syscall_return(struct pt_regs *regs) { } > static inline bool rseq_grant_slice_extension(unsigned long ti_work, unsigned long mask) { return false; } > #endif /* !CONFIG_RSEQ */