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 D50EEC5479D for ; Mon, 9 Jan 2023 13:28:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=rFKzmaaptb5L20oV+TI0ezesxI3pCejU/aPdpmVG/p4=; b=c3gNN7ZmPmLNy/ bnLnBI4ITXTqpeOPHijaNa9l7ZnPfFOZu8tWRHlz5g5xGWgt9ylpDKvDVb3YJ0vxvlCI48Rtrdg/m prj4v5OOGRnEPPBR2GdpeqsrGO+9bkyY38DzdHuk/OmWIPL9+WMvf0xmEMIBHgzEtbCdUQQZS7BcA ydQYT3TYDmO8clMkrkxXT3i670LOGy2AqNLmaXTSGxnnnJcZEK7LWABS25kSK5vYOi7DY7voNfIEn kcT4LnXbvo3Ijbl06w5nT+6NkSCdA4VJrU9htnto++rFGqoVK5MQme1uNOz2bdU8cz/jl/mXU6kC+ /X8V6bLSXZ/Taju1/AiA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1pEsB6-001a5g-Jo; Mon, 09 Jan 2023 13:27:04 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1pEsB0-001a1H-K1 for linux-arm-kernel@lists.infradead.org; Mon, 09 Jan 2023 13:27:00 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id E3D7DC14; Mon, 9 Jan 2023 05:27:32 -0800 (PST) Received: from FVFF77S0Q05N (unknown [10.57.46.123]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id D5C833F23F; Mon, 9 Jan 2023 05:26:49 -0800 (PST) Date: Mon, 9 Jan 2023 13:26:43 +0000 From: Mark Rutland To: Ard Biesheuvel Cc: linux-efi@vger.kernel.org, linux-arm-kernel@lists.infradead.org, will@kernel.org, catalin.marinas@arm.com, Lee Jones Subject: Re: [PATCH v3 1/2] arm64: efi: Avoid workqueue to check whether EFI runtime is live Message-ID: References: <20230106174703.1883495-1-ardb@kernel.org> <20230106174703.1883495-2-ardb@kernel.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20230106174703.1883495-2-ardb@kernel.org> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230109_052658_823538_DE0F66F6 X-CRM114-Status: GOOD ( 21.50 ) 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: , 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 Fri, Jan 06, 2023 at 06:47:02PM +0100, Ard Biesheuvel wrote: > Comparing current_work() against efi_rts_work.work is sufficient to > decide whether current is currently running EFI runtime services code at > any level in its call stack. > > However, there are other potential users of the EFI runtime stack, such > as the ACPI subsystem, which may invoke efi_call_virt_pointer() > directly, and so any sync exceptions occurring in firmware during those > calls are currently misidentified. > > So instead, let's check whether 'current' has preemption disabled, and > whether the stashed value of the thread stack pointer points into > current's thread stack. This can only be the case if current was > interrupted while running EFI runtime code. This implies that we should > clear the stashed value after switching back, to avoid false positives. > > Signed-off-by: Ard Biesheuvel Reviewed-by: Mark Rutland Thanks for this! Mark. > --- > arch/arm64/include/asm/efi.h | 9 +++++++++ > arch/arm64/kernel/efi-rt-wrapper.S | 6 ++++++ > arch/arm64/kernel/efi.c | 3 ++- > 3 files changed, 17 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/include/asm/efi.h b/arch/arm64/include/asm/efi.h > index 31d13a6001df49c4..f68d13c3a44e7bb2 100644 > --- a/arch/arm64/include/asm/efi.h > +++ b/arch/arm64/include/asm/efi.h > @@ -48,8 +48,17 @@ int efi_set_mapping_permissions(struct mm_struct *mm, efi_memory_desc_t *md); > }) > > extern spinlock_t efi_rt_lock; > +extern u64 *efi_rt_stack_top; > efi_status_t __efi_rt_asm_wrapper(void *, const char *, ...); > > +/* > + * efi_rt_stack_top[-1] contains the value the stack pointer had before > + * switching to the EFI runtime stack. > + */ > +#define current_in_efi() \ > + (!preemptible() && \ > + on_task_stack(current, READ_ONCE(efi_rt_stack_top[-1]), 1)) > + > #define ARCH_EFI_IRQ_FLAGS_MASK (PSR_D_BIT | PSR_A_BIT | PSR_I_BIT | PSR_F_BIT) > > /* > diff --git a/arch/arm64/kernel/efi-rt-wrapper.S b/arch/arm64/kernel/efi-rt-wrapper.S > index a00886410537d6a6..11f3ec9f09e86de6 100644 > --- a/arch/arm64/kernel/efi-rt-wrapper.S > +++ b/arch/arm64/kernel/efi-rt-wrapper.S > @@ -45,7 +45,10 @@ SYM_FUNC_START(__efi_rt_asm_wrapper) > mov x4, x6 > blr x8 > > + mov x16, sp > mov sp, x29 > + str xzr, [x16, #8] // clear recorded task SP value > + > ldp x1, x2, [sp, #16] > cmp x2, x18 > ldp x29, x30, [sp], #112 > @@ -70,6 +73,9 @@ SYM_FUNC_END(__efi_rt_asm_wrapper) > SYM_CODE_START(__efi_rt_asm_recover) > mov sp, x30 > > + ldr_l x16, efi_rt_stack_top // clear recorded task SP value > + str xzr, [x16, #-8] > + > ldp x19, x20, [sp, #32] > ldp x21, x22, [sp, #48] > ldp x23, x24, [sp, #64] > diff --git a/arch/arm64/kernel/efi.c b/arch/arm64/kernel/efi.c > index fab05de2e12dd5d8..b273900f45668587 100644 > --- a/arch/arm64/kernel/efi.c > +++ b/arch/arm64/kernel/efi.c > @@ -11,6 +11,7 @@ > #include > > #include > +#include > > static bool region_is_misaligned(const efi_memory_desc_t *md) > { > @@ -154,7 +155,7 @@ asmlinkage efi_status_t __efi_rt_asm_recover(void); > bool efi_runtime_fixup_exception(struct pt_regs *regs, const char *msg) > { > /* Check whether the exception occurred while running the firmware */ > - if (current_work() != &efi_rts_work.work || regs->pc >= TASK_SIZE_64) > + if (!current_in_efi() || regs->pc >= TASK_SIZE_64) > return false; > > pr_err(FW_BUG "Unable to handle %s in EFI runtime service\n", msg); > -- > 2.39.0 > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel