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 27CD1CEDD90 for ; Wed, 9 Oct 2024 13:11:55 +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:In-Reply-To: Content-Transfer-Encoding:Content-Type: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=+oIM/6L1ddZ9+w8/ibHsXts4Y3ZIuRGcRD4FqkptLws=; b=eFu4rMe+Dp7LlPf4tfneNoPsZd WaY76Ux5+bnbyVNoJUzkkKZn02DnK/TZGjvTrjcVUe6Jo9dQ/+pgrrrjYTS0vVbIBowJGV2Q5KBZF Fve+L6hi3dxLGpNqi88sAVYchYiYRGoeUEWn66nYInD3lXBxPOzSN986TA4s5YkCUmUlwTfpgsZcP /KwYACAUTialWsSDjIf+lREZgKETP0f6JgQTbjH2niPub8d/Bctk9GSA9ATLJSv1ub5XqlUOv2TAV QDkV6QHpzTCt2x8wkHEd51UYWUyvFm5HAH8m72uQV/JYoc7+50500yDE1Y3mr0mWd+iPqaEUfb0lg JUe9W5HA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1syWTd-00000009MDv-2ruu; Wed, 09 Oct 2024 13:11:41 +0000 Received: from nyc.source.kernel.org ([147.75.193.91]) by bombadil.infradead.org with esmtps (Exim 4.98 #2 (Red Hat Linux)) id 1syWSH-00000009M2w-3Q7d for linux-arm-kernel@lists.infradead.org; Wed, 09 Oct 2024 13:10:19 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by nyc.source.kernel.org (Postfix) with ESMTP id 1E0E0A4314E; Wed, 9 Oct 2024 13:10:08 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 99636C4CEC5; Wed, 9 Oct 2024 13:10:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1728479416; bh=3rSk0qpMy3mRiaF8HFu8PwiCPAK8Cf3r5DxZutgdUBM=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=dfFPoU37rt3pJvQ42mzAS+9f4v18U+dqeeaV9a4URYhutlLffKuInN0zqt+3Jsxpb Qjvcr5iqzzwC2PLKNUpvkve7KhykeKSTFQRvUceuQS34e2vaQQ92uj1tQSy1sXR4A0 v7pRy9PD6lPq61d1JLkVZHEZE1I3hcFmF39bMwx3ycVnH/gOX+bWBV2tP6FQ/fXWoy y3F0l5swnwgmtQFnQwO/XwulXBsOnZCnvIiFJDJnHuvg3+3GwOkKej5oSzF7zlCYcX sQvoVyIEGs17g21lNOgBoUKiEXs7cXhs2vCClkWB19p83dKZt37BO/YNgB/aOwLlOk R3QqAJfGpJwCA== Date: Wed, 9 Oct 2024 15:10:11 +0200 From: Lorenzo Pieralisi To: Marc Zyngier Cc: Zheng Zengkai , guohanjun@huawei.com, sudeep.holla@arm.com, mark.rutland@arm.com, rafael@kernel.org, lenb@kernel.org, daniel.lezcano@linaro.org, tglx@linutronix.de, linux-acpi@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] ACPI: GTDT: simplify acpi_gtdt_init() implementation Message-ID: References: <20241008082429.33646-1-zhengzengkai@huawei.com> <86v7y355zr.wl-maz@kernel.org> <57e9adb8-a34a-6d63-24b8-4ad0abb74bf9@huawei.com> <86r08p5x4g.wl-maz@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <86r08p5x4g.wl-maz@kernel.org> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20241009_061018_040982_41DA4840 X-CRM114-Status: GOOD ( 46.34 ) 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 Wed, Oct 09, 2024 at 12:33:35PM +0100, Marc Zyngier wrote: > On Tue, 08 Oct 2024 15:04:52 +0100, > Zheng Zengkai wrote: > > > > > > 在 2024/10/8 16:55, Marc Zyngier 写道: > > > On Tue, 08 Oct 2024 09:24:29 +0100, > > > Zheng Zengkai wrote: > > >> According to GTDT Table Structure of ACPI specification, the result of > > >> expression '(void *)gtdt + gtdt->platform_timer_offset' will be same > > >> with the expression '(void *)table + sizeof(struct acpi_table_gtdt)' > > > There is no such language in the spec. It simply says "Offset to the > > > Platform Timer Structure[] array from the start of this table". > > OK, I mean that in current code, the condition of this check is redundant. > > That's not my reading if it. Where do you see another validity check > that makes this one superfluous? > > > >> in function acpi_gtdt_init(), so the condition of the "invalid timer > > >> data" check will never be true, remove the EINVAL error check branch > > >> and change to void return type for acpi_gtdt_init() to simplify the > > >> function implementation and error handling by callers. > > > And ACPI tables are well known to be always correct, right? > > Not always, check is needed, but should be changed. > > You are not changing it, you are getting rid of it, and I don't see > you replacing it with anything else. > > > >> Besides, after commit c2743a36765d ("clocksource: arm_arch_timer: add > > >> GTDT support for memory-mapped timer"), acpi_gtdt_init() currently will > > >> not be called with parameter platform_timer_count set to NULL and we > > >> can explicitly initialize the integer variable which is used for storing > > >> the number of platform timers by caller to zero, so there is no need to > > >> do null pointer check for platform_timer_count in acpi_gtdt_init(), > > >> remove it to make code a bit more concise. > > >> > > >> Signed-off-by: Zheng Zengkai > > >> --- > > >> Changes in v2: > > >> - initialize 'ret' in gtdt_sbsa_gwdt_init() to silence build warning > > >> > > >> v1: https://lore.kernel.org/all/20240930030716.179992-1-zhengzengkai@huawei.com/ > > >> --- > > >> drivers/acpi/arm64/gtdt.c | 31 +++++++--------------------- > > >> drivers/clocksource/arm_arch_timer.c | 6 ++---- > > >> include/linux/acpi.h | 2 +- > > >> 3 files changed, 11 insertions(+), 28 deletions(-) > > >> > > >> diff --git a/drivers/acpi/arm64/gtdt.c b/drivers/acpi/arm64/gtdt.c > > >> index c0e77c1c8e09..7fe27c0edde7 100644 > > >> --- a/drivers/acpi/arm64/gtdt.c > > >> +++ b/drivers/acpi/arm64/gtdt.c > > >> @@ -147,45 +147,30 @@ bool __init acpi_gtdt_c3stop(int type) > > >> * @table: The pointer to GTDT table. > > >> * @platform_timer_count: It points to a integer variable which is used > > >> * for storing the number of platform timers. > > >> - * This pointer could be NULL, if the caller > > >> - * doesn't need this info. > > >> - * > > >> - * Return: 0 if success, -EINVAL if error. > > >> */ > > >> -int __init acpi_gtdt_init(struct acpi_table_header *table, > > >> +void __init acpi_gtdt_init(struct acpi_table_header *table, > > >> int *platform_timer_count) > > >> { > > >> - void *platform_timer; > > >> struct acpi_table_gtdt *gtdt; > > >> gtdt = container_of(table, struct acpi_table_gtdt, header); > > >> acpi_gtdt_desc.gtdt = gtdt; > > >> acpi_gtdt_desc.gtdt_end = (void *)table + table->length; > > >> acpi_gtdt_desc.platform_timer = NULL; > > >> - if (platform_timer_count) > > >> - *platform_timer_count = 0; > > >> if (table->revision < 2) { > > >> pr_warn("Revision:%d doesn't support Platform Timers.\n", > > >> table->revision); > > >> - return 0; > > >> + return; > > >> } > > >> if (!gtdt->platform_timer_count) { > > >> pr_debug("No Platform Timer.\n"); > > >> - return 0; > > >> + return; > > >> } > > >> - platform_timer = (void *)gtdt + gtdt->platform_timer_offset; > > >> - if (platform_timer < (void *)table + sizeof(struct acpi_table_gtdt)) { > > >> - pr_err(FW_BUG "invalid timer data.\n"); > > >> - return -EINVAL; > > >> - } > > >> - acpi_gtdt_desc.platform_timer = platform_timer; > > >> - if (platform_timer_count) > > >> - *platform_timer_count = gtdt->platform_timer_count; > > >> - > > >> - return 0; > > >> + acpi_gtdt_desc.platform_timer = (void *)gtdt + gtdt->platform_timer_offset; > > > And now you are trusting something that potentially points to some > > > unexpected location, blindly using it. It is bad enough that the > > > current checks are pretty poor (no check against the end of the > > > table for the first timer entry), but you are making it worse. > > > > > > M. > > > > Can I use the second and third bytes (the length) of platform timer > > structure to check against the end of the table ? > > That's how it is supposed to be done indeed. AFAICS I think first we need to check whether the platform_timer pointer is within gtdt bounds (< gtdt_end) before de-referencing what it points at to detect the (first) GT entry length and check that it is within gtdt_end too. We do that only in next_platform_timer() for subsequent GT blocks. I agree with Marc, current check is fine, we should add to it, not remove it. Thanks, Lorenzo