From patchwork Tue Dec 20 03:41:15 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Paulo Miguel Almeida X-Patchwork-Id: 13077496 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 gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (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 A55B8C4332F for ; Tue, 20 Dec 2022 03:41:34 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 3311310E067; Tue, 20 Dec 2022 03:41:32 +0000 (UTC) Received: from mail-pj1-x1036.google.com (mail-pj1-x1036.google.com [IPv6:2607:f8b0:4864:20::1036]) by gabe.freedesktop.org (Postfix) with ESMTPS id B442610E055; Tue, 20 Dec 2022 03:41:24 +0000 (UTC) Received: by mail-pj1-x1036.google.com with SMTP id w4-20020a17090ac98400b002186f5d7a4cso15238321pjt.0; Mon, 19 Dec 2022 19:41:24 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=content-disposition:mime-version:message-id:subject:cc:to:from:date :from:to:cc:subject:date:message-id:reply-to; bh=xVh7BhiLAFK1y5fgqjdCBQvyDDgKeEj33/rk76TBR5s=; b=eIyMUGuhIXBj94VjBrAUhYLj+94tayhIXD10HOZKzIQ6CrgTN/phMZCweKAwIaCB8k oamV0qlLPDCgbgw7XnOEvPb4i4TP9cIkGd0h5jj5uofBKK52E7+6LLxTAhvXfkmkIBip VSX/P9iBKBhYtqZnVypFSj6sPW0lssLLdT4W0nQg2vMyQGXiWd6B4I7Fkx++aZ6uiZoA BgE3YZdcwBbhaAOm9F0Z/X++ekd/r+gI3p14y42+3M4stYmaJu2zuHihydMPYqQgxlf0 a1c64nfggXO5y7B/yo7l9SuIvOrI0XMmDhcsfXkxUUYYMdTrJFeMwIoeTzYLQlXDqANx oUCg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-disposition:mime-version:message-id:subject:cc:to:from:date :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=xVh7BhiLAFK1y5fgqjdCBQvyDDgKeEj33/rk76TBR5s=; b=l5wsMSOqDSOK89ShuY6N0arp7H6RZ8wYzo70XeZyEt4koHIbEiunF7aZs2NVgRvpwz XVOjDD6snQKbWc8f9W8r5oX+tP/nTJLpfI6rwr4UC1UMjJMSLaPYkJO74huG6KbV86ql Jql/M+/rwN9rhuJkHVtPHd4SBUZPdu0u1qkIs4ddxyASXlOAzNwlcIFj28vIsJWPlg9R tAbEqS6exg7xzHUW8WGv+c0FXjWC/pleIv/kGJ9ss9/Fyhh2adPQM+1Yqtz0/jerxgeY NvjAswWv4zmjvGn0NWb9lWhHpQ7JYT1MraG3pbGpZt4692xzqgEqjFAI5QnyrEtdGm2j lDWQ== X-Gm-Message-State: ANoB5pl9kPdpp83nD8enBsSjd8HBUK6+PtWmIVXVoyBD4N+3mMPZnugo VylmvZKU4XcSK1+KP0zADOJp0jnzOdioO5IO X-Google-Smtp-Source: AA0mqf6scQ9/TUdhQyckyTVN2l+rTWw5xP6+kf2svgdOWFmDqEGeGWPdfv/YMte1IhWDSljq4EL8Fg== X-Received: by 2002:a17:902:6b08:b0:186:639f:6338 with SMTP id o8-20020a1709026b0800b00186639f6338mr11003150plk.6.1671507684172; Mon, 19 Dec 2022 19:41:24 -0800 (PST) Received: from mail.google.com (125-237-37-88-fibre.sparkbb.co.nz. [125.237.37.88]) by smtp.gmail.com with ESMTPSA id y16-20020a17090322d000b001896af10ca7sm7974566plg.134.2022.12.19.19.41.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 19 Dec 2022 19:41:23 -0800 (PST) Date: Tue, 20 Dec 2022 16:41:15 +1300 From: Paulo Miguel Almeida To: Zhenyu Wang , Zhi Wang , Jani Nikula , Joonas Lahtinen , Rodrigo Vivi , Tvrtko Ursulin , David Airlie , Daniel Vetter , intel-gvt-dev@lists.freedesktop.org, intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org Subject: [PATCH] [next] i915/gvt: Replace one-element array with flexible-array member Message-ID: MIME-Version: 1.0 Content-Disposition: inline X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: paulo.miguel.almeida.rodenas@gmail.com, linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" One-element arrays are deprecated, and we are replacing them with flexible array members instead. So, replace one-element array with flexible-array member in struct gvt_firmware_header and refactor the rest of the code accordingly. Additionally, previous implementation was allocating 8 bytes more than required to represent firmware_header + cfg_space data + mmio data. This helps with the ongoing efforts to tighten the FORTIFY_SOURCE routines on memcpy() and help us make progress towards globally enabling -fstrict-flex-arrays=3 [1]. Link: https://github.com/KSPP/linux/issues/79 Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101836 [1] Signed-off-by: Paulo Miguel Almeida Reviewed-by: Zhenyu Wang --- To make reviewing this patch easier, I'm pasting before/after struct sizes. pahole -C gvt_firmware_header before/drivers/gpu/drm/i915/gvt/firmware.o struct gvt_firmware_header { u64 magic; /* 0 8 */ u32 crc32; /* 8 4 */ u32 version; /* 12 4 */ u64 cfg_space_size; /* 16 8 */ u64 cfg_space_offset; /* 24 8 */ u64 mmio_size; /* 32 8 */ u64 mmio_offset; /* 40 8 */ unsigned char data[1]; /* 48 1 */ /* size: 56, cachelines: 1, members: 8 */ /* padding: 7 */ /* last cacheline: 56 bytes */ }; pahole -C gvt_firmware_header after/drivers/gpu/drm/i915/gvt/firmware.o struct gvt_firmware_header { u64 magic; /* 0 8 */ u32 crc32; /* 8 4 */ u32 version; /* 12 4 */ u64 cfg_space_size; /* 16 8 */ u64 cfg_space_offset; /* 24 8 */ u64 mmio_size; /* 32 8 */ u64 mmio_offset; /* 40 8 */ unsigned char data[]; /* 48 0 */ /* size: 48, cachelines: 1, members: 8 */ /* last cacheline: 48 bytes */ }; As you can see the additional byte of the fake-flexible array (data[1]) forced the compiler to pad the struct but those bytes aren't actually used as first & last bytes (of both cfg_space and mmio) are controlled by the <>_size and <>_offset members present in the gvt_firmware_header struct. --- drivers/gpu/drm/i915/gvt/firmware.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/i915/gvt/firmware.c b/drivers/gpu/drm/i915/gvt/firmware.c index a683c22d5b64..dce93738e98a 100644 --- a/drivers/gpu/drm/i915/gvt/firmware.c +++ b/drivers/gpu/drm/i915/gvt/firmware.c @@ -45,7 +45,7 @@ struct gvt_firmware_header { u64 cfg_space_offset; /* offset in the file */ u64 mmio_size; u64 mmio_offset; /* offset in the file */ - unsigned char data[1]; + unsigned char data[]; }; #define dev_to_drm_minor(d) dev_get_drvdata((d)) @@ -77,7 +77,7 @@ static int expose_firmware_sysfs(struct intel_gvt *gvt) unsigned long size, crc32_start; int ret; - size = sizeof(*h) + info->mmio_size + info->cfg_space_size; + size = offsetof(struct gvt_firmware_header, data) + info->mmio_size + info->cfg_space_size; firmware = vzalloc(size); if (!firmware) return -ENOMEM;