From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received-SPF: Pass (sender SPF authorized) identity=mailfrom; client-ip=134.134.136.24; helo=mga09.intel.com; envelope-from=ruiyu.ni@intel.com; receiver=edk2-devel@lists.01.org Received: from mga09.intel.com (mga09.intel.com [134.134.136.24]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ml01.01.org (Postfix) with ESMTPS id DD91F2217CE31 for ; Wed, 6 Dec 2017 01:26:49 -0800 (PST) Received: from fmsmga004.fm.intel.com ([10.253.24.48]) by orsmga102.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 06 Dec 2017 01:31:20 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.45,367,1508828400"; d="scan'208";a="10068639" Received: from ray-dev.ccr.corp.intel.com (HELO [10.239.9.14]) ([10.239.9.14]) by fmsmga004.fm.intel.com with ESMTP; 06 Dec 2017 01:31:19 -0800 To: Jian J Wang , edk2-devel@lists.01.org Cc: Michael D Kinney , Liming Gao References: <20171206073120.2248-1-jian.j.wang@intel.com> <20171206073120.2248-2-jian.j.wang@intel.com> From: "Ni, Ruiyu" Message-ID: <30755dcb-1e79-f8f1-70b3-3c5bad9d2a4b@Intel.com> Date: Wed, 6 Dec 2017 17:31:19 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.5.0 MIME-Version: 1.0 In-Reply-To: <20171206073120.2248-2-jian.j.wang@intel.com> Subject: Re: [PATCH 1/3] IntelFrameworkPkg/LegacyBios.h: Add a macro to guarantee page 0 access X-BeenThere: edk2-devel@lists.01.org X-Mailman-Version: 2.1.22 Precedence: list List-Id: EDK II Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 06 Dec 2017 09:26:50 -0000 Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit On 12/6/2017 3:31 PM, Jian J Wang wrote: > Due to the introduction of NULL pointer detection feature, page 0 will be > disabled if the feature is enabled, which will cause legacy code failed to > update legacy data in page 0. This macro is introduced to make sure the > page 0 is enabled before those code and restore the original status of it > afterwards. > > Another reason to introduce this macro is to eliminate the dependency on > the PcdNullPointerDetectionPropertyMask. Because this is a new PCD, it > could cause some backward compatibility issue for some old packages. > > This macro will simply check if the page 0 is disabled or not. If it's > disabled, it will enable it before code updating page 0 and disable it > afterwards. Otherwise, this macro will do nothing to page 0. > > The usage of the macro will be look like (similar to DEBUG_CODE macro): > > ACCESS_PAGE0_CODE( > { > > } > ); > > Cc: Liming Gao > Cc: Michael D Kinney > Contributed-under: TianoCore Contribution Agreement 1.1 > Signed-off-by: Jian J Wang > --- > IntelFrameworkPkg/Include/Protocol/LegacyBios.h | 34 +++++++++++++++++++++++++ > 1 file changed, 34 insertions(+) > > diff --git a/IntelFrameworkPkg/Include/Protocol/LegacyBios.h b/IntelFrameworkPkg/Include/Protocol/LegacyBios.h > index 641f101bce..f77c92ba21 100644 > --- a/IntelFrameworkPkg/Include/Protocol/LegacyBios.h > +++ b/IntelFrameworkPkg/Include/Protocol/LegacyBios.h > @@ -1518,6 +1518,40 @@ struct _EFI_LEGACY_BIOS_PROTOCOL { > EFI_LEGACY_BIOS_BOOT_UNCONVENTIONAL_DEVICE BootUnconventionalDevice; > }; > > +// > +// Legacy BIOS needs to access memory in page 0 (0-4095), which is disabled if > +// NULL pointer detection feature is enabled. Following macro can be used to > +// enable/disable page 0 before/after accessing it. > +// > +#define ACCESS_PAGE0_CODE(statements) \ > + do { \ > + EFI_STATUS Status_; \ > + EFI_GCD_MEMORY_SPACE_DESCRIPTOR Desc_; \ > + \ > + Status_ = gDS->GetMemorySpaceDescriptor (0, &Desc_); \ > + if (!EFI_ERROR (Status_)) { \ > + if ((Desc_.Attributes & EFI_MEMORY_RP) != 0) { \ > + Status_ = gDS->SetMemorySpaceAttributes ( \ > + 0, \ > + EFI_PAGES_TO_SIZE(1), \ > + Desc_.Attributes &= ~EFI_MEMORY_RP \ &= is used here so Desc_.Attributes is updated to have RP cleared. Then the below if will be always FALSE. > + ); \ > + ASSERT_EFI_ERROR (Status_); \ > + } \ > + \ > + statements; \ > + \ > + if ((Desc_.Attributes & EFI_MEMORY_RP) != 0) { \ > + Status_ = gDS->SetMemorySpaceAttributes ( \ > + 0, \ > + EFI_PAGES_TO_SIZE(1), \ > + Desc_.Attributes \ > + ); \ > + ASSERT_EFI_ERROR (Status_); \ > + } \ > + } \ > + } while (FALSE) > + > extern EFI_GUID gEfiLegacyBiosProtocolGuid; > > #endif > -- Thanks, Ray