From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) (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 E14D121E87982 for ; Thu, 14 Sep 2017 01:27:06 -0700 (PDT) Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 407EC7E425; Thu, 14 Sep 2017 08:30:05 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com 407EC7E425 Authentication-Results: ext-mx03.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx03.extmail.prod.ext.phx2.redhat.com; spf=fail smtp.mailfrom=lersek@redhat.com Received: from lacos-laptop-7.usersys.redhat.com (ovpn-120-83.rdu2.redhat.com [10.10.120.83]) by smtp.corp.redhat.com (Postfix) with ESMTP id 33BFC18005; Thu, 14 Sep 2017 08:30:02 +0000 (UTC) To: "Wang, Jian J" Cc: "Dong, Eric" , "Justen, Jordan L" , "edk2-devel@lists.01.org" , "Yao, Jiewen" , "Wolman, Ayellet" , "Kinney, Michael D" , "Zeng, Star" References: <20170913092507.12504-1-jian.j.wang@intel.com> <20170913092507.12504-5-jian.j.wang@intel.com> <848bc70b-b3f7-62fb-ef2d-df89ff8805a6@redhat.com> From: Laszlo Ersek Message-ID: <4dd43619-552e-9d0e-3d2b-ca9c1f3b80a3@redhat.com> Date: Thu, 14 Sep 2017 10:30:02 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.3.0 MIME-Version: 1.0 In-Reply-To: X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.27]); Thu, 14 Sep 2017 08:30:05 +0000 (UTC) Subject: Re: [PATCH 4/4] OvmfPkg/QemuVideoDxe: Update QemuVideoDxe driver to bypass NULL pointer detection if enabled. 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: Thu, 14 Sep 2017 08:27:07 -0000 Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit On 09/14/17 05:17, Wang, Jian J wrote: > For the use of arch protocol, there's one thing I mentioned is not > accurate. I actually tried gDS->SetMemorySpaceAttributes() but it > cannot change page attributes. That's why I have to turn to cpu arch > protocol. Thank you for the explanation. In that case, we cannot avoid violating the PI spec. I agree we can break the spec if it happens for security purposes, but in that case, I believe that hiding the implementation behind a library class is mandatory. Viewed from the spec side, accessing the CPU Arch protocol is a hack, and so it should not be spread to the source code of several driver modules. Thank you, Laszlo > > -----Original Message----- > From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf Of Wang, Jian J > Sent: Thursday, September 14, 2017 9:17 AM > To: Laszlo Ersek > Cc: Dong, Eric ; Justen, Jordan L ; edk2-devel@lists.01.org; Yao, Jiewen ; Wolman, Ayellet ; Kinney, Michael D ; Zeng, Star > Subject: Re: [edk2] [PATCH 4/4] OvmfPkg/QemuVideoDxe: Update QemuVideoDxe driver to bypass NULL pointer detection if enabled. > > Thanks for the comments and good advices. Sorry the format issues. > This is my first patch for this project. Too many details for me to get > familiar with. > > (1) Sure. > (2) I'll change that. > (3) I'll use the tool to ensure the patch format. > (4) I'll remove the ',' in name > (5) I'll add more description about it. > (6) You're right. I should use SetMemorySpaceAttributes() of DXE service > instead. The only reason I didn't do it is that I found > GetMemorySpaceDescriptor() doesn't return the same information > which SetMemorySpaceAttributes() just changed. So I feel using CPU > arch protocol is a bit safer. Anyway, I'll change it. > (7) I did put those macros in the install function before. To reduce the > number of changed files, I made current changes. You're right it's > not worthy. > (8) Using macro can help the readability, which is more important to me. > I know function can do the same. But it looks a bit heavy in this situation. > I have to admit replacing the macros with a library is a very good idea, > which brings the same readability. I didn't think of that before. Although > Library is still a little bit heavy to me but it's in a different way, I think it > worth a trying. > (9) Putting a space before open parenthesis is forced style? If so, I'll add it. > (10) You're right. Using library can reduce the disturbs to affected drivers > by this feature to the minimum. > > -----Original Message----- > From: Laszlo Ersek [mailto:lersek@redhat.com] > Sent: Thursday, September 14, 2017 7:35 AM > To: Wang, Jian J > Cc: edk2-devel@lists.01.org; Justen, Jordan L ; Dong, Eric ; Kinney, Michael D ; Wolman, Ayellet ; Yao, Jiewen ; Zeng, Star > Subject: Re: [edk2] [PATCH 4/4] OvmfPkg/QemuVideoDxe: Update QemuVideoDxe driver to bypass NULL pointer detection if enabled. > > Hi, > > some of the points I'm going to make have already been pointed out by > Jordan: > > (1) When posting a patch series, please collect the Cc: tags from all of > the patches, and add them *all* to the cover letter. This way everyone > will get a personal copy of the general description. > > > (2) The subject line is too long. One possible simplification: > > OvmfPkg/QemuVideoDxe: bypass NULL pointer detection > > > On 09/13/17 11:25, Wang, Jian J wrote: >> QemuVideoDxe driver will install VBE SHIM into page 0. If NULL pointer >> detection is enabled, page 0 must be enabled temporarily before >> installing and disabled again afterwards. For Windows 7 boot, BIT7 of >> PcdNullPointerDetectionPropertyMask must still be set to avoid hang. > > (3) Subject line and commit message both should not exceed 74 characters > line length. (Not sure how many chars PatchCheck.py actually enforces, I > always stick with 74, following the Linux kernel tradition.) > > I rewrapped the commit message here for readability. > > >> >> Cc: Jiewen Yao >> Cc: Eric Dong >> Cc: Star Zeng >> Cc: Laszlo Ersek >> Cc: Justen, Jordan L >> Cc: Kinney, Michael D >> Cc: Wolman, Ayellet >> Suggested-by: Wolman, Ayellet >> Contributed-under: TianoCore Contribution Agreement 1.1 >> Signed-off-by: Wang, Jian J > > (4) I think this is also something that Jordan had pointed out a long > time ago (apologies if I mis-remember): > > The strings after the tags should form correct email addresses, and if > there are various email meta-characters in them, like "." (dot) and "," > (comma), then they should be quoted, like this: > > Cc: "Justen, Jordan L" > Cc: "Kinney, Michael D" > Cc: "Wolman, Ayellet" > Suggested-by: "Wolman, Ayellet" > Signed-off-by: "Wang, Jian J" > > If you look at the actual addresses on the emails that have been sent > out, you can see they are all malformed. For example, I have: > > "Jordan L " for Jordan -- the part before the > comma was taken to be a separate email address (a malformed one). > > At least for my reply, I have fixed up the email addresses. > > > (5) The commit message mentions BIT7 of the new PCD. > > First, thanks for checking Windows 7 boot (and I'm happy that I got > suspicious of the feature with regard to Windows 7). I think BIT7 is a > good feature. > > However, please include the short description of that feature in the > commit message -- it is one sentence; "Disable NULL pointer detection > just after EndOfDxe." > > (I think BIT7 is a really smart feature, and I like *how* it is used in > "NULL_DETECTION_ENABLED" below. The check means, "if the protection is > enabled for DXE, and *not disabled* (== also enabled) after End-of-Dxe". > > This doesn't mean that I like the NULL_DETECTION_ENABLED macro itself; > more on that below.) > > >> --- >> OvmfPkg/QemuVideoDxe/Driver.c | 15 ++++++++++++++- >> OvmfPkg/QemuVideoDxe/Qemu.h | 16 ++++++++++++++++ >> OvmfPkg/QemuVideoDxe/QemuVideoDxe.inf | 2 ++ >> 3 files changed, 32 insertions(+), 1 deletion(-) >> >> diff --git a/OvmfPkg/QemuVideoDxe/Driver.c b/OvmfPkg/QemuVideoDxe/Driver.c >> index 0dce80e59b..ee0eed7214 100644 >> --- a/OvmfPkg/QemuVideoDxe/Driver.c >> +++ b/OvmfPkg/QemuVideoDxe/Driver.c >> @@ -194,6 +194,7 @@ QemuVideoControllerDriverStart ( >> PCI_TYPE00 Pci; >> QEMU_VIDEO_CARD *Card; >> EFI_PCI_IO_PROTOCOL *ChildPciIo; >> + EFI_CPU_ARCH_PROTOCOL *Cpu; > > (6) I believe I mentioned this in the earlier discussion, in some form, > but now I'll say it again: > > A UEFI driver has no business poking at the CPU Arch protocol. The PI > spec (1.6) states, > > 12.3 CPU Architectural Protocol > EFI_CPU_ARCH_PROTOCOL > > Summary > > Abstracts the processor services that are required to implement some > of the DXE services. This protocol must be produced by a boot service > or runtime DXE driver and may only be consumed by the DXE Foundation > and DXE drivers that produce architectural protocols. > > The DXE core is obviously free to use the CPU Arch protocol, but a UEFI > driver is forbidden from it, *even if* we say that, in this UEFI driver, > we are going to use DXE services. (Which come from the PI spec, and not > the UEFI spec.) > > Therefore, here we have to use gDS->SetMemorySpaceAttributes(). > > The gDS->SetMemorySpaceAttributes() service depends on the CPU Arch > protocol, by the PI spec. It is not easy to see, because the PI spec has > a formatting error in this area. If you look under > GetMemorySpaceDescriptor(), there is an error code > > EFI_NOT_AVAILABLE_YET The attributes cannot be set because CPU > architectural protocol is not available yet. > > Obviously this error code belongs to SetMemorySpaceAttributes(), not > GetMemorySpaceDescriptor(). > > Anyway, gDS should be used, architectural protocols shouldn't be. > > >> >> OldTpl = gBS->RaiseTPL (TPL_CALLBACK); >> >> @@ -479,7 +480,19 @@ QemuVideoControllerDriverStart ( >> #if defined MDE_CPU_IA32 || defined MDE_CPU_X64 >> if (Private->Variant == QEMU_VIDEO_BOCHS_MMIO || >> Private->Variant == QEMU_VIDEO_BOCHS) { >> - InstallVbeShim (Card->Name, Private->GraphicsOutput.Mode->FrameBufferBase); >> + // >> + // Prepare CPU arch protocol for NULL pointer detection >> + // >> + Status = gBS->LocateProtocol ( >> + &gEfiCpuArchProtocolGuid, >> + NULL, >> + (VOID **) &Cpu >> + ); >> + ASSERT_EFI_ERROR (Status); >> + >> + DISABLE_NULL_DETECTION(Cpu); >> + InstallVbeShim (Card->Name, Private->GraphicsOutput.Mode->FrameBufferBase); >> + ENABLE_NULL_DETECTION(Cpu); > > (7) The NULL detection disabling and enabling should bracket the > affected code as tightly as possible. > > So please move this into InstallVbeShim() accordingly. > > >> } >> #endif >> >> diff --git a/OvmfPkg/QemuVideoDxe/Qemu.h b/OvmfPkg/QemuVideoDxe/Qemu.h >> index 7fbb25b3ef..bb3bc6eb0f 100644 >> --- a/OvmfPkg/QemuVideoDxe/Qemu.h >> +++ b/OvmfPkg/QemuVideoDxe/Qemu.h >> @@ -25,6 +25,7 @@ >> #include >> #include >> #include >> +#include >> >> #include >> #include >> @@ -82,6 +83,21 @@ typedef struct { >> >> #define GRAPHICS_OUTPUT_INVALIDE_MODE_NUMBER 0xffff >> >> +// >> +// VBE code will access memory between 0-4095 which will cause page fault exception >> +// if NULL pointer detection mechanism is enabled. Following macros can be used to >> +// disable/enable NULL pointer detection before/after accessing those memory. >> +// >> +#define NULL_DETECTION_ENABLED ((PcdGet8(PcdNullPointerDetectionPropertyMask) & (BIT0|BIT7)) == BIT0) >> +#define DISABLE_NULL_DETECTION(Cpu) \ >> + if (NULL_DETECTION_ENABLED) { \ >> + (Cpu)->SetMemoryAttributes((Cpu), 0, EFI_PAGE_SIZE, 0); \ >> + } >> +#define ENABLE_NULL_DETECTION(Cpu) \ >> + if (NULL_DETECTION_ENABLED) { \ >> + (Cpu)->SetMemoryAttributes((Cpu), 0, EFI_PAGE_SIZE, EFI_MEMORY_RP); \ >> + } >> + > > (8) I believe Jordan too commented on these macros elsewhere (under > patch 1/4). > > In my opinion, this functionality should be extracted into a library > class, with a library instance that is suitable for at least UEFI_DRIVER > modules. (Maybe even for DXE_DRIVER modules.) > > You could add a separate library instance for SMM drivers, if that were > necessary. > > > (9) Style comment: please put one space character between the function > designator and the opening parenthesis. > > >> // >> // QEMU Video Private Data Structure >> // >> diff --git a/OvmfPkg/QemuVideoDxe/QemuVideoDxe.inf b/OvmfPkg/QemuVideoDxe/QemuVideoDxe.inf >> index 7c7d429bca..5d166eb99c 100644 >> --- a/OvmfPkg/QemuVideoDxe/QemuVideoDxe.inf >> +++ b/OvmfPkg/QemuVideoDxe/QemuVideoDxe.inf >> @@ -72,7 +72,9 @@ >> gEfiGraphicsOutputProtocolGuid # PROTOCOL BY_START >> gEfiDevicePathProtocolGuid # PROTOCOL BY_START >> gEfiPciIoProtocolGuid # PROTOCOL TO_START >> + gEfiCpuArchProtocolGuid >> >> [Pcd] >> gOptionRomPkgTokenSpaceGuid.PcdDriverSupportedEfiVersion >> + gEfiMdeModulePkgTokenSpaceGuid.PcdNullPointerDetectionPropertyMask > > (10) Instead of these, the library class that I described under (8) > should be added here. > > Any further dependencies like PCDs, protocols etc should be inherited by > the driver through the library instance that the platform DSC file > resolves the library class to. > > Bonus: should you realize that the feature is impossible to implement > without accessing the CPU Arch protocol directly, you could hide the > protocol GUID dependency in the library instance INF file, and I'd be > none the wiser. > > ... Well, I could at least pretend that. :) > > Thanks, > Laszlo > _______________________________________________ > edk2-devel mailing list > edk2-devel@lists.01.org > https://lists.01.org/mailman/listinfo/edk2-devel >