From: Ard Biesheuvel <a...@kernel.org> Shim's PE loader uses the EFI memory attributes protocol in a way that results in an immediate crash when invoking the loaded image unless the base and size of its executable segment are both aligned to 4k.
If this is not the case, it will strip the executable permissions from the memory allocation, but fail to add them back for the executable region, resulting in non-executable code. Unfortunately, the PE loader does not even bother invoking the protocol in this case (as it notices the misalignment), making it very hard for system firmware to work around this by attempting to infer the intent of the caller. So let's introduce a QEMU command line option to indicate that the protocol should not be exposed at all. -fw_cfg opt/org.tianocore/DisableMemAttrProtocol,string=y Cc: L�szl� �rsek <ler...@redhat.com> Cc: Gerd Hoffmann <kra...@redhat.com> Cc: Oliver Steffen <ostef...@redhat.com> Cc: Alexander Graf <g...@amazon.com> Link: https://gitlab.com/qemu-project/qemu/-/issues/1990 Signed-off-by: Ard Biesheuvel <a...@kernel.org> --- ArmVirtPkg/Library/PlatformBootManagerLib/PlatformBootManagerLib.inf | 2 + ArmVirtPkg/Library/PlatformBootManagerLib/PlatformBm.c | 56 ++++++++++++++++++++ 2 files changed, 58 insertions(+) diff --git a/ArmVirtPkg/Library/PlatformBootManagerLib/PlatformBootManagerLib.inf b/ArmVirtPkg/Library/PlatformBootManagerLib/PlatformBootManagerLib.inf index 997eb1a4429f..facd81a5d036 100644 --- a/ArmVirtPkg/Library/PlatformBootManagerLib/PlatformBootManagerLib.inf +++ b/ArmVirtPkg/Library/PlatformBootManagerLib/PlatformBootManagerLib.inf @@ -46,6 +46,7 @@ [LibraryClasses] PcdLib PlatformBmPrintScLib QemuBootOrderLib + QemuFwCfgSimpleParserLib QemuLoadImageLib ReportStatusCodeLib TpmPlatformHierarchyLib @@ -73,5 +74,6 @@ [Guids] [Protocols] gEfiFirmwareVolume2ProtocolGuid gEfiGraphicsOutputProtocolGuid + gEfiMemoryAttributeProtocolGuid gEfiPciRootBridgeIoProtocolGuid gVirtioDeviceProtocolGuid diff --git a/ArmVirtPkg/Library/PlatformBootManagerLib/PlatformBm.c b/ArmVirtPkg/Library/PlatformBootManagerLib/PlatformBm.c index 85c01351b09d..e17899100e4a 100644 --- a/ArmVirtPkg/Library/PlatformBootManagerLib/PlatformBm.c +++ b/ArmVirtPkg/Library/PlatformBootManagerLib/PlatformBm.c @@ -16,6 +16,7 @@ #include <Library/PcdLib.h> #include <Library/PlatformBmPrintScLib.h> #include <Library/QemuBootOrderLib.h> +#include <Library/QemuFwCfgSimpleParserLib.h> #include <Library/TpmPlatformHierarchyLib.h> #include <Library/UefiBootManagerLib.h> #include <Protocol/DevicePath.h> @@ -1111,6 +1112,49 @@ PlatformBootManagerBeforeConsole ( FilterAndProcess (&gEfiPciIoProtocolGuid, IsVirtioPciSerial, SetupVirtioSerial); } +/** + Uninstall the EFI memory attribute protocol if it exists. +**/ +STATIC +VOID +UninstallEfiMemoryAttributesProtocol ( + VOID + ) +{ + EFI_STATUS Status; + EFI_HANDLE Handle; + UINTN Size; + VOID *MemoryAttributeProtocol; + + Size = sizeof (Handle); + Status = gBS->LocateHandle ( + ByProtocol, + &gEfiMemoryAttributeProtocolGuid, + NULL, + &Size, + &Handle + ); + + if (EFI_ERROR (Status)) { + ASSERT (Status == EFI_NOT_FOUND); + return; + } + + Status = gBS->HandleProtocol ( + Handle, + &gEfiMemoryAttributeProtocolGuid, + &MemoryAttributeProtocol + ); + ASSERT_EFI_ERROR (Status); + + Status = gBS->UninstallProtocolInterface ( + Handle, + &gEfiMemoryAttributeProtocolGuid, + MemoryAttributeProtocol + ); + ASSERT_EFI_ERROR (Status); +} + /** Do the platform specific action after the console is ready Possible things that can be done in PlatformBootManagerAfterConsole: @@ -1129,12 +1173,24 @@ PlatformBootManagerAfterConsole ( ) { RETURN_STATUS Status; + BOOLEAN FwCfgBool; // // Show the splash screen. // BootLogoEnableLogo (); + // + // Work around shim's terminally broken use of the EFI memory attributes + // protocol, by just uninstalling it when requested on the QEMU command line. + // + Status = QemuFwCfgParseBool ( + "opt/org.tianocore/DisableMemAttrProtocol", + &FwCfgBool); + if (!RETURN_ERROR (Status) && FwCfgBool) { + UninstallEfiMemoryAttributesProtocol (); + } + // // Process QEMU's -kernel command line option. The kernel booted this way // will receive ACPI tables: in PlatformBootManagerBeforeConsole(), we -- 2.43.0.rc2.451.g8631bc7472-goog -=-=-=-=-=-=-=-=-=-=-=- Groups.io Links: You receive all messages sent to this group. View/Reply Online (#112027): https://edk2.groups.io/g/devel/message/112027 Mute This Topic: https://groups.io/mt/102967690/21656 Group Owner: devel+ow...@edk2.groups.io Unsubscribe: https://edk2.groups.io/g/devel/unsub [arch...@mail-archive.com] -=-=-=-=-=-=-=-=-=-=-=-