Per UEFI Spec 2.8 (UEFI_Spec_2_8_final.pdf, page 114) 5.2.3 Protective MBR Table 20. Protective MBR Partition Record protecting the entire disk
The description for BootIndicator states the following: > Set to 0x00 to indicate a non-bootable partition. If set to any > value other than 0x00 the behavior of this flag on non-UEFI > systems is undefined. Must be ignored by UEFI implementations. Unfortunately, we have been incorrectly assuming that the BootIndicator value must be 0x00, which leads to problems when the 'pmbr_boot' flag is set on a disk containing a GPT (such as with GNU parted). When the flag is set, the value changes to 0x01, causing this check to fail and the system is rendered unbootable despite it being valid from the perspective of the UEFI spec. To resolve this, we drop the check for the BootIndicator so that we stop caring about the value set there, which restores the capability to boot such disks. Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=3474 Cc: Chris Murphy <[email protected]> Cc: David Duncan <[email protected]> Cc: Lazlo Ersek <[email protected]> Cc: Hao A Wu <[email protected]> Cc: Ray Ni <[email protected]> Cc: Zhichao Gao <[email protected]> Signed-off-by: Neal Gompa <[email protected]> --- MdeModulePkg/Universal/Disk/PartitionDxe/Gpt.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/MdeModulePkg/Universal/Disk/PartitionDxe/Gpt.c b/MdeModulePkg/Universal/Disk/PartitionDxe/Gpt.c index aefb2d6ecb3f..efaff5e0808f 100644 --- a/MdeModulePkg/Universal/Disk/PartitionDxe/Gpt.c +++ b/MdeModulePkg/Universal/Disk/PartitionDxe/Gpt.c @@ -264,8 +264,7 @@ PartitionInstallGptChildHandles ( // Verify that the Protective MBR is valid // for (Index = 0; Index < MAX_MBR_PARTITIONS; Index++) { - if (ProtectiveMbr->Partition[Index].BootIndicator == 0x00 && - ProtectiveMbr->Partition[Index].OSIndicator == PMBR_GPT_PARTITION && + if (ProtectiveMbr->Partition[Index].OSIndicator == PMBR_GPT_PARTITION && UNPACK_UINT32 (ProtectiveMbr->Partition[Index].StartingLBA) == 1 ) { break; -- 2.31.1 -=-=-=-=-=-=-=-=-=-=-=- Groups.io Links: You receive all messages sent to this group. View/Reply Online (#77477): https://edk2.groups.io/g/devel/message/77477 Mute This Topic: https://groups.io/mt/83993973/21656 Group Owner: [email protected] Unsubscribe: https://edk2.groups.io/g/devel/unsub [[email protected]] -=-=-=-=-=-=-=-=-=-=-=-
