OpenDuetPkg

Acidanthera variant of DuetPkg. Specialties:

• Significantly improved boot performance.
• BDS is simplified to load EFI/OC/OpenCore.efi.
• EDID support removed for performance and compatibility.
• PCI option ROM support removed for security and performance.
• Setup and graphical interface removed.
• Resolved PCIe device path instead of PCI.
• Increased variable storage size to 64 KB.
• Always loads from bootstrapped volume first.
• Some changes inherited from Clover EFI bootloader.

Simplified bootstrap process

1. boot0 is loaded by BIOS from MBR at 7C00h.
2. boot0 finds active MBR or ESP GPT partition.
3. boot0 loads boot1 from found partition at E000h.
4. boot1 finds boot file at partition root.
5. boot1 loads boot at 20000h (begins with StartX64 or StartIA32).
6. Start enables paging (prebuilt for X64 or generated for IA32).
7. Start switches to native CPU mode (X64 or IA32) with paging.
8. Start jumps to concatentated EfiXX at 21000h (Efi64 or Efi32).
9. EfiXX loads EfiLdr (concatenated after EfiXX) at 10000h.
10. EfiLdr decompresses and maps DUETFV, DxeIpl, DxeCore.
11. EfiLdr jumps to DxeIpl, which starts DxeCore from DUETFV.
12. DxeCore starts BDS, which loads EFI/OC/OpenCore.efi.

Name	PHYS	VIRT
boot0	7C00h
boot1	E000h
Start	20000h	20000h
EfiXX	21000h	21000h
EfiLdr	22000h	10000h
DxeIpl+	22000h+	???

Error codes

• BOOT MISMATCH! - Bootstrap partition signature identification failed. BDS code will try to lookup EFI/OC/OpenCore.efi on any partition in 3 seconds.
• BOOT FAIL! - No bootable EFI/OC/OpenCore.efi file found on any partition. BDS code will dead-loop CPU in 3 seconds.

Compilation

By default ocbuild-like compilation is used via macbuild.tool. As an alternative it is possible to perform in-tree compilation by using INTREE=1 environment variable:

TARGETARCH=X64 TARGET=RELEASE INTREE=1 DuetPkg/macbuild.tool

Note: 32-bit version may not work properly when compiled with older Xcode version (tested 11.4.1).

Configuration

Builtin available drivers are set in OpenDuetPkg.fdf (included drivers) and OpenDuetPkg.dsc (compiled drivers, may not be included). Adding more drivers may result in the need to change firmware volume size. To do this update NumBlocks in DuetPkg.fdf (number of 64 KB blocks in the firmware).

Note: OHCI driver is not bundled with DuetPkg (and EDK II) and can be found in edk2-platforms/Silicon/Intel/QuarkSocPkg/QuarkSouthCluster/Usb/Ohci/Dxe.