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Diffstat (limited to 'Documentation/arch/x86/boot.rst')
| -rw-r--r-- | Documentation/arch/x86/boot.rst | 88 |
1 files changed, 55 insertions, 33 deletions
diff --git a/Documentation/arch/x86/boot.rst b/Documentation/arch/x86/boot.rst index 77e6163288db..6d36ce86fd8e 100644 --- a/Documentation/arch/x86/boot.rst +++ b/Documentation/arch/x86/boot.rst @@ -416,7 +416,7 @@ Offset/size: 0x210/1 Protocol: 2.00+ ============ ================== - If your boot loader has an assigned id (see table below), enter + If your boot loader has an assigned ID (see table below), enter 0xTV here, where T is an identifier for the boot loader and V is a version number. Otherwise, enter 0xFF here. @@ -431,31 +431,31 @@ Protocol: 2.00+ ext_loader_type <- 0x05 ext_loader_ver <- 0x23 - Assigned boot loader ids (hexadecimal): + Assigned boot loader IDs: == ======================================= - 0 LILO - (0x00 reserved for pre-2.00 bootloader) - 1 Loadlin - 2 bootsect-loader - (0x20, all other values reserved) - 3 Syslinux - 4 Etherboot/gPXE/iPXE - 5 ELILO - 7 GRUB - 8 U-Boot - 9 Xen - A Gujin - B Qemu - C Arcturus Networks uCbootloader - D kexec-tools - E Extended (see ext_loader_type) - F Special (0xFF = undefined) - 10 Reserved - 11 Minimal Linux Bootloader - <http://sebastian-plotz.blogspot.de> - 12 OVMF UEFI virtualization stack - 13 barebox + 0x0 LILO + (0x00 reserved for pre-2.00 bootloader) + 0x1 Loadlin + 0x2 bootsect-loader + (0x20, all other values reserved) + 0x3 Syslinux + 0x4 Etherboot/gPXE/iPXE + 0x5 ELILO + 0x7 GRUB + 0x8 U-Boot + 0x9 Xen + 0xA Gujin + 0xB Qemu + 0xC Arcturus Networks uCbootloader + 0xD kexec-tools + 0xE Extended (see ext_loader_type) + 0xF Special (0xFF = undefined) + 0x10 Reserved + 0x11 Minimal Linux Bootloader + <http://sebastian-plotz.blogspot.de> + 0x12 OVMF UEFI virtualization stack + 0x13 barebox == ======================================= Please contact <hpa@zytor.com> if you need a bootloader ID value assigned. @@ -1431,12 +1431,34 @@ The boot loader *must* fill out the following fields in bp:: All other fields should be zero. .. note:: - The EFI Handover Protocol is deprecated in favour of the ordinary PE/COFF - entry point, combined with the LINUX_EFI_INITRD_MEDIA_GUID based initrd - loading protocol (refer to [0] for an example of the bootloader side of - this), which removes the need for any knowledge on the part of the EFI - bootloader regarding the internal representation of boot_params or any - requirements/limitations regarding the placement of the command line - and ramdisk in memory, or the placement of the kernel image itself. - -[0] https://github.com/u-boot/u-boot/commit/ec80b4735a593961fe701cc3a5d717d4739b0fd0 + The EFI Handover Protocol is deprecated in favour of the ordinary PE/COFF + entry point described below. + +.. _pe-coff-entry-point: + +PE/COFF entry point +=================== + +When compiled with ``CONFIG_EFI_STUB=y``, the kernel can be executed as a +regular PE/COFF binary. See Documentation/admin-guide/efi-stub.rst for +implementation details. + +The stub loader can request the initrd via a UEFI protocol. For this to work, +the firmware or bootloader needs to register a handle which carries +implementations of the ``EFI_LOAD_FILE2`` protocol and the device path +protocol exposing the ``LINUX_EFI_INITRD_MEDIA_GUID`` vendor media device path. +In this case, a kernel booting via the EFI stub will invoke +``LoadFile2::LoadFile()`` method on the registered protocol to instruct the +firmware to load the initrd into a memory location chosen by the kernel/EFI +stub. + +This approach removes the need for any knowledge on the part of the EFI +bootloader regarding the internal representation of boot_params or any +requirements/limitations regarding the placement of the command line and +ramdisk in memory, or the placement of the kernel image itself. + +For sample implementations, refer to `the original u-boot implementation`_ or +`the OVMF implementation`_. + +.. _the original u-boot implementation: https://github.com/u-boot/u-boot/commit/ec80b4735a593961fe701cc3a5d717d4739b0fd0 +.. _the OVMF implementation: https://github.com/tianocore/edk2/blob/1780373897f12c25075f8883e073144506441168/OvmfPkg/LinuxInitrdDynamicShellCommand/LinuxInitrdDynamicShellCommand.c |