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authorLinus Torvalds <torvalds@linux-foundation.org>2013-11-12 05:48:30 +0400
committerLinus Torvalds <torvalds@linux-foundation.org>2013-11-12 05:48:30 +0400
commit69019d77c71472428a5d67ab8bb7cfa9145000d0 (patch)
tree370f038a801c5ceee5266bf95944a458bcc0bfbf /Documentation/x86
parent6df1e7f2e96721dfdbfd8a034e52bc81916f978c (diff)
parent88392e9dd5a524b8194f1045369c7d0eb16d9f32 (diff)
downloadlinux-69019d77c71472428a5d67ab8bb7cfa9145000d0.tar.xz
Merge branch 'x86-efi-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 EFI changes from Ingo Molnar: "Main changes: - Add support for earlyprintk=efi which uses the EFI framebuffer. Very useful for debugging boot problems. - EFI stub support for large memory maps (more than 128 entries) - EFI ARM support - this was mostly done by generalizing x86 <-> ARM platform differences, such as by moving x86 EFI code into drivers/firmware/efi/ and sharing it with ARM. - Documentation updates - misc fixes" * 'x86-efi-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (26 commits) x86/efi: Add EFI framebuffer earlyprintk support boot, efi: Remove redundant memset() x86/efi: Fix config_table_type array termination x86 efi: bugfix interrupt disabling sequence x86: EFI stub support for large memory maps efi: resolve warnings found on ARM compile efi: Fix types in EFI calls to match EFI function definitions. efi: Renames in handle_cmdline_files() to complete generalization. efi: Generalize handle_ramdisks() and rename to handle_cmdline_files(). efi: Allow efi_free() to be called with size of 0 efi: use efi_get_memory_map() to get final map for x86 efi: generalize efi_get_memory_map() efi: Rename __get_map() to efi_get_memory_map() efi: Move unicode to ASCII conversion to shared function. efi: Generalize relocate_kernel() for use by other architectures. efi: Move relocate_kernel() to shared file. efi: Enforce minimum alignment of 1 page on allocations. efi: Rename memory allocation/free functions efi: Add system table pointer argument to shared functions. efi: Move common EFI stub code from x86 arch code to common location ...
Diffstat (limited to 'Documentation/x86')
-rw-r--r--Documentation/x86/efi-stub.txt65
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diff --git a/Documentation/x86/efi-stub.txt b/Documentation/x86/efi-stub.txt
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- The EFI Boot Stub
- ---------------------------
-
-On the x86 platform, a bzImage can masquerade as a PE/COFF image,
-thereby convincing EFI firmware loaders to load it as an EFI
-executable. The code that modifies the bzImage header, along with the
-EFI-specific entry point that the firmware loader jumps to are
-collectively known as the "EFI boot stub", and live in
-arch/x86/boot/header.S and arch/x86/boot/compressed/eboot.c,
-respectively.
-
-By using the EFI boot stub it's possible to boot a Linux kernel
-without the use of a conventional EFI boot loader, such as grub or
-elilo. Since the EFI boot stub performs the jobs of a boot loader, in
-a certain sense it *IS* the boot loader.
-
-The EFI boot stub is enabled with the CONFIG_EFI_STUB kernel option.
-
-
-**** How to install bzImage.efi
-
-The bzImage located in arch/x86/boot/bzImage must be copied to the EFI
-System Partiion (ESP) and renamed with the extension ".efi". Without
-the extension the EFI firmware loader will refuse to execute it. It's
-not possible to execute bzImage.efi from the usual Linux file systems
-because EFI firmware doesn't have support for them.
-
-
-**** Passing kernel parameters from the EFI shell
-
-Arguments to the kernel can be passed after bzImage.efi, e.g.
-
- fs0:> bzImage.efi console=ttyS0 root=/dev/sda4
-
-
-**** The "initrd=" option
-
-Like most boot loaders, the EFI stub allows the user to specify
-multiple initrd files using the "initrd=" option. This is the only EFI
-stub-specific command line parameter, everything else is passed to the
-kernel when it boots.
-
-The path to the initrd file must be an absolute path from the
-beginning of the ESP, relative path names do not work. Also, the path
-is an EFI-style path and directory elements must be separated with
-backslashes (\). For example, given the following directory layout,
-
-fs0:>
- Kernels\
- bzImage.efi
- initrd-large.img
-
- Ramdisks\
- initrd-small.img
- initrd-medium.img
-
-to boot with the initrd-large.img file if the current working
-directory is fs0:\Kernels, the following command must be used,
-
- fs0:\Kernels> bzImage.efi initrd=\Kernels\initrd-large.img
-
-Notice how bzImage.efi can be specified with a relative path. That's
-because the image we're executing is interpreted by the EFI shell,
-which understands relative paths, whereas the rest of the command line
-is passed to bzImage.efi.