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
  ...
This commit is contained in:
Linus Torvalds 2013-11-12 10:48:30 +09:00
commit 69019d77c7
17 changed files with 1245 additions and 791 deletions

View file

@ -1,65 +0,0 @@
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.