linux/arch/x86
Matt Fleming b8ff87a615 x86/efi: Firmware agnostic handover entry points
The EFI handover code only works if the "bitness" of the firmware and
the kernel match, i.e. 64-bit firmware and 64-bit kernel - it is not
possible to mix the two. This goes against the tradition that a 32-bit
kernel can be loaded on a 64-bit BIOS platform without having to do
anything special in the boot loader. Linux distributions, for one thing,
regularly run only 32-bit kernels on their live media.

Despite having only one 'handover_offset' field in the kernel header,
EFI boot loaders use two separate entry points to enter the kernel based
on the architecture the boot loader was compiled for,

    (1) 32-bit loader: handover_offset
    (2) 64-bit loader: handover_offset + 512

Since we already have two entry points, we can leverage them to infer
the bitness of the firmware we're running on, without requiring any boot
loader modifications, by making (1) and (2) valid entry points for both
CONFIG_X86_32 and CONFIG_X86_64 kernels.

To be clear, a 32-bit boot loader will always use (1) and a 64-bit boot
loader will always use (2). It's just that, if a single kernel image
supports (1) and (2) that image can be used with both 32-bit and 64-bit
boot loaders, and hence both 32-bit and 64-bit EFI.

(1) and (2) must be 512 bytes apart at all times, but that is already
part of the boot ABI and we could never change that delta without
breaking existing boot loaders anyhow.

Signed-off-by: Matt Fleming <matt.fleming@intel.com>
2014-03-04 21:25:06 +00:00
..
boot x86/efi: Firmware agnostic handover entry points 2014-03-04 21:25:06 +00:00
configs x86, defconfig: Add DEVTMPFS and DEVTMPFS_MOUNT to *86*_defconfig 2013-11-04 20:01:55 -08:00
crypto crypto: aesni - fix build on x86 (32bit) 2014-01-15 11:36:34 +08:00
ia32 constify copy_siginfo_to_user{,32}() 2013-11-09 00:16:29 -05:00
include x86/efi: Firmware agnostic handover entry points 2014-03-04 21:25:06 +00:00
kernel Two fixes in the tracing utility. 2014-02-15 15:03:34 -08:00
kvm kvm: x86: move KVM_CAP_HYPERV_TIME outside #ifdef 2014-01-29 18:10:45 +01:00
lguest x86, asmlinkage, lguest: Fix C functions used by inline assembler 2014-01-29 22:17:17 -08:00
lib Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2014-01-25 11:17:34 -08:00
math-emu x86: math-emu: Drop already-disabled print of build date 2014-01-27 23:14:12 +01:00
mm x86/mm/pageattr: Always dump the right page table in an oops 2014-03-04 21:23:36 +00:00
net bpf: do not use reciprocal divide 2014-01-15 17:02:08 -08:00
oprofile perf: Fix arch_perf_out_copy_user default 2013-11-06 12:34:25 +01:00
pci ACPI and power management updates for 3.14-rc1 2014-01-24 15:51:02 -08:00
platform x86/efi: Add early thunk code to go from 64-bit to 32-bit 2014-03-04 21:25:04 +00:00
power x86, asmlinkage, power: Make various symbols used by the suspend asm code visible 2013-08-06 14:21:03 -07:00
realmode Merge commit 'f4bcd8ccddb02833340652e9f46f5127828eb79d' into x86/build 2014-01-29 09:07:00 -08:00
syscalls sched: Add new scheduler syscalls to support an extended scheduling parameters ABI 2014-01-13 13:41:04 +01:00
tools Merge commit 'f4bcd8ccddb02833340652e9f46f5127828eb79d' into x86/build 2014-01-29 09:07:00 -08:00
um um, x86: Fix vDSO build 2014-01-12 16:47:31 +01:00
vdso Merge branch 'x86-cleanups-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2014-01-20 12:03:57 -08:00
video
xen xen: properly account for _PAGE_NUMA during xen pte translations 2014-02-10 16:01:41 -08:00
.gitignore
Kbuild
Kconfig * Avoid WARN_ON() when mapping BGRT on Baytrail (EFI 32-bit). 2014-02-07 11:27:30 -08:00
Kconfig.cpu
Kconfig.debug x86: Disable CONFIG_X86_DECODER_SELFTEST in allmod/allyesconfigs 2014-02-05 14:10:30 -08:00
Makefile x86, build: Build 16-bit code with -m16 where possible 2014-01-30 08:05:36 -08:00
Makefile_32.cpu
Makefile.um