linux/arch/x86/platform
Matthew Garrett 916f676f8d x86, efi: Retain boot service code until after switching to virtual mode
UEFI stands for "Unified Extensible Firmware Interface", where "Firmware"
is an ancient African word meaning "Why do something right when you can
do it so wrong that children will weep and brave adults will cower before
you", and "UEI" is Celtic for "We missed DOS so we burned it into your
ROMs". The UEFI specification provides for runtime services (ie, another
way for the operating system to be forced to depend on the firmware) and
we rely on these for certain trivial tasks such as setting up the
bootloader. But some hardware fails to work if we attempt to use these
runtime services from physical mode, and so we have to switch into virtual
mode. So far so dreadful.

The specification makes it clear that the operating system is free to do
whatever it wants with boot services code after ExitBootServices() has been
called. SetVirtualAddressMap() can't be called until ExitBootServices() has
been. So, obviously, a whole bunch of EFI implementations call into boot
services code when we do that. Since we've been charmingly naive and
trusted that the specification may be somehow relevant to the real world,
we've already stuffed a picture of a penguin or something in that address
space. And just to make things more entertaining, we've also marked it
non-executable.

This patch allocates the boot services regions during EFI init and makes
sure that they're executable. Then, after SetVirtualAddressMap(), it
discards them and everyone lives happily ever after. Except for the ones
who have to work on EFI, who live sad lives haunted by the knowledge that
someone's eventually going to write yet another firmware specification.

[ hpa: adding this to urgent with a stable tag since it fixes currently-broken
  hardware.  However, I do not know what the dependencies are and so I do
  not know which -stable versions this may be a candidate for. ]

Signed-off-by: Matthew Garrett <mjg@redhat.com>
Link: http://lkml.kernel.org/r/1306331593-28715-1-git-send-email-mjg@redhat.com
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: <stable@kernel.org>
2011-05-25 17:03:53 -07:00
..
ce4100 x86: ce4100: Configure IOAPIC pins for USB and SATA to level type 2011-04-28 11:38:30 +02:00
efi x86, efi: Retain boot service code until after switching to virtual mode 2011-05-25 17:03:53 -07:00
iris x86: platform: Move iris to x86/platform where it belongs 2010-11-20 10:37:05 +01:00
mrst x86: Fix mrst sparse complaints 2011-05-07 10:52:30 +02:00
olpc Merge branch 'x86-platform-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2011-05-19 18:08:06 -07:00
scx200 x86: Move scx200 to platform 2010-10-27 14:30:01 +02:00
sfi Merge branch 'linus' into x86/apic-cleanups 2011-01-07 14:14:15 +01:00
uv x86, UV: Clean up uv_tlb.c 2011-05-25 14:20:14 +02:00
visws x86: visws: Fixup irq overhaul fallout 2011-04-04 16:51:15 +02:00
Makefile x86: platform: Move iris to x86/platform where it belongs 2010-11-20 10:37:05 +01:00