I was triggering a #GP(0) from userland when running with
CONFIG_EFI_MIXED and CONFIG_IA32_EMULATION, from what looked like
register corruption. Turns out that the mixed mode code was trashing the
contents of %ds, %es and %ss in __efi64_thunk().
Save and restore the contents of these segment registers across the call
to __efi64_thunk() so that we don't corrupt the CPU context.
Signed-off-by: Matt Fleming <matt.fleming@intel.com>
Some firmware appears to enable interrupts during boot service calls,
even if we've explicitly disabled them prior to the call. This is
actually allowed per the UEFI spec because boottime services expect to
be called with interrupts enabled.
So that's fine, we just need to ensure that we disable them again in
efi_enter32() before switching to a 64-bit GDT, otherwise an interrupt
may fire causing a 32-bit IRQ handler to run after we've left
compatibility mode.
Despite efi_enter32() being called both for boottime and runtime
services, this really only affects boottime because the runtime services
callchain is executed with interrupts disabled. See efi_thunk().
Signed-off-by: Matt Fleming <matt.fleming@intel.com>
Setup the runtime services based on whether we're booting in EFI native
mode or not. For non-native mode we need to thunk from 64-bit into
32-bit mode before invoking the EFI runtime services.
Using the runtime services after SetVirtualAddressMap() is slightly more
complicated because we need to ensure that all the addresses we pass to
the firmware are below the 4GB boundary so that they can be addressed
with 32-bit pointers, see efi_setup_page_tables().
Signed-off-by: Matt Fleming <matt.fleming@intel.com>
Implement the transition code to go from IA32e mode to protected mode in
the EFI boot stub. This is required to use 32-bit EFI services from a
64-bit kernel.
Since EFI boot stub is executed in an identity-mapped region, there's
not much we need to do before invoking the 32-bit EFI boot services.
However, we do reload the firmware's global descriptor table
(efi32_boot_gdt) in case things like timer events are still running in
the firmware.
Signed-off-by: Matt Fleming <matt.fleming@intel.com>
We map the EFI regions needed for runtime services non-contiguously,
with preserved alignment on virtual addresses starting from -4G down
for a total max space of 64G. This way, we provide for stable runtime
services addresses across kernels so that a kexec'd kernel can still use
them.
Thus, they're mapped in a separate pagetable so that we don't pollute
the kernel namespace.
Add an efi= kernel command line parameter for passing miscellaneous
options and chicken bits from the command line.
While at it, add a chicken bit called "efi=old_map" which can be used as
a fallback to the old runtime services mapping method in case there's
some b0rkage with a particular EFI implementation (haha, it is hard to
hold up the sarcasm here...).
Also, add the UEFI RT VA space to Documentation/x86/x86_64/mm.txt.
Signed-off-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>
Matt Fleming