On Mon, 17 Jun, at 07:50:16PM, Borislav Petkov wrote:
> From: Borislav Petkov <b...@suse.de>
>
> Due to the braindead design of EFI, we cannot map runtime services more
> than once for the duration of a booted system. Thus, if we want to use
> EFI runtime services in a kexec'ed kernel, maybe the only possible and
> sensible approach would be to map them 1:1 so that when the kexec kernel
> loads, it can simply call those addresses without the need for remapping
> (which doesn't work anyway).
>
> Furthermore, this mapping approach could be of help with b0rked EFI
> implementations for a different set of reasons.
>
> This implementation is 64-bit only for now.
>
> Signed-off-by: Borislav Petkov <b...@suse.de>
> ---
> arch/x86/include/asm/efi.h | 67 +++++++++++----
> arch/x86/platform/efi/efi.c | 165
> +++++++++++++++++++++++++++++-------
> arch/x86/platform/efi/efi_stub_64.S | 56 ++++++++++++
> 3 files changed, 240 insertions(+), 48 deletions(-)
[...]
> + .macro SWITCH_PGT
> + cmpb $0, efi_use_11_map
> + je 1f;
Actually, this needs to be,
cmpb $0, efi_use_11_map(%rip)
because this code is built into the EFI boot stub which isn't loaded at
a fixed address and needs to be position independent.
--
Matt Fleming, Intel Open Source Technology Center
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