On Fri, Oct 24, 2014 at 1:39 PM, Ard Biesheuvel
<ard.biesheuvel@xxxxxxxxxx> wrote:
> In order to support kexec, the kernel needs to be able to deal with the
> state of the UEFI firmware after SetVirtualAddressMap() has been called.
> To avoid having separate code paths for non-kexec and kexec, let's move
> the call to SetVirtualAddressMap() to the stub: this will guarantee us
> that it will only be called once (since the stub is not executed during
> kexec), and ensures that the UEFI state is identical between kexec and
> normal boot.
>
> This implies that the layout of the virtual mapping needs to be created
> by the stub as well. All regions are rounded up to a naturally aligned
> multiple of 64 KB (for compatibility with 64k pages kernels) and recorded
> in the UEFI memory map. The kernel proper reads those values and installs
> the mappings in a dedicated set of page tables that are swapped in during
> UEFI Runtime Services calls.
>
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
A questions grounded in my ignorance below...
> ---
> arch/arm64/include/asm/efi.h | 19 +++-
> arch/arm64/kernel/efi.c | 205 +++++++++++++++++++------------------
> drivers/firmware/efi/libstub/fdt.c | 104 ++++++++++++++++++-
> 3 files changed, 224 insertions(+), 104 deletions(-)
>
> @@ -69,9 +74,36 @@ static void __init efi_setup_idmap(void)
> }
> }
>
> +/*
> + * Translate a EFI virtual address into a physical address: this is necessary,
> + * as some data members of the EFI system table are virtually remapped after
> + * SetVirtualAddressMap() has been called.
> + */
> +static phys_addr_t __init efi_to_phys(unsigned long addr)
> +{
> + efi_memory_desc_t *md;
> +
> + for_each_efi_memory_desc(&memmap, md) {
> + if (!(md->attribute & EFI_MEMORY_RUNTIME))
> + continue;
> + if (md->virt_addr == 0)
> + /* no virtual mapping has been installed by the stub */
> + break;
> + if (md->virt_addr < addr &&
> + (addr - md->virt_addr) < (md->num_pages << EFI_PAGE_SHIFT))
> + return md->phys_addr + addr - md->virt_addr;
> + }
> +
> + WARN_ONCE(1, "UEFI virtual mapping incomplete or missing -- no entry found for 0x%lx\n",
> + addr);
> + return addr;
> +}
> +
Is function applicable to all EFI implementations? Should it be in the
common EFI code?
How much of this patch series is (theoretically) applicable to aarch32?
g.
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