• Matt Fleming's avatar
    x86/boot: EFI_MIXED should not prohibit loading above 4G · 745c5167
    Matt Fleming authored
    commit 7d453eee ("x86/efi: Wire up CONFIG_EFI_MIXED") introduced a
    regression for the functionality to load kernels above 4G. The relevant
    (incorrect) reasoning behind this change can be seen in the commit
    message,
    
      "The xloadflags field in the bzImage header is also updated to reflect
      that the kernel supports both entry points by setting both of
      XLF_EFI_HANDOVER_32 and XLF_EFI_HANDOVER_64 when CONFIG_EFI_MIXED=y.
      XLF_CAN_BE_LOADED_ABOVE_4G is disabled so that the kernel text is
      guaranteed to be addressable with 32-bits."
    
    This is obviously bogus since 32-bit EFI loaders will never place the
    kernel above the 4G mark. So this restriction is entirely unnecessary.
    
    But things are worse than that - since we want to encourage people to
    always compile with CONFIG_EFI_MIXED=y so that their kernels work out of
    the box for both 32-bit and 64-bit firmware, commit 7d453eee
    effectively disables XLF_CAN_BE_LOADED_ABOVE_4G completely.
    
    Remove the overzealous and superfluous restriction and restore the
    XLF_CAN_BE_LOADED_ABOVE_4G functionality.
    
    Cc: "H. Peter Anvin" <hpa@zytor.com>
    Cc: Dave Young <dyoung@redhat.com>
    Cc: Vivek Goyal <vgoyal@redhat.com>
    Signed-off-by: default avatarMatt Fleming <matt.fleming@intel.com>
    Link: http://lkml.kernel.org/r/1402140380-15377-1-git-send-email-matt@console-pimps.orgSigned-off-by: default avatarH. Peter Anvin <hpa@zytor.com>
    745c5167
header.S 12.4 KB