• Matt Fleming's avatar
    efi: Make 'efi_enabled' a function to query EFI facilities · 73923018
    Matt Fleming authored
    commit 83e68189745ad931c2afd45d8ee3303929233e7f upstream.
    
    Originally 'efi_enabled' indicated whether a kernel was booted from
    EFI firmware. Over time its semantics have changed, and it now
    indicates whether or not we are booted on an EFI machine with
    bit-native firmware, e.g. 64-bit kernel with 64-bit firmware.
    
    The immediate motivation for this patch is the bug report at,
    
        https://bugs.launchpad.net/ubuntu-cdimage/+bug/1040557
    
    which details how running a platform driver on an EFI machine that is
    designed to run under BIOS can cause the machine to become
    bricked. Also, the following report,
    
        https://bugzilla.kernel.org/show_bug.cgi?id=47121
    
    details how running said driver can also cause Machine Check
    Exceptions. Drivers need a new means of detecting whether they're
    running on an EFI machine, as sadly the expression,
    
        if (!efi_enabled)
    
    hasn't been a sufficient condition for quite some time.
    
    Users actually want to query 'efi_enabled' for different reasons -
    what they really want access to is the list of available EFI
    facilities.
    
    For instance, the x86 reboot code needs to know whether it can invoke
    the ResetSystem() function provided by the EFI runtime services, while
    the ACPI OSL code wants to know whether the EFI config tables were
    mapped successfully. There are also checks in some of the platform
    driver code to simply see if they're running on an EFI machine (which
    would make it a bad idea to do BIOS-y things).
    
    This patch is a prereq for the samsung-laptop fix patch.
    Signed-off-by: default avatarMatt Fleming <matt.fleming@intel.com>
    Cc: David Airlie <airlied@linux.ie>
    Cc: Corentin Chary <corentincj@iksaif.net>
    Cc: Matthew Garrett <mjg59@srcf.ucam.org>
    Cc: Dave Jiang <dave.jiang@intel.com>
    Cc: Olof Johansson <olof@lixom.net>
    Cc: Peter Jones <pjones@redhat.com>
    Cc: Colin Ian King <colin.king@canonical.com>
    Cc: Steve Langasek <steve.langasek@canonical.com>
    Cc: Tony Luck <tony.luck@intel.com>
    Cc: Konrad Rzeszutek Wilk <konrad@kernel.org>
    Cc: Rafael J. Wysocki <rjw@sisk.pl>
    Signed-off-by: default avatarH. Peter Anvin <hpa@linux.intel.com>
    Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
    73923018
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