On 08/28/13 14:52, Laszlo Ersek wrote:
> This filters the UEFI boot option list to those that the user requested
> via fw_cfg, reorders them, and kills off the (non-requested) rest. UEFI
> boot options of the form
>
>
> HD(1,800,4e000,87f09d6f-dc40-4eaf-b90b-9c2c7d4ffdb5)File(\EFI\opensuse\grubx64.efi)
>
> don't match *any* output from the OFW->UEFI device path translation,
> hence they are always removed. I assumed that would be no problem, since
> such (root-less, ie. relative) device paths should be unbootable anyway.
> Apparently edk2 can boot them nonetheless?
Sigh. Yes, that's the case. See BdsLibBootViaBootOption() in
"IntelFrameworkModulePkg/Library/GenericBdsLib/BdsBoot.c":
//
// If it's Device Path that starts with a hard drive path, append it with the
front part to compose a
// full device path
//
WorkingDevicePath = NULL;
if ((DevicePathType (DevicePath) == MEDIA_DEVICE_PATH) &&
(DevicePathSubType (DevicePath) == MEDIA_HARDDRIVE_DP)) {
WorkingDevicePath = BdsExpandPartitionPartialDevicePathToFull (
(HARDDRIVE_DEVICE_PATH *)DevicePath
);
if (WorkingDevicePath != NULL) {
DevicePath = WorkingDevicePath;
}
}
The simple StrnCmp() call in Match()
[OvmfPkg/Library/PlatformBdsLib/QemuBootOrder.c] regresses this logic,
because it kills the relative devpath -- starting with HD(...) -- before
it could reach the quoted completion.
I'm not sure how to resolve this -- even in theory. The OpenFirmware
device paths end *exactly before* the HD() part -- they simply don't
contain the necessary information. The output of *any* OFW->UEFI
translation can be matched *only* against the leading UEFI device
sub-path. Which the HD(...) format currently prepared by efibootmgr
lacks.
It could be worked around, maybe, by completing the relative devpath
(with BdsExpandPartitionPartialDevicePathToFull(), see above) before
matching it against the output of the OFW->UEFI translation.
Laszlo
------------------------------------------------------------------------------
Learn the latest--Visual Studio 2012, SharePoint 2013, SQL 2012, more!
Discover the easy way to master current and previous Microsoft technologies
and advance your career. Get an incredible 1,500+ hours of step-by-step
tutorial videos with LearnDevNow. Subscribe today and save!
http://pubads.g.doubleclick.net/gampad/clk?id=58040911&iu=/4140/ostg.clktrk
_______________________________________________
edk2-devel mailing list
edk2-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/edk2-devel
