Re: sending password from pre-efi boot prompt to iokit driver
Re: sending password from pre-efi boot prompt to iokit driver
- Subject: Re: sending password from pre-efi boot prompt to iokit driver
- From: David Elliott <email@hidden>
- Date: Thu, 2 Apr 2009 12:12:04 -0400
On Apr 1, 2009, at 1:15 PM, Joel Reymont wrote:
What mechanism should I use to share a password entered at the EFI
pre-boot prompt to a driver?
I thought of storing the password in NVRAM but don't believe it
would go away upon reboot. It's imperative that the password
evaporates once a machine is rebooted.
It's been a while since I looked at this but I'm almost certain that
the EFI variable protocol has the ability to store variables either in
NVRAM or in a temporary store. When you set the value of a variable
you specify where you want it to be stored.
So that probably will work. You should investigate it further,
perhaps by looking at the Tiano code.
Failing that, you can always produce a configuration table allocated
out of runtime RAM. The booter will examine all of the entries in the
system table's configuration table list and make the address of the
table data available as the table property of an entry in
IODeviceTree:/efi/configuration-table whose name is the GUID as a
string.
Or at least I _think_ the booter (boot.efi) just looks at all the
configuration tables listed by the system table and outputs their
pointers into the device tree. I can't imagine it being coded to
filter the list. Obviously without source it's impossible to know,
but this would be my guess.
-Dave
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