[PATCH 0/4] adding yaboot bootonce capabilities

[Dustin Kirkland]

adding yaboot bootonce capabilities

When testing potentially volatile Linux kernels, especially in automated
testing systems, it is often desirable to boot a kernel "exactly once",
and have the system return to normal, fallback, default operation on
subsequent boots.

The basic design is as follows:

User-space
        - Using ybin, a user specifies a particular kernel label to
        "--bootonce"
        - ybin validates that label, and uses nvsetenv to set the
        OpenFirmware environment variable "boot-once", and checks that
        that operation succeeded

Bootloader-space
        - On boot, yaboot checks for the value of the "boot-once" OF
        environment variable, stores that in a global "bootoncelabel"
        string, AND zeros out the OF environment value thereafter
        - If bootoncelabel matches a label, when printing the yaboot
        label menu, note that with "&" before the label
        - When setting the "default" kernel image, if bootoncelabel is
        set, use that instead of default

I've tested the following patch set fairly extensively on an IBM p570
LPAR.  Where possible, I've pasted those in the patch description.

Many thanks to Jeremy Kerr and Paul Mackerras for their advice and ideas
in the last couple of days, and the initial pointers from Paul Nasrat
some time ago.

:-Dustin