On Sep 30, 2008, at 12:21 PM, Sebastian Siewior wrote:
Milton Miller wrote:
|load: entry = 0x80053c flags = 0
|nr_segments = 2
|segment[0].buf = 0x1002b8f0
|segment[0].bufsz = 80
|segment[0].mem = (nil)
|segment[0].memsz = 1000
|segment[1].buf = 0x4803f008
|segment[1].bufsz = 3a3138
|segment[1].mem = 0x800000
|segment[1].memsz = 3b0000
I would expect a third segment (kernel/zImage, dtb, and purgatory),
but its not clear that you are getting that far yet.
segment 0 looks like a small segment which should create "boot loader
environment". That one does nothing.
Segment 1 is my cuImage. What is purgatory?
Purgatory is the code that runs between the old kernel exiting and the
new image loading. Its supposed to be where any registers, dynamic
memory structures, etc get set before calling the image supplied to
kexec user space. Its built as part of the kexec-tools suite as a
completley relocatable elf and selected and edited based on type of
image being loaded. For powerpc64 it is where we take the "boot" /
master cpu's physical id from r3, put it in the dtb header, and load
the address of r3 with the dtb before going into the kernel (for
vmlinux, and could do for zImage but don't have support upstream). If
you were booting a cuImage (as opossed to the code you are aparently
running, which is what grant called simple image, effectively), then
you would set any registers uboot leaves behind in this code.
The standard code supplied by kexec-tools also calculates a checkum
(sha1) of each loaded segment (except itself) and checks that vs the
sum calculated by kexec-tools userspace (printing a message that on
powerpc has no way to be displayed then going into an infinite
spinloop. Oh well, I digress.) and also where, for kdump, any memory
backup copy is performed when a specific memory segment is needed to
boot (eg initial page for ppc64 and classic32 that require interrupt
(exception) vectors to be in page 0-2).
The powerpc64 code reads the existing device tree from
/proc/device-tree and modifies a few things (initrd start, end,
bootargs = command line, and (for kdump) which memory is available and
usable to the kernel (vs reserved because it was used for the old
kernel, whose image we want to dump, and which could be under dma).
Now. The entry address in image->start is valid and is the
entrypoint of
the "custom" cuImage. Custom means that it does not depend any
register
values passed from u-boot (the original one needs a pointer to bd_t).
The only requirement is a valid 1:1 memory mapping.
ok sounds good. does this have the dtb in it too?
Yes it does.
ok. sounds like a simple image then ... ok to start with, but
eventually we want to dtb passed via the tool so we can set command
line etc.
I actually developed the powerpc 64 code this way to, and let someone
else make the standard tool work. But the standard tool is useful.
The branch above is taken, so I've found my current mapping
ok, but should you not be using PID0 explictly to say global only?
The kernel mapping should only be global and therefore that might be a
good idea.
obviously, a jtag or similar hardware debugger would be best. Second
I have here CodeWarrior usb tap but after more than one hour playing
with that thing I started to hack assembly char put. It helper more :)
kexec seems to work now :) I get "nobody cared irq X" from time to
time so I thing I have to fix here something.....
kexec is a bit harder than kdump in that you have to make sure all
devices have shutdown handlers. Easier for those that are modules
that can be loaded and unloaded (make sure they have a shutdown method
that is comparable to unload, or even unload in a script to test).
kdump is harder in that while the dma is left running in the old
kernel, the new kernel has to fit in the cracks left over, and has to
initialize devices that were not shutdown.
As a final note, it looks like you are currently replacing the code
in relocate_new_kernel with book-e code. Obviously this will need
refinement to select or move to heat_xx to merge.
Yep, this is next what is going to happen. I would prefer to have them
runtime switchable instead of build depend.
well, I am thinking that we will end up with one exit condition for all
book-e, one for classic 32, and one for powerpc64. I don't understand
what you think should be runtime switchable, unless you were thinking
about code that should be in purgatory (supplied by userspace as far as
the kernel is concerned).
Remember the exit point of the kernel is a single entry point (we cheat
and make it 2 on powerpc64, one for master and a second for slaves,
although for book-e we could follow epapr instead), and specified pages
of memory with user specified content. The state is supposed to be an
emulation of "mmu off", not "I just ran uboot and am its client
loader".
Again, I don't have any direct experience, but mauybe this gives you
some ideas.
Your hints helped. Thx for that.
sure. Maybe the new hits about purgatory will keep you on track too.
milton
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