Re: [Fastboot] [CFT] ELF Relocatable x86 and x86_64 bzImages

From: Eric W. Biederman
Date: Mon Aug 07 2006 - 14:07:56 EST

Don Zickus <dzickus@xxxxxxxxxx> writes:

> On Sat, Aug 05, 2006 at 10:07:01AM -0600, Eric W. Biederman wrote:
>> Don Zickus <dzickus@xxxxxxxxxx> writes:
>> >> The length error comes from lib/inflate.c
>> >>
>> >> I think it would be interesting to look at orig_len and bytes_out.
>> >>
>> >> My hunch is that I have tripped over a tool chain bug or a weird
>> >> alignment issue.
>> >
>> > I thought so too, but I took vmlinuz images from people (Vivek) who had it
>> > boot on their systems but those images still failed on my two machines.
>> >
>> >>
>> >> The error is the uncompressed length does not math the stored length
>> >> of the data before from before we compressed it. Now what is
>> >> fascinating is that our crc's match (as that check is performed first).
>> >>
>> >> Something is very slightly off and I don't see what it is.
>> >
>> > I printed out orig_len -> 5910532 (which matches vmlinux.bin)
>> > bytes_out -> 5910531
>> >
>> >>
>> >> After looking at the state variables I would probably start looking
>> >> at the uncompressed data to see if it really was decompressing
>> >> properly. If nothing else that is the kind of process that would tend
>> >> to spark a clue.
>> >
>> > I am not familiar with the code, so very few sparks are flying. I'll
>> > still dig through though. Thanks for the tips.
>> I guess the interesting thing to do would be to
>> - Recompute the crc to see if we still match.
>> - Possibly instrument of flush_window.
>> I have a strange feeling that the uncompressed data is getting corrupted
>> after we have flushed the window.
> It seems to be an AMD64 vs EM64T problem. AMD chipsets work but Intel
> chipsets don't.
> I also blindly incremented bytes_out (as a really cheap hack), it didn't
> work until I added some random putstr's below it (timing??). Then the
> kernel booted.
> Still looking into things.

Odd. I wonder if I'm missing a serializing instruction somewhere,
to ensure the effects of ``self modifying code'' aren't a problem.
As I read Intels Documentation if you have a jump before you get
to the code there shouldn't be a problem.

Still that doesn't really explain bytes_out.

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