Re: [Crash-utility] [PATCH/RFC] Fix relocation address
On Thu, 17 Dec 2009 11:17:56 -0500 (EST)
Dave Anderson <anderson(a)redhat.com> wrote:
> > So I started looking into the code and found something
which looks like
> > a typo in relocate() (patch below). Changing this makes crash work for me.
>
> Actually it's not a typo -- your patch would presumably break with all kernels
> that have a CONFIG_PHYSICAL_START is greater than CONFIG_PHYSICAL_ALIGN, which
> is what the patch was written to handle.
>
> What are your kernel's CONFIG_PHYSICAL_START and CONFIG_PHYSICAL_ALIGN
> values? Does crash work with your kernel on the live system?
You are right. I had problems with getting things working, so I've
played around with various settings. I had CONFIG_PHYSICAL_START set to
0 and CONFIG_PHYSICAL_ALIGN set to 0x100000. Setting these to e.g.,
0x100000 and 0x100000 unbreaks things again.
I don't need to supply --reloc either then, not sure what I did wrong
before. I'm sticking with sane settings from now on.
> Anyway, I believe that the fix would require support for
supplying a
> negative --reloc value.
On the other hand, if the config values were the other way around, the
problem didn't use to show up -- at least according to list item "1)"
below in the changelog:
1) Configure the kernel with CONFIG_PHYSICAL_START less than
or equal to CONFIG_PHYSICAL_ALIGN. Having done that, there
is no problem; the resultant vmlinux file will be loaded at
the address for which it was compiled, which has always
been the case.
I wonder if you can use the unpatched crash, but supply a --reloc
value that
will cause a wrap-around to the correct value?
Well, I suppose that would work if it was possible to supply a negative
--reloc value, but I'm not sure it's really worth it. What would be
nice would be to get a more descriptive error message.
Thanks for the help, please ignore the patch.
// Simon