Re: [Crash-utility] [PATCH/RFC] Fix relocation address

On Thu, 17 Dec 2009 11:17:56 -0500 (EST) Dave Anderson <anderson(a)redhat.com&gt; 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