IO memory read from /proc/vmcore leads to hang.

[Mahesh Jagannath Salgaonkar]

On 07/12/2016 03:16 AM, Daniel Walker wrote:
> 
> Hi,
> 
> I found found that on my Powerpc machine there is some IO memory which
> will cause the box to hang if I read it. It's a custom device that was
> added to the board for a special purpose.
> 
> I was looking for a way to exclude this memory from the dump, and while
> doing that I found that kexec makes a list of memory segments that go
> into the core file. I was wondering why most of the kexec architecture
> don't appear to exclude device memory like what's listed in /proc/iomem.
> 
> Is there a good reason why that's not the case?

Kexec/Kdump is designed to capture entire old kernel's memory that will
be available in /proc/vmcore. There is a different userspace tool called
'makedumpfile' (https://sourceforge.net/projects/makedumpfile/), which
can be used to exclude certain memory pages from the dump while reading
from /proc/vmcore. See if that helps you.

Thanks,
-Mahesh.

> 
> Daniel
> 
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