[PATCH 0/5] Add second memory region for crash kernel
H. Peter Anvin
hpa at zytor.com
Thu Apr 22 18:37:53 EDT 2010
On 04/22/2010 03:07 PM, Eric W. Biederman wrote:
> Have you tried loading a 64bit vmlinux directly into a higher address
> range? There may be a bit or two missing but you should be able to
> load a linux kernel above 4GB. I tested the basics of that mechanism
> when I made the 64bit relocatable kernel.
> I don't buy the argument that there is a direct connection between
> the amount of memory you have and how much memory it takes to dump it.
> Even an indirect connections seems suspicious.
We actually have a 64-bit entry point even in bzImage; it is at offset
+0x200 from the 32-bit entry point. Right now that offset is not
exported anywhere, but it has been stable for a very long time... at
least for as far back as the decompressor has been 64 bits.
The interface to the 64-bit code is by necessity wider, since there is
no such thing as paging off in 64-bit mode, but it probably isn't *too*
hard to figure out how page tables need to be set up in order to work
properly. At that point, it would be good to document it.
More information about the kexec