Currently /proc/iomem exports physical memory also apart from io device
memory.  But on i386, it truncates any memory more than 4GB.  This leads to
problems for kexec/kdump.

Kexec reads /proc/iomem to determine the system memory layout and prepares a
memory map based on that and passes it to the kernel being kexeced.  Given the
fact that memory more than 4GB has been truncated, new kernel never gets to
see and use that memory.

Kdump also reads /proc/iomem to determine the physical memory layout of the
system and encodes this informaiton in ELF headers.  After a crash new kernel
parses these ELF headers being used by previous kernel and vmcore is prepared
accordingly.  As memory more than 4GB has been truncated, kdump never sees
that memory and never prepares ELF headers for it.  Hence vmcore is truncated
and limited to 4GB even if there is more physical memory in the system.

This patch exports memory more than 4GB through /proc/iomem on i386.
Signed-off-by: NVivek Goyal <vgoyal@in.ibm.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>