On Fri, May 24, 2013 at 06:46:53PM +0200, Michael Holzheu wrote: > On Fri, 24 May 2013 11:28:49 -0400 > Vivek Goyal <vgoyal at redhat.com> wrote: > > > On Fri, May 24, 2013 at 05:06:26PM +0200, Michael Holzheu wrote: > > [snip] > > > As /proc/vmcore is the most used and useful interface, I prefer that > > we swap memory and put that info in elf headers. For /dev/oldme, I > > don't mind if we leave it as it is. If somebody really cares, then > > I guess we need to write a new command line option which /dev/mem > > can parse and which tells it about swaps so that /dev/oldmem can > > map things correctly. (This is better than hardcoding things). > > Besides of the potential /dev/oldmem issue, I still do not understand > the option of doing the swap in the elf header. Looks like I missed > here a fundamental design point of kdump :( > > Is that done by specifying different virtual and physical addresses in > the ELF header? Nope. We keep the virtual to physical address mapping same. We just modify the p_offset in PT_LOAD elf header to represent where actually the memory is present physically. And when /proc/vmcore reads the data, it reads it from p_offset. IOW, p_offset and p_paddr will be different for swapped memory but should be same for memory which has not been swapped. Thanks Vivek
