On Wed, Feb 29, 2012 at 5:32 PM, Simon Horman <horms at verge.net.au> wrote: > On Wed, Feb 29, 2012 at 05:23:10PM -0800, Eugene Surovegin wrote: >> On Wed, Feb 29, 2012 at 5:18 PM, Simon Horman <horms at verge.net.au> wrote: >> >> > On Wed, Feb 29, 2012 at 09:21:23AM -0800, Eugene Surovegin wrote: >> > > Per-CPU allocations are not guaranteed to be physically contiguous. >> > > However, kdump kernel and user-space code assumes that per-CPU >> > > memory, used for saving CPU registers on crash, is. >> > > This can cause corrupted /proc/vmcore in some cases - the main >> > > symptom being huge ELF note section. >> > > >> > > Force page alignment for note_buf_t to ensure that this assumption holds. >> > >> > Ouch. I'm surprised there is an allocation on crash, perhaps >> > it could at least be done earlier? And am I right in thinking >> > that this change increases the likely hood that the allocation >> > could fail? >> > >> >> I'm not following. This allocation is done on start-up, not on crash. >> If you cannot allocate this much memory on system boot, I'm not sure what >> else you can do on this system.... > > Sorry, my eyes deceived me. You are correct and I agree. > > Is it the case that note_buf_t is never larger than PAGE_SIZE? > If so I your patch looks good to me. Currently, maximum note size is hardcoded in kexec-tools to 1024 (MAX_NOTE_BYTES). Usually it's way less. IIRC on x86_64 it's 336 bytes. -- Eugene
