On Wed, Feb 29, 2012 at 05:39:55PM -0800, Eugene Surovegin wrote: > 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. Ok, understood. Reviewed-by: Simon Horman <horms at verge.net.au>
