[Crash-utility] [PATCH] add arm support for libgcore

[Dave Anderson]

----- Original Message -----
...
> > > The reason why I've included the ``page fault'' in the default warning
> > > message is to avoid the situation where users get confused they have
> > > successfully got complete user-space coredump.
> > >
> > > GDB tends to work well because part of user stack necessary for
> > > backtrace is not paged out most of time; of course, the backtrace
> > > would fail if paged-out.
> > >
> > > Thanks.
> > > HATAYAMA, Daisuke
> > >
> > 
> > I see, thanks for detailed explanation.
> > My another curious is whether we could refill those missing swapped page, if
> > we provide whole swap partition data?
> > 
> > Thanks,
> > Lei
> 
> Aren't most of those "page fault" references that you see
> during a gcore operation typically referring to pages that
> exist in the target task's virtual memory map but have not
> been referenced?

For example, none of these pages are swapped out:
 
 crash> gcore 1951
 gcore: WARNING: FPU may be inaccurate: 1951
 gcore: WARNING: page fault at 386df98000
 gcore: WARNING: page fault at 386df99000
 gcore: WARNING: page fault at 386df9e000
 gcore: WARNING: page fault at 386df9f000
 gcore: WARNING: page fault at 7fff632f3000
 gcore: WARNING: page fault at 7fff632f4000
 gcore: WARNING: page fault at 7fff632f5000
 gcore: WARNING: page fault at 7fff632f6000
 gcore: WARNING: page fault at 7fff632f7000
 gcore: WARNING: page fault at 7fff632f8000
 gcore: WARNING: page fault at 7fff632f9000
 gcore: WARNING: page fault at 7fff632fa000
 gcore: WARNING: page fault at 7fff632fb000
 gcore: WARNING: page fault at 7fff632fc000
 gcore: WARNING: page fault at 7fff632fd000
 gcore: WARNING: page fault at 7fff632fe000
 gcore: WARNING: page fault at 7fff632ff000
 gcore: WARNING: page fault at 7fff63300000
 gcore: WARNING: page fault at 7fff63301000
 gcore: WARNING: page fault at 7fff63302000
 gcore: WARNING: page fault at 7fff63303000
 gcore: WARNING: page fault at 7fff63304000
 gcore: WARNING: page fault at 7fff63305000
 Saved core.1951.system_crash
 crash>

In fact, no swap was used at all:

 crash> swap
 FILENAME           TYPE         SIZE      USED   PCT  PRIORITY
 /dm-1            PARTITION    5439480k       0k   0%     -1
 crash>

And here are the "page fault" pages from above, all either unreferenced
file-backed pages or unreferenced data pages:

 crash> vm -p
 ... [ cut ] ...
 VIRTUAL     PHYSICAL
 ... [ cut ] ...
 386df98000  FILE: /lib64/libc-2.12.so  OFFSET: 198000
 386df99000  FILE: /lib64/libc-2.12.so  OFFSET: 199000
 ... [ cut ] ...
 386df9e000  (not mapped)
 386df9f000  (not mapped)
 ... [ cut ] ...
 7fff632f3000  (not mapped)
 7fff632f4000  (not mapped)
 7fff632f5000  (not mapped)
 7fff632f6000  (not mapped)
 7fff632f7000  (not mapped)
 7fff632f8000  (not mapped)
 7fff632f9000  (not mapped)
 7fff632fa000  (not mapped)
 7fff632fb000  (not mapped)
 7fff632fc000  (not mapped)
 7fff632fd000  (not mapped)
 7fff632fe000  (not mapped)
 7fff632ff000  (not mapped)
 7fff63300000  (not mapped)
 7fff63301000  (not mapped)
 7fff63302000  (not mapped)
 7fff63303000  (not mapped)
 7fff63304000  (not mapped)
 7fff63305000  (not mapped)
 ...
 
Dave