[PATCH] x86_64: Don't write out segments from vsyscall32 DSO if it is not mapped

It's possible to get an invalid page fault in kernel mode when we try to
write out segments from vsyscall32 when dumping core for a 32bit process if
the vsyscall32 DSO is not mapped in its address space (which can happen if,
for example, ulimit -v 100 is run).

Signed-off-by: Suleiman Souhlal <suleiman@google.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>