vmcore: continue vmcore initialization if PT_NOTE is found empty
vmcore: continue vmcore initialization if PT_NOTE is found empty

Currently when an empty PT_NOTE is detected, vmcore initialization
fails.  It sounds too harsh.  Because PT_NOTE could be empty, for
example, one offlined a cpu but never restarted kdump service, and after
crash, PT_NOTE program header is there but no data contains.  It's
better to warn about the empty PT_NOTE and continue to initialise
vmcore.

And ultimately the multiple PT_NOTE are merged into a single one, all
empty PT_NOTE are discarded naturally during the merge.  So empty
PT_NOTE is not visible to user space and vmcore is as good as expected.

Signed-off-by: WANG Chao <c2aee7029fe382c8d64e1072d797631ac5391d91@redhat.com>
Cc: Vivek Goyal <61d11262d0d9873ddb5a887f48fcb04e8c5973d0@redhat.com>
Cc: HATAYAMA Daisuke <e293c7e13ecc029aa287dca4b8ecfdf8a10ea3b9@jp.fujitsu.com>
Cc: Greg Pearson <b1e95202550504f8c4c27303f2812e458915533b@hp.com>
Cc: Baoquan He <1b95acc14c82271bede46a8b6a84bd6be6240a7c@redhat.com>
Signed-off-by: Andrew Morton <5c1e68b099950c134891f0b6e179498a8ebe9cf9@linux-foundation.org>
Signed-off-by: Linus Torvalds <69652caca27c8b940640ad396ab71f93cacec34f@linux-foundation.org>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs