pstore: Add pmsg - user-space accessible pstore object

A secured user-space accessible pstore object. Writes
to /dev/pmsg0 are appended to the buffer, on reboot
the persistent contents are available in
/sys/fs/pstore/pmsg-ramoops-[ID].

One possible use is syslogd, or other daemon, can
write messages, then on reboot provides a means to
triage user-space activities leading up to a panic
as a companion to the pstore dmesg or console logs.

Signed-off-by: Mark Salyzyn <salyzyn@android.com>
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Tony Luck <tony.luck@intel.com>

diff --cc fs/pstore/Kconfig
Simple merge

diff --cc fs/pstore/Makefile
Simple merge

diff --cc fs/pstore/inode.c
Simple merge

diff --cc fs/pstore/internal.h
Simple merge

diff --cc fs/pstore/platform.c
Simple merge

diff --cc fs/pstore/pmsg.c
Simple merge

diff --cc fs/pstore/ram.c
Simple merge

diff --cc include/linux/pstore.h
Simple merge

diff --cc include/linux/pstore_ram.h
Simple merge