Fix error in __vsnprintf_chk()

__vsnprintf_chk() passed the wrong length argument to the vsnprintf()
call. I'm not aware of any specific bug this solves, but I found this
error while auditing the *_chk() functions to figure out why "rogue"
works when compiled with -DUSE_FORTIFY_LEVEL=1 but not with
USE_FORTIFY_LEVEL=2.

Signed-off-by: Nadav Har'El <nyh@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
virtio-blk: Switch to and add tracepoint

Switch the existing printout based debug info to tracepoint and add new
tracepoint.

Signed-off-by: Asias He <asias@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
core: make osv::run return shared pointer or null and store it on loader.cc

This restore the original behavior of osv::run in place before the mkfs.so and
cpiod.so split committed a day ago.

Signed-off-by: Benoit Canet <benoit@irqsave.net>
Reviewed-by: Nadav Har'El <nyh@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>