[0/4] xenstore domain: improve logging capabilities

Message

James Dingwall Dec. 4, 2019, 9:27 a.m. UTC

Hi,

When xenstore is run as a domain there is no way to get log messages from the
process.  This small series adds a new --trace-syslog option which will copy
trace() and xprintf() messages to syslog, in the MiniOS case this directs to
the kernel printk().  When it is enabled in the xenstore domain messages are
recorded on the hypervisor console according to the guest_loglvl.

A new xenstore control is also added so that the functionality can be toggled
dynamically at runtime.

I think there is possibly some room for further enhancements so that it is
more easily possible to log at different priorities rather than a simple
trace() = LOG_DEBUG, xprintf() = LOG_ERR.  Perhaps the addition of some
more macros similar to eprintf could be useful too.  If such change would
be considered useful then some guidance on the most appropriate direction
to take would be helpful.

The series is based on 4.11.3 but I can rebase it to master.

James