This provides a new sysprof-live-unwinder subprocess that runs as root to
allow accessing all processes on the system via /proc/$pid/. It is spawned
by sysprofd with various perf event FDs and a FD to write captures to.
Ideally the capture_fd is something that will naturally error if the client
application crashes (such as a socketpair() having the peer close). This
is not enforced but encouraged. Additionally, an event_fd is used to allow
the client application to signal the live-unwinder to exit.
Unwinding is performed by looking at the modules loaded into the target
pid and using libdwfl to access DWARF/CFI/etc state machinery. Stack data
does not touch the disk as it exists in a mmap buffer from perf and is
then translated into a callchain and sent to the Sysprof client.
Unwinding occurs as normal post-mortem though is improved through the use
of debuginfod to locate the appropriate symbols.
This removes -Dagent and just uses -Dtools as it only affects sysprof-cli
and sysprof-agent. We still need to patch sysprof-cli for recent changes
as we did for sysprof-agent though.
Additionally, we haven't used the v2 service in forever, so drop that as
I can't imagine anyone has been using it.
This allows consumers to get a RAPL profiler object on the D-Bus at
org.gnome.Sysprof3 with path /org/gnome/Sysprof3/RAPL. This can be used
by the clients to record extra power statistics.
It requires the `turbostat` program to be installed, and is provided in
packages such as `kernel-tools` on Fedora. Distributions may want to
ensure that is available as a dependency of Sysprof, but it is not
strictly required.
As we gain in usage, we need to be more careful about using a prefix
that will not collide with other symbols. So version 3 of our ABI will
change to using Sysprof/SYSPROF/sysprof as the various prefixes.
The soname/api version bump will happen later on this branch so that
things are easier to test up until then.
The big thing going on here is that we are going to split up the libraries
a bit better, and remove GObject from the capture library. The libsysprof
library will bring in the capture library statically, so we can export the
symbols we want.
Eventually, we will bump the version to sysprof-3, but not yet.
