hookup vsyscall replay

vsyscalls
see October 6th 2023 e-mail

io_uring

md5sum the executable and store a copy, so can reproduce later even
in the face of changing versions

Try having the PERF_FLAG_FD_NO_GROUP and
	PERF_FLAG_FD_OUTPUT flags work together.

Try passing a fd over a socket

Set breakpoint events on the mmap buffers?
Randomly mmap() existing events?
  - be sure to unmap once the event is destroyed

Try unmapping random page in middle of mmap buffer?

Forking -- make sure we clean up child threads?

Attaching to more pids (?)

For sysfs events, try also flipping a few random bits to try
to catch corner cases.

+ ->mmap2 support
+ double check why cpu is never set to -1?

Set relevant sample_stack_user flags.  If SAMPLE_STACK_USER set
try setting varios believable sample_stack_user values.

