break to debugger in bhyve

[Peter Grehan]

> Works fine for me once I compile with the ALT_BREAK_TO_DEBUGGER config option.

  Also works without that, but the sysctl (or tunable) has to be set:

root at bhyve-b1:~ # sysctl debug.kdb.alt_break_to_debugger=1
debug.kdb.alt_break_to_debugger: 0 -> 1

  (issued the 3-char sequence CR ~ ctl-b)

root at bhyve-b1:~ # KDB: enter: Break to debugger
[ thread pid 11 tid 100003 ]
Stopped at      kdb_alt_break_internal+0x17f:   movq    $0,kdb_why
db>

later,

Peter.