This fixes a panic when attaching to an already-stopped process after
r325028. While here, clean up a few other things in the control flow
of the 'sendsig' section:
- Only check for P_STOPPED_TRACE rather than either of P_STOPPED_SIG
or P_STOPPED_TRACE for most ptrace requests. The signal handling
code in kern_sig.c never sets just P_STOPPED_SIG for a traced
process, so if P_STOPPED_SIG is stopped, P_STOPPED_TRACE should be
set anyway. Remove a related debug printf. Assuming P_STOPPED_TRACE
permits simplifications in the 'sendsig:' block.
- Move the block to clear the pending thread state up into a new
block conditional on P_STOPPED_TRACE and handle delivering pending
signals to the reporting thread and clearing the reporting thread's
state in this block.
- Consolidate case to send a signal to the process in a single case
for PT_ATTACH. The only case that could have been in the else before
was a PT_ATTACH where P_STOPPED_SIG was not set, so both instances
of kern_psignal() collapse down to just PT_ATTACH.
Reported by: pho, mmel
Reviewed by: kib
Differential Revision: https://reviews.freebsd.org/D12837
dd16f28153