- In the initial description of si_addr, do not claim that it is
always the faulting instruction.
- For si_addr, document that it is generally set to the PC for
synchronous signals, but that it can be set to the the address of
the faulting memory reference including SIGSEGV and SIGBUS. In
particular, while SIGSEGV generally sets si_addr to the faulting
memory reference, SIGBUS can vary. On some platforms, some SIGBUS
signals set si_addr to the PC and other SIGBUS signals set si_addr
to the faulting address depending on the specific hardware
exception.
- For si_trapno, most (all?) synchronous signals should set this to
some value.