- Fix kernel stack unwinding end-of-function false-positive
The kernel stack unwinder assumes that any jr $ra indicates the end
of the current function. However, modern compilers generate code
that contains jr $ra at various places inside the function.
- Handle LLD inter-function padding when looking for the start of a
function.
- Use call site for symbol name/offset when unwinding
Currently we use the return address, which will normally just give
an output that's off by 8 from the actual call site. However, for
tail calls, this is particularly bad, as we end up printing the
symbol name for the function that comes after the one that made the
call. Instead we should go back two instructions from the return
address for the unwound program counter.
Submitted by: arichardson (1, 2), jrtc27 (3)
Reviewed by: arichardson
Obtained from: CheriBSD
Sponsored by: DARPA
Differential Revision: https://reviews.freebsd.org/D27363
2066d695bb