You signed in with another tab or window. Reload to refresh your session.You signed out in another tab or window. Reload to refresh your session.You switched accounts on another tab or window. Reload to refresh your session.
On LR machine, consider F calling G calling H, which grows stack.
The stack looks like
... locals ...
saved LR = return PC in F <- SP points here at morestack
H's frame (to be created)
At morestack, we save
gp.sched.pc = H's morestack call
gp.sched.sp = H's entry SP (the arrow above)
gp.sched.lr = return PC in G
Currently, when unwinding through morestack (if _TraceJumpStack
is set), we switch PC and SP but not LR. We then have
frame.pc = H's morestack call
frame.sp = H's entry SP (the arrow above)
As LR is not set, we load it from stack at *sp, so
frame.lr = return PC in F
As the SP hasn't decremented at the morestack call,
frame.fp = frame.sp = H's entry SP
Unwinding a frame, we have
frame.pc = old frame.lr = return PC in F
frame.sp = old frame.fp = H's entry SP a.k.a. G's SP
The PC and SP don't match. The unwinding will go off if F and G
have different frame sizes.
Fix this by preserving the LR when switching stack.
Also add code to detect infinite loop in unwinding.
TODO: add some test. I can reproduce the infinite loop (or throw
with added check) but the frequency is low.
TryBot-Result: Gopher Robot <firstname.lastname@example.org>
Run-TryBot: Cherry Mui <email@example.com>
Reviewed-by: Eric Fang <firstname.lastname@example.org>
Reviewed-by: Benny Siegert <email@example.com>
(cherry picked from commit 74f0009)
Reviewed-by: Austin Clements <firstname.lastname@example.org>