Running the profiler while Firefox runs in rr sometimes crashes, and it seems the SP register is far from the known stack area (ending at StackTop), which then proceeds to copy some protected memory.
Note that there was already a `start < end` test, this patch adds an equivalent test on the other side, allowing for a 1MB stack size. Observed stacks during quick testing were up to around 520KB, and the crashing rr case was in the trillions(!), so 1MB should be an appropriate number that should catch "wrong" SPs while allowing real stacks.
Differential Revision: https://phabricator.services.mozilla.com/D123605
dc9ead3c7b