Comment 44 for bug 111869

$ebp based frames are only highly unpredictable when they don't exist.
Unfortunately you can't detect this with certainty (i.e. if $ebp points
to the frame or is used for something else), that's where the problem is.
In normal compiled code (libc with its load of inline asm doesn't count
as that for some functions unfortunately) you can be sure that $ebp points
to a frame (if not compiled with omit-frame-pointer of course).

So, under the assumptions that we want this whole thing to get useful
backtraces out of segfaults, and that further such segfaults in libc are
not happening very often, but that they rather occur in application code
(without being called back from libc code, like with qsort), it seems sensible
to just rely on $ebp frames, even if it also has its share of problems.