• Austin Clements's avatar
    runtime: handle g0 stack overflows gracefully · 78561c4a
    Austin Clements authored
    Currently, if the runtime overflows the g0 stack on Windows, it leads
    to an infinite recursion:
    
    1. Something overflows the g0 stack bounds and calls morestack.
    
    2. morestack determines it's on the g0 stack and hence cannot grow the
    stack, so it calls badmorestackg0 (which prints "fatal: morestack on
    g0") followed by abort.
    
    3. abort performs an INT $3, which turns into a Windows
    _EXCEPTION_BREAKPOINT exception.
    
    4. This enters the Windows sigtramp, which ensures we're on the g0
    stack and calls exceptionhandler.
    
    5. exceptionhandler has a stack check prologue, so it determines that
    it's out of stack and calls morestack.
    
    6. goto 2
    
    Fix this by making the exception handler avoid stack checks until it
    has ruled out an abort and by blowing away the stack bounds in
    lastcontinuehandler before we print the final fatal traceback (which
    itself involves a lot of stack bounds checks).
    
    Fixes #21382.
    
    Change-Id: Ie66e91f708e18d131d97f22b43f9ac26f3aece5a
    Reviewed-on: https://go-review.googlesource.com/120857
    Run-TryBot: Austin Clements <austin@google.com>
    TryBot-Result: Gobot Gobot <gobot@golang.org>
    Reviewed-by: 's avatarIan Lance Taylor <iant@golang.org>
    Reviewed-by: 's avatarAlex Brainman <alex.brainman@gmail.com>
    78561c4a
panic.go 24.1 KB