[Bug 10503] Sid Meier's Alpha Centauri: Wine segfaults when clicking on a city.

[wine-bugs at winehq.org]

http://bugs.winehq.org/show_bug.cgi?id=10503


Anastasius Focht <focht at gmx.net> changed:

           What    |Removed                     |Added
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                 CC|                            |focht at gmx.net




--- Comment #8 from Anastasius Focht <focht at gmx.net>  2007-11-19 14:24:41 ---
Hello,

--- snip ---
This sounds like something that could generate a segmentation fault?
--- snip ---

sure.
That initial posting in the link you provided pretty summed it up.

That game code is "abusing" ESP while writing to DIB region, resulting in
access violation exception.
Wine detects the stack pointer being outside of thread stack range and hence
the warning.
Actually wine kills itself (double fault) when building the stack frame for the
raise function by relying on that invalid ESP from signal context (despite the
warning).

--- quote ---
So, what I'm wondering is if anyone who has experiance with the
exception handling code has any thoughts on how this problem can be
fixed.
--- quote ---

Well, general rule: do not rely on faulting context ESP while setting up
exception handling stuff
Wine has no knowledge at this point that the faulting thread is actually
abusing ESP.
There might be cases where the abused "counter" ESP has coincidentally a "good"
value (within thread stack limits) but wine cannot make safe assumptions at
this point (only print diagnostics).

A solution would be to generally use an alternate stack to build the raise
frame.
Maybe a specially reserved area, a stack page between TEB stack guard and
NtCurrentTeb()->Tib.StackLimit to safely build the frame.
This would prevent wine from accidentally damaging/overwriting parts of the
faulting thread stack with the raise frame, causing double faults.

Regards


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