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Re: Cyg32 on Win64 fails with stack-protector


On May 30 19:29, Bill Zissimopoulos wrote:
> Corinna, thanks for your response.
> 
> On 5/29/18, 9:59 AM, Corinna Vinschen wrote:
> 
> >Hi Ben,
> >
> >On Apr 27 19:12, Ben RUBSON wrote:
> >> Hi,
> >> 
> >> We are facing an issue with Cygwin 2.10 32 bits running on Windows 64
> >>bits.
> >> 
> >> Issue was found running EncFS FUSE FS using WinFsp.
> >> 
> >> When forking, and calling StartServiceCtrlDispatcher, program fails with
> >> 0xC0000028 / STATUS_BAD_STACK.
> >> 
> >> Testing several Cygwin versions reveals that issue was introduced
> >>between
> >> 2017-11-14 and 2017-12-01.
> >> And Bill (WinFsp author) found that compiling with -fno-stack-protector
> >> works around the issue.
> >> 
> >> There you can then find the full story and Bill's nice investigation :
> >> https://github.com/billziss-gh/winfsp/issues/161
> >> 
> >> Could it be possible something went wrong with Cygwin ?
> >> 
> >> Thank you very much for your support !
> >
> >Even with Bill's additionl info I have no idea what change in the
> >above time frame might be the culprit, especially since no change
> >has been made to stack handling.
> >
> >I suggest to build your own Cygwin and bisect it.  Also, you
> >may want to run your stuff under GDB and set breakpoints to, e.g.,
> >Cygwin's exception::handle method.  Make sure the cygwin1.dbg
> >file can be found by GDB.
> 
> There appear to be some SSP related commits in the discussed time frame.
> For example:
> 
> https://sourceware.org/git/?p=newlib-cygwin.git;a=commitdiff;h=0a5dfdbd1ba3
> 663a54fa1a7de1a6c4a0a3316a6e
> 
> Another possibility would be a change in the gcc default options between
> Cygwin 2.9 and Cygwin 2.10. I do not know if this is possible, but perhaps
> gcc in 2.9 compiles with -fstack-protector disabled by default and gcc in
> 2.10 compiles with it enabled by default?
> 
> Bill

I CCed Ken (gcc) and Yaakov (SSP) to get more qualified input than
my own Cygwin DLL centric view.


Corinna

-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Maintainer                 cygwin AT cygwin DOT com
Red Hat

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