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Date: Fri, 03 Feb 2006 16:32:04 +0000
From: Chris Taylor <chris AT equate DOT dyndns DOT org>
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To: Dave Bodenstab <dave AT bodenstab DOT org>
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Subject: Re: Possible bug with mmap on XP?
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Dave Bodenstab wrote:
> On Thu Feb  2 22:55:08 2006 Corinna Vinschen <corinna-cygwin AT cygwin DOT com> wrote:
> 
> 
>>>Is this the way things are supposed to work on XP?
>>
>>This is a constraint of the underlying OS, yes.  The old implementation
>>of mmap used up to 1.5.18 didn't support PROT_EXEC at all, it was just
>>fake.  Since 1.5.19, PROT_EXEC mapping is now supported correctly, which
>>means, the underlying NT functions are called requesting PAGE_EXECUTE
>>protection.
>>
>>But here's the problem.  To create file mappings with PAGE_EXECUTE
>>protection, the file must be opened with GENERIC_EXECUTE access. 
>>This is done internally in mmap, but it fails if the file doesn't
>>have the execute permission set.
>>
>>Whether or not this behaviour is backed by SUSv3, I'm not sure.  SUSv3
>>states "if an implementation cannot support the combination of access
>>types specified by prot, the call to mmap() shall fail.", so here's one
>>situation in which the implementation can't support the combination of
>>access types specified by prot.
> 
> 
> OK.
> 
> I would like to modify my program to set the required permissions.
> Is the mapping between Cygwin's uname()'s sysname and XP, NT, 98SE,
> 98, etc. available somewhere?  Actually, if I could just tell if the
> underlying windows is XP, that would be sufficient I think.  
> 
> Thanks.
> 
> 

XP == NT_5.1
2k == NT_5.0
98 == 4.10
95 == 4.0 (I believe)

I don't know what WinME is, and I don't particularly wish to either.
I /suspect/ that NT4 is likely to be NT_4.0, but this may have changed 
with the later service packs (doubtful though, in my opinion). I don't 
have an nt4 box to verify this with however.


Chris

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