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Re: Cygwin vsFTPd porting issues
Corinna,
On Mon, Jan 13, 2003 at 03:55:17PM +0100, Corinna Vinschen wrote:
> On Mon, Jan 13, 2003 at 09:36:24AM -0500, Jason Tishler wrote:
> > 160 37333219 [main] vsftpd 2232 fixup_mmaps_after_fork: ReadProcessMemory failed for MAP_PRIVATE address 0xB40000, Win32 error 299
> >
> > I will try to dig deeper to determine why ReadProcessMemory() is
> > failing with ERROR_PARTIAL_COPY (i.e., 299), but any help or
> > pointers will be greatly appreciated.
>
> If you can figure out why that happens, I'd really appreciate a simple
> testcase. Please compare the above with the strace output generated
> by mmap(), probably you will find a discrepancy like the address in
> the above strace output is not inside of a mapped block.
I haven't tried the above yet. See below...
> It's also a big difference if the mmap is mapped anonymously or to a
> file since the mmap() code behaves pretty different.
vsFTPd defaults to anonymous mappings under Cygwin. However, I forced
it to try file based mappings on Friday as a workaround, but this failed
in the same way. After reading the vsFTPd *and* Cygwin code some more,
it is clear why the behavior is the same. vsFTPd uses /dev/zero if
anonymous mappings are not available and Cygwin treats mappings to
/dev/zero the same as anonymous mappings.
> Another way would be to remove MAP_PRIVATE from the mmap() call and
> try again. MAP_PRIVATE is somewhat problematic on Windows hosts,
> unfortunately.
Replacing MAP_PRIVATE with MAP_SHARED worked around the mmap()/fork()
problem. Is this a reasonable accommodation? Or, should I try to get
MAP_PRIVATE to work?
Thanks,
Jason
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