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Date:      Wed, 24 Apr 2002 11:47:27 -0400 (EDT)
From:      Andrew Gallatin <gallatin@cs.duke.edu>
To:        Brandon S Allbery KF8NH <allbery@ece.cmu.edu>
Cc:        Kenneth Culver <culverk@alpha.yumyumyum.org>, freebsd-hackers@FreeBSD.ORG, FreeBSD-CURRENT List <freebsd-current@FreeBSD.ORG>
Subject:   Re: implementing linux mmap2 syscall
Message-ID:  <15558.54159.737973.56540@grasshopper.cs.duke.edu>
In-Reply-To: <1019662269.6094.1.camel@pyanfar.ece.cmu.edu>
References:  <15557.27747.802212.659760@grasshopper.cs.duke.edu> <20020423181748.W31638-100000@alpha.yumyumyum.org> <15558.46600.351433.784766@grasshopper.cs.duke.edu> <1019662269.6094.1.camel@pyanfar.ece.cmu.edu>

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Brandon S Allbery KF8NH writes:
 > On Wed, 2002-04-24 at 10:41, Andrew Gallatin wrote:
 > > Maybe the argument isn't where you expect it to be, but is there.
 > > Can you make a test program which calls mmap2 with its 6th arg as
 > > something unique like 0xdeadbeef?  Then print out (in hex :) the trapframe
 > > from the linux prepsyscall routine & see if you can find the deadbeef.
 > 
 > My recollection is that beyond 5 arguments, a pointer to the remaining
 > ones is passed.  (But my recollection may be wrong and I don't wish to
 > subject myself to the source cesspool at the moment....)
 > 

I think that's how it used to work.  Apparently, they've changed it
recently and they now pass 6 args in registers.  Eg, in the linux
kernel sources, old_mmap() fetches its args via copy_from_user(),
whereas the newer sys_mmap2() doesn't.

Drew

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