Date: Sat, 06 Dec 2003 17:16:00 -0800 From: Peter Wemm <peter@wemm.org> To: Daniel Eischen <eischen@vigrid.com> Cc: cvs-all@FreeBSD.org Subject: Re: cvs commit: src/lib/libc/amd64/gen makecontext.c Message-ID: <20031207011600.E70C32A7EA@canning.wemm.org> In-Reply-To: <Pine.GSO.4.10.10312042042001.1477-100000@pcnet5.pcnet.com>
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Daniel Eischen wrote: > On Thu, 4 Dec 2003, Peter Wemm wrote: > > > peter 2003/12/04 17:36:44 PST > > > > FreeBSD src repository > > > > Modified files: > > lib/libc/amd64/gen makecontext.c > > Log: > > "Fix" makecontext() so that the C code begins execution with its > > ABI-required stack alignment. C code expects that the push of the > > return address disturbed the 16 byte alignment and it will take correctiv e > > measures to fix it before making another call. Of course, if its wrong > > to start with, then all hell breaks loose. Essentially we "fix" this > > by making the stack alignment odd to start with. > > Hey, you didn't include this little bit of knowledge in your amd64 "notes" > that you sent me ;-) Heh. I never get it right. I've had to resort to things like this: assert((((long)__builtin_frame_address(0)) & 15 == 0), "misaligned stack!"); The trick of course is that gcc-3.3.3 is broken and __builtin_frame_address(0) doesn't actually work unless you compile *also* with -fno-omit-frame-pointer on amd64. Anyway, thats the only way I've ever been able to get this stuff sorted out. :-) Cheers, -Peter -- Peter Wemm - peter@wemm.org; peter@FreeBSD.org; peter@yahoo-inc.com "All of this is for nothing if we don't go to the stars" - JMS/B5
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