Date: Sat, 05 Jan 2008 10:16:33 +0000 From: Bruce Cran <bruce@cran.org.uk> To: Marco van de Voort <marcov@stack.nl> Cc: freebsd-hackers@freebsd.org, Ivan Voras <ivoras@freebsd.org> Subject: Re: Re: Architectures with strict alignment? Message-ID: <477F5901.3000006@cran.org.uk> In-Reply-To: <20080104131529.GA31354@stack.nl> References: <fl4c8o$vpu$1@ger.gmane.org> <20080104131529.GA31354@stack.nl>
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Marco van de Voort wrote: > On Sat, Dec 08, 2007 at 03:43:30AM +0100, Ivan Voras wrote: > > >> Which of the architectures FreeBSD supports (if any) have strict memory >> alignment requirements? (in the sense that accessing a 32-bit integer >> not aligned on a 32-bit address results in a hardware trap/exception). >> > > I do know that older PPCs (PowerPC603) have a requirement on aligning of > floats. > > IIRC the e.g. Linux the kernel hooks an exception handler that makes it > transparent for apps (at the cost of some performance), and NetBSD does not > I never ran FreeBSD on PPC, so I wouldn't know that one. > The newer 32-bit PPCs (G4 / PPC7447A) can't handle unaligned 64-bit accesses either - they generate a trap which gets handled by fix_unaligned in /sys/powerpc/powerpc/trap.c on FreeBSD. -- Bruce
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