memcpy limitation

[Bernd Walter]

On Thu, Jan 18, 2007 at 08:18:23PM +0100, Olivier Houchard wrote:
> On Thu, Jan 11, 2007 at 11:15:28AM +0100, Bernd Walter wrote:
> > I get a sigbus with the following:
> > #0  0x00033158 in $a () at lcp.c:939
> > 939           memcpy(&req, opt, sizeof req);
> > (gdb) print req
> > $1 = {hdr = {id = 0 '\0', len = 0 '\0'}, proto = 0, period = 0}
> > (gdb) print &req
> > $2 = (struct lqrreq *) 0xbfffe4a0
> > (gdb) print opt
> > $3 = (struct fsm_opt *) 0xbfffe5b6
> > 
> > Shouldn't memcpy work with any alignment?
> > 
> 
> It certainly does. Would you have a simple test case which reproduce this ?
> Or does it happen as soon as you try to do an unaligned copy ?
> I'm quite confused on why it would happen, memcpy is shared between the kernel
> and the userland, and in kernel I'm sure it does unaligned copies. 

It's a while back, but I remember from looking at the dissassembly that
it had nothing in common with our assembly function.
I thought this is a compiler internal.
Will try to do a small test case.
As a workaround I exchange the memcpy call with a bcopy.

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