Re: fs/binfmt_aout.o, Error: suffix or operands invalid for `cmp'[was Re: 2.6.1

[H. Peter Anvin]

Steven Rostedt wrote:
> > >
> > It's not (it's #APP, i.e. inline assembly); rather, it's an illegal
> > constraint.
>
> It's GCC optimizing a little too much.

No, it's not... it's the author of the inline assembly who told gcc a 
lie at what it was allowed to optimize.  The constraint is "g" 
(equivalent to "rmi"), but "rm" is the correct constraint.

There is already a patch in Andrew's repo for this.

>
> #define __range_ok(addr,size) ({ \
> 	unsigned long flag,sum; \
> 	__chk_user_ptr(addr); \
> 	asm("addl %3,%1 ; sbbl %0,%0; cmpl %1,%4; sbbl $0,%0" \
> 		:"=&r" (flag), "=r" (sum) \
> 		:"1" (addr),"g" ((int)(size)),"g" (current_thread_info()->addr_limit.seg)); \
> 	flag; })
>
> What happened was that gcc optimized the
> (current_thread_info()->addre_limit.seg to be a constant. Thus cmpl
> failed.

... perfectly legally so, given the "g" constraint.

	-hpa
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