Re: [PATCH x86/mm 6/6] x86-64 ia32 ptrace get/putreg32 current task

["H. Peter Anvin" <hpa@zytor.com>]

Chuck Ebbert wrote:
> On 11/29/2007 01:09 PM, Linus Torvalds wrote:
> > > >  	case offsetof(struct user32, regs.gs):
> > > >  		*val = child->thread.gsindex;
> > > > +		if (child == current)
> > > > +			asm("movl %%gs,%0" : "=r" (*val));
> > > Won't this return the kernel's GS instead of the user's?
> > No, %gs is untouched by the kernel, so it contains user space version, and 
> > getting the value directly from %gs looks correct.
>
> But this is x86_64, where swapgs is done on kernel entry.

For i386-x86_64 sharing, getting to the user segments probably should be 
macroized.  I'm thinking something like 
get_user_[cs|ds|es|fs|gs|ss](thread) in <asm/processor.h> doing the 
appropriate thing for different configurations.

	-hpa
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/