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

Roland McGrath
2007-11-29T22:22:52Z

> > 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?
[...]
> But this is x86_64, where swapgs is done on kernel entry.

As I understand it, and from what the documentation I have says, swapgs has
nothing to do with the %gs selector. It affects the "GS base register",
i.e. the MSR.

Thanks,
Roland