Re: pt_regs leak into userspace (was Re: [PATCH v3 20/71] ARC:Signal handling)

From: Al Viro
Date: Mon Feb 11 2013 - 09:07:19 EST

On Mon, Feb 11, 2013 at 11:30:50AM +0100, Jonas Bonn wrote:

> >> Is this really true? Don't setcontext and friends require that _all_
> >> the registers be part of sigcontext?
> >
> > But for an ABI - callee saved regs will anyhow be saved/restored even in
> > setcontext case ! So collecting it for that purpose seems useless, or am I missing
> > something here.
> Yes, I agree with you on the ABI bit... but set/get/swapcontext are
> special in that they use rt_sigreturn to "trick" the kernel into
> swapping out _all_ registers; it's a light-weight (userspace) context
> switch.
> (I really don't know this area very well, though, so I'm hoping
> somebody more knowledgable jumps in here... Al?)

I'd suggest asking itanic folks; they do *not* put callee-saved stuff into
sigcontext. AFAICS, they don't have setcontext() implemented as a syscall
at all - it's done as sigprocmask() + doing to callee-saved registers what
longjmp() does.
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at