On 11 February 2013 11:13, Vineet Gupta <Vineet.Gupta1@xxxxxxxxxxxx> wrote: > On Monday 11 February 2013 03:06 PM, Jonas Bonn wrote: >> On 11 February 2013 08:26, Vineet Gupta <Vineet.Gupta1@xxxxxxxxxxxx> wrote: >> >>> The only downside of this patch is that userspace signal stack grows in size, >>> since signal frame only cares about scratch regs (pt_regs), but has to accommodate >>> unused placeholder for callee regs too by virtue of using user_regs_struct. >> 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?) /Jonas -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
