On 02/08/2012 08:20 PM, Indan Zupancic wrote: > > CS is already available to user space, but any other value than 0x23 or 0x33 > will confuse user space, as that is all they know about. Apparently Xen uses > different values, but if those are static then user space can check for them > separately. But if the values change dynamically then some other way may be > needed. > > But does it make much sense to pass the CPU mode of user space if that mode > can be changed at any moment? I don't think it really does. Can you give an > example of how that info can be used by a ptracer? > Uh... you could make THAT argument about ANY register state! I believe H.J. can fill you in about the usage. > > Only confusion I can think of is someone following the register values > across a systemcall instruction. Then the swizzling may be unexpected. > But if they do that they could check how the sycall was entered and > compensate for that. (I can't think of any requirement why this would > need to be race-free.) > You'd have to know how you'd entered, which right now you don't have any way to know. -hpa -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
