On Fri, January 20, 2012 23:41, H. Peter Anvin wrote: > On 01/20/2012 02:40 PM, Roland McGrath wrote: >> If you change the size of a regset, then the new full size will be the size >> of the core file notes. Existing userland tools will not be expecting >> this, they expect a known exact size. If you need to add new stuff, it >> really is easier all around to add a new regset flavor. When adding a new >> one, you can make it variable-sized from the start so as to be extensible >> in the future. We did this for NT_X86_XSTATE, for example. >> > > Yes, that definitely seems cleaner. I would prefer Linus' way of just stuffing it into cs. Jamie also wanted a bit telling in what mode the userspace is running. That's 3 bits in total, with one bit telling whether the other bits are valid or not. Anything else? Maybe a bit telling whether it is syscall entry or exit? As all this is very x86_64 specific and cs is already used to figure out the mode, it seems overkill to add a new regset just for this. It's a lot easier for existing code to add an extra cs check than to use different register sets and different ptrace commands. Considering that PTRACE_GETREGSET is undocumented it's likely that existing code isn't using it much. Greetings, Indan -- 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
