On Sat, 30 Jan 2010, Steven Rostedt wrote: > > The kernel is limited to what instructions it can perform, no floating > point for example (of course there are some exceptions). Actually, the reason the kernel is limited to not performing floating point instructions is that teh kernel doesn't own the floating point register set - it's too big to save/restore, so the kernel leaves it alone. But for emulating an instruction from user space, it would be perfectly fine to do an FP instruction in kernel space, since we're explicitly doing it on behalf of user space, and with user space owning it. Of course, that would require that we _only_ touch the registers that user space wants us to touch, which is likely impossible in practice for anything but an execute-out-of-line model. > But generally, the instructions in the kernel should be easier to > emulate than in userspace. Yeah, we control the kernel instructions better, and we know what the environment is. For example, we never have to worry about vm86 mode or segments when we fix up kernel instructions, but user space can do anything, of course. Linus -- To unsubscribe from this list: send the line "unsubscribe linux-next" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
