On Wed, 30 Sep 2009, Arnd Bergmann wrote: > > Right, you still need to save all the registers from the entry code. > I was under the wrong assumption that task_pt_regs(current) > would give the full register set on all architectures. > > However, I'd still hope that a new system call can be defined in > a way that you only need to have an assembly wrapper to save > the full pt_regs, but no arch specific code to get the syscall arguments > out of that again. In do_clone(), you need a pointer to pt_regs and > the user stack pointer, but that can be generated from > user_stack_pointer(regs). I don't think it can. You don't know what the system call stack layout is. > Does task_pt_regs(current) give the right pointer on all architectures > or do we also need to pass the regs into the syscall? I do not believe that it gives the right pointer in general. In fact, I can guarantee it doesn't. Even on x86 it only works for certain contexts (non-vm86 mode at a minimum), and on architectures like alpha it's not at all sufficient, because even if you can locate the 'pt_regs' structure, you _also_ need the extra guarantees of the pt_regs being next to the extended signal state register structure - and that only happens for magic sequences like signal handling and explicit setups like fork/clone. So I do repeat: if you think you can do all of this in generic code, then you're sadly and totally mistaken. Don't even try. It may work on some architectures, but it's simply fundamentally _wrong_. Linus _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/containers
