On Wed, 25 Feb 2015 10:20:43 +0100 Ingo Molnar <mi...@kernel.org> wrote:
> But, if we do that, we can do even better, and also do an > optimization of the 64-bit entry path as well: we could > simply mask RAX with 0x3ff and not do a compare. Pad the > syscall table up to 0x400 (1024) entries and fill in the > table with sys_ni syscall entries. > > This is valid on 64-bit and 32-bit kernels as well, and it > allows the removal of a compare from the syscall entry > path, at the cost of a couple of kilobytes of unused > syscall table. > > The downside would be that if we ever grow past 1024 > syscall entries we'll be in trouble if new userspace calls > syscall 513 on an old kernel and gets syscall 1. What if we test against ~0x3ff and jump to sys_ni if anything is set. This would still work with new userspace calls on older kernels. -- Steve -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
