Hi all- We currently have some giant turds in the way that syscalls are numbered. We have the x86_32 table, which is totally sane other than some legacy multiplexers. Then we have the x86_64 table, which is, um, demented:
- The numbers don't match x86_32. I have no idea why. - We use bit 30, which triggers in_x32_syscall(). It should have been bit 31, bit I digress. - We have this weird set of extra x32 syscalls that start at 512. Who wants to bet whether we have no bugs if someone does syscall with, say, nr == 512 (i.e. not 512 | BIT(30)) or nr == (16 | BIT(30))? The latter would be non-compat ioctl with in_x32_syscall() set and hence in_compat_syscall() set. - Bloody restart_syscall() has a different number on x86_64 and x64_32, which is a big mess. I propose we consider some subset of the following: 1. Introduce restart_syscall_2(). Make its number be 1024. Maybe someday we could start using it instead of restart_syscall(). The only issue I can see is programs that allow restart_syscall() using seccomp but don't allow the new variant. 2. Introduce an outright ban on new syscalls with nr < 1024. 3. Introduce an outright ban on the addition of new __x32_compat syscalls. If new compat hacks are needed, they can use in_compat_syscall(), thank you very much. 4. Modify the wrappers of the __x32_compat entries so that they will return -ENOSYS if in_x32_syscall() returns false. 5. Adjust the scripts so that we only have to wire up new syscalls once. They'll have a nr above 1024, and they'll have the same nr on all x86 variants. Thoughts?
