On Thu, Aug 13, 2015 at 3:54 PM, Linus Torvalds <[email protected]> wrote: > On Thu, Aug 13, 2015 at 3:49 PM, Linus Torvalds > <[email protected]> wrote: >> >> Does the attached patch make sense and work? > > Btw, I'm not all that happy with it anyway. > > I still think Denys' patch also potentially changed what audit and > strace see for %rax in the pt_regs to -ENOSYS, which I'm not convinced > is a good change.
For better for for worse, the native 64-bit path changed several versions agi, and nothing broke that I'm aware of. The change was: commit 54eea9957f5763dd1a2555d7e4cb53b4dd389cc6 Author: Andy Lutomirski <[email protected]> Date: Fri Sep 5 15:13:55 2014 -0700 x86_64, entry: Treat regs->ax the same in fastpath and slowpath syscalls AFAIK, ptrace has always seen ax == -ENOSYS on syscall entry for native 64-bit syscalls. My change just simplified the fast path (which is invisible by ptrace for obvious reasons, unless someone traces fork or something along those lines *without*) and made it less different from the slow path. (IIRC it also simplified some stuff down the road.) Looking at 3.19's ia32entry.S, it has: sysenter_tracesys: #ifdef CONFIG_AUDITSYSCALL testl $(_TIF_WORK_SYSCALL_ENTRY & ~_TIF_SYSCALL_AUDIT),TI_flags+THREAD_INFO(%rsp,RIP-ARGOFFSET) jz sysenter_auditsys #endif SAVE_REST CLEAR_RREGS movq $-ENOSYS,RAX(%rsp)/* ptrace can change this for a bad syscall */ So I think it's always been the intent and practice that ptracers would see ax == -ENOSYS on syscall entry. IOW, whether this is good or bad, I don't think it's really a change. --Andy -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
