On Fri, Jul 10, 2015 at 7:12 AM, Eric W. Biederman <[email protected]> wrote: > Andy Lutomirski <[email protected]> writes: > >> On the other hand, sys_vm86 fails if the syscall slow path is in use. >> That means that quite a few Fedora versions (auditing), anything with >> ptrace, seccomp (before 3.16 IIRC), and anything with context tracking >> is probably actually *improved* by turning off the vm86 syscalls even >> for dosemu users. > > Is there any chance that vm86 is sufficiently badly broken before this > that we can conclude vm86 is not in use? It would really simplify this > discussion if we could point to code rot and say that it is clear that > no one has been testing this code path for ages, and that the code can't > possibly work the way it is now. That would just let us remove vm86. >
Having just written a pile of tests for it, I don't think so, as long as none of the syscall slow path stuff is in use :( >> It only says "[OK]" because my test case isn't careful enough. That's >> a failure. I suspect it was a much worse failure a couple versions >> ago before my ENOSYS-reworking patch went in. >> >> I'll try to confirm later this week that dosemu can really handle real >> mode without sys_vm86. > > I have not looked in ages but certainly on 64bit dosemu can. > > As someone else pointed out dosemu maps the zero page so that may also > be a point where vm86 support gets broken. Right. And someone pointed out that vbetool sometimes needs access to virtual (or emulated virtual) addresses above 3GB, and vm86 can't do that. --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/
