On Sat, Jun 28, 2014 at 10:07 AM, Pavel Machek <pa...@ucw.cz> wrote: > On Thu 2014-06-26 13:47:32, Andy Lutomirski wrote: >> On Thu, Jun 26, 2014 at 1:12 PM, H. Peter Anvin <h...@zytor.com> wrote: >> > The real question is if we care that sysret and iter don't match. On 32 >> > bits the situation is even more complex. >> >> At least for 64 bits, iret vs sysret is purely a kernel implementation >> detail (except where a tracer modifies things that are inaccessible to >> sysret), so ISTM it's worth one instruction to make them match. >> >> I noticed this thing while fiddling with moving some of the syscall >> tracing logic to C. This isn't a real problem, but it at least made >> me scratch my head. > > If possible, we'd like to trace programs without programs being noticed they > are > being traced. See subterfugue utility, for example. > > It is certainly worth one extra instruction.
I tend to agree. FWIW, I haven't looked at the ia32 stuff, but it should be possible to do something similar if it's not there already. The iret path can set any user state it wants. --Andy -- 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/
