Re: pseudo: host user contamination

[Seebs <seebs@seebs.net>]

On Tue, 27 Mar 2018 18:26:05 +0200
Enrico Scholz <enrico.scholz@sigma-chemnitz.de> wrote:

> Perhaps we have different man pages but e.g. [1] mentions only
> registers in the context of the kernel interface but not when
> entering/leaving syscall(2) itself.

And yet, it's syscall(2) doing the thing... or possibly it's not,
because it turns out I don't read IA64 assembly.

> When, then this is completely undocumented and a glibc-only thing.
> Other implementations[2] follow the behavior described in the man page
> and do not set some magic registers on return.

> I did not found the glibc syscall implementation for MIPS atm.

Hmm. In MIPS, it does appear that glibc's syscall is *using* the return
register, rather than writing to it.

Yeah, I misread the IA64 code.

I'm gonna go ahead and try to implement a wrapper. Until I've got test
cases available, it's gonna be a custom wrapper, that will ENOTSUP for
renameat2, and try to pass other things on naively.

But I think Andre and Enrico are right that the code in glibc is not
doing what I interpreted it as doing.

-s