Re: [PATCH] syscalls: Document OCI seccomp filter interactions & workaround

[Florian Weimer]

* Mark Wielaard:

> For valgrind the issue is statx which we try to use before falling back
> to stat64, fstatat or stat (depending on architecture, not all define
> all of these). The problem with these fallbacks is that under some
> containers (libseccomp versions) they might return EPERM instead of
> ENOSYS. This causes really obscure errors that are really hard to
> diagnose.

The probing sequence I proposed should also work for statx. 8-p

> Don't you have the same issue with glibc for those architectures that
> don't have fstatat or 32bit arches that need 64-bit time_t? And if so,
> how are you working around containers possibly returning EPERM instead
> of ENOSYS?

That's a good point.  I don't think many people run 32-bit containers in
the cloud.  The Y2038 changes in glibc impact 64-bit ports a little, but
mostly on the fringes (e.g., clock_nanosleep vs nanosleep).

Thanks,
Florian
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