On 2019-12-16, Florian Weimer <fweimer@xxxxxxxxxx> wrote:
> > diff --git a/include/uapi/linux/fcntl.h b/include/uapi/linux/fcntl.h
> > index 1d338357df8a..58c3a0e543c6 100644
> > --- a/include/uapi/linux/fcntl.h
> > +++ b/include/uapi/linux/fcntl.h
> > @@ -93,5 +93,40 @@
> >
> > #define AT_RECURSIVE 0x8000 /* Apply to the entire subtree */
> >
> > +/*
> > + * Arguments for how openat2(2) should open the target path. If @resolve is
> > + * zero, then openat2(2) operates very similarly to openat(2).
> > + *
> > + * However, unlike openat(2), unknown bits in @flags result in -EINVAL rather
> > + * than being silently ignored. @mode must be zero unless one of {O_CREAT,
> > + * O_TMPFILE} are set.
> > + *
> > + * @flags: O_* flags.
> > + * @mode: O_CREAT/O_TMPFILE file mode.
> > + * @resolve: RESOLVE_* flags.
> > + */
> > +struct open_how {
> > + __aligned_u64 flags;
> > + __u16 mode;
> > + __u16 __padding[3]; /* must be zeroed */
> > + __aligned_u64 resolve;
> > +};
> > +
> > +#define OPEN_HOW_SIZE_VER0 24 /* sizeof first published struct */
> > +#define OPEN_HOW_SIZE_LATEST OPEN_HOW_SIZE_VER0
> > +
> > +/* how->resolve flags for openat2(2). */
> > +#define RESOLVE_NO_XDEV 0x01 /* Block mount-point crossings
> > + (includes bind-mounts). */
> > +#define RESOLVE_NO_MAGICLINKS 0x02 /* Block traversal through procfs-style
> > + "magic-links". */
> > +#define RESOLVE_NO_SYMLINKS 0x04 /* Block traversal through all symlinks
> > + (implies OEXT_NO_MAGICLINKS) */
> > +#define RESOLVE_BENEATH 0x08 /* Block "lexical" trickery like
> > + "..", symlinks, and absolute
> > + paths which escape the dirfd. */
> > +#define RESOLVE_IN_ROOT 0x10 /* Make all jumps to "/" and ".."
> > + be scoped inside the dirfd
> > + (similar to chroot(2)). */
> >
> > #endif /* _UAPI_LINUX_FCNTL_H */
>
> Would it be possible to move these to a new UAPI header?
>
> In glibc, we currently do not #include <linux/fcntl.h>. We need some of
> the AT_* constants in POSIX mode, and the header is not necessarily
> namespace-clean. If there was a separate header for openat2 support, we
> could use that easily, and we would only have to maintain the baseline
> definitions (which never change).
Sure, (assuming nobody objects) I can move it to "linux/openat2.h".
--
Aleksa Sarai
Senior Software Engineer (Containers)
SUSE Linux GmbH
<https://www.cyphar.com/>
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