On 2019-12-16, Florian Weimer fweimer@redhat.com 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".