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Add fcntl sealing interfaces from Linux 3.17 to bits/fcntl-linux.h
- From: Joseph Myers <joseph at codesourcery dot com>
- To: <libc-alpha at sourceware dot org>
- Date: Wed, 6 Sep 2017 15:30:47 +0000
- Subject: Add fcntl sealing interfaces from Linux 3.17 to bits/fcntl-linux.h
- Authentication-results: sourceware.org; auth=none
While reviewing Linux 4.13 for glibc header changes needed, I noticed
that bits/fcntl-linux.h was missing F_ADD_SEALS etc. from Linux 3.17.
I didn't find any discussion indicating this omission is deliberate.
Now, these interfaces can only be used with file descriptors created
with memfd_create, and we don't have a memfd_create wrapper in glibc
(a patch was submitted in October 2014, albeit without documentation /
tests, and discussions continued over the next few months, but without
consensus on whether to add the interface - and we still lack any
general consensus on syscall wrappers), but I don't think that's a
reason to exclude the constants from bits/fcntl-linux.h (especially as
the header does not look compatible with simultaneously including
linux/fcntl.h).
(Some of those 2014/2015 discussions raised concerns about difficulty
using the memfd_create / sealing interface, but those seem to me more
like a question of whether it should be part of the OS-independent GNU
API - in my view, even fairly specialized syscalls ought to have
wrappers added to glibc if not obsolescent, but there may be cases
where we only want to include them in the Linux-specific API and
anything in the OS-independent GNU API should be different - rather
than being relevant to whether constants for use with fcntl should
appear in headers.)
2017-09-06 Joseph Myers <joseph@codesourcery.com>
* sysdeps/unix/sysv/linux/bits/fcntl-linux.h [__USE_GNU]
(F_ADD_SEALS): New macro.
[__USE_GNU] (F_GET_SEALS): Likewise.
[__USE_GNU] (F_SEAL_SEAL): Likewise.
[__USE_GNU] (F_SEAL_SHRINK): Likewise.
[__USE_GNU] (F_SEAL_GROW): Likewise.
[__USE_GNU] (F_SEAL_WRITE): Likewise.
diff --git a/sysdeps/unix/sysv/linux/bits/fcntl-linux.h b/sysdeps/unix/sysv/linux/bits/fcntl-linux.h
index 0cd0a5d..fc65fc2 100644
--- a/sysdeps/unix/sysv/linux/bits/fcntl-linux.h
+++ b/sysdeps/unix/sysv/linux/bits/fcntl-linux.h
@@ -202,6 +202,8 @@
# define F_NOTIFY 1026 /* Request notifications on a directory. */
# define F_SETPIPE_SZ 1031 /* Set pipe page size array. */
# define F_GETPIPE_SZ 1032 /* Set pipe page size array. */
+# define F_ADD_SEALS 1033 /* Add seals to file. */
+# define F_GET_SEALS 1034 /* Get seals for file. */
#endif
#ifdef __USE_XOPEN2K8
# define F_DUPFD_CLOEXEC 1030 /* Duplicate file descriptor with
@@ -271,6 +273,14 @@ struct f_owner_ex
};
#endif
+#ifdef __USE_GNU
+/* Types of seals. */
+# define F_SEAL_SEAL 0x0001 /* Prevent further seals from being set. */
+# define F_SEAL_SHRINK 0x0002 /* Prevent file from shrinking. */
+# define F_SEAL_GROW 0x0004 /* Prevent file from growing. */
+# define F_SEAL_WRITE 0x0008 /* Prevent writes. */
+#endif
+
/* Define some more compatibility macros to be backward compatible with
BSD systems which did not managed to hide these kernel macros. */
#ifdef __USE_MISC
--
Joseph S. Myers
joseph@codesourcery.com