mount_utils: add support for mount_setattr() syscall

configure.ac

@@ -652,8 +652,9 @@ AC_CHECK_HEADER([ifaddrs.h],
 AC_HEADER_MAJOR
 
 # Check for some syscalls functions
-AC_CHECK_FUNCS([setns pivot_root sethostname unshare rand_r confstr faccessat gettid memfd_create move_mount open_tree execveat clone3 fsopen fspick fsconfig fsmount, openat2, close_range, statvfs])
+AC_CHECK_FUNCS([setns pivot_root sethostname unshare rand_r confstr faccessat gettid memfd_create move_mount open_tree execveat clone3 fsopen fspick fsconfig fsmount, openat2, close_range, statvfs, mount_setattr])
 AC_CHECK_TYPES([__aligned_u64], [], [], [[#include <linux/types.h>]])
+AC_CHECK_TYPES([struct mount_attr], [], [], [[#include <linux/mount.h>]])
 AC_CHECK_TYPES([struct open_how], [], [], [[#include <linux/openat2.h>]])
 AC_CHECK_TYPES([struct clone_args], [], [], [[#include <linux/sched.h>]])
 AC_CHECK_MEMBERS([struct clone_args.set_tid],[],[],[[#include <linux/sched.h>]])

src/lxc/mount_utils.h

@@ -152,6 +152,10 @@
 #define MOUNT_ATTR_NODIRATIME 0x00000080 /* Do not update directory access times */
 #endif
 
+#ifndef MOUNT_ATTR_IDMAP
+#define MOUNT_ATTR_IDMAP 0x00100000
+#endif
+
 __hidden extern int mnt_attributes_new(unsigned int old_flags, unsigned int *new_flags);
 
 __hidden extern int mnt_attributes_old(unsigned int new_flags, unsigned int *old_flags);

src/lxc/syscall_numbers.h

@@ -680,4 +680,24 @@
 	#endif
 #endif
 
+#ifndef __NR_mount_setattr
+	#if defined __alpha__
+		#define __NR_mount_setattr 552
+	#elif defined _MIPS_SIM
+		#if _MIPS_SIM == _MIPS_SIM_ABI32	/* o32 */
+			#define __NR_mount_setattr (442 + 4000)
+		#endif
+		#if _MIPS_SIM == _MIPS_SIM_NABI32	/* n32 */
+			#define __NR_mount_setattr (442 + 6000)
+		#endif
+		#if _MIPS_SIM == _MIPS_SIM_ABI64	/* n64 */
+			#define __NR_mount_setattr (442 + 5000)
+		#endif
+	#elif defined __ia64__
+		#define __NR_mount_setattr (442 + 1024)
+	#else
+		#define __NR_mount_setattr 442
+	#endif
+#endif
+
 #endif /* __LXC_SYSCALL_NUMBERS_H */

src/lxc/syscall_wrappers.h

@@ -209,6 +209,24 @@ extern int fsmount(int fs_fd, unsigned int flags, unsigned int attr_flags);
 #endif
 
 /*
+ * mount_setattr()
+ */
+struct lxc_mount_attr {
+	__u64 attr_set;
+	__u64 attr_clr;
+	__u64 propagation;
+	__u64 userns_fd;
+};
+
+#ifndef HAVE_MOUNT_SETATTR
+static inline int mount_setattr(int dfd, const char *path, unsigned int flags,
+				struct lxc_mount_attr *attr, size_t size)
+{
+	return syscall(__NR_mount_setattr, dfd, path, flags, attr, size);
+}
+#endif
+
+/*
  * Arguments for how openat2(2) should open the target path. If only @flags and
  * @mode are non-zero, then openat2(2) operates very similarly to openat(2).
  *