linux-kernel - [PATCH v2 01/11] mount_setattr.2: document glibc >= 2.36 syscall wrappers

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Message-Id: <20250807-new-mount-api-v2-1-558a27b8068c@cyphar.com>
Date: Thu, 07 Aug 2025 03:44:35 +1000
From: Aleksa Sarai <cyphar@...har.com>
To: Alejandro Colomar <alx@...nel.org>
Cc: "Michael T. Kerrisk" <mtk.manpages@...il.com>, 
 Alexander Viro <viro@...iv.linux.org.uk>, Jan Kara <jack@...e.cz>, 
 Askar Safin <safinaskar@...omail.com>, 
 "G. Branden Robinson" <g.branden.robinson@...il.com>, 
 linux-man@...r.kernel.org, linux-api@...r.kernel.org, 
 linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org, 
 David Howells <dhowells@...hat.com>, Christian Brauner <brauner@...nel.org>, 
 Aleksa Sarai <cyphar@...har.com>
Subject: [PATCH v2 01/11] mount_setattr.2: document glibc >= 2.36 syscall
 wrappers

Glibc 2.36 added syscall wrappers for the entire family of fd-based
mount syscalls, including mount_setattr(2).  Thus it's no longer
necessary to instruct users to do raw syscall(2) operations.

Signed-off-by: Aleksa Sarai <cyphar@...har.com>
---
 man/man2/mount_setattr.2 | 45 +++++++--------------------------------------
 1 file changed, 7 insertions(+), 38 deletions(-)

diff --git a/man/man2/mount_setattr.2 b/man/man2/mount_setattr.2
index 60d9cf9de8aa..c96f0657f046 100644
--- a/man/man2/mount_setattr.2
+++ b/man/man2/mount_setattr.2
@@ -10,21 +10,12 @@ .SH LIBRARY
 .RI ( libc ,\~ \-lc )
 .SH SYNOPSIS
 .nf
-.BR "#include <linux/fcntl.h>" " /* Definition of " AT_* " constants */"
-.BR "#include <linux/mount.h>" " /* Definition of " MOUNT_ATTR_* " constants */"
-.BR "#include <sys/syscall.h>" " /* Definition of " SYS_* " constants */"
-.B #include <unistd.h>
+.BR "#include <fcntl.h>" "       /* Definition of " AT_* " constants */"
+.B #include <sys/mount.h>
 .P
-.BI "int syscall(SYS_mount_setattr, int " dirfd ", const char *" path ,
-.BI "            unsigned int " flags ", struct mount_attr *" attr \
-", size_t " size );
+.BI "int mount_setattr(int " dirfd ", const char *" path ", unsigned int " flags ","
+.BI "                  struct mount_attr *" attr ", size_t " size );"
 .fi
-.P
-.IR Note :
-glibc provides no wrapper for
-.BR mount_setattr (),
-necessitating the use of
-.BR syscall (2).
 .SH DESCRIPTION
 The
 .BR mount_setattr ()
@@ -586,6 +577,7 @@ .SH HISTORY
 .\" commit 7d6beb71da3cc033649d641e1e608713b8220290
 .\" commit 2a1867219c7b27f928e2545782b86daaf9ad50bd
 .\" commit 9caccd41541a6f7d6279928d9f971f6642c361af
+glibc 2.36.
 .SH NOTES
 .SS ID-mapped mounts
 Creating an ID-mapped mount makes it possible to
@@ -914,37 +906,14 @@ .SH EXAMPLES
 #include <err.h>
 #include <fcntl.h>
 #include <getopt.h>
-#include <linux/mount.h>
-#include <linux/types.h>
+#include <sys/mount.h>
+#include <sys/types.h>
 #include <stdbool.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
-#include <sys/syscall.h>
 #include <unistd.h>
 \&
-static inline int
-mount_setattr(int dirfd, const char *path, unsigned int flags,
-              struct mount_attr *attr, size_t size)
-{
-    return syscall(SYS_mount_setattr, dirfd, path, flags,
-                   attr, size);
-}
-\&
-static inline int
-open_tree(int dirfd, const char *filename, unsigned int flags)
-{
-    return syscall(SYS_open_tree, dirfd, filename, flags);
-}
-\&
-static inline int
-move_mount(int from_dirfd, const char *from_path,
-           int to_dirfd, const char *to_path, unsigned int flags)
-{
-    return syscall(SYS_move_mount, from_dirfd, from_path,
-                   to_dirfd, to_path, flags);
-}
-\&
 static const struct option longopts[] = {
     {"map\-mount",       required_argument,  NULL,  \[aq]a\[aq]},
     {"recursive",       no_argument,        NULL,  \[aq]b\[aq]},

-- 
2.50.1