sysctl: add and use base directory declarer and registration helper

Patch series "sysctl: add and use base directory declarer and
registration helper".

In this patch series we start addressing base directories, and so we
start with the "fs" sysctls.  The end goal is we end up completely
moving all "fs" sysctl knobs out from kernel/sysctl.

This patch (of 6):

Add a set of helpers which can be used to declare and register base
directory sysctls on their own.  We do this so we can later move each of
the base sysctl directories like "fs", "kernel", etc, to their own
respective files instead of shoving the declarations and registrations
all on kernel/sysctl.c.  The lazy approach has caught up and with this,
we just end up extending the list of base directories / sysctls on one
file and this makes maintenance difficult due to merge conflicts from
many developers.

The declarations are used first by kernel/sysctl.c for registration its
own base which over time we'll try to clean up.  It will be used in the
next patch to demonstrate how to cleanly deal with base sysctl
directories.

[mcgrof@kernel.org: null-terminate the ctl_table arrays]
Link: https://lkml.kernel.org/r/YafJY3rXDYnjK/gs@bombadil.infradead.org
Link: https://lkml.kernel.org/r/20211129211943.640266-1-mcgrof@kernel.org
Link: https://lkml.kernel.org/r/20211129211943.640266-2-mcgrof@kernel.org
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Kees Cook <keescook@chromium.org>
Cc: Iurii Zaikin <yzaikin@google.com>
Cc: Xiaoming Ni <nixiaoming@huawei.com>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: Stephen Kitt <steve@sk2.org>
Cc: Lukas Middendorf <kernel@tuxforce.de>
Cc: Antti Palosaari <crope@iki.fi>
Cc: Christian Brauner <christian.brauner@ubuntu.com>
Cc: Eric Biggers <ebiggers@google.com>
Cc: "Naveen N. Rao" <naveen.n.rao@linux.ibm.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
index b9d53b53d7698c823cf1b87c268e06b0c96364f7..95dfd195e04e39bbc959144506d2b0dc01f5b1a4 100644 (file)
--- a/fs/proc/proc_sysctl.c
+++ b/fs/proc/proc_sysctl.c
@@ -1646,6 +1646,15 @@ struct ctl_table_header *register_sysctl_table(struct ctl_table *table)
 }
 EXPORT_SYMBOL(register_sysctl_table);
 
+int __register_sysctl_base(struct ctl_table *base_table)
+{
+       struct ctl_table_header *hdr;
+
+       hdr = register_sysctl_table(base_table);
+       kmemleak_not_leak(hdr);
+       return 0;
+}
+
 static void put_links(struct ctl_table_header *header)
 {
        struct ctl_table_set *root_set = &sysctl_table_root.default_set;

diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
index 4294e9668bd517739ebc7189b2d58ccbb6a6e43a..02134a8abad7a92c1bd59cde3d6f7397924151b4 100644 (file)
--- a/include/linux/sysctl.h
+++ b/include/linux/sysctl.h
@@ -194,6 +194,20 @@ struct ctl_path {
 
 #ifdef CONFIG_SYSCTL
 
+#define DECLARE_SYSCTL_BASE(_name, _table)                             \
+static struct ctl_table _name##_base_table[] = {                       \
+       {                                                               \
+               .procname       = #_name,                               \
+               .mode           = 0555,                                 \
+               .child          = _table,                               \
+       },                                                              \
+       { },                                                            \
+}
+
+extern int __register_sysctl_base(struct ctl_table *base_table);
+
+#define register_sysctl_base(_name) __register_sysctl_base(_name##_base_table)
+
 void proc_sys_poll_notify(struct ctl_table_poll *poll);
 
 extern void setup_sysctl_set(struct ctl_table_set *p,
@@ -236,6 +250,16 @@ extern int no_unaligned_warning;
 extern struct ctl_table sysctl_mount_point[];
 
 #else /* CONFIG_SYSCTL */
+
+#define DECLARE_SYSCTL_BASE(_name, _table)
+
+static inline int __register_sysctl_base(struct ctl_table *base_table)
+{
+       return 0;
+}
+
+#define register_sysctl_base(table) __register_sysctl_base(table)
+
 static inline struct ctl_table_header *register_sysctl_table(struct ctl_table * table)
 {
        return NULL;

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index f79ec2cf8721a7cffe69426e5b5df8c6cfb66aed..12456a535059e67a6f2f97beec0857903b44a3a2 100644 (file)
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -2851,41 +2851,20 @@ static struct ctl_table dev_table[] = {
        { }
 };
 
-static struct ctl_table sysctl_base_table[] = {
-       {
-               .procname       = "kernel",
-               .mode           = 0555,
-               .child          = kern_table,
-       },
-       {
-               .procname       = "vm",
-               .mode           = 0555,
-               .child          = vm_table,
-       },
-       {
-               .procname       = "fs",
-               .mode           = 0555,
-               .child          = fs_table,
-       },
-       {
-               .procname       = "debug",
-               .mode           = 0555,
-               .child          = debug_table,
-       },
-       {
-               .procname       = "dev",
-               .mode           = 0555,
-               .child          = dev_table,
-       },
-       { }
-};
+DECLARE_SYSCTL_BASE(kernel, kern_table);
+DECLARE_SYSCTL_BASE(vm, vm_table);
+DECLARE_SYSCTL_BASE(fs, fs_table);
+DECLARE_SYSCTL_BASE(debug, debug_table);
+DECLARE_SYSCTL_BASE(dev, dev_table);
 
 int __init sysctl_init(void)
 {
-       struct ctl_table_header *hdr;
+       register_sysctl_base(kernel);
+       register_sysctl_base(vm);
+       register_sysctl_base(fs);
+       register_sysctl_base(debug);
+       register_sysctl_base(dev);
 
-       hdr = register_sysctl_table(sysctl_base_table);
-       kmemleak_not_leak(hdr);
        return 0;
 }
 #endif /* CONFIG_SYSCTL */