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-rw-r--r--include/linux/sysctl.h23
1 files changed, 17 insertions, 6 deletions
diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
index 1b24bd45e080..d98562f1df76 100644
--- a/include/linux/sysctl.h
+++ b/include/linux/sysctl.h
@@ -6,10 +6,17 @@
****************************************************************
****************************************************************
**
+ ** WARNING:
** The values in this file are exported to user space via
- ** the sysctl() binary interface. However this interface
- ** is unstable and deprecated and will be removed in the future.
- ** For a stable interface use /proc/sys.
+ ** the sysctl() binary interface. Do *NOT* change the
+ ** numbering of any existing values here, and do not change
+ ** any numbers within any one set of values. If you have to
+ ** have to redefine an existing interface, use a new number for it.
+ ** The kernel will then return -ENOTDIR to any application using
+ ** the old binary interface.
+ **
+ ** For new interfaces unless you really need a binary number
+ ** please use CTL_UNNUMBERED.
**
****************************************************************
****************************************************************
@@ -48,6 +55,7 @@ struct __sysctl_args {
#ifdef __KERNEL__
#define CTL_ANY -1 /* Matches any name */
#define CTL_NONE 0
+#define CTL_UNNUMBERED CTL_NONE /* sysctl without a binary number */
#endif
enum
@@ -961,8 +969,8 @@ extern ctl_handler sysctl_ms_jiffies;
/*
* Register a set of sysctl names by calling register_sysctl_table
* with an initialised array of ctl_table's. An entry with zero
- * ctl_name terminates the table. table->de will be set up by the
- * registration and need not be initialised in advance.
+ * ctl_name and NULL procname terminates the table. table->de will be
+ * set up by the registration and need not be initialised in advance.
*
* sysctl names can be mirrored automatically under /proc/sys. The
* procname supplied controls /proc naming.
@@ -973,7 +981,10 @@ extern ctl_handler sysctl_ms_jiffies;
* Leaf nodes in the sysctl tree will be represented by a single file
* under /proc; non-leaf nodes will be represented by directories. A
* null procname disables /proc mirroring at this node.
- *
+ *
+ * sysctl entries with a zero ctl_name will not be available through
+ * the binary sysctl interface.
+ *
* sysctl(2) can automatically manage read and write requests through
* the sysctl table. The data and maxlen fields of the ctl_table
* struct enable minimal validation of the values being written to be