linux-kernel - [PATCH v3 2/5] sysctl: kdoc'ify sysctl_writes

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Date:   Thu, 18 May 2017 20:35:51 -0700
From:   "Luis R. Rodriguez" <mcgrof@...nel.org>
To:     viro@...iv.linux.org.uk, akpm@...ux-foundation.org,
        ebiederm@...ssion.com, keescook@...omium.org, acme@...hat.com,
        mingo@...nel.org, mgorman@...e.de, subashab@...eaurora.org
Cc:     jeyu@...hat.com, rusty@...tcorp.com.au, swhiteho@...hat.com,
        deepa.kernel@...il.com, matt@...eblueprint.co.uk,
        adobriyan@...il.com, bp@...e.de, zlpnobody@...il.com,
        dmitry.torokhov@...il.com, shuah@...nel.org,
        torvalds@...ux-foundation.org, linux@...ck-us.net,
        linux-kernel@...r.kernel.org,
        "Luis R. Rodriguez" <mcgrof@...nel.org>
Subject: [PATCH v3 2/5] sysctl: kdoc'ify sysctl_writes_strict

Document the different sysctl_writes_strict modes in code.

Signed-off-by: Luis R. Rodriguez <mcgrof@...nel.org>
---
 kernel/sysctl.c | 29 +++++++++++++++++++++++++----
 1 file changed, 25 insertions(+), 4 deletions(-)

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 4dfba1a76cc3..02725178694a 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -174,11 +174,32 @@ extern int no_unaligned_warning;
 
 #ifdef CONFIG_PROC_SYSCTL
 
-#define SYSCTL_WRITES_LEGACY	-1
-#define SYSCTL_WRITES_WARN	 0
-#define SYSCTL_WRITES_STRICT	 1
+/**
+ * enum sysctl_writes_mode - supported sysctl write modes
+ *
+ * @SYSCTL_WRITES_LEGACY: each write syscall must fully contain the sysctl value
+ * 	to be written, and multiple writes on the same sysctl file descriptor
+ * 	will rewrite the sysctl value, regardless of file position. No warning
+ * 	is issued when the initial position is not 0.
+ * @SYSCTL_WRITES_WARN: same as above but warn when the initial file position is
+ * 	not 0.
+ * @SYSCTL_WRITES_STRICT: writes to numeric sysctl entries must always be at
+ * 	file position 0 and the value must be fully contained in the buffer
+ * 	sent to the write syscall. If dealing with strings respect the file
+ * 	position, but restrict this to the max length of the buffer, anything
+ * 	passed the max lenght will be ignored. Multiple writes will append
+ * 	to the buffer.
+ *
+ * These write modes control how current file position affects the behavior of
+ * updating sysctl values through the proc interface on each write.
+ */
+enum sysctl_writes_mode {
+	SYSCTL_WRITES_LEGACY		= -1,
+	SYSCTL_WRITES_WARN		= 0,
+	SYSCTL_WRITES_STRICT		= 1,
+};
 
-static int sysctl_writes_strict = SYSCTL_WRITES_STRICT;
+static enum sysctl_writes_mode sysctl_writes_strict = SYSCTL_WRITES_STRICT;
 
 static int proc_do_cad_pid(struct ctl_table *table, int write,
 		  void __user *buffer, size_t *lenp, loff_t *ppos);
-- 
2.11.0