sysctl: introduce new proc handler proc_dobool

[ Upstream commit a2071573d6346819cc4e5787b4206f2184985160 ]

This is to let bool variable could be correctly displayed in
big/little endian sysctl procfs. sizeof(bool) is arch dependent,
proc_dobool should work in all arches.

Suggested-by: Pan Xinhui <xinhui@linux.vnet.ibm.com>
Signed-off-by: Jia He <hejianet@gmail.com>
[thuth: rebased the patch to the current kernel version]
Signed-off-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

1 files changed, 42 insertions, 0 deletions

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index b29a9568ebbe..abe0f16d5364 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -546,6 +546,21 @@ static void proc_put_char(void **buf, size_t *size, char c)
 	}
 }
 
+static int do_proc_dobool_conv(bool *negp, unsigned long *lvalp,
+				int *valp,
+				int write, void *data)
+{
+	if (write) {
+		*(bool *)valp = *lvalp;
+	} else {
+		int val = *(bool *)valp;
+
+		*lvalp = (unsigned long)val;
+		*negp = false;
+	}
+	return 0;
+}
+
 static int do_proc_dointvec_conv(bool *negp, unsigned long *lvalp,
 				 int *valp,
 				 int write, void *data)
@@ -809,6 +824,26 @@ static int do_proc_douintvec(struct ctl_table *table, int write,
 }
 
 /**
+ * proc_dobool - read/write a bool
+ * @table: the sysctl table
+ * @write: %TRUE if this is a write to the sysctl file
+ * @buffer: the user buffer
+ * @lenp: the size of the user buffer
+ * @ppos: file position
+ *
+ * Reads/writes up to table->maxlen/sizeof(unsigned int) integer
+ * values from/to the user buffer, treated as an ASCII string.
+ *
+ * Returns 0 on success.
+ */
+int proc_dobool(struct ctl_table *table, int write, void *buffer,
+		size_t *lenp, loff_t *ppos)
+{
+	return do_proc_dointvec(table, write, buffer, lenp, ppos,
+				do_proc_dobool_conv, NULL);
+}
+
+/**
  * proc_dointvec - read a vector of integers
  * @table: the sysctl table
  * @write: %TRUE if this is a write to the sysctl file
@@ -1644,6 +1679,12 @@ int proc_dostring(struct ctl_table *table, int write,
 	return -ENOSYS;
 }
 
+int proc_dobool(struct ctl_table *table, int write,
+		void *buffer, size_t *lenp, loff_t *ppos)
+{
+	return -ENOSYS;
+}
+
 int proc_dointvec(struct ctl_table *table, int write,
 		  void *buffer, size_t *lenp, loff_t *ppos)
 {
@@ -3503,6 +3544,7 @@ int __init sysctl_init(void)
  * No sense putting this after each symbol definition, twice,
  * exception granted :-)
  */
+EXPORT_SYMBOL(proc_dobool);
 EXPORT_SYMBOL(proc_dointvec);
 EXPORT_SYMBOL(proc_douintvec);
 EXPORT_SYMBOL(proc_dointvec_jiffies);