[PATCH 1/2] sysctl: introduce new proc handler proc_dobool

Thomas Huth
2021-08-03T10:59:59Z

From: Jia He <hejianet@gmail.com>

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>
---
include/linux/sysctl.h | 2 ++
kernel/sysctl.c | 42 ++++++++++++++++++++++++++++++++++++++++++
2 files changed, 44 insertions(+)

diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
index d99ca99837de..1fa2b69c6fc3 100644
--- a/include/linux/sysctl.h
+++ b/include/linux/sysctl.h
@@ -48,6 +48,8 @@ typedef int proc_handler(struct ctl_table *ctl, int write, void *buffer,
size_t *lenp, loff_t *ppos);

int proc_dostring(struct ctl_table *, int, void *, size_t *, loff_t *);
+int proc_dobool(struct ctl_table *table, int write, void *buffer,
+ size_t *lenp, loff_t *ppos);
int proc_dointvec(struct ctl_table *, int, void *, size_t *, loff_t *);
int proc_douintvec(struct ctl_table *, int, void *, size_t *, loff_t *);
int proc_dointvec_minmax(struct ctl_table *, int, void *, size_t *, loff_t *);
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 272f4a272f8c..25e49b4d8049 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -536,6 +536,21 @@ 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)
@@ -798,6 +813,26 @@ static int do_proc_douintvec(struct ctl_table *table, int write,
buffer, lenp, ppos, conv, data);
}

+/**
+ * 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
@@ -1630,6 +1665,12 @@ 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)
{
@@ -3425,6 +3466,7 @@ 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);
--
2.27.0