[PATCH 02/11] tty/sysrq: constify the sysrq API

Emil Velikov
2020-05-13T21:46:44Z

The user is not supposed to thinker with the underlying sysrq_key_op.
Make that explicit by adding a handful of const notations.

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jiri Slaby <jslaby@suse.com>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
---
Please keep me in the CC list, as I'm not subscribed to the list.

IMHO it would be better if this gets merged this via the tty tree.
---
Documentation/admin-guide/sysrq.rst | 10 +++++-----
drivers/tty/sysrq.c | 16 ++++++++--------
include/linux/sysrq.h | 16 ++++++++--------
3 files changed, 21 insertions(+), 21 deletions(-)

diff --git a/Documentation/admin-guide/sysrq.rst b/Documentation/admin-guide/sysrq.rst
index a46209f4636c..e6424d8c5846 100644
--- a/Documentation/admin-guide/sysrq.rst
+++ b/Documentation/admin-guide/sysrq.rst
@@ -231,13 +231,13 @@ prints help, and C) an action_msg string, that will print right before your
handler is called. Your handler must conform to the prototype in 'sysrq.h'.

After the ``sysrq_key_op`` is created, you can call the kernel function
-``register_sysrq_key(int key, struct sysrq_key_op *op_p);`` this will
+``register_sysrq_key(int key, const struct sysrq_key_op *op_p);`` this will
register the operation pointed to by ``op_p`` at table key 'key',
if that slot in the table is blank. At module unload time, you must call
-the function ``unregister_sysrq_key(int key, struct sysrq_key_op *op_p)``, which
-will remove the key op pointed to by 'op_p' from the key 'key', if and only if
-it is currently registered in that slot. This is in case the slot has been
-overwritten since you registered it.
+the function ``unregister_sysrq_key(int key, const struct sysrq_key_op *op_p)``,
+which will remove the key op pointed to by 'op_p' from the key 'key', if and
+only if it is currently registered in that slot. This is in case the slot has
+been overwritten since you registered it.

The Magic SysRQ system works by registering key operations against a key op
lookup table, which is defined in 'drivers/tty/sysrq.c'. This key table has
diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c
index 1741134cabca..091c64a3cef0 100644
--- a/drivers/tty/sysrq.c
+++ b/drivers/tty/sysrq.c
@@ -518,9 +518,9 @@ static int sysrq_key_table_key2index(int key)
/*
* get and put functions for the table, exposed to modules.
*/
-static struct sysrq_key_op *__sysrq_get_key_op(int key)
+static const struct sysrq_key_op *__sysrq_get_key_op(int key)
{
- struct sysrq_key_op *op_p = NULL;
+ const struct sysrq_key_op *op_p = NULL;
int i;

i = sysrq_key_table_key2index(key);
@@ -530,7 +530,7 @@ static struct sysrq_key_op *__sysrq_get_key_op(int key)
return op_p;
}

-static void __sysrq_put_key_op(int key, struct sysrq_key_op *op_p)
+static void __sysrq_put_key_op(int key, const struct sysrq_key_op *op_p)
{
int i = sysrq_key_table_key2index(key);

@@ -540,7 +540,7 @@ static void __sysrq_put_key_op(int key, struct sysrq_key_op *op_p)

void __handle_sysrq(int key, bool check_mask)
{
- struct sysrq_key_op *op_p;
+ const struct sysrq_key_op *op_p;
int orig_log_level;
int orig_suppress_printk;
int i;
@@ -1063,8 +1063,8 @@ int sysrq_toggle_support(int enable_mask)
}
EXPORT_SYMBOL_GPL(sysrq_toggle_support);

-static int __sysrq_swap_key_ops(int key, struct sysrq_key_op *insert_op_p,
- struct sysrq_key_op *remove_op_p)
+static int __sysrq_swap_key_ops(int key, const struct sysrq_key_op *insert_op_p,
+ const struct sysrq_key_op *remove_op_p)
{
int retval;

@@ -1087,13 +1087,13 @@ static int __sysrq_swap_key_ops(int key, struct sysrq_key_op *insert_op_p,
return retval;
}

-int register_sysrq_key(int key, struct sysrq_key_op *op_p)
+int register_sysrq_key(int key, const struct sysrq_key_op *op_p)
{
return __sysrq_swap_key_ops(key, op_p, NULL);
}
EXPORT_SYMBOL(register_sysrq_key);

-int unregister_sysrq_key(int key, struct sysrq_key_op *op_p)
+int unregister_sysrq_key(int key, const struct sysrq_key_op *op_p)
{
return __sysrq_swap_key_ops(key, NULL, op_p);
}
diff --git a/include/linux/sysrq.h b/include/linux/sysrq.h
index 9b51f98e5f60..479028391c08 100644
--- a/include/linux/sysrq.h
+++ b/include/linux/sysrq.h
@@ -30,10 +30,10 @@
#define SYSRQ_ENABLE_RTNICE 0x0100

struct sysrq_key_op {
- void (*handler)(int);
- char *help_msg;
- char *action_msg;
- int enable_mask;
+ void (* const handler)(int);
+ const char * const help_msg;
+ const char * const action_msg;
+ const int enable_mask;
};

#ifdef CONFIG_MAGIC_SYSRQ
@@ -45,8 +45,8 @@ struct sysrq_key_op {

void handle_sysrq(int key);
void __handle_sysrq(int key, bool check_mask);
-int register_sysrq_key(int key, struct sysrq_key_op *op);
-int unregister_sysrq_key(int key, struct sysrq_key_op *op);
+int register_sysrq_key(int key, const struct sysrq_key_op *op);
+int unregister_sysrq_key(int key, const struct sysrq_key_op *op);
extern struct sysrq_key_op *__sysrq_reboot_op;

int sysrq_toggle_support(int enable_mask);
@@ -62,12 +62,12 @@ static inline void __handle_sysrq(int key, bool check_mask)
{
}

-static inline int register_sysrq_key(int key, struct sysrq_key_op *op)
+static inline int register_sysrq_key(int key, const struct sysrq_key_op *op)
{
return -EINVAL;
}

-static inline int unregister_sysrq_key(int key, struct sysrq_key_op *op)
+static inline int unregister_sysrq_key(int key, const struct sysrq_key_op *op)
{
return -EINVAL;
}
--
2.25.1