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tty/sysrq: constify the sysrq API

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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>
Link: https://lore.kernel.org/r/20200513214351.2138580-2-emil.l.velikov@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Emil Velikov 2020-05-13 22:43:42 +01:00 committed by Greg Kroah-Hartman
parent 0f1c9688a1
commit 23cbedf812
3 changed files with 21 additions and 21 deletions
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10
Documentation/admin-guide/sysrq.rst
View File

@ -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

16
drivers/tty/sysrq.c
View File

@ -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);
}

16
include/linux/sysrq.h
View File

@ -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;
}