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param: locking for kernel parameters

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There may be cases (most obviously, sysfs-writable charp parameters) where
a module needs to prevent sysfs access to parameters.

Rather than express this in terms of a big lock, the functions are
expressed in terms of what they protect against.  This is clearer, esp.
if the implementation changes to a module-level or even param-level lock.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Reviewed-by: Takashi Iwai <tiwai@suse.de>
Tested-by: Phil Carmody <ext-phil.2.carmody@nokia.com>
This commit is contained in:
Rusty Russell 2010-08-11 23:04:19 -06:00
parent 914dcaa84c
commit 907b29eb41
2 changed files with 82 additions and 7 deletions
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56
include/linux/moduleparam.h
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@ -130,6 +130,62 @@ __check_old_set_param(int (*oldset)(const char *, struct kernel_param *))
#define module_param(name, type, perm) \
module_param_named(name, name, type, perm)
/**
* kparam_block_sysfs_write - make sure a parameter isn't written via sysfs.
* @name: the name of the parameter
*
* There's no point blocking write on a paramter that isn't writable via sysfs!
*/
#define kparam_block_sysfs_write(name) \
do { \
BUG_ON(!(__param_##name.perm & 0222)); \
__kernel_param_lock(); \
} while (0)
/**
* kparam_unblock_sysfs_write - allows sysfs to write to a parameter again.
* @name: the name of the parameter
*/
#define kparam_unblock_sysfs_write(name) \
do { \
BUG_ON(!(__param_##name.perm & 0222)); \
__kernel_param_unlock(); \
} while (0)
/**
* kparam_block_sysfs_read - make sure a parameter isn't read via sysfs.
* @name: the name of the parameter
*
* This also blocks sysfs writes.
*/
#define kparam_block_sysfs_read(name) \
do { \
BUG_ON(!(__param_##name.perm & 0444)); \
__kernel_param_lock(); \
} while (0)
/**
* kparam_unblock_sysfs_read - allows sysfs to read a parameter again.
* @name: the name of the parameter
*/
#define kparam_unblock_sysfs_read(name) \
do { \
BUG_ON(!(__param_##name.perm & 0444)); \
__kernel_param_unlock(); \
} while (0)
#ifdef CONFIG_SYSFS
extern void __kernel_param_lock(void);
extern void __kernel_param_unlock(void);
#else
static inline void __kernel_param_lock(void)
{
}
static inline void __kernel_param_unlock(void)
{
}
#endif
#ifndef MODULE
/**
* core_param - define a historical core kernel parameter.