用户空间和内核空间传递数据:get_user;put_user;copy_to_user;copy_from_user
2009-06-02 11:10
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转自:http://hi.baidu.com/wjq_qust/blog/item/0f8d8cd6a6ca782d07088bdb.htmlhttp://hi.baidu.com/wjq_qust/blog/item/e14c2ba4e090eff59052eed9.html
1. put_user
Name
put_user-- Write a simple value into user space.Synopsis
put_user
( x, ptr);
[/code]
Arguments
xValue to copy to user space.
ptr
Destination address, in user space.
Context
User context only. This function may sleep.Description
This macro copies a single simple value from kernel space to userspace. It supports simple types like char and int, but not larger data
types like structures or arrays.
ptr
must have pointer-to-simple-variable type, and x
must be assignable to the result of dereferencing ptr
.
Returns zero on success, or -EFAULT on error.
2. get_user
Name
get_user-- Get a simple variable from user space.Synopsis
get_user
( x, ptr);
[/code]
Arguments
xVariable to store result.
ptr
Source address, in user space.
Context
User context only. This function may sleep.Description
This macro copies a single simple variable from user space to kernelspace. It supports simple types like char and int, but not larger data
types like structures or arrays.
ptr
must have pointer-to-simple-variable type, and the result of dereferencing ptr
must be assignable to x
without a cast.
Returns zero on success, or -EFAULT on error. On error, the variable x
is set to zero.
1. copy_to_user
Name
copy_to_user -- Copy a block of data into user space.Synopsis
unsigned long copy_to_user
(void __user * to, const void * from, unsigned long n);
[/code]
Arguments
toDestination address, in user space.
from
Source address, in kernel space.
n
Number of bytes to copy.
Context
User context only. This function may sleep.Description
Copy data from kernel space to user space.Returns number of bytes that could not be copied. On success, this will be zero.
2. copy_from_user
Name
copy_from_user -- Copy a block of data from user space.Synopsis
unsigned long copy_from_user
(void * to, const void __user * from, unsigned long n);
[/code]
Arguments
toDestination address, in kernel space.
from
Source address, in user space.
n
Number of bytes to copy.
Context
User context only. This function may sleep.Description
Copy data from user space to kernel space.Returns number of bytes that could not be copied. On success, this will be zero.
If some data could not be copied, this function will pad the copied data to the requested size using zero bytes.
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