UserKernelDataAccess

This is the following step of "Character Device".

Implement the read and write interface between user and kernel space of the file operation.

copy_from_user and copy_to_user

• copy_from_user: Copy a block of data from user space into kernel space.

• copy_to_user: Copy a block of data into user space from kernel space.

• Why not access the buffer in the arguments directly? http://stackoverflow.com/questions/12666493/why-do-you-have-to-use-copy-to-user-copy-from-user-to-access-user-space-from

Steps

1. make
2. insmod example.ko
3. dmesg
4. mknod /dev/example c 60 0
5. chmod 666 /dev/example (for accessing from other users)
6. Do some file operations with the /dev/example, like file open, read, write, close.
7. dmesg
8. rmmod example.ko
9. rm /dev/example
10. make clean