On Wed, Nov 27, 2013 at 9:57 PM, 乃宏周 <naive231@gmail.com> wrote:
In module code:
*unsigned char buf[20];*
*struct file *device;*
*device = filp_open(...);*
*device->f_op->read(device,buf,20,&device->f_pos);*
In signature(interface) of *read()* of *struct file*, *buf* should came from user-space. I fed my buffer, and I get correct data from that, Is that correct? Shouldn't I provide a user-space buffer to that ?
Some convention in kernel programming: long do_sys_open(int dfd, const char __user *filename, int flags, umode_t mode) { here __user is used for declaration - explicitly saying that the pointer is pointing to userspace data. without it, all pointer necessarily need to point to kernel allocated memory, and u used copy_from_user() to copy data from userspace to kernel pointer.
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-- Regards, Peter Teoh