Commit 61a707c5 authored by Christoph Hellwig's avatar Christoph Hellwig
Browse files

fs: add a __kernel_read helper 



This is the counterpart to __kernel_write, and skip the rw_verify_area
call compared to kernel_read.

Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
parent 53ad8626

fs/read_write.c

+23 −0
Original line number Diff line number Diff line
@@ -430,6 +430,29 @@ ssize_t __vfs_read(struct file *file, char __user *buf, size_t count, 
		return -EINVAL;

}



ssize_t __kernel_read(struct file *file, void *buf, size_t count, loff_t *pos)

{

	mm_segment_t old_fs = get_fs();

	ssize_t ret;



	if (WARN_ON_ONCE(!(file->f_mode & FMODE_READ)))

		return -EINVAL;

	if (!(file->f_mode & FMODE_CAN_READ))

		return -EINVAL;



	if (count > MAX_RW_COUNT)

		count =  MAX_RW_COUNT;

	set_fs(KERNEL_DS);

	ret = __vfs_read(file, (void __user *)buf, count, pos);

	set_fs(old_fs);

	if (ret > 0) {

		fsnotify_access(file);

		add_rchar(current, ret);

	}

	inc_syscr(current);

	return ret;

}



ssize_t kernel_read(struct file *file, void *buf, size_t count, loff_t *pos)

{

	mm_segment_t old_fs;

include/linux/fs.h

+1 −0
Original line number Diff line number Diff line
@@ -3033,6 +3033,7 @@ extern int kernel_read_file_from_path_initns(const char *, void **, loff_t *, lo 
extern int kernel_read_file_from_fd(int, void **, loff_t *, loff_t,

				    enum kernel_read_file_id);

extern ssize_t kernel_read(struct file *, void *, size_t, loff_t *);

ssize_t __kernel_read(struct file *file, void *buf, size_t count, loff_t *pos);

extern ssize_t kernel_write(struct file *, const void *, size_t, loff_t *);

extern ssize_t __kernel_write(struct file *, const void *, size_t, loff_t *);

extern struct file * open_exec(const char *);