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: Christoph Hellwig <hch@lst.de>

diff --git a/fs/read_write.c b/fs/read_write.c
index 96e8e35..21c9d90 100644 (file)
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -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;

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 3f881a8..22cbe7b 100644 (file)
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -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 *);