Hi Greg,
On Sat, Jul 4, 2020 at 4:05 PM Greg Kroah-Hartman gregkh@linuxfoundation.org wrote:
It's a tiny syscall, meant to allow a user to do a single "open this file, read into this buffer, and close the file" all in a single shot.
Should be good for reading "tiny" files like sysfs, procfs, and other "small" files.
There is no restarting the syscall, this is a "simple" syscall, with the attempt to make reading "simple" files easier with less syscall overhead.
Cc: Alexander Viro viro@zeniv.linux.org.uk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
Thanks for your patch!
--- a/fs/open.c +++ b/fs/open.c
+SYSCALL_DEFINE5(readfile, int, dfd, const char __user *, filename,
char __user *, buffer, size_t, bufsize, int, flags)+{
struct open_flags op;struct open_how how;struct file *file;loff_t pos = 0;int retval;/* only accept a small subset of O_ flags that make sense */if ((flags & (O_NOFOLLOW | O_NOATIME)) != flags)return -EINVAL;/* add some needed flags to be able to open the file properly */flags |= O_RDONLY | O_LARGEFILE;how = build_open_how(flags, 0000);retval = build_open_flags(&how, &op);if (retval)return retval;file = readfile_open(dfd, filename, &op);if (IS_ERR(file))return PTR_ERR(file);retval = vfs_read(file, buffer, bufsize, &pos);
Should there be a way for the user to be informed that the file doesn't fit in the provided buffer (.e.g. -EFBIG)?
filp_close(file, NULL);return retval;+}
Gr{oetje,eeting}s,
Geert