Commit 5b24a7a2aa2040c8c50c3b71122901d01661ff78 introduced the unsafe_get_user and unsafe_put_user replacement functions for batched calls to put_user and get_user. I'm trying to make the kernel smaller and reduce stac/clac overhead on x86 by substituting the new functions for such batched calls. But there's no corresponding unsafe_copy_to_user() or unsafe_copy_from_user() functions to copy an arbitrary-sized buffer to and from userspace without calling access_ok and __uaccess_begin/end.
I know that the matter of replacing these uaccess functions has been discussed at length (see https://lkml.org/lkml/2017/5/13/134), so before I started hacking away implementing new unsafe_copy_{to,from}_user functions, I wanted to ask if a solution to this is already being worked on or if there's some way of accomplishing this goal without new functions. To illustrate, here's a batched function call (from fs/fat/dir.c): if (put_user(0, d2->d_name) || put_user(0, &d2->d_reclen) || copy_to_user(d1->d_name, name, name_len) || // etc... goto efault; This should read: if (!access_ok(VERIFY_WRITE, d1, 2*sizeof(*infop)) goto efault; user_access_begin(); unsafe_put_user(0, d2->d_name, efault) unsafe_put_user(0, &d2->d_reclen, efault) unsafe_copy_to_user(d1->d_name, name, name_len, efault); // we don't have // this function // etc... user_access_end(); Thanks.
