On Tue, 19 Mar 2024 at 09:37, Alexander Potapenko <glider@xxxxxxxxxx> wrote:
>
> if (copy_mc_fragile_enabled) {
> __uaccess_begin();
> + instrument_copy_to_user(dst, src, len);
> ret = copy_mc_fragile((__force void *)dst, src, len);
> __uaccess_end();
I'd actually prefer that instrument_copy_to_user() to be *outside* the
__uaccess_begin.
In fact, I'm a bit surprised that objtool didn't complain about it in that form.
__uaccess_begin() causes the CPU to accept kernel accesses to user
mode, and I don't think instrument_copy_to_user() has any business
actually touching user mode memory.
In fact it might be better to rename the function and change the prototype to
instrument_src(src, len);
because you really can't sanely instrument the destination of a user
copy, but "instrument_src()" might be useful in other situations than
just user copies.
Hmm?
Linus
