On Tue Jan 19, 2021 at 6:33 AM CST, Christophe Leroy wrote: > > > Le 19/01/2021 à 03:11, Michael Ellerman a écrit : > > "Christopher M. Riedl" <c...@codefail.de> writes: > >> On Mon Jan 11, 2021 at 7:22 AM CST, Christophe Leroy wrote: > >>> Le 09/01/2021 à 04:25, Christopher M. Riedl a écrit : > >>>> Implement raw_copy_from_user_allowed() which assumes that userspace read > >>>> access is open. Use this new function to implement raw_copy_from_user(). > >>>> Finally, wrap the new function to follow the usual "unsafe_" convention > >>>> of taking a label argument. > >>> > >>> I think there is no point implementing raw_copy_from_user_allowed(), see > >>> https://github.com/linuxppc/linux/commit/4b842e4e25b1 and > >>> https://patchwork.ozlabs.org/project/linuxppc-dev/patch/8c74fc9ce8131cabb10b3e95dc0e430f396ee83e.1610369143.git.christophe.le...@csgroup.eu/ > >>> > >>> You should simply do: > >>> > >>> #define unsafe_copy_from_user(d, s, l, e) \ > >>> unsafe_op_wrap(__copy_tofrom_user((__force void __user *)d, s, l), e) > >>> > >> > >> I gave this a try and the signal ops decreased by ~8K. Now, to be > >> honest, I am not sure what an "acceptable" benchmark number here > >> actually is - so maybe this is ok? Same loss with both radix and hash: > >> > >> | | hash | radix | > >> | ------------------------------------ | ------ | ------ | > >> | linuxppc/next | 118693 | 133296 | > >> | linuxppc/next w/o KUAP+KUEP | 228911 | 228654 | > >> | unsafe-signal64 | 200480 | 234067 | > >> | unsafe-signal64 (__copy_tofrom_user) | 192467 | 225119 | > >> > >> To put this into perspective, prior to KUAP and uaccess flush, signal > >> performance in this benchmark was ~290K on hash. > > > > If I'm doing the math right 8K is ~4% of the best number. > > > > It seems like 4% is worth a few lines of code to handle these constant > > sizes. It's not like we have performance to throw away. > > > > Or, we should chase down where the call sites are that are doing small > > constant copies with copy_to/from_user() and change them to use > > get/put_user(). > > > > Christopher, when you say you gave it a try, is I my series or only the > following ? > > #define unsafe_copy_from_user(d, s, l, e) \ > unsafe_op_wrap(__copy_tofrom_user((__force void __user *)d, s, l), e) >
I only used the above to replace this patch in my series (so none of my changes implementing raw_copy_from_user_allowed() are included). > > Because I see no use of unsafe_copy_from_user() that would explain that. > > Christophe
