Re: [PATCH net-next v3 02/17] zinc: introduce minimal cryptography library

On 12 September 2018 at 20:34, Eric Biggers [off-list ref] wrote:

On Wed, Sep 12, 2018 at 08:19:21PM +0200, Ard Biesheuvel wrote:

quoted

On 12 September 2018 at 20:16, Jason A. Donenfeld [off-list ref] wrote:

quoted

Hi Eric,

On Wed, Sep 12, 2018 at 12:08 AM Eric Biggers [off-list ref] wrote:

quoted

I'd strongly prefer the assembly to be readable too.  Jason, I'm not sure if
you've actually read through the asm from the OpenSSL implementations, but the
generated .S files actually do lose a lot of semantic information that was in
the original .pl scripts.

The thing to keep in mind is that the .S was not directly and blindly
generated from the .pl. We started with the output of the .pl, and
then, particularly in the case of x86_64, worked with it a lot, and
now it's something a bit different. We've definitely spent a lot of
time reading that assembly.

Can we please have those changes as a separate patch? Preferably to
the .pl file rather than the .S file, so we can easily distinguish the
code from upstream from the code that you modified.

quoted

I'll see if I can improve the readability with some register name
remapping on ARM. No guarantees, but I'll play a bit and see if I can
make it a bit better.

Jason

FWIW, yesterday I made a modified version of poly1305-armv4.pl that generates an
asm file that works in kernel mode.  The changes are actually pretty small, and
I think we can get them upstream into OpenSSL like they were for sha256-armv4.pl
and sha512-armv4.pl.  I'll start a thread with Andy Polyakov and you two.

But I don't have time to help with all the many OpenSSL asm files Jason is
proposing, just maybe poly1305-armv4 and chacha-armv4 for now.

Thanks Eric. I reached out to Andy Polyakov off line, and he is happy
to work with us again on this, although he did point out that our
experiences on ARM may not extrapolate to x86_64, given the fact that
the perl sources there also contain parameterization for the calling
convention differences between Windows and SysV.