[crypto,0/2] smaller blake2s code size on m68k and other small platforms

Message

Jason A. Donenfeld Jan. 11, 2022, 1:49 p.m. UTC

Hi,

Geert emailed me this afternoon concerned about blake2s codesize on m68k
and other small systems. We identified two extremely effective ways of
chopping down the size. One of them moves some wireguard-specific things
into wireguard proper. The other one adds a slower codepath for
CONFIG_CC_OPTIMIZE_FOR_SIZE configurations. I really don't like that
slower codepath, but since it is configuration gated, at least it stays
out of the way except for people who know they need a tiny kernel image

Thanks,
Jason

Jason A. Donenfeld (2):
  lib/crypto: blake2s-generic: reduce code size on small systems
  lib/crypto: blake2s: move hmac construction into wireguard

 drivers/net/wireguard/noise.c | 45 ++++++++++++++++++++++++++++++-----
 include/crypto/blake2s.h      |  3 ---
 lib/crypto/blake2s-generic.c  | 30 +++++++++++++----------
 lib/crypto/blake2s-selftest.c | 31 ------------------------
 lib/crypto/blake2s.c          | 37 ----------------------------
 5 files changed, 57 insertions(+), 89 deletions(-)

Comments

Jason A. Donenfeld Jan. 11, 2022, 6:10 p.m. UTC | #1

Hi,

Geert emailed me this afternoon concerned about blake2s codesize on m68k
and other small systems. We identified two effective ways of chopping
down the size. One of them moves some wireguard-specific things into
wireguard proper. The other one adds a slower codepath for small
machines to blake2s. This worked, and was v1 of this patchset, but I
wasn't so much of a fan. Then someone pointed out that the generic C
SHA-1 implementation is still unrolled, which is a *lot* of extra code.
Simply rerolling that saves about as much as v1 did. So, we instead do
that in this v2 patchset. SHA-1 is being phased out, and soon it won't
be included at all (hopefully). And nothing performance-oriented has
anything to do with it anyway.

The result of these two patches mitigates Geert's feared code size
increase for 5.17.

Thanks,
Jason


Jason A. Donenfeld (2):
  lib/crypto: blake2s: move hmac construction into wireguard
  lib/crypto: sha1: re-roll loops to reduce code size

 drivers/net/wireguard/noise.c |  45 +++++++++++--
 include/crypto/blake2s.h      |   3 -
 lib/crypto/blake2s-selftest.c |  31 ---------
 lib/crypto/blake2s.c          |  37 -----------
 lib/sha1.c                    | 117 ++++++++--------------------------
 5 files changed, 64 insertions(+), 169 deletions(-)