Re: [PATCH v2 4/4] crypto: x86/sha256-ni - simplify do_4rounds

[Stefan Kanthak]

"Eric Biggers" <ebiggers@xxxxxxxxxx> wrote:

> On Mon, Apr 15, 2024 at 10:41:07PM +0200, Stefan Kanthak wrote:
[...]
>> At last the final change: write the macro straightforward and SIMPLE,
>> closely matching NIST.FIPS.180-4.pdf and their order of operations.
>> 
>> @@ ...
>> +.macro  sha256  m0 :req, m1 :req, m2 :req, m3 :req
>> +.if \@ < 4
>> +        movdqu  \@*16(DATA_PTR), \m0
>> +        pshufb  SHUF_MASK, \m0          # \m0 = {w(\@*16), w(\@*16+1), w(\@*16+2), w(\@*16+3)}
>> +.else
>> +                                        # \m0 = {w(\@*16-16), w(\@*16-15), w(\@*16-14), w(\@*16-13)}
>> +                                        # \m1 = {w(\@*16-12), w(\@*16-11), w(\@*16-10), w(\@*16-9)}
>> +                                        # \m2 = {w(\@*16-8),  w(\@*16-7),  w(\@*16-6),  w(\@*16-5)}
>> +                                        # \m3 = {w(\@*16-4),  w(\@*16-3),  w(\@*16-2),  w(\@*16-1)}
>> +        sha256msg1 \m1, \m0
>> +        movdqa     \m3, TMP
>> +        palignr    $4, \m2, TMP
>> +        paddd      TMP, \m0
>> +        sha256msg2 \m3, \m0             # \m0 = {w(\@*16), w(\@*16+1), w(\@*16+2), w(\@*16+3)}
>> +.endif
>> +        movdqa      (\@-8)*16(SHA256CONSTANTS), MSG
>> +        paddd       \m0, MSG
>> +        sha256rnds2 STATE0, STATE1      # STATE1 = {f', e', b', a'}
>> +        punpckhqdq  MSG, MSG
>> +        sha256rnds2 STATE1, STATE0      # STATE0 = {f", e", b", a"},
>> +                                        # STATE1 = {h", g", d", c"}
>> +.endm
>> 
>> JFTR: you may simplify this further using .altmacro and generate \m0 to \m3
>>       as MSG%(4-\@&3), MSG%(5-\@&3), MSG%(6-\@&3) and MSG%(7-\@&3) within
>>       the macro, thus getting rid of its 4 arguments.
>> 
>> @@ ...
>> +.rept 4                                 # 4*4*4 rounds
>> +        sha256  MSG0, MSG1, MSG2, MSG3
>> +        sha256  MSG1, MSG2, MSG3, MSG0
>> +        sha256  MSG2, MSG3, MSG0, MSG1
>> +        sha256  MSG3, MSG0, MSG1, MSG2
>> +.endr
> 
> Could you please send a real patch, following
> Documentation/process/submitting-patches.rst?  It's hard to understand what
> you're proposing here.

1) I replace your macro (which unfortunately follows Tim Chens twisted code)
   COMPLETELY with a clean and simple implementation: message schedule first,
   update of state variables last.
   You don't need ".if \i >= 12 && \i < 60"/".if \i >= 4 && \i < 52" at all!

2) I replace the .irp which invokes your macro with a .rept: my macro uses \@
   instead of an argument for the round number.

<https://sourceware.org/binutils/docs/as.html#Macro>

| \@
|    as maintains a counter of how many macros it has executed in this pseudo-
|    variable; you can copy that number to your output with '\@', but only
|    within a macro definition. 

That's all.

regards
Stefan