linux-kernel - Re: [PATCH 2/3] lib/crypto: poly1305: Consolidate into single module

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Message-ID: <20250821041445.GH185832@quark>
Date: Thu, 21 Aug 2025 00:14:45 -0400
From: Eric Biggers <ebiggers@...nel.org>
To: linux-crypto@...r.kernel.org
Cc: linux-kernel@...r.kernel.org, Ard Biesheuvel <ardb@...nel.org>,
	"Jason A . Donenfeld" <Jason@...c4.com>,
	Zhihang Shao <zhihang.shao.iscas@...il.com>
Subject: Re: [PATCH 2/3] lib/crypto: poly1305: Consolidate into single module

On Sat, Aug 16, 2025 at 12:43:52PM -0700, Eric Biggers wrote:
> -perlasm-flavour-$(CONFIG_32BIT) := o32
> -perlasm-flavour-$(CONFIG_64BIT) := 64
> -
> -quiet_cmd_perlasm = PERLASM $@
> -      cmd_perlasm = $(PERL) $(<) $(perlasm-flavour-y) $(@)
> -
> -$(obj)/poly1305-core.S: $(src)/poly1305-mips.pl FORCE
> -	$(call if_changed,perlasm)
[...]
> +ifeq ($(CONFIG_MIPS),y)
> +libpoly1305-y += mips/poly1305-core.o
> +poly1305-perlasm-flavour-$(CONFIG_32BIT) := o32
> +poly1305-perlasm-flavour-$(CONFIG_64BIT) := 64
> +quiet_cmd_perlasm_poly1305 = PERLASM $@
> +      cmd_perlasm_poly1305 = $(PERL) $< $(poly1305-perlasm-flavour-y) $@
> +$(obj)/mips/poly1305-core.S: $(src)/mips/poly1305-mips.pl
> +	$(call if_changed,perlasm_poly1305)
> +endif

Small issue that I noticed: I removed the "FORCE" from the rule for
poly1305-core.S since none of the other perlasm rules had it.  But it's
actually needed because, unlike the other perlasm rules, this one uses
'if_changed' instead of 'cmd'.  'if_changed' requires FORCE.  And I
believe it does need to use 'if_changed', since the contents of the
generated .S file depends on the perlasm-flavour passed as an argument
to the perl script.  That can change when the kernel config changes.

So, TLDR: I'll restore the FORCE to the rule, and add a comment.

The RISC-V optimized Poly1305 code added by the third patch will need
if_changed and FORCE for the same reason.

Of course, it's unfortunate that these are written in Perl at all.  But
that is the convention used by Andy / CRYPTOGAMS, so that is what we'll
use unless someone wants to rewrite it...

- Eric