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Subject: Re: [PATCH v2 09/13] RISC-V: crypto: add Zvknha/b accelerated
 SHA224/256 implementations
From:   Jerry Shih <jerry.shih@sifive.com>
In-Reply-To: <20231128041235.GJ1463@sol.localdomain>
Date:   Tue, 28 Nov 2023 15:16:53 +0800
Cc:     Paul Walmsley <paul.walmsley@sifive.com>, palmer@dabbelt.com,
        Albert Ou <aou@eecs.berkeley.edu>, herbert@gondor.apana.org.au,
        davem@davemloft.net, conor.dooley@microchip.com, ardb@kernel.org,
        heiko@sntech.de, phoebe.chen@sifive.com, hongrong.hsu@sifive.com,
        linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
        linux-crypto@vger.kernel.org
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Message-Id: <51190E7A-25BD-4D9A-AADF-02FE2A280508@sifive.com>
References: <20231127070703.1697-1-jerry.shih@sifive.com>
 <20231127070703.1697-10-jerry.shih@sifive.com>
 <20231128041235.GJ1463@sol.localdomain>
To:     Eric Biggers <ebiggers@kernel.org>
Precedence: bulk

On Nov 28, 2023, at 12:12, Eric Biggers <ebiggers@kernel.org> wrote:
> On Mon, Nov 27, 2023 at 03:06:59PM +0800, Jerry Shih wrote:
>> +/*
>> + * sha256 using zvkb and zvknha/b vector crypto extension
>> + *
>> + * This asm function will just take the first 256-bit as the sha256 =
state from
>> + * the pointer to `struct sha256_state`.
>> + */
>> +asmlinkage void
>> +sha256_block_data_order_zvkb_zvknha_or_zvknhb(struct sha256_state =
*digest,
>> +					      const u8 *data, int =
num_blks);
>=20
> The SHA-2 and SM3 assembly functions are potentially being called =
using indirect
> calls, depending on whether the compiler optimizes out the indirect =
call that
> exists in the code or not.  These assembly functions also are not =
defined using
> SYM_TYPED_FUNC_START.  This is not compatible with Control Flow =
Integrity
> (CONFIG_CFI_CLANG); these indirect calls might generate CFI failures.
>=20
> I recommend using wrapper functions to avoid this issue, like what is =
done in
> arch/arm64/crypto/sha2-ce-glue.c.
>=20
> - Eric

Here is the previous review comment for the assembly function wrapper:
> > +asmlinkage void sha256_block_data_order_zvbb_zvknha(u32 *digest, =
const void *data,
> > +					unsigned int num_blks);
> > +
> > +static void __sha256_block_data_order(struct sha256_state *sst, u8 =
const *src,
> > +				      int blocks)
> > +{
> > +	sha256_block_data_order_zvbb_zvknha(sst->state, src, blocks);
> > +}
> Having a double-underscored function wrap around a non-underscored one =
like this
> isn't conventional for Linux kernel code.  IIRC some of the other =
crypto code
> happens to do this, but it really is supposed to be the other way =
around.
>=20
> I think you should just declare the assembly function to take a =
'struct
> sha256_state', with a comment mentioning that only the 'u32 state[8]' =
at the
> beginning is actually used.  That's what =
arch/x86/crypto/sha256_ssse3_glue.c
> does, for example.  Then, __sha256_block_data_order() would be =
unneeded.

Do you mean that we need the wrapper functions back for both SHA-* and =
SM3?
If yes, we also don't need to check the state offset like:
	BUILD_BUG_ON(offsetof(struct sha256_state, state) !=3D 0);

Could we just use the `SYM_TYPED_FUNC_START` in asm directly without the
wrappers?

-Jerry=