Re: [PATCH 1/2] PBL: add pbl_sha256()

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

On 7/10/26 19:01, Lucas Stach wrote:
> Am Donnerstag, dem 09.07.2026 um 13:14 +0200 schrieb Sascha Hauer:
>> The PBL open-codes SHA-256 as sha256_init()/sha256_update()/sha256_final()
>> wherever it needs to hash a blob, which always uses the generic C transform.
>> Add pbl_sha256(), a one-shot helper that hides this behind a single call and
>> is free to pick the best transform available in the PBL. For now it only
>> wraps the generic C implementation; an accelerated path is added on top in a
>> later commit.
>>
>> Convert pbl_barebox_verify() in pbl/decomp.c to the new helper as the first
>> user.
>>
>> Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
>> ---
>>  include/crypto/pbl-sha.h |  4 ++++
>>  pbl/Makefile             |  1 +
>>  pbl/decomp.c             |  6 +-----
>>  pbl/sha256.c             | 25 +++++++++++++++++++++++++
>>  4 files changed, 31 insertions(+), 5 deletions(-)
>>
>> diff --git a/include/crypto/pbl-sha.h b/include/crypto/pbl-sha.h
>> index 7d323ab479..2508448ab4 100644
>> --- a/include/crypto/pbl-sha.h
>> +++ b/include/crypto/pbl-sha.h
>> @@ -3,6 +3,7 @@
>>  
>>  #define __PBL_SHA_H_
>>  
>> +#include <crypto/sha.h>
>>  #include <digest.h>
>>  #include <types.h>
>>  
>> @@ -10,4 +11,7 @@ int sha256_init(struct digest *desc);
>>  int sha256_update(struct digest *desc, const void *data, unsigned long len);
>>  int sha256_final(struct digest *desc, u8 *out);
>>  
>> +/* One-shot SHA-256 that picks the best transform available in the PBL. */
>> +void pbl_sha256(const void *buf, size_t len, u8 out[SHA256_DIGEST_SIZE]);
>> +
>>  #endif /* __PBL-SHA_H_ */
>> diff --git a/pbl/Makefile b/pbl/Makefile
>> index 45cfbf5fba..4506f192fe 100644
>> --- a/pbl/Makefile
>> +++ b/pbl/Makefile
>> @@ -6,6 +6,7 @@
>>  pbl-y += misc.o
>>  pbl-y += string.o
>>  pbl-y += malloc.o
>> +pbl-y += sha256.o
>>  pbl-$(CONFIG_HAVE_IMAGE_COMPRESSION) += decomp.o
>>  pbl-$(CONFIG_LIBFDT) += fdt.o
>>  pbl-$(CONFIG_PBL_CONSOLE) += console.o
>> diff --git a/pbl/decomp.c b/pbl/decomp.c
>> index 1539a6b67e..2b3c35012f 100644
>> --- a/pbl/decomp.c
>> +++ b/pbl/decomp.c
>> @@ -58,8 +58,6 @@ extern unsigned char sha_sum_end[];
>>  int pbl_barebox_verify(const void *compressed_start, unsigned int len,
>>  		       const void *hash, unsigned int hash_len)
>>  {
>> -	struct sha256_state sha_state = { 0 };
>> -	struct digest d = { .ctx = &sha_state };
>>  	char computed_hash[SHA256_DIGEST_SIZE];
>>  	int i;
>>  	const char *char_hash = hash;
>> @@ -67,9 +65,7 @@ int pbl_barebox_verify(const void *compressed_start, unsigned int len,
>>  	if (hash_len != SHA256_DIGEST_SIZE)
>>  		return -1;
>>  
>> -	sha256_init(&d);
>> -	sha256_update(&d, compressed_start, len);
>> -	sha256_final(&d, computed_hash);
>> +	pbl_sha256(compressed_start, len, computed_hash);
>>  	if (IS_ENABLED(CONFIG_DEBUG_LL)) {
>>  		puts_ll("CH ");
>>  
>> diff --git a/pbl/sha256.c b/pbl/sha256.c
>> new file mode 100644
>> index 0000000000..86e54f8a25
>> --- /dev/null
>> +++ b/pbl/sha256.c
>> @@ -0,0 +1,25 @@
>> +// SPDX-License-Identifier: GPL-2.0-only
>> +/*
>> + * pbl_sha256() - one-shot SHA-256 for the PBL, picking the best available
>> + * transform (ARMv8 Crypto Extensions if present, else generic C).
> 
> This file isn't ARMv8 specific, so I don't really see why the comment
> would reference a specific implementation.
> 
>> + */
>> +
>> +#include <common.h>
>> +#include <crypto/sha.h>
>> +#include <crypto/pbl-sha.h>
>> +#include <digest.h>
>> +
>> +static void pbl_sha256_generic(const void *buf, size_t len, u8 *out)
>> +{
>> +	struct sha256_state state = { };
>> +	struct digest d = { .ctx = &state, .length = SHA256_DIGEST_SIZE };
>> +
>> +	sha256_init(&d);
>> +	sha256_update(&d, buf, len);
>> +	sha256_final(&d, out);
>> +}
>> +
>> +void pbl_sha256(const void *buf, size_t len, u8 out[SHA256_DIGEST_SIZE])
> 
> That's a weird way to write "u8 *out"...

Not weird enough: If we make it

u8 out[static SHA256_DIGEST_SIZE])

Compiler can emit some useful warnings if it deduces buffer isn't big enough.

Cheers,
Ahmad

> 
>> +{
>> +	pbl_sha256_generic(buf, len, out);
>> +}
> 
> 


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