lib/crypto: mips: Disable Octeon SHA code on little-endian kernels

commit dd2a4edb26e1c78823c50ba10c42f2d3de2e5ec4 upstream.

Kernels built for the MIPS64-based Cavium Octeon SoCs are normally big-endian, but little-endian builds are also supported. Currently, the SHA-1, SHA-256, and SHA-512 code using the Octeon crypto co-processor is enabled in both builds.

This code is untestable without the hardware. However, based on the code itself, it is implausible that it computes hash values correctly in little-endian builds. Such builds write many incorrect values to COP2:

- SHA-1 and SHA-256: The 64-bit integer that contains the last two 32-bit message words of each block is written to COP2 entirely byte-reflected, due to missing endianness conversion in octeon_sha1_start() and octeon_sha256_start() to compensate for using native 64-bit loads from the message bytes. This differs from all the earlier message words which are written correctly.

Furthermore, the state is written to COP2 with each 32-bit word byte-reflected within each 64-bit integer, due to incorrect use of 64-bit endianness conversion in write_octeon_64bit_hash_dword() when the state is kept in memory in native-endian 32-bit words.

- SHA-512: All the 64-bit message words are written to COP2 byte-reflected, due to missing endianness conversion in write_octeon_64bit_block_sha512() and octeon_sha512_start(). The SHA-512 state words seem to be written correctly.

Big-endian kernels aren't affected by these bugs. These bugs also aren't new; this code has been broken on little-endian ever since it and Octeon little-endian support were first added in v4.1.

Commit d2a948d2db68 ("MIPS: Octeon: Make octeon-md5 driver endian-agnostic") made the MD5 code work on little-endian kernels by adding 64-bit endianness conversions to the COP2 macros used by MD5 (some of which are shared by SHA-1 and SHA-256, despite those algorithms keeping the state words in native-endian instead of MD5's little-endian, causing some of the strange behavior described above). However, SHA-1, SHA-256, and SHA-512 were never fixed to work on little-endian kernels.

Therefore, disable the Octeon SHA-1, SHA-256, and SHA-512 code in little-endian kernels. This causes the generic code that actually computes hash values correctly to be used instead.

---
 arch/mips/crypto/Kconfig | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

index ee9604fd20372..f951a75dfef32 100644
@@ -34,7 +34,7 @@ config CRYPTO_MD5_OCTEON
 
 config CRYPTO_SHA1_OCTEON
 	tristate "Hash functions: SHA-1 (OCTEON)"
-	depends on CPU_CAVIUM_OCTEON
+	depends on CPU_CAVIUM_OCTEON && CPU_BIG_ENDIAN
 	select CRYPTO_SHA1
 	select CRYPTO_HASH
 	help

@@ -44,7 +44,7 @@ config CRYPTO_SHA1_OCTEON
 
 config CRYPTO_SHA256_OCTEON
 	tristate "Hash functions: SHA-224 and SHA-256 (OCTEON)"
-	depends on CPU_CAVIUM_OCTEON
+	depends on CPU_CAVIUM_OCTEON && CPU_BIG_ENDIAN
 	select CRYPTO_SHA256
 	select CRYPTO_HASH
 	help

@@ -54,7 +54,7 @@ config CRYPTO_SHA256_OCTEON
 
 config CRYPTO_SHA512_OCTEON
 	tristate "Hash functions: SHA-384 and SHA-512 (OCTEON)"
-	depends on CPU_CAVIUM_OCTEON
+	depends on CPU_CAVIUM_OCTEON && CPU_BIG_ENDIAN
 	select CRYPTO_SHA512
 	select CRYPTO_HASH
 	help

base-commit: d3417611a3b40b7f04a29e558cebac2bf69889d7

2.56.0