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lib/crypto: mips/chacha: Fix clang build and remove unneeded byteswap

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commit 22375adaa0d9fbba9646c8e2b099c6e87c97bfae upstream.

The MIPS32r2 ChaCha code has never been buildable with the clang
assembler.  First, clang doesn't support the 'rotl' pseudo-instruction:

    error: unknown instruction, did you mean: rol, rotr?

Second, clang requires that both operands of the 'wsbh' instruction be
explicitly given:

    error: too few operands for instruction

To fix this, align the code with the real instruction set by (1) using
the real instruction 'rotr' instead of the nonstandard pseudo-
instruction 'rotl', and (2) explicitly giving both operands to 'wsbh'.

To make removing the use of 'rotl' a bit easier, also remove the
unnecessary special-casing for big endian CPUs at
.Lchacha_mips_xor_bytes.  The tail handling is actually
endian-independent since it processes one byte at a time.  On big endian
CPUs the old code byte-swapped SAVED_X, then iterated through it in
reverse order.  But the byteswap and reverse iteration canceled out.

Tested with chacha20poly1305-selftest in QEMU using "-M malta" with both
little endian and big endian mips32r2 kernels.

Fixes: 49aa7c00ed ("crypto: mips/chacha - import 32r2 ChaCha code from Zinc")
Cc: stable@vger.kernel.org
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202505080409.EujEBwA0-lkp@intel.com/
Link: https://lore.kernel.org/r/20250619225535.679301-1-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Eric Biggers
2025-06-19 15:55:35 -07:00
committed by Greg Kroah-Hartman
parent e603142ed9
commit 87e491d6b4
1 changed files with 7 additions and 13 deletions
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20
arch/mips/crypto/chacha-core.S
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@@ -55,17 +55,13 @@
#if __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
#define MSB 0
#define LSB 3
#define ROTx rotl
#define ROTR(n) rotr n, 24
#define CPU_TO_LE32(n) \
wsbh n; \
wsbh n, n; \
rotr n, 16;
#else
#define MSB 3
#define LSB 0
#define ROTx rotr
#define CPU_TO_LE32(n)
#define ROTR(n)
#endif
#define FOR_EACH_WORD(x) \
@@ -192,10 +188,10 @@ CONCAT3(.Lchacha_mips_xor_aligned_, PLUS_ONE(x), _b: ;) \
xor X(W), X(B); \
xor X(Y), X(C); \
xor X(Z), X(D); \
rotl X(V), S; \
rotl X(W), S; \
rotl X(Y), S; \
rotl X(Z), S;
rotr X(V), 32 - S; \
rotr X(W), 32 - S; \
rotr X(Y), 32 - S; \
rotr X(Z), 32 - S;
.text
.set reorder
@@ -372,21 +368,19 @@ chacha_crypt_arch:
/* First byte */
lbu T1, 0(IN)
addiu $at, BYTES, 1
CPU_TO_LE32(SAVED_X)
ROTR(SAVED_X)
xor T1, SAVED_X
sb T1, 0(OUT)
beqz $at, .Lchacha_mips_xor_done
/* Second byte */
lbu T1, 1(IN)
addiu $at, BYTES, 2
ROTx SAVED_X, 8
rotr SAVED_X, 8
xor T1, SAVED_X
sb T1, 1(OUT)
beqz $at, .Lchacha_mips_xor_done
/* Third byte */
lbu T1, 2(IN)
ROTx SAVED_X, 8
rotr SAVED_X, 8
xor T1, SAVED_X
sb T1, 2(OUT)
b .Lchacha_mips_xor_done