linux-kernel - [PATCH 2/2] lib/crypto: x86/sha256: Remove unnecessary checks for nblocks==0

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Message-ID: <20250704023958.73274-3-ebiggers@kernel.org>
Date: Thu,  3 Jul 2025 19:39:58 -0700
From: Eric Biggers <ebiggers@...nel.org>
To: linux-crypto@...r.kernel.org
Cc: linux-kernel@...r.kernel.org,
	x86@...nel.org,
	Ard Biesheuvel <ardb@...nel.org>,
	"Jason A . Donenfeld" <Jason@...c4.com>,
	Eric Biggers <ebiggers@...nel.org>
Subject: [PATCH 2/2] lib/crypto: x86/sha256: Remove unnecessary checks for nblocks==0

Since sha256_blocks() is called only with nblocks >= 1, remove
unnecessary checks for nblocks == 0 from the x86 SHA-256 assembly code.

Signed-off-by: Eric Biggers <ebiggers@...nel.org>
---
 lib/crypto/x86/sha256-avx-asm.S   | 3 ---
 lib/crypto/x86/sha256-avx2-asm.S  | 1 -
 lib/crypto/x86/sha256-ni-asm.S    | 3 ---
 lib/crypto/x86/sha256-ssse3-asm.S | 3 ---
 4 files changed, 10 deletions(-)

diff --git a/lib/crypto/x86/sha256-avx-asm.S b/lib/crypto/x86/sha256-avx-asm.S
index 798a7f07fa013..c1aceb3ba3a3a 100644
--- a/lib/crypto/x86/sha256-avx-asm.S
+++ b/lib/crypto/x86/sha256-avx-asm.S
@@ -355,11 +355,10 @@ SYM_FUNC_START(sha256_transform_avx)
 
 	subq    $STACK_SIZE, %rsp	# allocate stack space
 	and	$~15, %rsp		# align stack pointer
 
 	shl     $6, NUM_BLKS		# convert to bytes
-	jz      .Ldone_hash
 	add     INP, NUM_BLKS		# pointer to end of data
 	mov     NUM_BLKS, _INP_END(%rsp)
 
 	## load initial digest
 	mov     4*0(CTX), a
@@ -444,12 +443,10 @@ SYM_FUNC_START(sha256_transform_avx)
 	mov     _INP(%rsp), INP
 	add     $64, INP
 	cmp     _INP_END(%rsp), INP
 	jne     .Lloop0
 
-.Ldone_hash:
-
 	mov	%rbp, %rsp
 	popq	%rbp
 	popq    %r15
 	popq    %r14
 	popq    %r13
diff --git a/lib/crypto/x86/sha256-avx2-asm.S b/lib/crypto/x86/sha256-avx2-asm.S
index 62a46993359e6..eb8836fb9695c 100644
--- a/lib/crypto/x86/sha256-avx2-asm.S
+++ b/lib/crypto/x86/sha256-avx2-asm.S
@@ -533,11 +533,10 @@ SYM_FUNC_START(sha256_transform_rorx)
 
 	subq	$STACK_SIZE, %rsp
 	and	$-32, %rsp	# align rsp to 32 byte boundary
 
 	shl	$6, NUM_BLKS	# convert to bytes
-	jz	.Ldone_hash
 	lea	-64(INP, NUM_BLKS), NUM_BLKS # pointer to last block
 	mov	NUM_BLKS, _INP_END(%rsp)
 
 	cmp	NUM_BLKS, INP
 	je	.Lonly_one_block
diff --git a/lib/crypto/x86/sha256-ni-asm.S b/lib/crypto/x86/sha256-ni-asm.S
index 9ebbacbb9c13b..4bd9490ffc662 100644
--- a/lib/crypto/x86/sha256-ni-asm.S
+++ b/lib/crypto/x86/sha256-ni-asm.S
@@ -110,11 +110,10 @@
  */
 .text
 SYM_FUNC_START(sha256_ni_transform)
 
 	shl		$6, NUM_BLKS		/*  convert to bytes */
-	jz		.Ldone_hash
 	add		DATA_PTR, NUM_BLKS	/* pointer to end of data */
 
 	/*
 	 * load initial hash values
 	 * Need to reorder these appropriately
@@ -161,12 +160,10 @@ SYM_FUNC_START(sha256_ni_transform)
 	pshufd		$0x1B, STATE1, STATE1		/* DCBA */
 
 	movdqu		STATE1, 0*16(STATE_PTR)
 	movdqu		STATE0, 1*16(STATE_PTR)
 
-.Ldone_hash:
-
 	RET
 SYM_FUNC_END(sha256_ni_transform)
 
 .section	.rodata.cst256.K256, "aM", @progbits, 256
 .align 64
diff --git a/lib/crypto/x86/sha256-ssse3-asm.S b/lib/crypto/x86/sha256-ssse3-asm.S
index 3b602b7d43fad..0a2719661784c 100644
--- a/lib/crypto/x86/sha256-ssse3-asm.S
+++ b/lib/crypto/x86/sha256-ssse3-asm.S
@@ -363,11 +363,10 @@ SYM_FUNC_START(sha256_transform_ssse3)
 
 	subq    $STACK_SIZE, %rsp
 	and	$~15, %rsp
 
 	shl     $6, NUM_BLKS		 # convert to bytes
-	jz      .Ldone_hash
 	add     INP, NUM_BLKS
 	mov     NUM_BLKS, _INP_END(%rsp) # pointer to end of data
 
 	## load initial digest
 	mov     4*0(CTX), a
@@ -456,12 +455,10 @@ SYM_FUNC_START(sha256_transform_ssse3)
 	mov     _INP(%rsp), INP
 	add     $64, INP
 	cmp     _INP_END(%rsp), INP
 	jne     .Lloop0
 
-.Ldone_hash:
-
 	mov	%rbp, %rsp
 	popq	%rbp
 	popq    %r15
 	popq    %r14
 	popq    %r13
-- 
2.50.0