lib/crypto/x86/chacha-avx2-x86_64.S

Source file repositories/reference/linux-study-clean/lib/crypto/x86/chacha-avx2-x86_64.S

File Facts

System
Linux kernel
Corpus path
lib/crypto/x86/chacha-avx2-x86_64.S
Extension
.S
Size
25009 bytes
Lines
1022
Domain
Kernel Services
Bucket
lib
Inferred role
Kernel Services: lib
Status
atlas-only

Why This File Exists

Shared kernel service surface used by multiple subsystems, including helpers, cryptography, virtualization support, and async I/O infrastructure.

Dependency Surface

Detected Declarations

Annotated Snippet

#include <linux/linkage.h>

.section	.rodata.cst32.ROT8, "aM", @progbits, 32
.align 32
ROT8:	.octa 0x0e0d0c0f0a09080b0605040702010003
	.octa 0x0e0d0c0f0a09080b0605040702010003

.section	.rodata.cst32.ROT16, "aM", @progbits, 32
.align 32
ROT16:	.octa 0x0d0c0f0e09080b0a0504070601000302
	.octa 0x0d0c0f0e09080b0a0504070601000302

.section	.rodata.cst32.CTRINC, "aM", @progbits, 32
.align 32
CTRINC:	.octa 0x00000003000000020000000100000000
	.octa 0x00000007000000060000000500000004

.section	.rodata.cst32.CTR2BL, "aM", @progbits, 32
.align 32
CTR2BL:	.octa 0x00000000000000000000000000000000
	.octa 0x00000000000000000000000000000001

.section	.rodata.cst32.CTR4BL, "aM", @progbits, 32
.align 32
CTR4BL:	.octa 0x00000000000000000000000000000002
	.octa 0x00000000000000000000000000000003

.text

SYM_FUNC_START(chacha_2block_xor_avx2)
	# %rdi: Input state matrix, s
	# %rsi: up to 2 data blocks output, o
	# %rdx: up to 2 data blocks input, i
	# %rcx: input/output length in bytes
	# %r8d: nrounds

	# This function encrypts two ChaCha blocks by loading the state
	# matrix twice across four AVX registers. It performs matrix operations
	# on four words in each matrix in parallel, but requires shuffling to
	# rearrange the words after each round.

	vzeroupper

	# x0..3[0-2] = s0..3
	vbroadcasti128	0x00(%rdi),%ymm0
	vbroadcasti128	0x10(%rdi),%ymm1
	vbroadcasti128	0x20(%rdi),%ymm2
	vbroadcasti128	0x30(%rdi),%ymm3

	vpaddd		CTR2BL(%rip),%ymm3,%ymm3

	vmovdqa		%ymm0,%ymm8
	vmovdqa		%ymm1,%ymm9
	vmovdqa		%ymm2,%ymm10
	vmovdqa		%ymm3,%ymm11

	vmovdqa		ROT8(%rip),%ymm4
	vmovdqa		ROT16(%rip),%ymm5

	mov		%rcx,%rax

.Ldoubleround:

	# x0 += x1, x3 = rotl32(x3 ^ x0, 16)
	vpaddd		%ymm1,%ymm0,%ymm0
	vpxor		%ymm0,%ymm3,%ymm3
	vpshufb		%ymm5,%ymm3,%ymm3

	# x2 += x3, x1 = rotl32(x1 ^ x2, 12)
	vpaddd		%ymm3,%ymm2,%ymm2

Annotation

Implementation Notes