lib/crypto/arm64/chacha-neon-core.S

Source file repositories/reference/linux-study-clean/lib/crypto/arm64/chacha-neon-core.S

File Facts

System
Linux kernel
Corpus path
lib/crypto/arm64/chacha-neon-core.S
Extension
.S
Size
18605 bytes
Lines
790
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>
#include <asm/assembler.h>
#include <asm/cache.h>

	.text
	.align		6

/*
 * chacha_permute - permute one block
 *
 * Permute one 64-byte block where the state matrix is stored in the four NEON
 * registers v0-v3.  It performs matrix operations on four words in parallel,
 * but requires shuffling to rearrange the words after each round.
 *
 * The round count is given in w3.
 *
 * Clobbers: w3, x10, v4, v12
 */
SYM_FUNC_START_LOCAL(chacha_permute)

	adr_l		x10, ROT8
	ld1		{v12.4s}, [x10]

.Ldoubleround:
	// x0 += x1, x3 = rotl32(x3 ^ x0, 16)
	add		v0.4s, v0.4s, v1.4s
	eor		v3.16b, v3.16b, v0.16b
	rev32		v3.8h, v3.8h

	// x2 += x3, x1 = rotl32(x1 ^ x2, 12)
	add		v2.4s, v2.4s, v3.4s
	eor		v4.16b, v1.16b, v2.16b
	shl		v1.4s, v4.4s, #12
	sri		v1.4s, v4.4s, #20

	// x0 += x1, x3 = rotl32(x3 ^ x0, 8)
	add		v0.4s, v0.4s, v1.4s
	eor		v3.16b, v3.16b, v0.16b
	tbl		v3.16b, {v3.16b}, v12.16b

	// x2 += x3, x1 = rotl32(x1 ^ x2, 7)
	add		v2.4s, v2.4s, v3.4s
	eor		v4.16b, v1.16b, v2.16b
	shl		v1.4s, v4.4s, #7
	sri		v1.4s, v4.4s, #25

	// x1 = shuffle32(x1, MASK(0, 3, 2, 1))
	ext		v1.16b, v1.16b, v1.16b, #4
	// x2 = shuffle32(x2, MASK(1, 0, 3, 2))
	ext		v2.16b, v2.16b, v2.16b, #8
	// x3 = shuffle32(x3, MASK(2, 1, 0, 3))
	ext		v3.16b, v3.16b, v3.16b, #12

	// x0 += x1, x3 = rotl32(x3 ^ x0, 16)
	add		v0.4s, v0.4s, v1.4s
	eor		v3.16b, v3.16b, v0.16b
	rev32		v3.8h, v3.8h

	// x2 += x3, x1 = rotl32(x1 ^ x2, 12)
	add		v2.4s, v2.4s, v3.4s
	eor		v4.16b, v1.16b, v2.16b
	shl		v1.4s, v4.4s, #12
	sri		v1.4s, v4.4s, #20

	// x0 += x1, x3 = rotl32(x3 ^ x0, 8)
	add		v0.4s, v0.4s, v1.4s
	eor		v3.16b, v3.16b, v0.16b
	tbl		v3.16b, {v3.16b}, v12.16b

	// x2 += x3, x1 = rotl32(x1 ^ x2, 7)

Annotation

Implementation Notes