lib/crypto/memneq.c

Source file repositories/reference/linux-study-clean/lib/crypto/memneq.c

File Facts

System
Linux kernel
Corpus path
lib/crypto/memneq.c
Extension
.c
Size
6561 bytes
Lines
175
Domain
Kernel Services
Bucket
lib
Inferred role
Kernel Services: exported/initcall integration point
Status
integration implementation candidate

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 <crypto/utils.h>
#include <linux/export.h>
#include <linux/module.h>
#include <linux/unaligned.h>

/* Generic path for arbitrary size */
static inline unsigned long
__crypto_memneq_generic(const void *a, const void *b, size_t size)
{
	unsigned long neq = 0;

#if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
	while (size >= sizeof(unsigned long)) {
		neq |= get_unaligned((unsigned long *)a) ^
		       get_unaligned((unsigned long *)b);
		OPTIMIZER_HIDE_VAR(neq);
		a += sizeof(unsigned long);
		b += sizeof(unsigned long);
		size -= sizeof(unsigned long);
	}
#endif /* CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS */
	while (size > 0) {
		neq |= *(unsigned char *)a ^ *(unsigned char *)b;
		OPTIMIZER_HIDE_VAR(neq);
		a += 1;
		b += 1;
		size -= 1;
	}
	return neq;
}

/* Loop-free fast-path for frequently used 16-byte size */
static inline unsigned long __crypto_memneq_16(const void *a, const void *b)
{
	unsigned long neq = 0;

#ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
	if (sizeof(unsigned long) == 8) {
		neq |= get_unaligned((unsigned long *)a) ^
		       get_unaligned((unsigned long *)b);
		OPTIMIZER_HIDE_VAR(neq);
		neq |= get_unaligned((unsigned long *)(a + 8)) ^
		       get_unaligned((unsigned long *)(b + 8));
		OPTIMIZER_HIDE_VAR(neq);
	} else if (sizeof(unsigned int) == 4) {
		neq |= get_unaligned((unsigned int *)a) ^
		       get_unaligned((unsigned int *)b);
		OPTIMIZER_HIDE_VAR(neq);
		neq |= get_unaligned((unsigned int *)(a + 4)) ^
		       get_unaligned((unsigned int *)(b + 4));
		OPTIMIZER_HIDE_VAR(neq);
		neq |= get_unaligned((unsigned int *)(a + 8)) ^
		       get_unaligned((unsigned int *)(b + 8));
		OPTIMIZER_HIDE_VAR(neq);
		neq |= get_unaligned((unsigned int *)(a + 12)) ^
		       get_unaligned((unsigned int *)(b + 12));
		OPTIMIZER_HIDE_VAR(neq);
	} else
#endif /* CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS */
	{
		neq |= *(unsigned char *)(a)    ^ *(unsigned char *)(b);
		OPTIMIZER_HIDE_VAR(neq);
		neq |= *(unsigned char *)(a+1)  ^ *(unsigned char *)(b+1);
		OPTIMIZER_HIDE_VAR(neq);
		neq |= *(unsigned char *)(a+2)  ^ *(unsigned char *)(b+2);
		OPTIMIZER_HIDE_VAR(neq);
		neq |= *(unsigned char *)(a+3)  ^ *(unsigned char *)(b+3);
		OPTIMIZER_HIDE_VAR(neq);
		neq |= *(unsigned char *)(a+4)  ^ *(unsigned char *)(b+4);
		OPTIMIZER_HIDE_VAR(neq);
		neq |= *(unsigned char *)(a+5)  ^ *(unsigned char *)(b+5);
		OPTIMIZER_HIDE_VAR(neq);
		neq |= *(unsigned char *)(a+6)  ^ *(unsigned char *)(b+6);
		OPTIMIZER_HIDE_VAR(neq);
		neq |= *(unsigned char *)(a+7)  ^ *(unsigned char *)(b+7);
		OPTIMIZER_HIDE_VAR(neq);
		neq |= *(unsigned char *)(a+8)  ^ *(unsigned char *)(b+8);
		OPTIMIZER_HIDE_VAR(neq);
		neq |= *(unsigned char *)(a+9)  ^ *(unsigned char *)(b+9);
		OPTIMIZER_HIDE_VAR(neq);
		neq |= *(unsigned char *)(a+10) ^ *(unsigned char *)(b+10);
		OPTIMIZER_HIDE_VAR(neq);
		neq |= *(unsigned char *)(a+11) ^ *(unsigned char *)(b+11);
		OPTIMIZER_HIDE_VAR(neq);
		neq |= *(unsigned char *)(a+12) ^ *(unsigned char *)(b+12);
		OPTIMIZER_HIDE_VAR(neq);
		neq |= *(unsigned char *)(a+13) ^ *(unsigned char *)(b+13);
		OPTIMIZER_HIDE_VAR(neq);
		neq |= *(unsigned char *)(a+14) ^ *(unsigned char *)(b+14);
		OPTIMIZER_HIDE_VAR(neq);

Annotation

Implementation Notes