arch/arm64/lib/memset.S

Source file repositories/reference/linux-study-clean/arch/arm64/lib/memset.S

File Facts

System
Linux kernel
Corpus path
arch/arm64/lib/memset.S
Extension
.S
Size
4929 bytes
Lines
229
Domain
Architecture Layer
Bucket
arch/arm64
Inferred role
Architecture Layer: exported/initcall integration point
Status
integration implementation candidate

Why This File Exists

CPU and platform-specific kernel glue: boot entry, traps, syscall entry, interrupts, page tables, context switch, and low-level barriers.

Dependency Surface

Detected Declarations

Annotated Snippet

#include <linux/linkage.h>
#include <asm/assembler.h>
#include <asm/cache.h>

/*
 * Fill in the buffer with character c (alignment handled by the hardware)
 *
 * Parameters:
 *	x0 - buf
 *	x1 - c
 *	x2 - n
 * Returns:
 *	x0 - buf
 */

dstin		.req	x0
val_x		.req	x1
val		.req	w1
count		.req	x2
tmp1		.req	x3
tmp1w		.req	w3
tmp2		.req	x4
tmp2w		.req	w4
zva_len_x	.req	x5
zva_len		.req	w5
zva_bits_x	.req	x6

A_l		.req	x7
A_lw		.req	w7
dst		.req	x8
tmp3w		.req	w9
tmp3		.req	x9

SYM_FUNC_START_LOCAL(__pi_memset_generic)
	mov	dst, dstin	/* Preserve return value.  */
	and	A_lw, val, #255
	orr	A_lw, A_lw, A_lw, lsl #8
	orr	A_lw, A_lw, A_lw, lsl #16
	orr	A_l, A_l, A_l, lsl #32

	cmp	count, #15
	b.hi	.Lover16_proc
	/*All store maybe are non-aligned..*/
	tbz	count, #3, 1f
	str	A_l, [dst], #8
1:
	tbz	count, #2, 2f
	str	A_lw, [dst], #4
2:
	tbz	count, #1, 3f
	strh	A_lw, [dst], #2
3:
	tbz	count, #0, 4f
	strb	A_lw, [dst]
4:
	ret

.Lover16_proc:
	/*Whether  the start address is aligned with 16.*/
	neg	tmp2, dst
	ands	tmp2, tmp2, #15
	b.eq	.Laligned
/*
* The count is not less than 16, we can use stp to store the start 16 bytes,
* then adjust the dst aligned with 16.This process will make the current
* memory address at alignment boundary.
*/
	stp	A_l, A_l, [dst] /*non-aligned store..*/
	/*make the dst aligned..*/
	sub	count, count, tmp2

Annotation

Implementation Notes