arch/sh/lib/__clear_user.S

Source file repositories/reference/linux-study-clean/arch/sh/lib/__clear_user.S

File Facts

System
Linux kernel
Corpus path
arch/sh/lib/__clear_user.S
Extension
.S
Size
1827 bytes
Lines
110
Domain
Architecture Layer
Bucket
arch/sh
Inferred role
Architecture Layer: arch/sh
Status
atlas-only

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/page.h>

ENTRY(__clear_user)
	!
	mov	#0, r0
	mov	#0xffffffe0, r1
	!
	! r4..(r4+31)&~32 	   -------- not aligned	[ Area 0 ]
	! (r4+31)&~32..(r4+r5)&~32 -------- aligned	[ Area 1 ]
	! (r4+r5)&~32..r4+r5       -------- not aligned	[ Area 2 ]
	!
	! Clear area 0
	mov	r4, r2
	!
	tst	r1, r5		! length < 32
	bt	.Larea2		! skip to remainder
	!
	add	#31, r2
	and	r1, r2
	cmp/eq	r4, r2
	bt	.Larea1
	mov	r2, r3
	sub	r4, r3
	mov	r3, r7
	mov	r4, r2
	!
.L0:	dt	r3
0:	mov.b	r0, @r2
	bf/s	.L0
	 add	#1, r2
	!
	sub	r7, r5
	mov	r2, r4
.Larea1:
	mov	r4, r3
	add	r5, r3
	and	r1, r3
	cmp/hi	r2, r3
	bf	.Larea2
	!
	! Clear area 1
#if defined(CONFIG_CPU_SH4)
1:	movca.l	r0, @r2
#else
1:	mov.l	r0, @r2
#endif
	add	#4, r2
2:	mov.l	r0, @r2
	add	#4, r2
3:	mov.l	r0, @r2
	add	#4, r2
4:	mov.l	r0, @r2
	add	#4, r2
5:	mov.l	r0, @r2
	add	#4, r2
6:	mov.l	r0, @r2
	add	#4, r2
7:	mov.l	r0, @r2
	add	#4, r2
8:	mov.l	r0, @r2
	add	#4, r2
	cmp/hi	r2, r3
	bt/s	1b
	 nop
	!
	! Clear area 2
.Larea2:
	mov	r4, r3
	add	r5, r3

Annotation

Implementation Notes