arch/arm/lib/putuser.S

File Facts

System

Linux kernel

Corpus path

arch/arm/lib/putuser.S

Extension

.S

Size

2052 bytes

Lines

96

Domain

Architecture Layer

Bucket

arch/arm

Inferred role

Architecture Layer: arch/arm

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.

• CPU and platform-specific kernel glue: boot entry, traps, syscall entry, interrupts, page tables, context switch, and low-level barriers.
• Touches user memory; correctness depends on fault-safe copying and privilege boundary handling.

Dependency Surface

• linux/linkage.h
• asm/assembler.h
• asm/errno.h
• asm/domain.h

Detected Declarations

• No top-level syscall, struct, function, initcall, or export declaration detected by the generator.

Annotated Snippet

#include <linux/linkage.h>
#include <asm/assembler.h>
#include <asm/errno.h>
#include <asm/domain.h>

ENTRY(__put_user_1)
	check_uaccess r0, 1, r1, ip, __put_user_bad
1: TUSER(strb)	r2, [r0]
	mov	r0, #0
	ret	lr
ENDPROC(__put_user_1)

ENTRY(__put_user_2)
	check_uaccess r0, 2, r1, ip, __put_user_bad
#if __LINUX_ARM_ARCH__ >= 6

2: TUSER(strh)	r2, [r0]

#else

	mov	ip, r2, lsr #8
#ifndef __ARMEB__
2: TUSER(strb)	r2, [r0], #1
3: TUSER(strb)	ip, [r0]
#else
2: TUSER(strb)	ip, [r0], #1
3: TUSER(strb)	r2, [r0]
#endif

#endif /* __LINUX_ARM_ARCH__ >= 6 */
	mov	r0, #0
	ret	lr
ENDPROC(__put_user_2)

ENTRY(__put_user_4)
	check_uaccess r0, 4, r1, ip, __put_user_bad
4: TUSER(str)	r2, [r0]
	mov	r0, #0
	ret	lr
ENDPROC(__put_user_4)

ENTRY(__put_user_8)
	check_uaccess r0, 8, r1, ip, __put_user_bad
#ifdef CONFIG_THUMB2_KERNEL
5: TUSER(str)	r2, [r0]
6: TUSER(str)	r3, [r0, #4]
#else
5: TUSER(str)	r2, [r0], #4
6: TUSER(str)	r3, [r0]
#endif
	mov	r0, #0
	ret	lr
ENDPROC(__put_user_8)

__put_user_bad:
	mov	r0, #-EFAULT
	ret	lr
ENDPROC(__put_user_bad)

.pushsection __ex_table, "a"
	.long	1b, __put_user_bad
	.long	2b, __put_user_bad
#if __LINUX_ARM_ARCH__ < 6
	.long	3b, __put_user_bad
#endif
	.long	4b, __put_user_bad
	.long	5b, __put_user_bad
	.long	6b, __put_user_bad
.popsection

Annotation

• Immediate include surface: `linux/linkage.h`, `asm/assembler.h`, `asm/errno.h`, `asm/domain.h`.
• Atlas domain: Architecture Layer / arch/arm.
• Implementation status: atlas-only.
• This snippet crosses the user/kernel memory boundary; validate fault handling and access checks before translating the pattern.

Implementation Notes

• This generated page is the file-by-file coverage layer; curated subsystem chapters should link here when they synthesize a multi-file control flow.
• Core OS pages should be promoted from atlas-only to deep-reviewed when they explain data structures, invariants, locking, lifecycle, and C implementation snippets.
• Driver-family pages are intentionally pattern-oriented unless they are part of the selected PCIe/NVMe representative device path.