arch/arm/include/asm/futex.h

Source file repositories/reference/linux-study-clean/arch/arm/include/asm/futex.h

File Facts

System
Linux kernel
Corpus path
arch/arm/include/asm/futex.h
Extension
.h
Size
4357 bytes
Lines
181
Domain
Architecture Layer
Bucket
arch/arm
Inferred role
Architecture Layer: implementation source
Status
source 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

#ifndef _ASM_ARM_FUTEX_H
#define _ASM_ARM_FUTEX_H

#ifdef __KERNEL__

#include <linux/futex.h>
#include <linux/uaccess.h>
#include <asm/errno.h>

#define __futex_atomic_ex_table(err_reg)			\
	"3:\n"							\
	"	.pushsection __ex_table,\"a\"\n"		\
	"	.align	3\n"					\
	"	.long	1b, 4f, 2b, 4f\n"			\
	"	.popsection\n"					\
	"	.pushsection .text.fixup,\"ax\"\n"		\
	"	.align	2\n"					\
	"4:	mov	%0, " err_reg "\n"			\
	"	b	3b\n"					\
	"	.popsection"

#ifdef CONFIG_SMP

#define __futex_atomic_op(insn, ret, oldval, tmp, uaddr, oparg)	\
({								\
	unsigned int __ua_flags;				\
	smp_mb();						\
	prefetchw(uaddr);					\
	__ua_flags = uaccess_save_and_enable();			\
	__asm__ __volatile__(					\
	"1:	ldrex	%1, [%3]\n"				\
	"	" insn "\n"					\
	"2:	strex	%2, %0, [%3]\n"				\
	"	teq	%2, #0\n"				\
	"	bne	1b\n"					\
	"	mov	%0, #0\n"				\
	__futex_atomic_ex_table("%5")				\
	: "=&r" (ret), "=&r" (oldval), "=&r" (tmp)		\
	: "r" (uaddr), "r" (oparg), "Ir" (-EFAULT)		\
	: "cc", "memory");					\
	uaccess_restore(__ua_flags);				\
})

static inline int
futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
			      u32 oldval, u32 newval)
{
	unsigned int __ua_flags;
	int ret;
	u32 val;

	if (!access_ok(uaddr, sizeof(u32)))
		return -EFAULT;

	smp_mb();
	/* Prefetching cannot fault */
	prefetchw(uaddr);
	__ua_flags = uaccess_save_and_enable();
	__asm__ __volatile__("@futex_atomic_cmpxchg_inatomic\n"
	"1:	ldrex	%1, [%4]\n"
	"	teq	%1, %2\n"
	"	ite	eq	@ explicit IT needed for the 2b label\n"
	"2:	strexeq	%0, %3, [%4]\n"
	"	movne	%0, #0\n"
	"	teq	%0, #0\n"
	"	bne	1b\n"
	__futex_atomic_ex_table("%5")
	: "=&r" (ret), "=&r" (val)
	: "r" (oldval), "r" (newval), "r" (uaddr), "Ir" (-EFAULT)
	: "cc", "memory");
	uaccess_restore(__ua_flags);
	smp_mb();

	*uval = val;
	return ret;
}

#else /* !SMP, we can work around lack of atomic ops by disabling preemption */

#include <linux/preempt.h>
#include <asm/domain.h>

#define __futex_atomic_op(insn, ret, oldval, tmp, uaddr, oparg)	\
({								\
	unsigned int __ua_flags = uaccess_save_and_enable();	\
	__asm__ __volatile__(					\
	"1:	" TUSER(ldr) "	%1, [%3]\n"			\
	"	" insn "\n"					\
	"2:	" TUSER(str) "	%0, [%3]\n"			\
	"	mov	%0, #0\n"				\

Annotation

Implementation Notes