linux_kernel/arch/mips/include/asm/syscall.h

/*
 * Access to user system call parameters and results
 *
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 *
 * See asm-generic/syscall.h for descriptions of what we must do here.
 *
 * Copyright (C) 2012 Ralf Baechle <ralf@linux-mips.org>
 */

#ifndef __ASM_MIPS_SYSCALL_H
#define __ASM_MIPS_SYSCALL_H

#include <linux/compiler.h>
#include <linux/audit.h>
#include <linux/elf-em.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/uaccess.h>
#include <asm/ptrace.h>

static inline long syscall_get_nr(struct task_struct *task,
				  struct pt_regs *regs)
{
	return regs->regs[2];
}

static inline unsigned long mips_get_syscall_arg(unsigned long *arg,
	struct task_struct *task, struct pt_regs *regs, unsigned int n)
{
	unsigned long usp __maybe_unused = regs->regs[29];

	switch (n) {
	case 0: case 1: case 2: case 3:
		*arg = regs->regs[4 + n];

		return 0;

#ifdef CONFIG_32BIT
	case 4: case 5: case 6: case 7:
		return get_user(*arg, (int *)usp + 4 * n);
#endif

#ifdef CONFIG_64BIT
	case 4: case 5: case 6: case 7:
#ifdef CONFIG_MIPS32_O32
		if (test_thread_flag(TIF_32BIT_REGS))
			return get_user(*arg, (int *)usp + 4 * n);
		else
#endif
			*arg = regs->regs[4 + n];

		return 0;
#endif

	default:
		BUG();
	}

	unreachable();
}

static inline long syscall_get_return_value(struct task_struct *task,
					    struct pt_regs *regs)
{
	return regs->regs[2];
}

static inline void syscall_set_return_value(struct task_struct *task,
					    struct pt_regs *regs,
					    int error, long val)
{
	if (error) {
		regs->regs[2] = -error;
		regs->regs[7] = -1;
	} else {
		regs->regs[2] = val;
		regs->regs[7] = 0;
	}
}

static inline void syscall_get_arguments(struct task_struct *task,
					 struct pt_regs *regs,
					 unsigned int i, unsigned int n,
					 unsigned long *args)
{
	int ret;

	while (n--)
		ret |= mips_get_syscall_arg(args++, task, regs, i++);

	/*
	 * No way to communicate an error because this is a void function.
	 */
#if 0
	return ret;
#endif
}

extern const unsigned long sys_call_table[];
extern const unsigned long sys32_call_table[];
extern const unsigned long sysn32_call_table[];

static inline int __syscall_get_arch(void)
{
	int arch = EM_MIPS;
#ifdef CONFIG_64BIT
	arch |=  __AUDIT_ARCH_64BIT;
#endif
#if defined(__LITTLE_ENDIAN)
	arch |=  __AUDIT_ARCH_LE;
#endif
	return arch;
}

#endif	/* __ASM_MIPS_SYSCALL_H */