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* Copyright (C) 2016 Imagination Technologies
* Author: Paul Burton <>
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the
* Free Software Foundation; either version 2 of the License, or (at your
* option) any later version.
#ifndef __MIPS_ASM_DSEMUL_H__
#define __MIPS_ASM_DSEMUL_H__
#include <asm/break.h>
#include <asm/inst.h>
/* Break instruction with special math emu break code set */
#define BREAK_MATH(micromips) (((micromips) ? 0x7 : 0xd) | (BRK_MEMU << 16))
/* When used as a frame index, indicates the lack of a frame */
#define BD_EMUFRAME_NONE ((int)BIT(31))
struct mm_struct;
struct pt_regs;
struct task_struct;
* mips_dsemul() - 'Emulate' an instruction from a branch delay slot
* @regs: User thread register context.
* @ir: The instruction to be 'emulated'.
* @branch_pc: The PC of the branch instruction.
* @cont_pc: The PC to continue at following 'emulation'.
* Emulate or execute an arbitrary MIPS instruction within the context of
* the current user thread. This is used primarily to handle instructions
* in the delay slots of emulated branch instructions, for example FP
* branch instructions on systems without an FPU.
* Return: Zero on success, negative if ir is a NOP, signal number on failure.
extern int mips_dsemul(struct pt_regs *regs, mips_instruction ir,
unsigned long branch_pc, unsigned long cont_pc);
* do_dsemulret() - Return from a delay slot 'emulation' frame
* @xcp: User thread register context.
* Call in response to the BRK_MEMU break instruction used to return to
* the kernel from branch delay slot 'emulation' frames following a call
* to mips_dsemul(). Restores the user thread PC to the value that was
* passed as the cpc parameter to mips_dsemul().
* Return: True if an emulation frame was returned from, else false.
extern bool do_dsemulret(struct pt_regs *xcp);
* dsemul_thread_cleanup() - Cleanup thread 'emulation' frame
* @tsk: The task structure associated with the thread
* If the thread @tsk has a branch delay slot 'emulation' frame
* allocated to it then free that frame.
* Return: True if a frame was freed, else false.
extern bool dsemul_thread_cleanup(struct task_struct *tsk);
* dsemul_thread_rollback() - Rollback from an 'emulation' frame
* @regs: User thread register context.
* If the current thread, whose register context is represented by @regs,
* is executing within a delay slot 'emulation' frame then exit that
* frame. The PC will be rolled back to the branch if the instruction
* that was being 'emulated' has not yet executed, or advanced to the
* continuation PC if it has.
* Return: True if a frame was exited, else false.
extern bool dsemul_thread_rollback(struct pt_regs *regs);
* dsemul_mm_cleanup() - Cleanup per-mm delay slot 'emulation' state
* @mm: The struct mm_struct to cleanup state for.
* Cleanup state for the given @mm, ensuring that any memory allocated
* for delay slot 'emulation' book-keeping is freed. This is to be called
* before @mm is freed in order to avoid memory leaks.
extern void dsemul_mm_cleanup(struct mm_struct *mm);
#endif /* __MIPS_ASM_DSEMUL_H__ */