LXR linux/arch/mips/include/asm/dsemul.h

   1/*
   2 * Copyright (C) 2016 Imagination Technologies
   3 * Author: Paul Burton <paul.burton@mips.com>
   4 *
   5 * This program is free software; you can redistribute it and/or modify it
   6 * under the terms of the GNU General Public License as published by the
   7 * Free Software Foundation;  either version 2 of the  License, or (at your
   8 * option) any later version.
   9 */
  10
  11#ifndef __MIPS_ASM_DSEMUL_H__
  12#define __MIPS_ASM_DSEMUL_H__
  13
  14#include <asm/break.h>
  15#include <asm/inst.h>
  16
  17/* Break instruction with special math emu break code set */
  18#define BREAK_MATH(micromips)   (((micromips) ? 0x7 : 0xd) | (BRK_MEMU << 16))
  19
  20/* When used as a frame index, indicates the lack of a frame */
  21#define BD_EMUFRAME_NONE        ((int)BIT(31))
  22
  23struct mm_struct;
  24struct pt_regs;
  25struct task_struct;
  26
  27/**
  28 * mips_dsemul() - 'Emulate' an instruction from a branch delay slot
  29 * @regs:       User thread register context.
  30 * @ir:         The instruction to be 'emulated'.
  31 * @branch_pc:  The PC of the branch instruction.
  32 * @cont_pc:    The PC to continue at following 'emulation'.
  33 *
  34 * Emulate or execute an arbitrary MIPS instruction within the context of
  35 * the current user thread. This is used primarily to handle instructions
  36 * in the delay slots of emulated branch instructions, for example FP
  37 * branch instructions on systems without an FPU.
  38 *
  39 * Return: Zero on success, negative if ir is a NOP, signal number on failure.
  40 */
  41extern int mips_dsemul(struct pt_regs *regs, mips_instruction ir,
  42                       unsigned long branch_pc, unsigned long cont_pc);
  43
  44/**
  45 * do_dsemulret() - Return from a delay slot 'emulation' frame
  46 * @xcp:        User thread register context.
  47 *
  48 * Call in response to the BRK_MEMU break instruction used to return to
  49 * the kernel from branch delay slot 'emulation' frames following a call
  50 * to mips_dsemul(). Restores the user thread PC to the value that was
  51 * passed as the cpc parameter to mips_dsemul().
  52 *
  53 * Return: True if an emulation frame was returned from, else false.
  54 */
  55extern bool do_dsemulret(struct pt_regs *xcp);
  56
  57/**
  58 * dsemul_thread_cleanup() - Cleanup thread 'emulation' frame
  59 * @tsk: The task structure associated with the thread
  60 *
  61 * If the thread @tsk has a branch delay slot 'emulation' frame
  62 * allocated to it then free that frame.
  63 *
  64 * Return: True if a frame was freed, else false.
  65 */
  66extern bool dsemul_thread_cleanup(struct task_struct *tsk);
  67
  68/**
  69 * dsemul_thread_rollback() - Rollback from an 'emulation' frame
  70 * @regs:       User thread register context.
  71 *
  72 * If the current thread, whose register context is represented by @regs,
  73 * is executing within a delay slot 'emulation' frame then exit that
  74 * frame. The PC will be rolled back to the branch if the instruction
  75 * that was being 'emulated' has not yet executed, or advanced to the
  76 * continuation PC if it has.
  77 *
  78 * Return: True if a frame was exited, else false.
  79 */
  80extern bool dsemul_thread_rollback(struct pt_regs *regs);
  81
  82/**
  83 * dsemul_mm_cleanup() - Cleanup per-mm delay slot 'emulation' state
  84 * @mm:         The struct mm_struct to cleanup state for.
  85 *
  86 * Cleanup state for the given @mm, ensuring that any memory allocated
  87 * for delay slot 'emulation' book-keeping is freed. This is to be called
  88 * before @mm is freed in order to avoid memory leaks.
  89 */
  90extern void dsemul_mm_cleanup(struct mm_struct *mm);
  91
  92#endif /* __MIPS_ASM_DSEMUL_H__ */
  93