arch/mips/include/asm/dsemul.h

   1 /*
   2  * Copyright (C) 2016 Imagination Technologies
   3  * Author: Paul Burton <paul.burton@imgtec.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
  23 struct mm_struct;
  24 struct pt_regs;
  25 struct 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  */
  41 extern 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  */
  55 extern 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  */
  66 extern 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  */
  80 extern 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  */
  90 extern void dsemul_mm_cleanup(struct mm_struct *mm);
  91
  92 #endif /* __MIPS_ASM_DSEMUL_H__ */