arch/mips/include/asm/dsemul.h

   1 /* SPDX-License-Identifier: GPL-2.0-or-later */
   2 /*
   3  * Copyright (C) 2016 Imagination Technologies
   4  * Author: Paul Burton <paul.burton@mips.com>
   5  */
   6
   7 #ifndef __MIPS_ASM_DSEMUL_H__
   8 #define __MIPS_ASM_DSEMUL_H__
   9
  10 #include <asm/break.h>
  11 #include <asm/inst.h>
  12
  13 /* Break instruction with special math emu break code set */
  14 #define BREAK_MATH(micromips)   (((micromips) ? 0x7 : 0xd) | (BRK_MEMU << 16))
  15
  16 /* When used as a frame index, indicates the lack of a frame */
  17 #define BD_EMUFRAME_NONE        ((int)BIT(31))
  18
  19 struct mm_struct;
  20 struct pt_regs;
  21 struct task_struct;
  22
  23 /**
  24  * mips_dsemul() - 'Emulate' an instruction from a branch delay slot
  25  * @regs:       User thread register context.
  26  * @ir:         The instruction to be 'emulated'.
  27  * @branch_pc:  The PC of the branch instruction.
  28  * @cont_pc:    The PC to continue at following 'emulation'.
  29  *
  30  * Emulate or execute an arbitrary MIPS instruction within the context of
  31  * the current user thread. This is used primarily to handle instructions
  32  * in the delay slots of emulated branch instructions, for example FP
  33  * branch instructions on systems without an FPU.
  34  *
  35  * Return: Zero on success, negative if ir is a NOP, signal number on failure.
  36  */
  37 extern int mips_dsemul(struct pt_regs *regs, mips_instruction ir,
  38                        unsigned long branch_pc, unsigned long cont_pc);
  39
  40 /**
  41  * do_dsemulret() - Return from a delay slot 'emulation' frame
  42  * @xcp:        User thread register context.
  43  *
  44  * Call in response to the BRK_MEMU break instruction used to return to
  45  * the kernel from branch delay slot 'emulation' frames following a call
  46  * to mips_dsemul(). Restores the user thread PC to the value that was
  47  * passed as the cpc parameter to mips_dsemul().
  48  *
  49  * Return: True if an emulation frame was returned from, else false.
  50  */
  51 #ifdef CONFIG_MIPS_FP_SUPPORT
  52 extern bool do_dsemulret(struct pt_regs *xcp);
  53 #else
  54 static inline bool do_dsemulret(struct pt_regs *xcp)
  55 {
  56         return false;
  57 }
  58 #endif
  59
  60 /**
  61  * dsemul_thread_cleanup() - Cleanup thread 'emulation' frame
  62  * @tsk: The task structure associated with the thread
  63  *
  64  * If the thread @tsk has a branch delay slot 'emulation' frame
  65  * allocated to it then free that frame.
  66  *
  67  * Return: True if a frame was freed, else false.
  68  */
  69 #ifdef CONFIG_MIPS_FP_SUPPORT
  70 extern bool dsemul_thread_cleanup(struct task_struct *tsk);
  71 #else
  72 static inline bool dsemul_thread_cleanup(struct task_struct *tsk)
  73 {
  74         return false;
  75 }
  76 #endif
  77 /**
  78  * dsemul_thread_rollback() - Rollback from an 'emulation' frame
  79  * @regs:       User thread register context.
  80  *
  81  * If the current thread, whose register context is represented by @regs,
  82  * is executing within a delay slot 'emulation' frame then exit that
  83  * frame. The PC will be rolled back to the branch if the instruction
  84  * that was being 'emulated' has not yet executed, or advanced to the
  85  * continuation PC if it has.
  86  *
  87  * Return: True if a frame was exited, else false.
  88  */
  89 #ifdef CONFIG_MIPS_FP_SUPPORT
  90 extern bool dsemul_thread_rollback(struct pt_regs *regs);
  91 #else
  92 static inline bool dsemul_thread_rollback(struct pt_regs *regs)
  93 {
  94         return false;
  95 }
  96 #endif
  97
  98 /**
  99  * dsemul_mm_cleanup() - Cleanup per-mm delay slot 'emulation' state
 100  * @mm:         The struct mm_struct to cleanup state for.
 101  *
 102  * Cleanup state for the given @mm, ensuring that any memory allocated
 103  * for delay slot 'emulation' book-keeping is freed. This is to be called
 104  * before @mm is freed in order to avoid memory leaks.
 105  */
 106 #ifdef CONFIG_MIPS_FP_SUPPORT
 107 extern void dsemul_mm_cleanup(struct mm_struct *mm);
 108 #else
 109 static inline void dsemul_mm_cleanup(struct mm_struct *mm)
 110 {
 111         /* no-op */
 112 }
 113 #endif
 114
 115 #endif /* __MIPS_ASM_DSEMUL_H__ */