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
19struct mm_struct;
20struct pt_regs;
21struct 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 */
37extern 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
52extern bool do_dsemulret(struct pt_regs *xcp);
53#else
54static 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
70extern bool dsemul_thread_cleanup(struct task_struct *tsk);
71#else
72static 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
90extern bool dsemul_thread_rollback(struct pt_regs *regs);
91#else
92static 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
107extern void dsemul_mm_cleanup(struct mm_struct *mm);
108#else
109static inline void dsemul_mm_cleanup(struct mm_struct *mm)
110{
111	/* no-op */
112}
113#endif
114
115#endif /* __MIPS_ASM_DSEMUL_H__ */
116