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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__ */
93