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
do_dsemulret(struct pt_regs * xcp)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
dsemul_thread_cleanup(struct task_struct * tsk)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
dsemul_thread_rollback(struct pt_regs * regs)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
dsemul_mm_cleanup(struct mm_struct * mm)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__ */
116