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__ */