include/asm/dsemul.h

0001 /* SPDX-License-Identifier: GPL-2.0-or-later */
0002 /*
0003  * Copyright (C) 2016 Imagination Technologies
0004  * Author: Paul Burton <paul.burton@mips.com>
0005  */
0006
0007 #ifndef __MIPS_ASM_DSEMUL_H__
0008 #define __MIPS_ASM_DSEMUL_H__
0009
0010 #include <asm/break.h>
0011 #include <asm/inst.h>
0012
0013 /* Break instruction with special math emu break code set */
0014 #define BREAK_MATH(micromips)   (((micromips) ? 0x7 : 0xd) | (BRK_MEMU << 16))
0015
0016 /* When used as a frame index, indicates the lack of a frame */
0017 #define BD_EMUFRAME_NONE    ((int)BIT(31))
0018
0019 struct mm_struct;
0020 struct pt_regs;
0021 struct task_struct;
0022
0023 /**
0024  * mips_dsemul() - 'Emulate' an instruction from a branch delay slot
0025  * @regs:   User thread register context.
0026  * @ir:     The instruction to be 'emulated'.
0027  * @branch_pc:  The PC of the branch instruction.
0028  * @cont_pc:    The PC to continue at following 'emulation'.
0029  *
0030  * Emulate or execute an arbitrary MIPS instruction within the context of
0031  * the current user thread. This is used primarily to handle instructions
0032  * in the delay slots of emulated branch instructions, for example FP
0033  * branch instructions on systems without an FPU.
0034  *
0035  * Return: Zero on success, negative if ir is a NOP, signal number on failure.
0036  */
0037 extern int mips_dsemul(struct pt_regs *regs, mips_instruction ir,
0038                unsigned long branch_pc, unsigned long cont_pc);
0039
0040 /**
0041  * do_dsemulret() - Return from a delay slot 'emulation' frame
0042  * @xcp:    User thread register context.
0043  *
0044  * Call in response to the BRK_MEMU break instruction used to return to
0045  * the kernel from branch delay slot 'emulation' frames following a call
0046  * to mips_dsemul(). Restores the user thread PC to the value that was
0047  * passed as the cpc parameter to mips_dsemul().
0048  *
0049  * Return: True if an emulation frame was returned from, else false.
0050  */
0051 #ifdef CONFIG_MIPS_FP_SUPPORT
0052 extern bool do_dsemulret(struct pt_regs *xcp);
0053 #else
0054 static inline bool do_dsemulret(struct pt_regs *xcp)
0055 {
0056     return false;
0057 }
0058 #endif
0059
0060 /**
0061  * dsemul_thread_cleanup() - Cleanup thread 'emulation' frame
0062  * @tsk: The task structure associated with the thread
0063  *
0064  * If the thread @tsk has a branch delay slot 'emulation' frame
0065  * allocated to it then free that frame.
0066  *
0067  * Return: True if a frame was freed, else false.
0068  */
0069 #ifdef CONFIG_MIPS_FP_SUPPORT
0070 extern bool dsemul_thread_cleanup(struct task_struct *tsk);
0071 #else
0072 static inline bool dsemul_thread_cleanup(struct task_struct *tsk)
0073 {
0074     return false;
0075 }
0076 #endif
0077 /**
0078  * dsemul_thread_rollback() - Rollback from an 'emulation' frame
0079  * @regs:   User thread register context.
0080  *
0081  * If the current thread, whose register context is represented by @regs,
0082  * is executing within a delay slot 'emulation' frame then exit that
0083  * frame. The PC will be rolled back to the branch if the instruction
0084  * that was being 'emulated' has not yet executed, or advanced to the
0085  * continuation PC if it has.
0086  *
0087  * Return: True if a frame was exited, else false.
0088  */
0089 #ifdef CONFIG_MIPS_FP_SUPPORT
0090 extern bool dsemul_thread_rollback(struct pt_regs *regs);
0091 #else
0092 static inline bool dsemul_thread_rollback(struct pt_regs *regs)
0093 {
0094     return false;
0095 }
0096 #endif
0097
0098 /**
0099  * dsemul_mm_cleanup() - Cleanup per-mm delay slot 'emulation' state
0100  * @mm:     The struct mm_struct to cleanup state for.
0101  *
0102  * Cleanup state for the given @mm, ensuring that any memory allocated
0103  * for delay slot 'emulation' book-keeping is freed. This is to be called
0104  * before @mm is freed in order to avoid memory leaks.
0105  */
0106 #ifdef CONFIG_MIPS_FP_SUPPORT
0107 extern void dsemul_mm_cleanup(struct mm_struct *mm);
0108 #else
0109 static inline void dsemul_mm_cleanup(struct mm_struct *mm)
0110 {
0111     /* no-op */
0112 }
0113 #endif
0114
0115 #endif /* __MIPS_ASM_DSEMUL_H__ */