1 /* 2 * Copyright (C) 2016 Imagination Technologies 3 * Author: Paul Burton <paul.burton@mips.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