1 //===-- xray_mips.cpp -------------------------------------------*- C++ -*-===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 // 9 // This file is a part of XRay, a dynamic runtime instrumentation system. 10 // 11 // Implementation of MIPS-specific routines (32-bit). 12 // 13 //===----------------------------------------------------------------------===// 14 #include "sanitizer_common/sanitizer_common.h" 15 #include "xray_defs.h" 16 #include "xray_interface_internal.h" 17 #include <atomic> 18 19 namespace __xray { 20 21 // The machine codes for some instructions used in runtime patching. 22 enum PatchOpcodes : uint32_t { 23 PO_ADDIU = 0x24000000, // addiu rt, rs, imm 24 PO_SW = 0xAC000000, // sw rt, offset(sp) 25 PO_LUI = 0x3C000000, // lui rs, %hi(address) 26 PO_ORI = 0x34000000, // ori rt, rs, %lo(address) 27 PO_JALR = 0x0000F809, // jalr rs 28 PO_LW = 0x8C000000, // lw rt, offset(address) 29 PO_B44 = 0x1000000b, // b #44 30 PO_NOP = 0x0, // nop 31 }; 32 33 enum RegNum : uint32_t { 34 RN_T0 = 0x8, 35 RN_T9 = 0x19, 36 RN_RA = 0x1F, 37 RN_SP = 0x1D, 38 }; 39 40 inline static uint32_t encodeInstruction(uint32_t Opcode, uint32_t Rs, 41 uint32_t Rt, 42 uint32_t Imm) XRAY_NEVER_INSTRUMENT { 43 return (Opcode | Rs << 21 | Rt << 16 | Imm); 44 } 45 46 inline static uint32_t 47 encodeSpecialInstruction(uint32_t Opcode, uint32_t Rs, uint32_t Rt, uint32_t Rd, 48 uint32_t Imm) XRAY_NEVER_INSTRUMENT { 49 return (Rs << 21 | Rt << 16 | Rd << 11 | Imm << 6 | Opcode); 50 } 51 52 inline static bool patchSled(const bool Enable, const uint32_t FuncId, 53 const XRaySledEntry &Sled, 54 void (*TracingHook)()) XRAY_NEVER_INSTRUMENT { 55 // When |Enable| == true, 56 // We replace the following compile-time stub (sled): 57 // 58 // xray_sled_n: 59 // B .tmpN 60 // 11 NOPs (44 bytes) 61 // .tmpN 62 // ADDIU T9, T9, 44 63 // 64 // With the following runtime patch: 65 // 66 // xray_sled_n (32-bit): 67 // addiu sp, sp, -8 ;create stack frame 68 // nop 69 // sw ra, 4(sp) ;save return address 70 // sw t9, 0(sp) ;save register t9 71 // lui t9, %hi(__xray_FunctionEntry/Exit) 72 // ori t9, t9, %lo(__xray_FunctionEntry/Exit) 73 // lui t0, %hi(function_id) 74 // jalr t9 ;call Tracing hook 75 // ori t0, t0, %lo(function_id) ;pass function id (delay slot) 76 // lw t9, 0(sp) ;restore register t9 77 // lw ra, 4(sp) ;restore return address 78 // addiu sp, sp, 8 ;delete stack frame 79 // 80 // We add 44 bytes to t9 because we want to adjust the function pointer to 81 // the actual start of function i.e. the address just after the noop sled. 82 // We do this because gp displacement relocation is emitted at the start of 83 // of the function i.e after the nop sled and to correctly calculate the 84 // global offset table address, t9 must hold the address of the instruction 85 // containing the gp displacement relocation. 86 // FIXME: Is this correct for the static relocation model? 87 // 88 // Replacement of the first 4-byte instruction should be the last and atomic 89 // operation, so that the user code which reaches the sled concurrently 90 // either jumps over the whole sled, or executes the whole sled when the 91 // latter is ready. 92 // 93 // When |Enable|==false, we set back the first instruction in the sled to be 94 // B #44 95 96 uint32_t *Address = reinterpret_cast<uint32_t *>(Sled.address()); 97 if (Enable) { 98 uint32_t LoTracingHookAddr = 99 reinterpret_cast<int32_t>(TracingHook) & 0xffff; 100 uint32_t HiTracingHookAddr = 101 (reinterpret_cast<int32_t>(TracingHook) >> 16) & 0xffff; 102 uint32_t LoFunctionID = FuncId & 0xffff; 103 uint32_t HiFunctionID = (FuncId >> 16) & 0xffff; 104 Address[2] = encodeInstruction(PatchOpcodes::PO_SW, RegNum::RN_SP, 105 RegNum::RN_RA, 0x4); 106 Address[3] = encodeInstruction(PatchOpcodes::PO_SW, RegNum::RN_SP, 107 RegNum::RN_T9, 0x0); 108 Address[4] = encodeInstruction(PatchOpcodes::PO_LUI, 0x0, RegNum::RN_T9, 109 HiTracingHookAddr); 110 Address[5] = encodeInstruction(PatchOpcodes::PO_ORI, RegNum::RN_T9, 111 RegNum::RN_T9, LoTracingHookAddr); 112 Address[6] = encodeInstruction(PatchOpcodes::PO_LUI, 0x0, RegNum::RN_T0, 113 HiFunctionID); 114 Address[7] = encodeSpecialInstruction(PatchOpcodes::PO_JALR, RegNum::RN_T9, 115 0x0, RegNum::RN_RA, 0X0); 116 Address[8] = encodeInstruction(PatchOpcodes::PO_ORI, RegNum::RN_T0, 117 RegNum::RN_T0, LoFunctionID); 118 Address[9] = encodeInstruction(PatchOpcodes::PO_LW, RegNum::RN_SP, 119 RegNum::RN_T9, 0x0); 120 Address[10] = encodeInstruction(PatchOpcodes::PO_LW, RegNum::RN_SP, 121 RegNum::RN_RA, 0x4); 122 Address[11] = encodeInstruction(PatchOpcodes::PO_ADDIU, RegNum::RN_SP, 123 RegNum::RN_SP, 0x8); 124 uint32_t CreateStackSpaceInstr = encodeInstruction( 125 PatchOpcodes::PO_ADDIU, RegNum::RN_SP, RegNum::RN_SP, 0xFFF8); 126 std::atomic_store_explicit( 127 reinterpret_cast<std::atomic<uint32_t> *>(Address), 128 uint32_t(CreateStackSpaceInstr), std::memory_order_release); 129 } else { 130 std::atomic_store_explicit( 131 reinterpret_cast<std::atomic<uint32_t> *>(Address), 132 uint32_t(PatchOpcodes::PO_B44), std::memory_order_release); 133 } 134 return true; 135 } 136 137 bool patchFunctionEntry(const bool Enable, const uint32_t FuncId, 138 const XRaySledEntry &Sled, 139 void (*Trampoline)()) XRAY_NEVER_INSTRUMENT { 140 return patchSled(Enable, FuncId, Sled, Trampoline); 141 } 142 143 bool patchFunctionExit(const bool Enable, const uint32_t FuncId, 144 const XRaySledEntry &Sled) XRAY_NEVER_INSTRUMENT { 145 return patchSled(Enable, FuncId, Sled, __xray_FunctionExit); 146 } 147 148 bool patchFunctionTailExit(const bool Enable, const uint32_t FuncId, 149 const XRaySledEntry &Sled) XRAY_NEVER_INSTRUMENT { 150 // FIXME: In the future we'd need to distinguish between non-tail exits and 151 // tail exits for better information preservation. 152 return patchSled(Enable, FuncId, Sled, __xray_FunctionExit); 153 } 154 155 bool patchCustomEvent(const bool Enable, const uint32_t FuncId, 156 const XRaySledEntry &Sled) XRAY_NEVER_INSTRUMENT { 157 // FIXME: Implement in mips? 158 return false; 159 } 160 161 bool patchTypedEvent(const bool Enable, const uint32_t FuncId, 162 const XRaySledEntry &Sled) XRAY_NEVER_INSTRUMENT { 163 // FIXME: Implement in mips? 164 return false; 165 } 166 167 } // namespace __xray 168 169 extern "C" void __xray_ArgLoggerEntry() XRAY_NEVER_INSTRUMENT { 170 // FIXME: this will have to be implemented in the trampoline assembly file 171 } 172