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
19namespace __xray {
20
21// The machine codes for some instructions used in runtime patching.
22enum 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
33enum RegNum : uint32_t {
34 RN_T0 = 0x8,
35 RN_T9 = 0x19,
36 RN_RA = 0x1F,
37 RN_SP = 0x1D,
38};
39
40inline 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
46inline static uint32_t
47encodeSpecialInstruction(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
52inline 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(Opcode: PatchOpcodes::PO_SW, Rs: RegNum::RN_SP,
105 Rt: RegNum::RN_RA, Imm: 0x4);
106 Address[3] = encodeInstruction(Opcode: PatchOpcodes::PO_SW, Rs: RegNum::RN_SP,
107 Rt: RegNum::RN_T9, Imm: 0x0);
108 Address[4] = encodeInstruction(Opcode: PatchOpcodes::PO_LUI, Rs: 0x0, Rt: RegNum::RN_T9,
109 Imm: HiTracingHookAddr);
110 Address[5] = encodeInstruction(Opcode: PatchOpcodes::PO_ORI, Rs: RegNum::RN_T9,
111 Rt: RegNum::RN_T9, Imm: LoTracingHookAddr);
112 Address[6] = encodeInstruction(Opcode: PatchOpcodes::PO_LUI, Rs: 0x0, Rt: RegNum::RN_T0,
113 Imm: HiFunctionID);
114 Address[7] = encodeSpecialInstruction(Opcode: PatchOpcodes::PO_JALR, Rs: RegNum::RN_T9,
115 Rt: 0x0, Rd: RegNum::RN_RA, Imm: 0X0);
116 Address[8] = encodeInstruction(Opcode: PatchOpcodes::PO_ORI, Rs: RegNum::RN_T0,
117 Rt: RegNum::RN_T0, Imm: LoFunctionID);
118 Address[9] = encodeInstruction(Opcode: PatchOpcodes::PO_LW, Rs: RegNum::RN_SP,
119 Rt: RegNum::RN_T9, Imm: 0x0);
120 Address[10] = encodeInstruction(Opcode: PatchOpcodes::PO_LW, Rs: RegNum::RN_SP,
121 Rt: RegNum::RN_RA, Imm: 0x4);
122 Address[11] = encodeInstruction(Opcode: PatchOpcodes::PO_ADDIU, Rs: RegNum::RN_SP,
123 Rt: RegNum::RN_SP, Imm: 0x8);
124 uint32_t CreateStackSpaceInstr = encodeInstruction(
125 Opcode: PatchOpcodes::PO_ADDIU, Rs: RegNum::RN_SP, Rt: RegNum::RN_SP, Imm: 0xFFF8);
126 std::atomic_store_explicit(
127 a: reinterpret_cast<std::atomic<uint32_t> *>(Address),
128 i: uint32_t(CreateStackSpaceInstr), m: std::memory_order_release);
129 } else {
130 std::atomic_store_explicit(
131 a: reinterpret_cast<std::atomic<uint32_t> *>(Address),
132 i: uint32_t(PatchOpcodes::PO_B44), m: std::memory_order_release);
133 }
134 return true;
135}
136
137bool patchFunctionEntry(const bool Enable, const uint32_t FuncId,
138 const XRaySledEntry &Sled,
139 void (*Trampoline)()) XRAY_NEVER_INSTRUMENT {
140 return patchSled(Enable, FuncId, Sled, TracingHook: Trampoline);
141}
142
143bool patchFunctionExit(const bool Enable, const uint32_t FuncId,
144 const XRaySledEntry &Sled) XRAY_NEVER_INSTRUMENT {
145 return patchSled(Enable, FuncId, Sled, TracingHook: __xray_FunctionExit);
146}
147
148bool 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, TracingHook: __xray_FunctionExit);
153}
154
155bool 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
161bool 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
169extern "C" void __xray_ArgLoggerEntry() XRAY_NEVER_INSTRUMENT {
170 // FIXME: this will have to be implemented in the trampoline assembly file
171}
172

source code of compiler-rt/lib/xray/xray_mips.cpp