1//===-- xray_AArch64.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 AArch64-specific routines (64-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#include <cassert>
19
20extern "C" void __clear_cache(void *start, void *end);
21
22namespace __xray {
23
24// The machine codes for some instructions used in runtime patching.
25enum class PatchOpcodes : uint32_t {
26 PO_StpX0X30SP_m16e = 0xA9BF7BE0, // STP X0, X30, [SP, #-16]!
27 PO_LdrX16_12 = 0x58000070, // LDR X16, #12
28 PO_BlrX16 = 0xD63F0200, // BLR X16
29 PO_LdpX0X30SP_16 = 0xA8C17BE0, // LDP X0, X30, [SP], #16
30 PO_B32 = 0x14000008 // B #32
31};
32
33inline static bool patchSled(const bool Enable, const uint32_t FuncId,
34 const XRaySledEntry &Sled,
35 void (*TracingHook)()) XRAY_NEVER_INSTRUMENT {
36 // When |Enable| == true,
37 // We replace the following compile-time stub (sled):
38 //
39 // xray_sled_n:
40 // B #32
41 // 7 NOPs (24 bytes)
42 //
43 // With the following runtime patch:
44 //
45 // xray_sled_n:
46 // STP X0, X30, [SP, #-16]! ; PUSH {r0, lr}
47 // LDR W17, #12 ; W17 := function ID
48 // LDR X16,#12 ; X16 := address of the trampoline
49 // BLR X16
50 // ;DATA: 32 bits of function ID
51 // ;DATA: lower 32 bits of the address of the trampoline
52 // ;DATA: higher 32 bits of the address of the trampoline
53 // LDP X0, X30, [SP], #16 ; POP {r0, lr}
54 //
55 // Replacement of the first 4-byte instruction should be the last and atomic
56 // operation, so that the user code which reaches the sled concurrently
57 // either jumps over the whole sled, or executes the whole sled when the
58 // latter is ready.
59 //
60 // When |Enable|==false, we set back the first instruction in the sled to be
61 // B #32
62
63 uint32_t *FirstAddress = reinterpret_cast<uint32_t *>(Sled.address());
64 uint32_t *CurAddress = FirstAddress + 1;
65 if (Enable) {
66 *CurAddress++ = 0x18000071; // ldr w17, #12
67 *CurAddress = uint32_t(PatchOpcodes::PO_LdrX16_12);
68 CurAddress++;
69 *CurAddress = uint32_t(PatchOpcodes::PO_BlrX16);
70 CurAddress++;
71 *CurAddress = FuncId;
72 CurAddress++;
73 *reinterpret_cast<void (**)()>(CurAddress) = TracingHook;
74 CurAddress += 2;
75 *CurAddress = uint32_t(PatchOpcodes::PO_LdpX0X30SP_16);
76 CurAddress++;
77 std::atomic_store_explicit(
78 a: reinterpret_cast<std::atomic<uint32_t> *>(FirstAddress),
79 i: uint32_t(PatchOpcodes::PO_StpX0X30SP_m16e), m: std::memory_order_release);
80 } else {
81 std::atomic_store_explicit(
82 a: reinterpret_cast<std::atomic<uint32_t> *>(FirstAddress),
83 i: uint32_t(PatchOpcodes::PO_B32), m: std::memory_order_release);
84 }
85 __clear_cache(start: reinterpret_cast<char *>(FirstAddress),
86 end: reinterpret_cast<char *>(CurAddress));
87 return true;
88}
89
90bool patchFunctionEntry(const bool Enable, const uint32_t FuncId,
91 const XRaySledEntry &Sled,
92 const XRayTrampolines &Trampolines,
93 bool LogArgs) XRAY_NEVER_INSTRUMENT {
94 auto Trampoline =
95 LogArgs ? Trampolines.LogArgsTrampoline : Trampolines.EntryTrampoline;
96 return patchSled(Enable, FuncId, Sled, TracingHook: Trampoline);
97}
98
99bool patchFunctionExit(
100 const bool Enable, const uint32_t FuncId, const XRaySledEntry &Sled,
101 const XRayTrampolines &Trampolines) XRAY_NEVER_INSTRUMENT {
102 return patchSled(Enable, FuncId, Sled, TracingHook: Trampolines.ExitTrampoline);
103}
104
105bool patchFunctionTailExit(
106 const bool Enable, const uint32_t FuncId, const XRaySledEntry &Sled,
107 const XRayTrampolines &Trampolines) XRAY_NEVER_INSTRUMENT {
108 return patchSled(Enable, FuncId, Sled, TracingHook: Trampolines.TailExitTrampoline);
109}
110
111// AArch64AsmPrinter::LowerPATCHABLE_EVENT_CALL generates this code sequence:
112//
113// .Lxray_event_sled_N:
114// b 1f
115// save x0 and x1 (and also x2 for TYPED_EVENT_CALL)
116// set up x0 and x1 (and also x2 for TYPED_EVENT_CALL)
117// bl __xray_CustomEvent or __xray_TypedEvent
118// restore x0 and x1 (and also x2 for TYPED_EVENT_CALL)
119// 1f
120//
121// There are 6 instructions for EVENT_CALL and 9 for TYPED_EVENT_CALL.
122//
123// Enable: b .+24 => nop
124// Disable: nop => b .+24
125bool patchCustomEvent(const bool Enable, const uint32_t FuncId,
126 const XRaySledEntry &Sled) XRAY_NEVER_INSTRUMENT {
127 uint32_t Inst = Enable ? 0xd503201f : 0x14000006;
128 std::atomic_store_explicit(
129 a: reinterpret_cast<std::atomic<uint32_t> *>(Sled.address()), i: Inst,
130 m: std::memory_order_release);
131 return false;
132}
133
134// Enable: b +36 => nop
135// Disable: nop => b +36
136bool patchTypedEvent(const bool Enable, const uint32_t FuncId,
137 const XRaySledEntry &Sled) XRAY_NEVER_INSTRUMENT {
138 uint32_t Inst = Enable ? 0xd503201f : 0x14000009;
139 std::atomic_store_explicit(
140 a: reinterpret_cast<std::atomic<uint32_t> *>(Sled.address()), i: Inst,
141 m: std::memory_order_release);
142 return false;
143}
144
145// FIXME: Maybe implement this better?
146bool probeRequiredCPUFeatures() XRAY_NEVER_INSTRUMENT { return true; }
147
148} // namespace __xray
149

source code of compiler-rt/lib/xray/xray_AArch64.cpp