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
20 extern "C" void __clear_cache(void *start, void *end);
21
22 namespace __xray {
23
24 // The machine codes for some instructions used in runtime patching.
25 enum 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
patchSled(const bool Enable,const uint32_t FuncId,const XRaySledEntry & Sled,void (* TracingHook)())33 inline 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 reinterpret_cast<std::atomic<uint32_t> *>(FirstAddress),
79 uint32_t(PatchOpcodes::PO_StpX0X30SP_m16e), std::memory_order_release);
80 } else {
81 std::atomic_store_explicit(
82 reinterpret_cast<std::atomic<uint32_t> *>(FirstAddress),
83 uint32_t(PatchOpcodes::PO_B32), std::memory_order_release);
84 }
85 __clear_cache(reinterpret_cast<char *>(FirstAddress),
86 reinterpret_cast<char *>(CurAddress));
87 return true;
88 }
89
patchFunctionEntry(const bool Enable,const uint32_t FuncId,const XRaySledEntry & Sled,void (* Trampoline)())90 bool patchFunctionEntry(const bool Enable, const uint32_t FuncId,
91 const XRaySledEntry &Sled,
92 void (*Trampoline)()) XRAY_NEVER_INSTRUMENT {
93 return patchSled(Enable, FuncId, Sled, Trampoline);
94 }
95
patchFunctionExit(const bool Enable,const uint32_t FuncId,const XRaySledEntry & Sled)96 bool patchFunctionExit(const bool Enable, const uint32_t FuncId,
97 const XRaySledEntry &Sled) XRAY_NEVER_INSTRUMENT {
98 return patchSled(Enable, FuncId, Sled, __xray_FunctionExit);
99 }
100
patchFunctionTailExit(const bool Enable,const uint32_t FuncId,const XRaySledEntry & Sled)101 bool patchFunctionTailExit(const bool Enable, const uint32_t FuncId,
102 const XRaySledEntry &Sled) XRAY_NEVER_INSTRUMENT {
103 return patchSled(Enable, FuncId, Sled, __xray_FunctionTailExit);
104 }
105
106 // AArch64AsmPrinter::LowerPATCHABLE_EVENT_CALL generates this code sequence:
107 //
108 // .Lxray_event_sled_N:
109 // b 1f
110 // save x0 and x1 (and also x2 for TYPED_EVENT_CALL)
111 // set up x0 and x1 (and also x2 for TYPED_EVENT_CALL)
112 // bl __xray_CustomEvent or __xray_TypedEvent
113 // restore x0 and x1 (and also x2 for TYPED_EVENT_CALL)
114 // 1f
115 //
116 // There are 6 instructions for EVENT_CALL and 9 for TYPED_EVENT_CALL.
117 //
118 // Enable: b .+24 => nop
119 // Disable: nop => b .+24
patchCustomEvent(const bool Enable,const uint32_t FuncId,const XRaySledEntry & Sled)120 bool patchCustomEvent(const bool Enable, const uint32_t FuncId,
121 const XRaySledEntry &Sled) XRAY_NEVER_INSTRUMENT {
122 uint32_t Inst = Enable ? 0xd503201f : 0x14000006;
123 std::atomic_store_explicit(
124 reinterpret_cast<std::atomic<uint32_t> *>(Sled.address()), Inst,
125 std::memory_order_release);
126 return false;
127 }
128
129 // Enable: b +36 => nop
130 // Disable: nop => b +36
patchTypedEvent(const bool Enable,const uint32_t FuncId,const XRaySledEntry & Sled)131 bool patchTypedEvent(const bool Enable, const uint32_t FuncId,
132 const XRaySledEntry &Sled) XRAY_NEVER_INSTRUMENT {
133 uint32_t Inst = Enable ? 0xd503201f : 0x14000009;
134 std::atomic_store_explicit(
135 reinterpret_cast<std::atomic<uint32_t> *>(Sled.address()), Inst,
136 std::memory_order_release);
137 return false;
138 }
139
140 // FIXME: Maybe implement this better?
probeRequiredCPUFeatures()141 bool probeRequiredCPUFeatures() XRAY_NEVER_INSTRUMENT { return true; }
142
143 } // namespace __xray
144