xref: /freebsd/contrib/llvm-project/compiler-rt/lib/xray/xray_AArch64.cpp (revision e32fecd0c2c3ee37c47ee100f169e7eb0282a873)
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_LdrW0_12 = 0x18000060,        // LDR W0, #12
28   PO_LdrX16_12 = 0x58000070,       // LDR X16, #12
29   PO_BlrX16 = 0xD63F0200,          // BLR X16
30   PO_LdpX0X30SP_16 = 0xA8C17BE0,   // LDP X0, X30, [SP], #16
31   PO_B32 = 0x14000008              // B #32
32 };
33 
34 inline static bool patchSled(const bool Enable, const uint32_t FuncId,
35                              const XRaySledEntry &Sled,
36                              void (*TracingHook)()) XRAY_NEVER_INSTRUMENT {
37   // When |Enable| == true,
38   // We replace the following compile-time stub (sled):
39   //
40   // xray_sled_n:
41   //   B #32
42   //   7 NOPs (24 bytes)
43   //
44   // With the following runtime patch:
45   //
46   // xray_sled_n:
47   //   STP X0, X30, [SP, #-16]! ; PUSH {r0, lr}
48   //   LDR W0, #12 ; W0 := function ID
49   //   LDR X16,#12 ; X16 := address of the trampoline
50   //   BLR X16
51   //   ;DATA: 32 bits of function ID
52   //   ;DATA: lower 32 bits of the address of the trampoline
53   //   ;DATA: higher 32 bits of the address of the trampoline
54   //   LDP X0, X30, [SP], #16 ; POP {r0, lr}
55   //
56   // Replacement of the first 4-byte instruction should be the last and atomic
57   // operation, so that the user code which reaches the sled concurrently
58   // either jumps over the whole sled, or executes the whole sled when the
59   // latter is ready.
60   //
61   // When |Enable|==false, we set back the first instruction in the sled to be
62   //   B #32
63 
64   uint32_t *FirstAddress = reinterpret_cast<uint32_t *>(Sled.address());
65   uint32_t *CurAddress = FirstAddress + 1;
66   if (Enable) {
67     *CurAddress = uint32_t(PatchOpcodes::PO_LdrW0_12);
68     CurAddress++;
69     *CurAddress = uint32_t(PatchOpcodes::PO_LdrX16_12);
70     CurAddress++;
71     *CurAddress = uint32_t(PatchOpcodes::PO_BlrX16);
72     CurAddress++;
73     *CurAddress = FuncId;
74     CurAddress++;
75     *reinterpret_cast<void (**)()>(CurAddress) = TracingHook;
76     CurAddress += 2;
77     *CurAddress = uint32_t(PatchOpcodes::PO_LdpX0X30SP_16);
78     CurAddress++;
79     std::atomic_store_explicit(
80         reinterpret_cast<std::atomic<uint32_t> *>(FirstAddress),
81         uint32_t(PatchOpcodes::PO_StpX0X30SP_m16e), std::memory_order_release);
82   } else {
83     std::atomic_store_explicit(
84         reinterpret_cast<std::atomic<uint32_t> *>(FirstAddress),
85         uint32_t(PatchOpcodes::PO_B32), std::memory_order_release);
86   }
87   __clear_cache(reinterpret_cast<char *>(FirstAddress),
88                 reinterpret_cast<char *>(CurAddress));
89   return true;
90 }
91 
92 bool patchFunctionEntry(const bool Enable, const uint32_t FuncId,
93                         const XRaySledEntry &Sled,
94                         void (*Trampoline)()) XRAY_NEVER_INSTRUMENT {
95   return patchSled(Enable, FuncId, Sled, Trampoline);
96 }
97 
98 bool patchFunctionExit(const bool Enable, const uint32_t FuncId,
99                        const XRaySledEntry &Sled) XRAY_NEVER_INSTRUMENT {
100   return patchSled(Enable, FuncId, Sled, __xray_FunctionExit);
101 }
102 
103 bool patchFunctionTailExit(const bool Enable, const uint32_t FuncId,
104                            const XRaySledEntry &Sled) XRAY_NEVER_INSTRUMENT {
105   return patchSled(Enable, FuncId, Sled, __xray_FunctionTailExit);
106 }
107 
108 bool patchCustomEvent(const bool Enable, const uint32_t FuncId,
109                       const XRaySledEntry &Sled)
110     XRAY_NEVER_INSTRUMENT { // FIXME: Implement in aarch64?
111   return false;
112 }
113 
114 bool patchTypedEvent(const bool Enable, const uint32_t FuncId,
115                      const XRaySledEntry &Sled) XRAY_NEVER_INSTRUMENT {
116   // FIXME: Implement in aarch64?
117   return false;
118 }
119 
120 // FIXME: Maybe implement this better?
121 bool probeRequiredCPUFeatures() XRAY_NEVER_INSTRUMENT { return true; }
122 
123 } // namespace __xray
124 
125 extern "C" void __xray_ArgLoggerEntry() XRAY_NEVER_INSTRUMENT {
126   // FIXME: this will have to be implemented in the trampoline assembly file
127 }
128