1//===-- ubsan_value.cpp ---------------------------------------------------===//
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// Representation of a runtime value, as marshaled from the generated code to
10// the ubsan runtime.
11//
12//===----------------------------------------------------------------------===//
13
14#include "ubsan_platform.h"
15#if CAN_SANITIZE_UB
16#include "ubsan_value.h"
17#include "sanitizer_common/sanitizer_common.h"
18#include "sanitizer_common/sanitizer_libc.h"
19#include "sanitizer_common/sanitizer_mutex.h"
20
21#if SANITIZER_APPLE
22#include <dlfcn.h>
23#endif
24
25using namespace __ubsan;
26
27typedef const char *(*ObjCGetClassNameTy)(void *);
28
29const char *__ubsan::getObjCClassName(ValueHandle Pointer) {
30#if SANITIZER_APPLE
31 // We need to query the ObjC runtime for some information, but do not want
32 // to introduce a static dependency from the ubsan runtime onto ObjC. Try to
33 // grab a handle to the ObjC runtime used by the process.
34 static bool AttemptedDlopen = false;
35 static void *ObjCHandle = nullptr;
36 static void *ObjCObjectGetClassName = nullptr;
37
38 // Prevent threads from racing to dlopen().
39 static __sanitizer::StaticSpinMutex Lock;
40 {
41 __sanitizer::SpinMutexLock Guard(&Lock);
42
43 if (!AttemptedDlopen) {
44 ObjCHandle = dlopen(
45 "/usr/lib/libobjc.A.dylib",
46 RTLD_LAZY // Only bind symbols when used.
47 | RTLD_LOCAL // Only make symbols available via the handle.
48 | RTLD_NOLOAD // Do not load the dylib, just grab a handle if the
49 // image is already loaded.
50 | RTLD_FIRST // Only search the image pointed-to by the handle.
51 );
52 AttemptedDlopen = true;
53 if (!ObjCHandle)
54 return nullptr;
55 ObjCObjectGetClassName = dlsym(ObjCHandle, "object_getClassName");
56 }
57 }
58
59 if (!ObjCObjectGetClassName)
60 return nullptr;
61
62 return ObjCGetClassNameTy(ObjCObjectGetClassName)((void *)Pointer);
63#else
64 return nullptr;
65#endif
66}
67
68SIntMax Value::getSIntValue() const {
69 CHECK(getType().isSignedIntegerTy());
70 if (isInlineInt()) {
71 // Val was zero-extended to ValueHandle. Sign-extend from original width
72 // to SIntMax.
73 const unsigned ExtraBits =
74 sizeof(SIntMax) * 8 - getType().getIntegerBitWidth();
75 return SIntMax(UIntMax(Val) << ExtraBits) >> ExtraBits;
76 }
77 if (getType().getIntegerBitWidth() == 64)
78 return *reinterpret_cast<s64*>(Val);
79#if HAVE_INT128_T
80 if (getType().getIntegerBitWidth() == 128)
81 return *reinterpret_cast<s128*>(Val);
82#else
83 if (getType().getIntegerBitWidth() == 128)
84 UNREACHABLE("libclang_rt.ubsan was built without __int128 support");
85#endif
86 UNREACHABLE("unexpected bit width");
87}
88
89UIntMax Value::getUIntValue() const {
90 CHECK(getType().isUnsignedIntegerTy());
91 if (isInlineInt())
92 return Val;
93 if (getType().getIntegerBitWidth() == 64)
94 return *reinterpret_cast<u64*>(Val);
95#if HAVE_INT128_T
96 if (getType().getIntegerBitWidth() == 128)
97 return *reinterpret_cast<u128*>(Val);
98#else
99 if (getType().getIntegerBitWidth() == 128)
100 UNREACHABLE("libclang_rt.ubsan was built without __int128 support");
101#endif
102 UNREACHABLE("unexpected bit width");
103}
104
105UIntMax Value::getPositiveIntValue() const {
106 if (getType().isUnsignedIntegerTy())
107 return getUIntValue();
108 SIntMax Val = getSIntValue();
109 CHECK(Val >= 0);
110 return Val;
111}
112
113/// Get the floating-point value of this object, extended to a long double.
114/// These are always passed by address (our calling convention doesn't allow
115/// them to be passed in floating-point registers, so this has little cost).
116FloatMax Value::getFloatValue() const {
117 CHECK(getType().isFloatTy());
118 if (isInlineFloat()) {
119 switch (getType().getFloatBitWidth()) {
120#if 0
121 // FIXME: OpenCL / NEON 'half' type. LLVM can't lower the conversion
122 // from '__fp16' to 'long double'.
123 case 16: {
124 __fp16 Value;
125 internal_memcpy(&Value, &Val, 4);
126 return Value;
127 }
128#endif
129 case 32: {
130 float Value;
131#if defined(__BYTE_ORDER__) && __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
132 // For big endian the float value is in the last 4 bytes.
133 // On some targets we may only have 4 bytes so we count backwards from
134 // the end of Val to account for both the 32-bit and 64-bit cases.
135 internal_memcpy(&Value, ((const char*)(&Val + 1)) - 4, 4);
136#else
137 internal_memcpy(dest: &Value, src: &Val, n: 4);
138#endif
139 return Value;
140 }
141 case 64: {
142 double Value;
143 internal_memcpy(dest: &Value, src: &Val, n: 8);
144 return Value;
145 }
146 }
147 } else {
148 switch (getType().getFloatBitWidth()) {
149 case 64: return *reinterpret_cast<double*>(Val);
150 case 80: return *reinterpret_cast<long double*>(Val);
151 case 96: return *reinterpret_cast<long double*>(Val);
152 case 128: return *reinterpret_cast<long double*>(Val);
153 }
154 }
155 UNREACHABLE("unexpected floating point bit width");
156}
157
158#endif // CAN_SANITIZE_UB
159