1 // Copyright 2019 The Chromium Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
5 #include "base/immediate_crash.h"
9 #include "base/base_paths.h"
10 #include "base/clang_profiling_buildflags.h"
11 #include "base/compiler_specific.h"
12 #include "base/containers/span.h"
13 #include "base/files/file_path.h"
14 #include "base/path_service.h"
15 #include "base/ranges/algorithm.h"
16 #include "base/scoped_native_library.h"
17 #include "base/strings/string_number_conversions.h"
18 #include "build/build_config.h"
19 #include "build/buildflag.h"
20 #include "testing/gtest/include/gtest/gtest.h"
21 #include "third_party/abseil-cpp/absl/types/optional.h"
27 // If IMMEDIATE_CRASH() is not treated as noreturn by the compiler, the compiler
28 // will complain that not all paths through this function return a value.
29 int ALLOW_UNUSED_TYPE TestImmediateCrashTreatedAsNoReturn() {
33 #if defined(ARCH_CPU_X86_FAMILY)
34 // This is tricksy and false, since x86 instructions are not all one byte long,
35 // but there is no better alternative short of implementing an x86 instruction
37 using Instruction = uint8_t;
39 // https://software.intel.com/en-us/download/intel-64-and-ia-32-architectures-sdm-combined-volumes-1-2a-2b-2c-2d-3a-3b-3c-3d-and-4
40 // Look for RET opcode (0xc3). Note that 0xC3 is a substring of several
41 // other opcodes (VMRESUME, MOVNTI), and can also be encoded as part of an
42 // argument to another opcode. None of these other cases are expected to be
43 // present, so a simple byte scan should be Good Enoughâ„¢.
44 constexpr Instruction kRet = 0xc3;
46 constexpr Instruction kRequiredBody[] = {0xcc, 0x0f, 0x0b};
47 constexpr Instruction kOptionalFooter[] = {};
49 #elif defined(ARCH_CPU_ARMEL)
50 using Instruction = uint16_t;
52 // T32 opcode reference: https://developer.arm.com/docs/ddi0487/latest
53 // Actually BX LR, canonical encoding:
54 constexpr Instruction kRet = 0x4770;
56 constexpr Instruction kRequiredBody[] = {0xbe00, 0xde00};
57 constexpr Instruction kOptionalFooter[] = {};
59 #elif defined(ARCH_CPU_ARM64)
60 using Instruction = uint32_t;
62 // A64 opcode reference: https://developer.arm.com/docs/ddi0487/latest
63 // Use an enum here rather than separate constexpr vars because otherwise some
64 // of the vars will end up unused on each platform, upsetting
65 // -Wunused-const-variable.
67 // There are multiple valid encodings of return (which is really a special
68 // form of branch). This is the one clang seems to use:
72 kBrkF000 = 0xd43e0000,
78 constexpr Instruction kRequiredBody[] = {kBrkF000, kBrk1};
79 constexpr Instruction kOptionalFooter[] = {};
83 constexpr Instruction kRequiredBody[] = {kBrk0, kHlt0};
84 // Some clangs emit a BRK #1 for __builtin_unreachable(), but some do not, so
85 // it is allowed but not required to occur.
86 constexpr Instruction kOptionalFooter[] = {kBrk1};
90 constexpr Instruction kRequiredBody[] = {kBrk0, kHlt0};
91 constexpr Instruction kOptionalFooter[] = {};
97 // This function loads a shared library that defines two functions,
98 // TestFunction1 and TestFunction2. It then returns the bytes of the body of
99 // whichever of those functions happens to come first in the library.
100 void GetTestFunctionInstructions(std::vector<Instruction>* body) {
101 FilePath helper_library_path;
102 #if !defined(OS_ANDROID) && !defined(OS_FUCHSIA)
103 // On Android M, DIR_EXE == /system/bin when running base_unittests.
104 // On Fuchsia, NativeLibrary understands the native convention that libraries
105 // are not colocated with the binary.
106 ASSERT_TRUE(PathService::Get(DIR_EXE, &helper_library_path));
108 helper_library_path = helper_library_path.AppendASCII(
109 GetNativeLibraryName("immediate_crash_test_helper"));
110 #if defined(OS_ANDROID) && defined(COMPONENT_BUILD)
111 helper_library_path = helper_library_path.ReplaceExtension(".cr.so");
113 ScopedNativeLibrary helper_library(helper_library_path);
114 ASSERT_TRUE(helper_library.is_valid())
115 << "shared library load failed: "
116 << helper_library.GetError()->ToString();
118 void* a = helper_library.GetFunctionPointer("TestFunction1");
120 void* b = helper_library.GetFunctionPointer("TestFunction2");
123 #if defined(ARCH_CPU_ARMEL)
124 // Routines loaded from a shared library will have the LSB in the pointer set
125 // if encoded as T32 instructions. The rest of this test assumes T32.
126 ASSERT_TRUE(reinterpret_cast<uintptr_t>(a) & 0x1)
127 << "Expected T32 opcodes but found A32 opcodes instead.";
128 ASSERT_TRUE(reinterpret_cast<uintptr_t>(b) & 0x1)
129 << "Expected T32 opcodes but found A32 opcodes instead.";
131 // Mask off the lowest bit.
132 a = reinterpret_cast<void*>(reinterpret_cast<uintptr_t>(a) & ~uintptr_t{0x1});
133 b = reinterpret_cast<void*>(reinterpret_cast<uintptr_t>(b) & ~uintptr_t{0x1});
136 // There are two identical test functions starting at a and b, which may
137 // occur in the library in either order. Grab whichever one comes first,
138 // and use the address of the other to figure out where it ends.
139 const Instruction* const start = static_cast<Instruction*>(std::min(a, b));
140 const Instruction* const end = static_cast<Instruction*>(std::max(a, b));
142 for (const Instruction& instruction : make_span(start, end))
143 body->push_back(instruction);
146 absl::optional<std::vector<Instruction>> ExpectImmediateCrashInvocation(
147 std::vector<Instruction> instructions) {
148 auto iter = instructions.begin();
149 for (const auto inst : kRequiredBody) {
150 if (iter == instructions.end())
151 return absl::nullopt;
152 EXPECT_EQ(inst, *iter);
155 return absl::make_optional(
156 std::vector<Instruction>(iter, instructions.end()));
159 std::vector<Instruction> MaybeSkipOptionalFooter(
160 std::vector<Instruction> instructions) {
161 auto iter = instructions.begin();
162 for (const auto inst : kOptionalFooter) {
163 if (iter == instructions.end() || *iter != inst)
167 return std::vector<Instruction>(iter, instructions.end());
170 #if BUILDFLAG(USE_CLANG_COVERAGE)
171 bool MatchPrefix(const std::vector<Instruction>& haystack,
172 const base::span<const Instruction>& needle) {
173 for (size_t i = 0; i < needle.size(); i++) {
174 if (i >= haystack.size() || needle[i] != haystack[i])
180 std::vector<Instruction> DropUntilMatch(
181 std::vector<Instruction> haystack,
182 const base::span<const Instruction>& needle) {
183 while (!haystack.empty() && !MatchPrefix(haystack, needle))
184 haystack.erase(haystack.begin());
187 #endif // USE_CLANG_COVERAGE
189 std::vector<Instruction> MaybeSkipCoverageHook(
190 std::vector<Instruction> instructions) {
191 #if BUILDFLAG(USE_CLANG_COVERAGE)
192 // Warning: it is not illegal for the entirety of the expected crash sequence
193 // to appear as a subsequence of the coverage hook code. If that happens, this
194 // code will falsely exit early, having not found the real expected crash
195 // sequence, so this may not adequately ensure that the immediate crash
196 // sequence is present. We do check when not under coverage, at least.
197 return DropUntilMatch(instructions, base::make_span(kRequiredBody));
200 #endif // USE_CLANG_COVERAGE
205 // Attempts to verify the actual instructions emitted by IMMEDIATE_CRASH().
206 // While the test results are highly implementation-specific, this allows macro
207 // changes (e.g. CLs like https://crrev.com/671123) to be verified using the
208 // trybots/waterfall, without having to build and disassemble Chrome on
209 // multiple platforms. This makes it easier to evaluate changes to
210 // IMMEDIATE_CRASH() against its requirements (e.g. size of emitted sequence,
211 // whether or not multiple IMMEDIATE_CRASH sequences can be folded together, et
212 // cetera). Please see immediate_crash.h for more details about the
215 // Note that C++ provides no way to get the size of a function. Instead, the
216 // test relies on a shared library which defines only two functions and assumes
217 // the two functions will be laid out contiguously as a heuristic for finding
218 // the size of the function.
219 TEST(ImmediateCrashTest, ExpectedOpcodeSequence) {
220 std::vector<Instruction> body;
221 ASSERT_NO_FATAL_FAILURE(GetTestFunctionInstructions(&body));
222 SCOPED_TRACE(HexEncode(body.data(), body.size() * sizeof(Instruction)));
224 auto it = ranges::find(body, kRet);
225 ASSERT_NE(body.end(), it) << "Failed to find return opcode";
228 body = std::vector<Instruction>(it, body.end());
229 absl::optional<std::vector<Instruction>> result = MaybeSkipCoverageHook(body);
230 result = ExpectImmediateCrashInvocation(result.value());
231 result = MaybeSkipOptionalFooter(result.value());
232 result = MaybeSkipCoverageHook(result.value());
233 result = ExpectImmediateCrashInvocation(result.value());