1 /*
2 * Copyright (C) 2024 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 #include "gtest/gtest.h"
18
19 #include <sys/mman.h>
20 #include <unistd.h> // sysconf(_SC_PAGESIZE)
21
22 #include <cinttypes>
23 #include <cstdint>
24 #include <cstdio>
25 #include <memory>
26
27 namespace {
28
29 constexpr bool kExactMapping = true;
30
31 template <bool kIsExactMapping = false>
IsExecutable(void * ptr,size_t size)32 bool IsExecutable(void* ptr, size_t size) {
33 uintptr_t addr = reinterpret_cast<uintptr_t>(ptr);
34 std::unique_ptr<FILE, decltype(&fclose)> fp(fopen("/proc/self/maps", "re"), fclose);
35 if (fp == nullptr) {
36 ADD_FAILURE() << "Cannot open /proc/self/maps";
37 return false;
38 }
39
40 char line[BUFSIZ];
41 while (fgets(line, sizeof(line), fp.get()) != nullptr) {
42 uintptr_t start;
43 uintptr_t end;
44 char prot[5]; // sizeof("rwxp")
45 if (sscanf(line, "%" SCNxPTR "-%" SCNxPTR " %4s", &start, &end, prot) == 3) {
46 bool is_match;
47 if constexpr (kIsExactMapping) {
48 is_match = (addr == start);
49 if (is_match) {
50 EXPECT_EQ(start + size, end);
51 }
52 } else {
53 is_match = (addr >= start) && (addr < end);
54 if (is_match) {
55 EXPECT_LE(addr + size, end);
56 }
57 }
58 if (is_match) {
59 return prot[2] == 'x';
60 }
61 }
62 }
63 ADD_FAILURE() << "Didn't find address " << reinterpret_cast<void*>(addr) << " in /proc/self/maps";
64 return false;
65 }
66
TEST(ProcSelfMaps,ExecutableFromMmap)67 TEST(ProcSelfMaps, ExecutableFromMmap) {
68 const size_t kPageSize = sysconf(_SC_PAGESIZE);
69 uint8_t* mapping = reinterpret_cast<uint8_t*>(
70 mmap(0, 3 * kPageSize, PROT_READ, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0));
71 ASSERT_NE(mapping, nullptr);
72
73 ASSERT_FALSE(IsExecutable(mapping, 3 * kPageSize));
74
75 void* exec_mapping = mmap(mapping + kPageSize,
76 kPageSize,
77 PROT_READ | PROT_EXEC,
78 MAP_FIXED | MAP_PRIVATE | MAP_ANONYMOUS,
79 -1,
80 0);
81 ASSERT_NE(exec_mapping, nullptr);
82
83 ASSERT_FALSE(IsExecutable(mapping, kPageSize));
84 // Surrounding mappings can be merged with adjacent mappings. But this one must match exactly.
85 ASSERT_TRUE(IsExecutable<kExactMapping>(mapping + kPageSize, kPageSize));
86 ASSERT_FALSE(IsExecutable(mapping + 2 * kPageSize, kPageSize));
87
88 ASSERT_EQ(munmap(mapping, 3 * kPageSize), 0);
89 }
90
TEST(ProcSelfMaps,ExecutableFromMprotect)91 TEST(ProcSelfMaps, ExecutableFromMprotect) {
92 const size_t kPageSize = sysconf(_SC_PAGESIZE);
93 uint8_t* mapping = reinterpret_cast<uint8_t*>(
94 mmap(0, 3 * kPageSize, PROT_READ, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0));
95 ASSERT_NE(mapping, nullptr);
96
97 ASSERT_FALSE(IsExecutable(mapping, 3 * kPageSize));
98
99 ASSERT_EQ(mprotect(mapping + kPageSize, kPageSize, PROT_READ | PROT_EXEC), 0);
100
101 ASSERT_FALSE(IsExecutable(mapping, kPageSize));
102 // Surrounding mappings can be merged with adjacent mappings. But this one must match exactly.
103 ASSERT_TRUE(IsExecutable<kExactMapping>(mapping + kPageSize, kPageSize));
104 ASSERT_FALSE(IsExecutable(mapping + 2 * kPageSize, kPageSize));
105
106 ASSERT_EQ(munmap(mapping, 3 * kPageSize), 0);
107 }
108
109 } // namespace
110