1 /*
2 * Copyright (C) 2023 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 <signal.h>
20 #include <string.h>
21 #include <sys/mman.h>
22
23 namespace {
24
25 // Verify that nested signal handlers on an alternate stack do not interfere with others' stack
26 // variables.
27
28 constexpr size_t kStackSize = 16 * 4096; // from bionic/tests/pthread_test.cpp, fails if less.
29 void* g_ss = nullptr;
30
31 constexpr size_t kAccessSize = 4096;
32 void* g_access_1;
33 void* g_access_2;
34
HandleSignalOnAccess(int,siginfo_t *,void *)35 void HandleSignalOnAccess(int, siginfo_t*, void*) {
36 char ss_var[32];
37
38 // Check handler runs on alternate stack.
39 const char* ss_start = static_cast<const char*>(g_ss);
40 EXPECT_GE(ss_var, ss_start);
41 EXPECT_LT(ss_var, ss_start + kStackSize);
42
43 if (g_access_2 == nullptr) {
44 // First signal.
45 // Initialize stack.
46 strncpy(ss_var, "firstfirstfirst", sizeof(ss_var));
47
48 // Force second signal.
49 // Because of SA_NODEFER, it should be a nested signal handler call.
50 g_access_2 = mmap(nullptr, kAccessSize, PROT_NONE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
51 ASSERT_NE(g_access_2, MAP_FAILED);
52 *static_cast<int*>(g_access_2) = 2;
53
54 // Check second signal didn't screw the stack up.
55 ASSERT_EQ(strncmp(ss_var, "firstfirstfirst", sizeof(ss_var)), 0);
56
57 // Fix first signal.
58 ASSERT_EQ(mprotect(g_access_1, kAccessSize, PROT_READ | PROT_WRITE), 0);
59 } else {
60 // Second signal.
61 // Initialize stack with something different.
62 strncpy(ss_var, "secondsecondsecond", sizeof(ss_var));
63
64 // Fix second signal.
65 ASSERT_EQ(mprotect(g_access_2, kAccessSize, PROT_READ | PROT_WRITE), 0);
66 }
67 }
68
TEST(Signal,Sigaltstack)69 TEST(Signal, Sigaltstack) {
70 // Set signal handler for failed access.
71 // Use alternate stack if available.
72 // Allow nested handler call.
73 struct sigaction sa {};
74 sa.sa_sigaction = HandleSignalOnAccess;
75 sa.sa_flags = SA_SIGINFO | SA_NODEFER | SA_ONSTACK;
76 struct sigaction old_sa {};
77 ASSERT_EQ(sigaction(SIGSEGV, &sa, &old_sa), 0);
78
79 // Install alternate signal stack.
80 g_ss = mmap(nullptr, kStackSize, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
81 ASSERT_NE(g_ss, MAP_FAILED);
82 stack_t ss{};
83 ss.ss_sp = g_ss;
84 ss.ss_size = kStackSize;
85 stack_t old_ss{};
86 ASSERT_EQ(sigaltstack(&ss, &old_ss), 0);
87
88 g_access_2 = nullptr;
89
90 // Force first signal.
91 g_access_1 = mmap(nullptr, kAccessSize, PROT_NONE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
92 ASSERT_NE(g_access_1, MAP_FAILED);
93 *static_cast<int*>(g_access_1) = 1;
94
95 ASSERT_EQ(sigaction(SIGSEGV, &old_sa, nullptr), 0);
96 ASSERT_EQ(sigaltstack(&old_ss, nullptr), 0);
97 ASSERT_EQ(munmap(g_ss, kStackSize), 0);
98 ASSERT_EQ(munmap(g_access_1, kAccessSize), 0);
99 ASSERT_EQ(munmap(g_access_2, kAccessSize), 0);
100 }
101
102 } // namespace
103