syscall_unittest.cc revision 5f1c94371a64b3196d4be9466099bb892df9b88e 
1// Copyright (c) 2012 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.
4
5#include "sandbox/linux/seccomp-bpf/syscall.h"
6
7#include <asm/unistd.h>
8#include <fcntl.h>
9#include <sys/mman.h>
10#include <sys/syscall.h>
11#include <sys/types.h>
12#include <unistd.h>
13
14#include <vector>
15
16#include "base/basictypes.h"
17#include "base/posix/eintr_wrapper.h"
18#include "build/build_config.h"
19#include "sandbox/linux/seccomp-bpf/bpf_tests.h"
20#include "sandbox/linux/seccomp-bpf/sandbox_bpf.h"
21#include "sandbox/linux/tests/unit_tests.h"
22#include "testing/gtest/include/gtest/gtest.h"
23
24namespace sandbox {
25
26namespace {
27
28// Different platforms use different symbols for the six-argument version
29// of the mmap() system call. Test for the correct symbol at compile time.
30#ifdef __NR_mmap2
31const int kMMapNr = __NR_mmap2;
32#else
33const int kMMapNr = __NR_mmap;
34#endif
35
36TEST(Syscall, InvalidCallReturnsENOSYS) {
37  EXPECT_EQ(-ENOSYS, Syscall::InvalidCall());
38}
39
40TEST(Syscall, WellKnownEntryPoint) {
41// Test that Syscall::Call(-1) is handled specially. Don't do this on ARM,
42// where syscall(-1) crashes with SIGILL. Not running the test is fine, as we
43// are still testing ARM code in the next set of tests.
44#if !defined(__arm__)
45  EXPECT_NE(Syscall::Call(-1), syscall(-1));
46#endif
47
48// If possible, test that Syscall::Call(-1) returns the address right
49// after
50// a kernel entry point.
51#if defined(__i386__)
52  EXPECT_EQ(0x80CDu, ((uint16_t*)Syscall::Call(-1))[-1]);  // INT 0x80
53#elif defined(__x86_64__)
54  EXPECT_EQ(0x050Fu, ((uint16_t*)Syscall::Call(-1))[-1]);  // SYSCALL
55#elif defined(__arm__)
56#if defined(__thumb__)
57  EXPECT_EQ(0xDF00u, ((uint16_t*)Syscall::Call(-1))[-1]);  // SWI 0
58#else
59  EXPECT_EQ(0xEF000000u, ((uint32_t*)Syscall::Call(-1))[-1]);  // SVC 0
60#endif
61#elif defined(__mips__)
62  // Opcode for MIPS sycall is in the lower 16-bits
63  EXPECT_EQ(0x0cu, (((uint32_t*)Syscall::Call(-1))[-1]) & 0x0000FFFF);
64#else
65#warning Incomplete test case; need port for target platform
66#endif
67}
68
69TEST(Syscall, TrivialSyscallNoArgs) {
70  // Test that we can do basic system calls
71  EXPECT_EQ(Syscall::Call(__NR_getpid), syscall(__NR_getpid));
72}
73
74TEST(Syscall, TrivialSyscallOneArg) {
75  int new_fd;
76  // Duplicate standard error and close it.
77  ASSERT_GE(new_fd = Syscall::Call(__NR_dup, 2), 0);
78  int close_return_value = IGNORE_EINTR(Syscall::Call(__NR_close, new_fd));
79  ASSERT_EQ(close_return_value, 0);
80}
81
82TEST(Syscall, TrivialFailingSyscall) {
83  errno = -42;
84  int ret = Syscall::Call(__NR_dup, -1);
85  ASSERT_EQ(-EBADF, ret);
86  // Verify that Syscall::Call does not touch errno.
87  ASSERT_EQ(-42, errno);
88}
89
90// SIGSYS trap handler that will be called on __NR_uname.
91intptr_t CopySyscallArgsToAux(const struct arch_seccomp_data& args, void* aux) {
92  // |aux| is our BPF_AUX pointer.
93  std::vector<uint64_t>* const seen_syscall_args =
94      static_cast<std::vector<uint64_t>*>(aux);
95  BPF_ASSERT(arraysize(args.args) == 6);
96  seen_syscall_args->assign(args.args, args.args + arraysize(args.args));
97  return -ENOMEM;
98}
99
100ErrorCode CopyAllArgsOnUnamePolicy(SandboxBPF* sandbox,
101                                   int sysno,
102                                   std::vector<uint64_t>* aux) {
103  if (!SandboxBPF::IsValidSyscallNumber(sysno)) {
104    return ErrorCode(ENOSYS);
105  }
106  if (sysno == __NR_uname) {
107    return sandbox->Trap(CopySyscallArgsToAux, aux);
108  } else {
109    return ErrorCode(ErrorCode::ERR_ALLOWED);
110  }
111}
112
113// We are testing Syscall::Call() by making use of a BPF filter that
114// allows us
115// to inspect the system call arguments that the kernel saw.
116BPF_TEST(Syscall,
117         SyntheticSixArgs,
118         CopyAllArgsOnUnamePolicy,
119         std::vector<uint64_t> /* (*BPF_AUX) */) {
120  const int kExpectedValue = 42;
121  // In this test we only pass integers to the kernel. We might want to make
122  // additional tests to try other types. What we will see depends on
123  // implementation details of kernel BPF filters and we will need to document
124  // the expected behavior very clearly.
125  int syscall_args[6];
126  for (size_t i = 0; i < arraysize(syscall_args); ++i) {
127    syscall_args[i] = kExpectedValue + i;
128  }
129
130  // We could use pretty much any system call we don't need here. uname() is
131  // nice because it doesn't have any dangerous side effects.
132  BPF_ASSERT(Syscall::Call(__NR_uname,
133                           syscall_args[0],
134                           syscall_args[1],
135                           syscall_args[2],
136                           syscall_args[3],
137                           syscall_args[4],
138                           syscall_args[5]) == -ENOMEM);
139
140  // We expect the trap handler to have copied the 6 arguments.
141  BPF_ASSERT(BPF_AUX->size() == 6);
142
143  // Don't loop here so that we can see which argument does cause the failure
144  // easily from the failing line.
145  // uint64_t is the type passed to our SIGSYS handler.
146  BPF_ASSERT((*BPF_AUX)[0] == static_cast<uint64_t>(syscall_args[0]));
147  BPF_ASSERT((*BPF_AUX)[1] == static_cast<uint64_t>(syscall_args[1]));
148  BPF_ASSERT((*BPF_AUX)[2] == static_cast<uint64_t>(syscall_args[2]));
149  BPF_ASSERT((*BPF_AUX)[3] == static_cast<uint64_t>(syscall_args[3]));
150  BPF_ASSERT((*BPF_AUX)[4] == static_cast<uint64_t>(syscall_args[4]));
151  BPF_ASSERT((*BPF_AUX)[5] == static_cast<uint64_t>(syscall_args[5]));
152}
153
154TEST(Syscall, ComplexSyscallSixArgs) {
155  int fd;
156  ASSERT_LE(0, fd = Syscall::Call(__NR_open, "/dev/null", O_RDWR, 0L));
157
158  // Use mmap() to allocate some read-only memory
159  char* addr0;
160  ASSERT_NE(
161      (char*)NULL,
162      addr0 = reinterpret_cast<char*>(Syscall::Call(kMMapNr,
163                                                    (void*)NULL,
164                                                    4096,
165                                                    PROT_READ,
166                                                    MAP_PRIVATE | MAP_ANONYMOUS,
167                                                    fd,
168                                                    0L)));
169
170  // Try to replace the existing mapping with a read-write mapping
171  char* addr1;
172  ASSERT_EQ(addr0,
173            addr1 = reinterpret_cast<char*>(
174                Syscall::Call(kMMapNr,
175                              addr0,
176                              4096L,
177                              PROT_READ | PROT_WRITE,
178                              MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED,
179                              fd,
180                              0L)));
181  ++*addr1;  // This should not seg fault
182
183  // Clean up
184  EXPECT_EQ(0, Syscall::Call(__NR_munmap, addr1, 4096L));
185  EXPECT_EQ(0, IGNORE_EINTR(Syscall::Call(__NR_close, fd)));
186
187  // Check that the offset argument (i.e. the sixth argument) is processed
188  // correctly.
189  ASSERT_GE(fd = Syscall::Call(__NR_open, "/proc/self/exe", O_RDONLY, 0L), 0);
190  char* addr2, *addr3;
191  ASSERT_NE((char*)NULL,
192            addr2 = reinterpret_cast<char*>(Syscall::Call(
193                kMMapNr, (void*)NULL, 8192L, PROT_READ, MAP_PRIVATE, fd, 0L)));
194  ASSERT_NE((char*)NULL,
195            addr3 = reinterpret_cast<char*>(Syscall::Call(kMMapNr,
196                                                          (void*)NULL,
197                                                          4096L,
198                                                          PROT_READ,
199                                                          MAP_PRIVATE,
200                                                          fd,
201#if defined(__NR_mmap2)
202                                                          1L
203#else
204                                                          4096L
205#endif
206                                                          )));
207  EXPECT_EQ(0, memcmp(addr2 + 4096, addr3, 4096));
208
209  // Just to be absolutely on the safe side, also verify that the file
210  // contents matches what we are getting from a read() operation.
211  char buf[8192];
212  EXPECT_EQ(8192, Syscall::Call(__NR_read, fd, buf, 8192L));
213  EXPECT_EQ(0, memcmp(addr2, buf, 8192));
214
215  // Clean up
216  EXPECT_EQ(0, Syscall::Call(__NR_munmap, addr2, 8192L));
217  EXPECT_EQ(0, Syscall::Call(__NR_munmap, addr3, 4096L));
218  EXPECT_EQ(0, IGNORE_EINTR(Syscall::Call(__NR_close, fd)));
219}
220
221}  // namespace
222
223}  // namespace sandbox
224