src/client/linux/minidump_writer/linux_dumper_unittest.cc

// Copyright (c) 2009, Google Inc.
// All rights reserved.
//
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// modification, are permitted provided that the following conditions are
// met:
//
//     * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
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// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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#include <string>

#include <fcntl.h>
#include <limits.h>
#include <unistd.h>
#include <signal.h>
#include <stdint.h>
#include <sys/mman.h>
#include <sys/poll.h>
#include <sys/stat.h>
#include <sys/types.h>

#include "breakpad_googletest_includes.h"
#include "client/linux/minidump_writer/linux_dumper.h"
#include "common/linux/eintr_wrapper.h"
#include "common/linux/file_id.h"
#include "common/memory.h"

using std::string;
using namespace google_breakpad;

namespace {
typedef testing::Test LinuxDumperTest;

string GetHelperBinary() {
  // Locate helper binary next to the current binary.
  char self_path[PATH_MAX];
  if (readlink("/proc/self/exe", self_path, sizeof(self_path) - 1) == -1) {
    return "";
  }
  string helper_path(self_path);
  size_t pos = helper_path.rfind('/');
  if (pos == string::npos) {
    return "";
  }
  helper_path.erase(pos + 1);
  helper_path += "linux_dumper_unittest_helper";

  return helper_path;
}

}

TEST(LinuxDumperTest, Setup) {
  LinuxDumper dumper(getpid());
}

TEST(LinuxDumperTest, FindMappings) {
  LinuxDumper dumper(getpid());
  ASSERT_TRUE(dumper.Init());

  ASSERT_TRUE(dumper.FindMapping(reinterpret_cast<void*>(getpid)));
  ASSERT_TRUE(dumper.FindMapping(reinterpret_cast<void*>(printf)));
  ASSERT_FALSE(dumper.FindMapping(NULL));
}

TEST(LinuxDumperTest, ThreadList) {
  LinuxDumper dumper(getpid());
  ASSERT_TRUE(dumper.Init());

  ASSERT_GE(dumper.threads().size(), (size_t)1);
  bool found = false;
  for (size_t i = 0; i < dumper.threads().size(); ++i) {
    if (dumper.threads()[i] == getpid()) {
      found = true;
      break;
    }
  }
}

// Helper stack class to close a file descriptor and unmap
// a mmap'ed mapping.
class StackHelper {
public:
  StackHelper(int fd, char* mapping, size_t size)
    : fd_(fd), mapping_(mapping), size_(size) {}
  ~StackHelper() {
    munmap(mapping_, size_);
    close(fd_);
  }

private:
  int fd_;
  char* mapping_;
  size_t size_;
};

TEST(LinuxDumperTest, MergedMappings) {
  string helper_path(GetHelperBinary());
  if (helper_path.empty()) {
    FAIL() << "Couldn't find helper binary";
    exit(1);
  }

  // mmap two segments out of the helper binary, one
  // enclosed in the other, but with different protections.
  const size_t kPageSize = sysconf(_SC_PAGESIZE);
  const size_t kMappingSize = 3 * kPageSize;
  int fd = open(helper_path.c_str(), O_RDONLY);
  ASSERT_NE(-1, fd);
  char* mapping =
    reinterpret_cast<char*>(mmap(NULL,
                                 kMappingSize,
                                 PROT_READ,
                                 MAP_SHARED,
                                 fd,
                                 0));
  ASSERT_TRUE(mapping);

  const u_int64_t kMappingAddress = reinterpret_cast<u_int64_t>(mapping);

  // Ensure that things get cleaned up.
  StackHelper helper(fd, mapping, kMappingSize);

  // Carve a page out of the first mapping with different permissions.
  char* inside_mapping =  reinterpret_cast<char*>(mmap(mapping + 2 *kPageSize,
                                 kPageSize,
                                 PROT_NONE,
                                 MAP_SHARED | MAP_FIXED,
                                 fd,
                                 // Map a different offset just to
                                 // better test real-world conditions.
                                 kPageSize));
  ASSERT_TRUE(inside_mapping);

  // Now check that LinuxDumper interpreted the mappings properly.
  LinuxDumper dumper(getpid());
  ASSERT_TRUE(dumper.Init());
  int mapping_count = 0;
  for (unsigned i = 0; i < dumper.mappings().size(); ++i) {
    const MappingInfo& mapping = *dumper.mappings()[i];
    if (strcmp(mapping.name, helper_path.c_str()) == 0) {
      // This mapping should encompass the entire original mapped
      // range.
      EXPECT_EQ(kMappingAddress, mapping.start_addr);
      EXPECT_EQ(kMappingSize, mapping.size);
      EXPECT_EQ(0, mapping.offset);
      mapping_count++;
    }
  }
  EXPECT_EQ(1, mapping_count);
}

// Comment out this test due to crosbug.com/6757.  Only seems to
// fail on heavily loaded buildbots and is written with timing
// assumptions.
#if 0
TEST(LinuxDumperTest, VerifyStackReadWithMultipleThreads) {
  static const int kNumberOfThreadsInHelperProgram = 5;
  char kNumberOfThreadsArgument[2];
  sprintf(kNumberOfThreadsArgument, "%d", kNumberOfThreadsInHelperProgram);

  int fds[2];
  ASSERT_NE(-1, pipe(fds));

  pid_t child_pid = fork();
  if (child_pid == 0) {
    // In child process.
    close(fds[0]);

    string helper_path(GetHelperBinary());
    if (helper_path.empty()) {
      FAIL() << "Couldn't find helper binary";
      exit(1);
    }

    // Pass the pipe fd and the number of threads as arguments.
    char pipe_fd_string[8];
    sprintf(pipe_fd_string, "%d", fds[1]);
    execl(helper_path.c_str(),
          "linux_dumper_unittest_helper",
          pipe_fd_string,
          kNumberOfThreadsArgument,
          NULL);
    // Kill if we get here.
    printf("Errno from exec: %d", errno);
    FAIL() << "Exec of " << helper_path << " failed: " << strerror(errno);
    exit(0);
  }
  close(fds[1]);
  // Wait for the child process to signal that it's ready.
  struct pollfd pfd;
  memset(&pfd, 0, sizeof(pfd));
  pfd.fd = fds[0];
  pfd.events = POLLIN | POLLERR;

  const int r = HANDLE_EINTR(poll(&pfd, 1, 1000));
  ASSERT_EQ(1, r);
  ASSERT_TRUE(pfd.revents & POLLIN);
  uint8_t junk;
  read(fds[0], &junk, sizeof(junk));
  close(fds[0]);

  // Child is ready now.
  LinuxDumper dumper(child_pid);
  ASSERT_TRUE(dumper.Init());
  EXPECT_EQ((size_t)kNumberOfThreadsInHelperProgram, dumper.threads().size());
  EXPECT_TRUE(dumper.ThreadsSuspend());

  ThreadInfo one_thread;
  for(size_t i = 0; i < dumper.threads().size(); ++i) {
    EXPECT_TRUE(dumper.ThreadInfoGet(dumper.threads()[i], &one_thread));
    // In the helper program, we stored a pointer to the thread id in a
    // specific register. Check that we can recover its value.
#if defined(__ARM_EABI__)
    pid_t *process_tid_location = (pid_t *)(one_thread.regs.uregs[3]);
#elif defined(__i386)
    pid_t *process_tid_location = (pid_t *)(one_thread.regs.ecx);
#elif defined(__x86_64)
    pid_t *process_tid_location = (pid_t *)(one_thread.regs.rcx);
#else
#error This test has not been ported to this platform.
#endif
    pid_t one_thread_id;
    dumper.CopyFromProcess(&one_thread_id,
                           dumper.threads()[i],
                           process_tid_location,
                           4);
    EXPECT_EQ(dumper.threads()[i], one_thread_id);
  }
  kill(child_pid, SIGKILL);
}
#endif

TEST(LinuxDumperTest, BuildProcPath) {
  const pid_t pid = getpid();
  LinuxDumper dumper(pid);

  char maps_path[256] = "dummymappath";
  char maps_path_expected[256];
  snprintf(maps_path_expected, sizeof(maps_path_expected),
           "/proc/%d/maps", pid);
  dumper.BuildProcPath(maps_path, pid, "maps");
  ASSERT_STREQ(maps_path, maps_path_expected);

  // In release mode, we expect BuildProcPath to handle the invalid
  // parameters correctly and fill map_path with an empty
  // NULL-terminated string.
#ifdef NDEBUG
  snprintf(maps_path, sizeof(maps_path), "dummymappath");
  dumper.BuildProcPath(maps_path, 0, "maps");
  EXPECT_STREQ(maps_path, "");

  snprintf(maps_path, sizeof(maps_path), "dummymappath");
  dumper.BuildProcPath(maps_path, getpid(), "");
  EXPECT_STREQ(maps_path, "");

  snprintf(maps_path, sizeof(maps_path), "dummymappath");
  dumper.BuildProcPath(maps_path, getpid(), NULL);
  EXPECT_STREQ(maps_path, "");
#endif
}

#if !defined(__ARM_EABI__)
// Ensure that the linux-gate VDSO is included in the mapping list.
TEST(LinuxDumperTest, MappingsIncludeLinuxGate) {
  LinuxDumper dumper(getpid());
  ASSERT_TRUE(dumper.Init());

  void* linux_gate_loc = dumper.FindBeginningOfLinuxGateSharedLibrary(getpid());
  ASSERT_TRUE(linux_gate_loc);
  bool found_linux_gate = false;

  const wasteful_vector<MappingInfo*> mappings = dumper.mappings();
  const MappingInfo* mapping;
  for (unsigned i = 0; i < mappings.size(); ++i) {
    mapping = mappings[i];
    if (!strcmp(mapping->name, kLinuxGateLibraryName)) {
      found_linux_gate = true;
      break;
    }
  }
  EXPECT_TRUE(found_linux_gate);
  EXPECT_EQ(linux_gate_loc, reinterpret_cast<void*>(mapping->start_addr));
  EXPECT_EQ(0, memcmp(linux_gate_loc, ELFMAG, SELFMAG));
}

// Ensure that the linux-gate VDSO can generate a non-zeroed File ID.
TEST(LinuxDumperTest, LinuxGateMappingID) {
  LinuxDumper dumper(getpid());
  ASSERT_TRUE(dumper.Init());

  bool found_linux_gate = false;
  const wasteful_vector<MappingInfo*> mappings = dumper.mappings();
  unsigned index = 0;
  for (unsigned i = 0; i < mappings.size(); ++i) {
    if (!strcmp(mappings[i]->name, kLinuxGateLibraryName)) {
      found_linux_gate = true;
      index = i;
      break;
    }
  }
  ASSERT_TRUE(found_linux_gate);

  uint8_t identifier[sizeof(MDGUID)];
  ASSERT_TRUE(dumper.ElfFileIdentifierForMapping(*mappings[index],
                                                 true,
                                                 index,
                                                 identifier));
  uint8_t empty_identifier[sizeof(MDGUID)];
  memset(empty_identifier, 0, sizeof(empty_identifier));
  EXPECT_NE(0, memcmp(empty_identifier, identifier, sizeof(identifier)));
}

// Ensure that the linux-gate VDSO can generate a non-zeroed File ID
// from a child process.
TEST(LinuxDumperTest, LinuxGateMappingIDChild) {
  int fds[2];
  ASSERT_NE(-1, pipe(fds));

  // Fork a child so ptrace works.
  const pid_t child = fork();
  if (child == 0) {
    close(fds[1]);
    // Now wait forever for the parent.
    char b;
    HANDLE_EINTR(read(fds[0], &b, sizeof(b)));
    close(fds[0]);
    syscall(__NR_exit);
  }
  close(fds[0]);

  LinuxDumper dumper(child);
  ASSERT_TRUE(dumper.Init());

  bool found_linux_gate = false;
  const wasteful_vector<MappingInfo*> mappings = dumper.mappings();
  unsigned index = 0;
  for (unsigned i = 0; i < mappings.size(); ++i) {
    if (!strcmp(mappings[i]->name, kLinuxGateLibraryName)) {
      found_linux_gate = true;
      index = i;
      break;
    }
  }
  ASSERT_TRUE(found_linux_gate);

  // Need to suspend the child so ptrace actually works.
  ASSERT_TRUE(dumper.ThreadsSuspend());
  uint8_t identifier[sizeof(MDGUID)];
  ASSERT_TRUE(dumper.ElfFileIdentifierForMapping(*mappings[index],
                                                 true,
                                                 index,
                                                 identifier));
  uint8_t empty_identifier[sizeof(MDGUID)];
  memset(empty_identifier, 0, sizeof(empty_identifier));
  EXPECT_NE(0, memcmp(empty_identifier, identifier, sizeof(identifier)));
  EXPECT_TRUE(dumper.ThreadsResume());
  close(fds[1]);
}
#endif

TEST(LinuxDumperTest, FileIDsMatch) {
  // Calculate the File ID of our binary using both
  // FileID::ElfFileIdentifier and LinuxDumper::ElfFileIdentifierForMapping
  // and ensure that we get the same result from both.
  char exe_name[PATH_MAX];
  ssize_t len = readlink("/proc/self/exe", exe_name, PATH_MAX - 1);
  ASSERT_NE(len, -1);
  exe_name[len] = '\0';

  int fds[2];
  ASSERT_NE(-1, pipe(fds));

  // Fork a child so ptrace works.
  const pid_t child = fork();
  if (child == 0) {
    close(fds[1]);
    // Now wait forever for the parent.
    char b;
    HANDLE_EINTR(read(fds[0], &b, sizeof(b)));
    close(fds[0]);
    syscall(__NR_exit);
  }
  close(fds[0]);

  LinuxDumper dumper(child);
  ASSERT_TRUE(dumper.Init());
  const wasteful_vector<MappingInfo*> mappings = dumper.mappings();
  bool found_exe = false;
  unsigned i;
  for (i = 0; i < mappings.size(); ++i) {
    const MappingInfo* mapping = mappings[i];
    if (!strcmp(mapping->name, exe_name)) {
      found_exe = true;
      break;
    }
  }
  ASSERT_TRUE(found_exe);

  uint8_t identifier1[sizeof(MDGUID)];
  uint8_t identifier2[sizeof(MDGUID)];
  EXPECT_TRUE(dumper.ElfFileIdentifierForMapping(*mappings[i], true, i,
                                                 identifier1));
  FileID fileid(exe_name);
  EXPECT_TRUE(fileid.ElfFileIdentifier(identifier2));
  char identifier_string1[37];
  char identifier_string2[37];
  FileID::ConvertIdentifierToString(identifier1, identifier_string1,
                                    37);
  FileID::ConvertIdentifierToString(identifier2, identifier_string2,
                                    37);
  EXPECT_STREQ(identifier_string1, identifier_string2);
  close(fds[1]);
}