client/linux/minidump_writer/linux_ptrace_dumper_unittest.cc - breakpad/breakpad/src - Git at Google

 // Copyright (c) 2009, Google Inc.
 // All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
 // 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.
 //     * Neither the name of Google Inc. nor the names of its
 // 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
 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

 // linux_ptrace_dumper_unittest.cc:
 // Unit tests for google_breakpad::LinuxPtraceDumoer.
 //
 // This file was renamed from linux_dumper_unittest.cc and modified due
 // to LinuxDumper being splitted into two classes.

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

 #include <string>

 #include "breakpad_googletest_includes.h"
 #include "client/linux/minidump_writer/linux_ptrace_dumper.h"
 #include "client/linux/minidump_writer/minidump_writer_unittest_utils.h"
 #include "common/linux/eintr_wrapper.h"
 #include "common/linux/file_id.h"
 #include "common/linux/ignore_ret.h"
 #include "common/linux/safe_readlink.h"
 #include "common/memory.h"
 #include "common/using_std_string.h"

 using namespace google_breakpad;

 namespace {

 typedef testing::Test LinuxPtraceDumperTest;

 }  // namespace

 TEST(LinuxPtraceDumperTest, Setup) {
   LinuxPtraceDumper dumper(getpid());
 }

 TEST(LinuxPtraceDumperTest, FindMappings) {
   LinuxPtraceDumper 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(LinuxPtraceDumperTest, ThreadList) {
   LinuxPtraceDumper 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(LinuxPtraceDumperTest, 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) << "Failed to open file: " << helper_path
                     << ", Error: " << strerror(errno);
   char* mapping =
     reinterpret_cast<char*>(mmap(NULL,
                                  kMappingSize,
                                  PROT_READ,
                                  MAP_SHARED,
                                  fd,
                                  0));
   ASSERT_TRUE(mapping);

   const uintptr_t kMappingAddress = reinterpret_cast<uintptr_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 LinuxPtraceDumper interpreted the mappings properly.
   LinuxPtraceDumper 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);
 }

 TEST(LinuxPtraceDumperTest, 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 all child threads to indicate that they have started
   for (int threads = 0; threads < kNumberOfThreadsInHelperProgram; threads++) {
     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;
     ASSERT_EQ(read(fds[0], &junk, sizeof(junk)), sizeof(junk));
   }
   close(fds[0]);

   // There is a race here because we may stop a child thread before
   // it is actually running the busy loop. Empirically this sleep
   // is sufficient to avoid the race.
   usleep(100000);

   // Children are ready now.
   LinuxPtraceDumper 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.GetThreadInfoByIndex(i, &one_thread));
     const void* stack;
     size_t stack_len;
     EXPECT_TRUE(dumper.GetStackInfo(&stack, &stack_len,
         one_thread.stack_pointer));
     // 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);
   }
   EXPECT_TRUE(dumper.ThreadsResume());
   kill(child_pid, SIGKILL);

   // Reap child
   int status;
   ASSERT_NE(-1, HANDLE_EINTR(waitpid(child_pid, &status, 0)));
   ASSERT_TRUE(WIFSIGNALED(status));
   ASSERT_EQ(SIGKILL, WTERMSIG(status));
 }

 TEST(LinuxPtraceDumperTest, BuildProcPath) {
   const pid_t pid = getpid();
   LinuxPtraceDumper dumper(pid);

   char maps_path[NAME_MAX] = "";
   char maps_path_expected[NAME_MAX];
   snprintf(maps_path_expected, sizeof(maps_path_expected),
            "/proc/%d/maps", pid);
   EXPECT_TRUE(dumper.BuildProcPath(maps_path, pid, "maps"));
   EXPECT_STREQ(maps_path_expected, maps_path);

   EXPECT_FALSE(dumper.BuildProcPath(NULL, pid, "maps"));
   EXPECT_FALSE(dumper.BuildProcPath(maps_path, 0, "maps"));
   EXPECT_FALSE(dumper.BuildProcPath(maps_path, pid, ""));
   EXPECT_FALSE(dumper.BuildProcPath(maps_path, pid, NULL));

   char long_node[NAME_MAX];
   size_t long_node_len = NAME_MAX - strlen("/proc/123") - 1;
   memset(long_node, 'a', long_node_len);
   long_node[long_node_len] = '\0';
   EXPECT_FALSE(dumper.BuildProcPath(maps_path, 123, long_node));
 }

 #if !defined(__ARM_EABI__)
 // Ensure that the linux-gate VDSO is included in the mapping list.
 TEST(LinuxPtraceDumperTest, MappingsIncludeLinuxGate) {
   LinuxPtraceDumper 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(LinuxPtraceDumperTest, LinuxGateMappingID) {
   LinuxPtraceDumper 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(LinuxPtraceDumperTest, 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;
     IGNORE_RET(HANDLE_EINTR(read(fds[0], &b, sizeof(b))));
     close(fds[0]);
     syscall(__NR_exit);
   }
   close(fds[0]);

   LinuxPtraceDumper 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(LinuxPtraceDumperTest, 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];
   ASSERT_TRUE(SafeReadLink("/proc/self/exe", exe_name));

   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;
     IGNORE_RET(HANDLE_EINTR(read(fds[0], &b, sizeof(b))));
     close(fds[0]);
     syscall(__NR_exit);
   }
   close(fds[0]);

   LinuxPtraceDumper 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]);
 }
	// Copyright (c) 2009, Google Inc.
	// All rights reserved.
	//
	// Redistribution and use in source and binary forms, with or without
	// 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.
	// * Neither the name of Google Inc. nor the names of its
	// 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
	// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
	// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
	// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
	// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
	// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
	// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
	// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
	// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
	// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
	// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

	// linux_ptrace_dumper_unittest.cc:
	// Unit tests for google_breakpad::LinuxPtraceDumoer.
	//
	// This file was renamed from linux_dumper_unittest.cc and modified due
	// to LinuxDumper being splitted into two classes.

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

	#include <string>

	#include "breakpad_googletest_includes.h"
	#include "client/linux/minidump_writer/linux_ptrace_dumper.h"
	#include "client/linux/minidump_writer/minidump_writer_unittest_utils.h"
	#include "common/linux/eintr_wrapper.h"
	#include "common/linux/file_id.h"
	#include "common/linux/ignore_ret.h"
	#include "common/linux/safe_readlink.h"
	#include "common/memory.h"
	#include "common/using_std_string.h"

	using namespace google_breakpad;

	namespace {

	typedef testing::Test LinuxPtraceDumperTest;

	} // namespace

	TEST(LinuxPtraceDumperTest, Setup) {
	LinuxPtraceDumper dumper(getpid());
	}

	TEST(LinuxPtraceDumperTest, FindMappings) {
	LinuxPtraceDumper 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(LinuxPtraceDumperTest, ThreadList) {
	LinuxPtraceDumper 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(LinuxPtraceDumperTest, 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) << "Failed to open file: " << helper_path
	<< ", Error: " << strerror(errno);
	char* mapping =
	reinterpret_cast<char*>(mmap(NULL,
	kMappingSize,
	PROT_READ,
	MAP_SHARED,
	fd,
	0));
	ASSERT_TRUE(mapping);

	const uintptr_t kMappingAddress = reinterpret_cast<uintptr_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 LinuxPtraceDumper interpreted the mappings properly.
	LinuxPtraceDumper 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);
	}

	TEST(LinuxPtraceDumperTest, 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 all child threads to indicate that they have started
	for (int threads = 0; threads < kNumberOfThreadsInHelperProgram; threads++) {
	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;
	ASSERT_EQ(read(fds[0], &junk, sizeof(junk)), sizeof(junk));
	}
	close(fds[0]);

	// There is a race here because we may stop a child thread before
	// it is actually running the busy loop. Empirically this sleep
	// is sufficient to avoid the race.
	usleep(100000);

	// Children are ready now.
	LinuxPtraceDumper 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.GetThreadInfoByIndex(i, &one_thread));
	const void* stack;
	size_t stack_len;
	EXPECT_TRUE(dumper.GetStackInfo(&stack, &stack_len,
	one_thread.stack_pointer));
	// 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);
	}
	EXPECT_TRUE(dumper.ThreadsResume());
	kill(child_pid, SIGKILL);

	// Reap child
	int status;
	ASSERT_NE(-1, HANDLE_EINTR(waitpid(child_pid, &status, 0)));
	ASSERT_TRUE(WIFSIGNALED(status));
	ASSERT_EQ(SIGKILL, WTERMSIG(status));
	}

	TEST(LinuxPtraceDumperTest, BuildProcPath) {
	const pid_t pid = getpid();
	LinuxPtraceDumper dumper(pid);

	char maps_path[NAME_MAX] = "";
	char maps_path_expected[NAME_MAX];
	snprintf(maps_path_expected, sizeof(maps_path_expected),
	"/proc/%d/maps", pid);
	EXPECT_TRUE(dumper.BuildProcPath(maps_path, pid, "maps"));
	EXPECT_STREQ(maps_path_expected, maps_path);

	EXPECT_FALSE(dumper.BuildProcPath(NULL, pid, "maps"));
	EXPECT_FALSE(dumper.BuildProcPath(maps_path, 0, "maps"));
	EXPECT_FALSE(dumper.BuildProcPath(maps_path, pid, ""));
	EXPECT_FALSE(dumper.BuildProcPath(maps_path, pid, NULL));

	char long_node[NAME_MAX];
	size_t long_node_len = NAME_MAX - strlen("/proc/123") - 1;
	memset(long_node, 'a', long_node_len);
	long_node[long_node_len] = '\0';
	EXPECT_FALSE(dumper.BuildProcPath(maps_path, 123, long_node));
	}

	#if !defined(__ARM_EABI__)
	// Ensure that the linux-gate VDSO is included in the mapping list.
	TEST(LinuxPtraceDumperTest, MappingsIncludeLinuxGate) {
	LinuxPtraceDumper 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(LinuxPtraceDumperTest, LinuxGateMappingID) {
	LinuxPtraceDumper 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(LinuxPtraceDumperTest, 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;
	IGNORE_RET(HANDLE_EINTR(read(fds[0], &b, sizeof(b))));
	close(fds[0]);
	syscall(__NR_exit);
	}
	close(fds[0]);

	LinuxPtraceDumper 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(LinuxPtraceDumperTest, 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];
	ASSERT_TRUE(SafeReadLink("/proc/self/exe", exe_name));

	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;
	IGNORE_RET(HANDLE_EINTR(read(fds[0], &b, sizeof(b))));
	close(fds[0]);
	syscall(__NR_exit);
	}
	close(fds[0]);

	LinuxPtraceDumper 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]);
	}