fork_detect_test.cc

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/* Copyright (c) 2020, Google Inc.
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
 * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
 * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
 * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */
 
#include <openssl/base.h>
 
// TSAN cannot cope with this test and complains that "starting new threads
// after multi-threaded fork is not supported".
#if defined(OPENSSL_LINUX) && !defined(OPENSSL_TSAN)
#include <errno.h>
#include <inttypes.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
 
#include <functional>
 
#if defined(OPENSSL_THREADS)
#include <thread>
#include <vector>
#endif
 
#include <gtest/gtest.h>
 
#include "fork_detect.h"
 
 
static pid_t WaitpidEINTR(pid_t pid, int *out_status, int options) {
  pid_t ret;
  do {
    ret = waitpid(pid, out_status, options);
  } while (ret < 0 && errno == EINTR);
 
  return ret;
}
 
// The *InChild functions run inside a child process and must report errors via
// |stderr| and |_exit| rather than GTest.
 
static void CheckGenerationInChild(const char *name, uint64_t expected) {
  uint64_t generation = CRYPTO_get_fork_generation();
  if (generation != expected) {
    fprintf(stderr, "%s generation (#1) was %" PRIu64 ", wanted %" PRIu64 ".\n",
            name, generation, expected);
    _exit(1);
  }
 
  // The generation should be stable.
  generation = CRYPTO_get_fork_generation();
  if (generation != expected) {
    fprintf(stderr, "%s generation (#2) was %" PRIu64 ", wanted %" PRIu64 ".\n",
            name, generation, expected);
    _exit(1);
  }
}
 
// ForkInChild forks a child which runs |f|. If the child exits unsuccessfully,
// this function will also exit unsuccessfully.
static void ForkInChild(std::function<void()> f) {
  fflush(stderr);  // Avoid duplicating any buffered output.
 
  const pid_t pid = fork();
  if (pid < 0) {
    perror("fork");
    _exit(1);
  } else if (pid == 0) {
    f();
    _exit(0);
  }
 
  // Wait for the child and pass its exit code up.
  int status;
  if (WaitpidEINTR(pid, &status, 0) < 0) {
    perror("waitpid");
    _exit(1);
  }
  if (!WIFEXITED(status)) {
    fprintf(stderr, "Child did not exit cleanly.\n");
    _exit(1);
  }
  if (WEXITSTATUS(status) != 0) {
    // Pass the failure up.
    _exit(WEXITSTATUS(status));
  }
}
 
TEST(ForkDetect, Test) {
  const uint64_t start = CRYPTO_get_fork_generation();
  if (start == 0) {
    fprintf(stderr, "Fork detection not supported. Skipping test.\n");
    return;
  }
 
  // The fork generation should be stable.
  EXPECT_EQ(start, CRYPTO_get_fork_generation());
 
  fflush(stderr);
  const pid_t child = fork();
 
  if (child == 0) {
    // Fork grandchildren before observing the fork generation. The
    // grandchildren will observe |start| + 1.
    for (int i = 0; i < 2; i++) {
      ForkInChild([&] { CheckGenerationInChild("Grandchild", start + 1); });
    }
 
    // Now the child also observes |start| + 1. This is fine because it has
    // already diverged from the grandchild at this point.
    CheckGenerationInChild("Child", start + 1);
 
    // Forked grandchildren will now observe |start| + 2.
    for (int i = 0; i < 2; i++) {
      ForkInChild([&] { CheckGenerationInChild("Grandchild", start + 2); });
    }
 
#if defined(OPENSSL_THREADS)
    // The fork generation logic itself must be thread-safe. We test this in a
    // child process to capture the actual fork detection. This segment is meant
    // to be tested in TSan.
    ForkInChild([&] {
      std::vector<std::thread> threads(4);
      for (int i = 0; i < 2; i++) {
        for (auto &t : threads) {
          t = std::thread(
              [&] { CheckGenerationInChild("Grandchild thread", start + 2); });
        }
        for (auto &t : threads) {
          t.join();
        }
      }
    });
#endif  // OPENSSL_THREADS
 
    // The child still observes |start| + 1.
    CheckGenerationInChild("Child", start + 1);
    _exit(0);
  }
 
  ASSERT_GT(child, 0) << "Error in fork: " << strerror(errno);
  int status;
  ASSERT_EQ(child, WaitpidEINTR(child, &status, 0))
      << "Error in waitpid: " << strerror(errno);
  ASSERT_TRUE(WIFEXITED(status));
  EXPECT_EQ(0, WEXITSTATUS(status)) << "Error in child process";
 
  // We still observe |start|.
  EXPECT_EQ(start, CRYPTO_get_fork_generation());
}
 
#endif  // OPENSSL_LINUX && !OPENSSL_TSAN