gecko/b2g/app/B2GLoader.cpp

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set sw=2 ts=2 autoindent cindent expandtab: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this file,
 * You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "nsXULAppAPI.h"
#include "nsXPCOMGlue.h"
#include "nsStringGlue.h"
#include "nsCOMPtr.h"
#include "nsIFile.h"
#include "BinaryPath.h"
#include "nsAutoPtr.h"

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/socket.h>

#include <dlfcn.h>

#include "nsXPCOMPrivate.h" // for MAXPATHLEN and XPCOM_DLL

#define ASSERT(x) if (!(x)) { MOZ_CRASH(); }


// Functions being loaded by XPCOMGlue
XRE_ProcLoaderServiceRunType XRE_ProcLoaderServiceRun;
XRE_ProcLoaderClientInitType XRE_ProcLoaderClientInit;

static const nsDynamicFunctionLoad kXULFuncs[] = {
  { "XRE_ProcLoaderServiceRun", (NSFuncPtr*) &XRE_ProcLoaderServiceRun },
  { "XRE_ProcLoaderClientInit", (NSFuncPtr*) &XRE_ProcLoaderClientInit },
  { nullptr, nullptr }
};

static int
GetDirnameSlash(const char *aPath, char *aOutDir, int aMaxLen)
{
  char *lastSlash = strrchr(aPath, XPCOM_FILE_PATH_SEPARATOR[0]);
  if (lastSlash == nullptr) {
    return 0;
  }
  int cpsz = lastSlash - aPath + 1; // include slash
  if (aMaxLen <= cpsz) {
    return 0;
  }
  strncpy(aOutDir, aPath, cpsz);
  aOutDir[cpsz] = 0;
  return cpsz;
}

static bool
GetXPCOMPath(const char *aProgram, char *aOutPath, int aMaxLen)
{
  nsAutoArrayPtr<char> progBuf(new char[aMaxLen]);
  nsresult rv = mozilla::BinaryPath::Get(aProgram, progBuf);
  NS_ENSURE_SUCCESS(rv, false);

  int len = GetDirnameSlash(progBuf, aOutPath, aMaxLen);
  NS_ENSURE_TRUE(!!len, false);

  NS_ENSURE_TRUE((len + sizeof(XPCOM_DLL)) < aMaxLen, false);
  char *afterSlash = aOutPath + len;
  strcpy(afterSlash, XPCOM_DLL);
  return true;
}

static bool
LoadLibxul(const char *aXPCOMPath)
{
  nsresult rv;

  XPCOMGlueEnablePreload();
  rv = XPCOMGlueStartup(aXPCOMPath);
  NS_ENSURE_SUCCESS(rv, false);

  rv = XPCOMGlueLoadXULFunctions(kXULFuncs);
  NS_ENSURE_SUCCESS(rv, false);

  return true;
}

static bool
LoadStaticData(const char *aProgram)
{
  char xpcomPath[MAXPATHLEN];
  bool ok = GetXPCOMPath(aProgram, xpcomPath, MAXPATHLEN);
  NS_ENSURE_TRUE(ok, false);

  ok = LoadLibxul(xpcomPath);
  return ok;
}

/**
 * Fork and run parent and child process.
 *
 * The parent is the b2g process and child for Nuwa.
 */
static int
RunProcesses(int argc, const char *argv[])
{
  /*
   * The original main() of the b2g process.  It is renamed to
   * b2g_main() for the b2g loader.
   */
  int b2g_main(int argc, const char *argv[]);

  int ipcSockets[2] = {-1, -1};
  int r = socketpair(AF_LOCAL, SOCK_STREAM, 0, ipcSockets);
  ASSERT(r == 0);
  int parentSock = ipcSockets[0];
  int childSock = ipcSockets[1];

  r = fcntl(parentSock, F_SETFL, O_NONBLOCK);
  ASSERT(r != -1);
  r = fcntl(childSock, F_SETFL, O_NONBLOCK);
  ASSERT(r != -1);

  pid_t pid = fork();
  ASSERT(pid >= 0);
  bool isChildProcess = pid == 0;

  close(isChildProcess ? parentSock : childSock);

  if (isChildProcess) {
    /* The Nuwa process */
    /* This provides the IPC service of loading Nuwa at the process.
     * The b2g process would send a IPC message of loading Nuwa
     * as the replacement of forking and executing plugin-container.
     */
    return XRE_ProcLoaderServiceRun(getppid(), childSock, argc, argv);
  }

  // The b2g process
  int childPid = pid;
  XRE_ProcLoaderClientInit(childPid, parentSock);
  return b2g_main(argc, argv);
}

/**
 * B2G Loader is responsible for loading the b2g process and the
 * Nuwa process.  It forks into the parent process, for the b2g
 * process, and the child process, for the Nuwa process.
 *
 * The loader loads libxul and performs initialization of static data
 * before forking, so relocation of libxul and static data can be
 * shared between the b2g process, the Nuwa process, and the content
 * processes.
 */
int
main(int argc, const char* argv[])
{
  const char *program = argv[0];
  /*
   * Before fork(), libxul and static data of Gecko are loaded for
   * sharing.
   */
  bool ok = LoadStaticData(program);
  if (!ok) {
    return 255;
  }

  return RunProcesses(argc, argv);
}