path: root/xpcom/build/PoisonIOInterposerMac.cpp

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* 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 "PoisonIOInterposer.h"
// Disabled until bug 1658385 is fixed.
#ifndef __aarch64__
#  include "mach_override.h"
#endif

#include "mozilla/ArrayUtils.h"
#include "mozilla/Assertions.h"
#include "mozilla/DebugOnly.h"
#include "mozilla/IOInterposer.h"
#include "mozilla/Mutex.h"
#include "mozilla/ProcessedStack.h"
#include "mozilla/Telemetry.h"
#include "mozilla/UniquePtrExtensions.h"
#include "nsPrintfCString.h"
#include "mozilla/StackWalk.h"
#include "nsTraceRefcnt.h"
#include "prio.h"

#include <algorithm>
#include <vector>

#include <sys/param.h>
#include <sys/stat.h>
#include <sys/socket.h>
#include <sys/uio.h>
#include <aio.h>
#include <dlfcn.h>
#include <fcntl.h>
#include <unistd.h>

#ifdef MOZ_REPLACE_MALLOC
#  include "replace_malloc_bridge.h"
#endif

namespace {

// Bit tracking if poisoned writes are enabled
static bool sIsEnabled = false;

// Check if writes are dirty before reporting IO
static bool sOnlyReportDirtyWrites = false;

// Routines for write validation
bool IsValidWrite(int aFd, const void* aWbuf, size_t aCount);
bool IsIPCWrite(int aFd, const struct stat& aBuf);

/******************************** IO AutoTimer ********************************/

/**
 * RAII class for timing the duration of an I/O call and reporting the result
 * to the mozilla::IOInterposeObserver API.
 */
class MacIOAutoObservation : public mozilla::IOInterposeObserver::Observation {
 public:
  MacIOAutoObservation(mozilla::IOInterposeObserver::Operation aOp, int aFd)
      : mozilla::IOInterposeObserver::Observation(
            aOp, sReference, sIsEnabled && !mozilla::IsDebugFile(aFd)),
        mFd(aFd),
        mHasQueriedFilename(false) {}

  MacIOAutoObservation(mozilla::IOInterposeObserver::Operation aOp, int aFd,
                       const void* aBuf, size_t aCount)
      : mozilla::IOInterposeObserver::Observation(
            aOp, sReference,
            sIsEnabled && !mozilla::IsDebugFile(aFd) &&
                IsValidWrite(aFd, aBuf, aCount)),
        mFd(aFd),
        mHasQueriedFilename(false) {}

  // Custom implementation of
  // mozilla::IOInterposeObserver::Observation::Filename
  void Filename(nsAString& aFilename) override;

  ~MacIOAutoObservation() { Report(); }

 private:
  int mFd;
  bool mHasQueriedFilename;
  nsString mFilename;
  static const char* sReference;
};

const char* MacIOAutoObservation::sReference = "PoisonIOInterposer";

// Get filename for this observation
void MacIOAutoObservation::Filename(nsAString& aFilename) {
  // If mHasQueriedFilename is true, then we already have it
  if (mHasQueriedFilename) {
    aFilename = mFilename;
    return;
  }

  char filename[MAXPATHLEN];
  if (fcntl(mFd, F_GETPATH, filename) != -1) {
    CopyUTF8toUTF16(filename, mFilename);
  } else {
    mFilename.Truncate();
  }
  mHasQueriedFilename = true;

  aFilename = mFilename;
}

/****************************** Write Validation ******************************/

// We want to detect "actual" writes, not IPC. Some IPC mechanisms are
// implemented with file descriptors, so filter them out.
bool IsIPCWrite(int aFd, const struct stat& aBuf) {
  if ((aBuf.st_mode & S_IFMT) == S_IFIFO) {
    return true;
  }

  if ((aBuf.st_mode & S_IFMT) != S_IFSOCK) {
    return false;
  }

  sockaddr_storage address;
  socklen_t len = sizeof(address);
  if (getsockname(aFd, (sockaddr*)&address, &len) != 0) {
    return true;  // Ignore the aFd if we can't find what it is.
  }

  return address.ss_family == AF_UNIX;
}

// We want to report actual disk IO not things that don't move bits on the disk
bool IsValidWrite(int aFd, const void* aWbuf, size_t aCount) {
  // Ignore writes of zero bytes, Firefox does some during shutdown.
  if (aCount == 0) {
    return false;
  }

  {
    struct stat buf;
    int rv = fstat(aFd, &buf);
    if (rv != 0) {
      return true;
    }

    if (IsIPCWrite(aFd, buf)) {
      return false;
    }
  }

  // For writev we pass a nullptr aWbuf. We should only get here from
  // dbm, and it uses write, so assert that we have aWbuf.
  if (!aWbuf) {
    return true;
  }

  // Break, here if we're allowed to report non-dirty writes
  if (!sOnlyReportDirtyWrites) {
    return true;
  }

  // As a really bad hack, accept writes that don't change the on disk
  // content. This is needed because dbm doesn't keep track of dirty bits
  // and can end up writing the same data to disk twice. Once when the
  // user (nss) asks it to sync and once when closing the database.
  auto wbuf2 = mozilla::MakeUniqueFallible<char[]>(aCount);
  if (!wbuf2) {
    return true;
  }
  off_t pos = lseek(aFd, 0, SEEK_CUR);
  if (pos == -1) {
    return true;
  }
  ssize_t r = read(aFd, wbuf2.get(), aCount);
  if (r < 0 || (size_t)r != aCount) {
    return true;
  }
  int cmp = memcmp(aWbuf, wbuf2.get(), aCount);
  if (cmp != 0) {
    return true;
  }
  off_t pos2 = lseek(aFd, pos, SEEK_SET);
  if (pos2 != pos) {
    return true;
  }

  // Otherwise this is not a valid write
  return false;
}

/*************************** Function Interception  ***************************/

/** Structure for declaration of function override */
struct FuncData {
  const char* Name;     // Name of the function for the ones we use dlsym
  const void* Wrapper;  // The function that we will replace 'Function' with
  void* Function;       // The function that will be replaced with 'Wrapper'
  void* Buffer;         // Will point to the jump buffer that lets us call
                        // 'Function' after it has been replaced.
};

// Wrap aio_write. We have not seen it before, so just assert/report it.
typedef ssize_t (*aio_write_t)(struct aiocb* aAioCbp);
ssize_t wrap_aio_write(struct aiocb* aAioCbp);
FuncData aio_write_data = {0, (void*)wrap_aio_write, (void*)aio_write};
ssize_t wrap_aio_write(struct aiocb* aAioCbp) {
  MacIOAutoObservation timer(mozilla::IOInterposeObserver::OpWrite,
                             aAioCbp->aio_fildes);

  aio_write_t old_write = (aio_write_t)aio_write_data.Buffer;
  return old_write(aAioCbp);
}

// Wrap pwrite-like functions.
// We have not seen them before, so just assert/report it.
typedef ssize_t (*pwrite_t)(int aFd, const void* buf, size_t aNumBytes,
                            off_t aOffset);
template <FuncData& foo>
ssize_t wrap_pwrite_temp(int aFd, const void* aBuf, size_t aNumBytes,
                         off_t aOffset) {
  MacIOAutoObservation timer(mozilla::IOInterposeObserver::OpWrite, aFd);
  pwrite_t old_write = (pwrite_t)foo.Buffer;
  return old_write(aFd, aBuf, aNumBytes, aOffset);
}

// Define a FuncData for a pwrite-like functions.
#define DEFINE_PWRITE_DATA(X, NAME) \
  FuncData X##_data = {NAME, (void*)wrap_pwrite_temp<X##_data>};

// This exists everywhere.
DEFINE_PWRITE_DATA(pwrite, "pwrite")
// These exist on 32 bit OS X
DEFINE_PWRITE_DATA(pwrite_NOCANCEL_UNIX2003, "pwrite$NOCANCEL$UNIX2003");
DEFINE_PWRITE_DATA(pwrite_UNIX2003, "pwrite$UNIX2003");
// This exists on 64 bit OS X
DEFINE_PWRITE_DATA(pwrite_NOCANCEL, "pwrite$NOCANCEL");

typedef ssize_t (*writev_t)(int aFd, const struct iovec* aIov, int aIovCount);
template <FuncData& foo>
ssize_t wrap_writev_temp(int aFd, const struct iovec* aIov, int aIovCount) {
  MacIOAutoObservation timer(mozilla::IOInterposeObserver::OpWrite, aFd,
                             nullptr, aIovCount);
  writev_t old_write = (writev_t)foo.Buffer;
  return old_write(aFd, aIov, aIovCount);
}

// Define a FuncData for a writev-like functions.
#define DEFINE_WRITEV_DATA(X, NAME) \
  FuncData X##_data = {NAME, (void*)wrap_writev_temp<X##_data>};

// This exists everywhere.
DEFINE_WRITEV_DATA(writev, "writev");
// These exist on 32 bit OS X
DEFINE_WRITEV_DATA(writev_NOCANCEL_UNIX2003, "writev$NOCANCEL$UNIX2003");
DEFINE_WRITEV_DATA(writev_UNIX2003, "writev$UNIX2003");
// This exists on 64 bit OS X
DEFINE_WRITEV_DATA(writev_NOCANCEL, "writev$NOCANCEL");

typedef ssize_t (*write_t)(int aFd, const void* aBuf, size_t aCount);
template <FuncData& foo>
ssize_t wrap_write_temp(int aFd, const void* aBuf, size_t aCount) {
  MacIOAutoObservation timer(mozilla::IOInterposeObserver::OpWrite, aFd, aBuf,
                             aCount);
  write_t old_write = (write_t)foo.Buffer;
  return old_write(aFd, aBuf, aCount);
}

// Define a FuncData for a write-like functions.
#define DEFINE_WRITE_DATA(X, NAME) \
  FuncData X##_data = {NAME, (void*)wrap_write_temp<X##_data>};

// This exists everywhere.
DEFINE_WRITE_DATA(write, "write");
// These exist on 32 bit OS X
DEFINE_WRITE_DATA(write_NOCANCEL_UNIX2003, "write$NOCANCEL$UNIX2003");
DEFINE_WRITE_DATA(write_UNIX2003, "write$UNIX2003");
// This exists on 64 bit OS X
DEFINE_WRITE_DATA(write_NOCANCEL, "write$NOCANCEL");

FuncData* Functions[] = {&aio_write_data,

                         &pwrite_data,          &pwrite_NOCANCEL_UNIX2003_data,
                         &pwrite_UNIX2003_data, &pwrite_NOCANCEL_data,

                         &write_data,           &write_NOCANCEL_UNIX2003_data,
                         &write_UNIX2003_data,  &write_NOCANCEL_data,

                         &writev_data,          &writev_NOCANCEL_UNIX2003_data,
                         &writev_UNIX2003_data, &writev_NOCANCEL_data};

const int NumFunctions = mozilla::ArrayLength(Functions);

}  // namespace

/******************************** IO Poisoning ********************************/

namespace mozilla {

void InitPoisonIOInterposer() {
  // Enable reporting from poisoned write methods
  sIsEnabled = true;

  // Make sure we only poison writes once!
  static bool WritesArePoisoned = false;
  if (WritesArePoisoned) {
    return;
  }
  WritesArePoisoned = true;

  // stdout and stderr are OK.
  MozillaRegisterDebugFD(1);
  MozillaRegisterDebugFD(2);

#ifdef MOZ_REPLACE_MALLOC
  // The contract with InitDebugFd is that the given registry can be used
  // at any moment, so the instance needs to persist longer than the scope
  // of this functions.
  static DebugFdRegistry registry;
  ReplaceMalloc::InitDebugFd(registry);
#endif

  for (int i = 0; i < NumFunctions; ++i) {
    FuncData* d = Functions[i];
    if (!d->Function) {
      d->Function = dlsym(RTLD_DEFAULT, d->Name);
    }
    if (!d->Function) {
      continue;
    }

    // Disable the interposer on arm64 until there's
    // a mach_override_ptr implementation.
#ifndef __aarch64__
    // Temporarily disable the interposer on macOS x64
    // while dynamic code disablement rides the trains.
#  ifdef MOZ_INTERPOSER_FORCE_MACOS_X64
    DebugOnly<mach_error_t> t =
        mach_override_ptr(d->Function, d->Wrapper, &d->Buffer);
    MOZ_ASSERT(t == err_none);
#  endif  // MOZ_INTERPOSER_FORCE_MACOS_X64
#endif
  }
}

void OnlyReportDirtyWrites() { sOnlyReportDirtyWrites = true; }

// Never called! See bug 1647107.
void ClearPoisonIOInterposer() {
  // Not sure how or if we can unpoison the functions. Would be nice, but no
  // worries we won't need to do this anyway.
  sIsEnabled = false;
}

}  // namespace mozilla