gecko-dev/xpcom/build/PoisonIOInterposerMac.cpp

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C++

/* -*- 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"
#include "mach_override.h"
#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 "plstr.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 {
using namespace mozilla;
// 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 IOInterposeObserver API.
*/
class MacIOAutoObservation : public IOInterposeObserver::Observation
{
public:
MacIOAutoObservation(IOInterposeObserver::Operation aOp, int aFd)
: IOInterposeObserver::Observation(aOp, sReference, sIsEnabled &&
!IsDebugFile(aFd))
, mFd(aFd)
, mHasQueriedFilename(false)
, mFilename(nullptr)
{
}
MacIOAutoObservation(IOInterposeObserver::Operation aOp, int aFd,
const void* aBuf, size_t aCount)
: IOInterposeObserver::Observation(aOp, sReference, sIsEnabled &&
!IsDebugFile(aFd) &&
IsValidWrite(aFd, aBuf, aCount))
, mFd(aFd)
, mHasQueriedFilename(false)
, mFilename(nullptr)
{
}
// Custom implementation of IOInterposeObserver::Observation::Filename
const char16_t* Filename() override;
~MacIOAutoObservation()
{
Report();
if (mFilename) {
free(mFilename);
mFilename = nullptr;
}
}
private:
int mFd;
bool mHasQueriedFilename;
char16_t* mFilename;
static const char* sReference;
};
const char* MacIOAutoObservation::sReference = "PoisonIOInterposer";
// Get filename for this observation
const char16_t*
MacIOAutoObservation::Filename()
{
// If mHasQueriedFilename is true, then we already have it
if (mHasQueriedFilename) {
return mFilename;
}
char filename[MAXPATHLEN];
if (fcntl(mFd, F_GETPATH, filename) != -1) {
mFilename = UTF8ToNewUnicode(nsDependentCString(filename));
} else {
mFilename = nullptr;
}
mHasQueriedFilename = true;
// Return filename
return 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 = 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(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(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(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(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 = 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;
}
DebugOnly<mach_error_t> t = mach_override_ptr(d->Function, d->Wrapper,
&d->Buffer);
MOZ_ASSERT(t == err_none);
}
}
void
OnlyReportDirtyWrites()
{
sOnlyReportDirtyWrites = true;
}
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