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/* -*- 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
#include "mozilla/Maybe.h"
#include "mozilla/Mutex.h"
#include "mozilla/UniquePtr.h"
#include <algorithm>
#include "PoisonIOInterposer.h"
#include "prlock.h"
#ifdef MOZ_REPLACE_MALLOC
# include "replace_malloc_bridge.h"
#endif
// Auxiliary method to convert file descriptors to ids
#if defined(XP_WIN)
# include <io.h>
inline mozilla::Maybe<intptr_t> FileDescriptorToHandle(int aFd) {
intptr_t handle = _get_osfhandle(aFd);
if ((handle == -1) || (handle == -2)) {
// -1: Invalid handle. -2: stdin/out/err not associated with a stream.
return mozilla::Nothing();
}
return mozilla::Some(handle);
}
#else
inline mozilla::Maybe<intptr_t> FileDescriptorToHandle(int aFd) {
return mozilla::Some<intptr_t>(aFd);
}
#endif /* if not XP_WIN */
namespace {
class DebugFilesAutoLock final {
public:
static PRLock* getDebugFileIDsLock() {
static PRLock* sLock = PR_NewLock();
return sLock;
}
DebugFilesAutoLock() { PR_Lock(getDebugFileIDsLock()); }
~DebugFilesAutoLock() { PR_Unlock(getDebugFileIDsLock()); }
};
// The ChunkedList<T> class implements, at the high level, a non-iterable
// list of instances of T. Its goal is to be somehow minimalist for the
// use case of storing the debug files handles here, with the property of
// not requiring a lock to look up whether it contains a specific value.
// It is also chunked in blocks of chunk_size bytes so that its
// initialization doesn't require a memory allocation, while keeping the
// possibility to increase its size as necessary. Note that chunks are
// never deallocated (except in the destructor).
// All operations are essentially O(N) but N is not expected to be large
// enough to matter.
template <typename T, size_t chunk_size = 64>
class ChunkedList {
struct ListChunk {
static const size_t kLength =
(chunk_size - sizeof(ListChunk*)) / sizeof(mozilla::Atomic<T>);
mozilla::Atomic<T> mElements[kLength];
mozilla::UniquePtr<ListChunk> mNext;
ListChunk() : mNext(nullptr) {}
};
ListChunk mList;
mozilla::Atomic<size_t> mLength;
public:
ChunkedList() : mLength(0) {}
~ChunkedList() {
// There can be writes happening after this destructor runs, so keep
// the list contents and don't reset mLength. But if there are more
// elements left than the first chunk can hold, then all hell breaks
// loose for any write that would happen after that because any extra
// chunk would be deallocated, so just crash in that case.
MOZ_RELEASE_ASSERT(mLength <= ListChunk::kLength);
}
// Add an element at the end of the last chunk of the list. Create a new
// chunk if there is not enough room.
// This is not thread-safe with another thread calling Add or Remove.
void Add(T aValue) {
ListChunk* list = &mList;
size_t position = mLength;
for (; position >= ListChunk::kLength; position -= ListChunk::kLength) {
if (!list->mNext) {
list->mNext.reset(new ListChunk());
}
list = list->mNext.get();
}
// Use an order of operations that ensures any racing Contains call
// can't be hurt.
list->mElements[position] = aValue;
mLength++;
}
// Remove an element from the list by replacing it with the last element
// of the list, and then shrinking the list.
// This is not thread-safe with another thread calling Add or Remove.
void Remove(T aValue) {
if (!mLength) {
return;
}
ListChunk* list = &mList;
size_t last = mLength - 1;
do {
size_t position = 0;
// Look for an element matching the given value.
for (; position < ListChunk::kLength; position++) {
if (aValue == list->mElements[position]) {
ListChunk* last_list = list;
// Look for the last element in the list, starting from where we are
// instead of starting over.
for (; last >= ListChunk::kLength; last -= ListChunk::kLength) {
last_list = last_list->mNext.get();
}
// Use an order of operations that ensures any racing Contains call
// can't be hurt.
T value = last_list->mElements[last];
list->mElements[position] = value;
mLength--;
return;
}
}
last -= ListChunk::kLength;
list = list->mNext.get();
} while (list);
}
// Returns whether the list contains the given value. It is meant to be safe
// to use without locking, with the tradeoff of being not entirely accurate
// if another thread adds or removes an element while this function runs.
bool Contains(T aValue) {
ListChunk* list = &mList;
// Fix the range of the lookup to whatever the list length is when the
// function is called.
size_t length = mLength;
do {
size_t list_length = ListChunk::kLength;
list_length = std::min(list_length, length);
for (size_t position = 0; position < list_length; position++) {
if (aValue == list->mElements[position]) {
return true;
}
}
length -= ListChunk::kLength;
list = list->mNext.get();
} while (list);
return false;
}
};
typedef ChunkedList<intptr_t> FdList;
// Return a list used to hold the IDs of the current debug files. On unix
// an ID is a file descriptor. On Windows it is a file HANDLE.
FdList& getDebugFileIDs() {
static FdList DebugFileIDs;
return DebugFileIDs;
}
} // namespace
namespace mozilla {
// Auxiliary Method to test if a file descriptor is registered to be ignored
// by the poisoning IO interposer
bool IsDebugFile(intptr_t aFileID) {
return getDebugFileIDs().Contains(aFileID);
}
} // namespace mozilla
extern "C" {
void MozillaRegisterDebugHandle(intptr_t aHandle) {
DebugFilesAutoLock lockedScope;
FdList& DebugFileIDs = getDebugFileIDs();
MOZ_ASSERT(!DebugFileIDs.Contains(aHandle));
DebugFileIDs.Add(aHandle);
}
void MozillaRegisterDebugFD(int aFd) {
mozilla::Maybe<intptr_t> handle = FileDescriptorToHandle(aFd);
if (!handle.isSome()) {
return;
}
MozillaRegisterDebugHandle(handle.value());
}
void MozillaRegisterDebugFILE(FILE* aFile) {
int fd = fileno(aFile);
if (fd == 1 || fd == 2) {
return;
}
MozillaRegisterDebugFD(fd);
}
void MozillaUnRegisterDebugHandle(intptr_t aHandle) {
DebugFilesAutoLock lockedScope;
FdList& DebugFileIDs = getDebugFileIDs();
MOZ_ASSERT(DebugFileIDs.Contains(aHandle));
DebugFileIDs.Remove(aHandle);
}
void MozillaUnRegisterDebugFD(int aFd) {
mozilla::Maybe<intptr_t> handle = FileDescriptorToHandle(aFd);
if (!handle.isSome()) {
return;
}
MozillaUnRegisterDebugHandle(handle.value());
}
void MozillaUnRegisterDebugFILE(FILE* aFile) {
int fd = fileno(aFile);
if (fd == 1 || fd == 2) {
return;
}
fflush(aFile);
MozillaUnRegisterDebugFD(fd);
}
} // extern "C"
#ifdef MOZ_REPLACE_MALLOC
void mozilla::DebugFdRegistry::RegisterHandle(intptr_t aHandle) {
MozillaRegisterDebugHandle(aHandle);
}
void mozilla::DebugFdRegistry::UnRegisterHandle(intptr_t aHandle) {
MozillaUnRegisterDebugHandle(aHandle);
}
#endif