llvm-6502/lib/Support/MemoryBuffer.cpp
Argyrios Kyrtzidis 541b2a4aa3 In MemoryBuffer::getOpenFile() make sure that the buffer is null-terminated if
the caller requested a null-terminated one.

When mapping the file there could be a racing issue that resulted in the file being larger
than the FileSize passed by the caller. We already have an assertion
for this in MemoryBuffer::init() but have a runtime guarantee that
the buffer will be null-terminated, so do a copy that adds a null-terminator.

Protects against crash of rdar://11161822.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@154082 91177308-0d34-0410-b5e6-96231b3b80d8
2012-04-05 04:23:56 +00:00

391 lines
14 KiB
C++

//===--- MemoryBuffer.cpp - Memory Buffer implementation ------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the MemoryBuffer interface.
//
//===----------------------------------------------------------------------===//
#include "llvm/Support/MemoryBuffer.h"
#include "llvm/ADT/OwningPtr.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/Config/config.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/Errno.h"
#include "llvm/Support/Path.h"
#include "llvm/Support/Process.h"
#include "llvm/Support/Program.h"
#include "llvm/Support/system_error.h"
#include <cassert>
#include <cstdio>
#include <cstring>
#include <cerrno>
#include <new>
#include <sys/types.h>
#include <sys/stat.h>
#if !defined(_MSC_VER) && !defined(__MINGW32__)
#include <unistd.h>
#else
#include <io.h>
#endif
#include <fcntl.h>
using namespace llvm;
//===----------------------------------------------------------------------===//
// MemoryBuffer implementation itself.
//===----------------------------------------------------------------------===//
MemoryBuffer::~MemoryBuffer() { }
/// init - Initialize this MemoryBuffer as a reference to externally allocated
/// memory, memory that we know is already null terminated.
void MemoryBuffer::init(const char *BufStart, const char *BufEnd,
bool RequiresNullTerminator) {
assert((!RequiresNullTerminator || BufEnd[0] == 0) &&
"Buffer is not null terminated!");
BufferStart = BufStart;
BufferEnd = BufEnd;
}
//===----------------------------------------------------------------------===//
// MemoryBufferMem implementation.
//===----------------------------------------------------------------------===//
/// CopyStringRef - Copies contents of a StringRef into a block of memory and
/// null-terminates it.
static void CopyStringRef(char *Memory, StringRef Data) {
memcpy(Memory, Data.data(), Data.size());
Memory[Data.size()] = 0; // Null terminate string.
}
/// GetNamedBuffer - Allocates a new MemoryBuffer with Name copied after it.
template <typename T>
static T *GetNamedBuffer(StringRef Buffer, StringRef Name,
bool RequiresNullTerminator) {
char *Mem = static_cast<char*>(operator new(sizeof(T) + Name.size() + 1));
CopyStringRef(Mem + sizeof(T), Name);
return new (Mem) T(Buffer, RequiresNullTerminator);
}
namespace {
/// MemoryBufferMem - Named MemoryBuffer pointing to a block of memory.
class MemoryBufferMem : public MemoryBuffer {
public:
MemoryBufferMem(StringRef InputData, bool RequiresNullTerminator) {
init(InputData.begin(), InputData.end(), RequiresNullTerminator);
}
virtual const char *getBufferIdentifier() const {
// The name is stored after the class itself.
return reinterpret_cast<const char*>(this + 1);
}
virtual BufferKind getBufferKind() const {
return MemoryBuffer_Malloc;
}
};
}
/// getMemBuffer - Open the specified memory range as a MemoryBuffer. Note
/// that InputData must be a null terminated if RequiresNullTerminator is true!
MemoryBuffer *MemoryBuffer::getMemBuffer(StringRef InputData,
StringRef BufferName,
bool RequiresNullTerminator) {
return GetNamedBuffer<MemoryBufferMem>(InputData, BufferName,
RequiresNullTerminator);
}
/// getMemBufferCopy - Open the specified memory range as a MemoryBuffer,
/// copying the contents and taking ownership of it. This has no requirements
/// on EndPtr[0].
MemoryBuffer *MemoryBuffer::getMemBufferCopy(StringRef InputData,
StringRef BufferName) {
MemoryBuffer *Buf = getNewUninitMemBuffer(InputData.size(), BufferName);
if (!Buf) return 0;
memcpy(const_cast<char*>(Buf->getBufferStart()), InputData.data(),
InputData.size());
return Buf;
}
/// getNewUninitMemBuffer - Allocate a new MemoryBuffer of the specified size
/// that is not initialized. Note that the caller should initialize the
/// memory allocated by this method. The memory is owned by the MemoryBuffer
/// object.
MemoryBuffer *MemoryBuffer::getNewUninitMemBuffer(size_t Size,
StringRef BufferName) {
// Allocate space for the MemoryBuffer, the data and the name. It is important
// that MemoryBuffer and data are aligned so PointerIntPair works with them.
size_t AlignedStringLen =
RoundUpToAlignment(sizeof(MemoryBufferMem) + BufferName.size() + 1,
sizeof(void*)); // TODO: Is sizeof(void*) enough?
size_t RealLen = AlignedStringLen + Size + 1;
char *Mem = static_cast<char*>(operator new(RealLen, std::nothrow));
if (!Mem) return 0;
// The name is stored after the class itself.
CopyStringRef(Mem + sizeof(MemoryBufferMem), BufferName);
// The buffer begins after the name and must be aligned.
char *Buf = Mem + AlignedStringLen;
Buf[Size] = 0; // Null terminate buffer.
return new (Mem) MemoryBufferMem(StringRef(Buf, Size), true);
}
/// getNewMemBuffer - Allocate a new MemoryBuffer of the specified size that
/// is completely initialized to zeros. Note that the caller should
/// initialize the memory allocated by this method. The memory is owned by
/// the MemoryBuffer object.
MemoryBuffer *MemoryBuffer::getNewMemBuffer(size_t Size, StringRef BufferName) {
MemoryBuffer *SB = getNewUninitMemBuffer(Size, BufferName);
if (!SB) return 0;
memset(const_cast<char*>(SB->getBufferStart()), 0, Size);
return SB;
}
/// getFileOrSTDIN - Open the specified file as a MemoryBuffer, or open stdin
/// if the Filename is "-". If an error occurs, this returns null and fills
/// in *ErrStr with a reason. If stdin is empty, this API (unlike getSTDIN)
/// returns an empty buffer.
error_code MemoryBuffer::getFileOrSTDIN(StringRef Filename,
OwningPtr<MemoryBuffer> &result,
int64_t FileSize) {
if (Filename == "-")
return getSTDIN(result);
return getFile(Filename, result, FileSize);
}
error_code MemoryBuffer::getFileOrSTDIN(const char *Filename,
OwningPtr<MemoryBuffer> &result,
int64_t FileSize) {
if (strcmp(Filename, "-") == 0)
return getSTDIN(result);
return getFile(Filename, result, FileSize);
}
//===----------------------------------------------------------------------===//
// MemoryBuffer::getFile implementation.
//===----------------------------------------------------------------------===//
namespace {
/// MemoryBufferMMapFile - This represents a file that was mapped in with the
/// sys::Path::MapInFilePages method. When destroyed, it calls the
/// sys::Path::UnMapFilePages method.
class MemoryBufferMMapFile : public MemoryBufferMem {
public:
MemoryBufferMMapFile(StringRef Buffer, bool RequiresNullTerminator)
: MemoryBufferMem(Buffer, RequiresNullTerminator) { }
~MemoryBufferMMapFile() {
static int PageSize = sys::Process::GetPageSize();
uintptr_t Start = reinterpret_cast<uintptr_t>(getBufferStart());
size_t Size = getBufferSize();
uintptr_t RealStart = Start & ~(PageSize - 1);
size_t RealSize = Size + (Start - RealStart);
sys::Path::UnMapFilePages(reinterpret_cast<const char*>(RealStart),
RealSize);
}
virtual BufferKind getBufferKind() const {
return MemoryBuffer_MMap;
}
};
}
error_code MemoryBuffer::getFile(StringRef Filename,
OwningPtr<MemoryBuffer> &result,
int64_t FileSize,
bool RequiresNullTerminator) {
// Ensure the path is null terminated.
SmallString<256> PathBuf(Filename.begin(), Filename.end());
return MemoryBuffer::getFile(PathBuf.c_str(), result, FileSize,
RequiresNullTerminator);
}
error_code MemoryBuffer::getFile(const char *Filename,
OwningPtr<MemoryBuffer> &result,
int64_t FileSize,
bool RequiresNullTerminator) {
int OpenFlags = O_RDONLY;
#ifdef O_BINARY
OpenFlags |= O_BINARY; // Open input file in binary mode on win32.
#endif
int FD = ::open(Filename, OpenFlags);
if (FD == -1)
return error_code(errno, posix_category());
error_code ret = getOpenFile(FD, Filename, result, FileSize, FileSize,
0, RequiresNullTerminator);
close(FD);
return ret;
}
static bool shouldUseMmap(int FD,
size_t FileSize,
size_t MapSize,
off_t Offset,
bool RequiresNullTerminator,
int PageSize) {
// We don't use mmap for small files because this can severely fragment our
// address space.
if (MapSize < 4096*4)
return false;
if (!RequiresNullTerminator)
return true;
// If we don't know the file size, use fstat to find out. fstat on an open
// file descriptor is cheaper than stat on a random path.
// FIXME: this chunk of code is duplicated, but it avoids a fstat when
// RequiresNullTerminator = false and MapSize != -1.
if (FileSize == size_t(-1)) {
struct stat FileInfo;
// TODO: This should use fstat64 when available.
if (fstat(FD, &FileInfo) == -1) {
return error_code(errno, posix_category());
}
FileSize = FileInfo.st_size;
}
// If we need a null terminator and the end of the map is inside the file,
// we cannot use mmap.
size_t End = Offset + MapSize;
assert(End <= FileSize);
if (End != FileSize)
return false;
// Don't try to map files that are exactly a multiple of the system page size
// if we need a null terminator.
if ((FileSize & (PageSize -1)) == 0)
return false;
return true;
}
error_code MemoryBuffer::getOpenFile(int FD, const char *Filename,
OwningPtr<MemoryBuffer> &result,
uint64_t FileSize, uint64_t MapSize,
int64_t Offset,
bool RequiresNullTerminator) {
static int PageSize = sys::Process::GetPageSize();
// Default is to map the full file.
if (MapSize == uint64_t(-1)) {
// If we don't know the file size, use fstat to find out. fstat on an open
// file descriptor is cheaper than stat on a random path.
if (FileSize == uint64_t(-1)) {
struct stat FileInfo;
// TODO: This should use fstat64 when available.
if (fstat(FD, &FileInfo) == -1) {
return error_code(errno, posix_category());
}
FileSize = FileInfo.st_size;
}
MapSize = FileSize;
}
if (shouldUseMmap(FD, FileSize, MapSize, Offset, RequiresNullTerminator,
PageSize)) {
off_t RealMapOffset = Offset & ~(PageSize - 1);
off_t Delta = Offset - RealMapOffset;
size_t RealMapSize = MapSize + Delta;
if (const char *Pages = sys::Path::MapInFilePages(FD,
RealMapSize,
RealMapOffset)) {
result.reset(GetNamedBuffer<MemoryBufferMMapFile>(
StringRef(Pages + Delta, MapSize), Filename, RequiresNullTerminator));
if (RequiresNullTerminator && result->getBufferEnd()[0] != '\0') {
// There could be a racing issue that resulted in the file being larger
// than the FileSize passed by the caller. We already have an assertion
// for this in MemoryBuffer::init() but have a runtime guarantee that
// the buffer will be null-terminated here, so do a copy that adds a
// null-terminator.
result.reset(MemoryBuffer::getMemBufferCopy(result->getBuffer(),
Filename));
}
return error_code::success();
}
}
MemoryBuffer *Buf = MemoryBuffer::getNewUninitMemBuffer(MapSize, Filename);
if (!Buf) {
// Failed to create a buffer. The only way it can fail is if
// new(std::nothrow) returns 0.
return make_error_code(errc::not_enough_memory);
}
OwningPtr<MemoryBuffer> SB(Buf);
char *BufPtr = const_cast<char*>(SB->getBufferStart());
size_t BytesLeft = MapSize;
#ifndef HAVE_PREAD
if (lseek(FD, Offset, SEEK_SET) == -1)
return error_code(errno, posix_category());
#endif
while (BytesLeft) {
#ifdef HAVE_PREAD
ssize_t NumRead = ::pread(FD, BufPtr, BytesLeft, MapSize-BytesLeft+Offset);
#else
ssize_t NumRead = ::read(FD, BufPtr, BytesLeft);
#endif
if (NumRead == -1) {
if (errno == EINTR)
continue;
// Error while reading.
return error_code(errno, posix_category());
}
if (NumRead == 0) {
assert(0 && "We got inaccurate FileSize value or fstat reported an "
"invalid file size.");
*BufPtr = '\0'; // null-terminate at the actual size.
break;
}
BytesLeft -= NumRead;
BufPtr += NumRead;
}
result.swap(SB);
return error_code::success();
}
//===----------------------------------------------------------------------===//
// MemoryBuffer::getSTDIN implementation.
//===----------------------------------------------------------------------===//
error_code MemoryBuffer::getSTDIN(OwningPtr<MemoryBuffer> &result) {
// Read in all of the data from stdin, we cannot mmap stdin.
//
// FIXME: That isn't necessarily true, we should try to mmap stdin and
// fallback if it fails.
sys::Program::ChangeStdinToBinary();
const ssize_t ChunkSize = 4096*4;
SmallString<ChunkSize> Buffer;
ssize_t ReadBytes;
// Read into Buffer until we hit EOF.
do {
Buffer.reserve(Buffer.size() + ChunkSize);
ReadBytes = read(0, Buffer.end(), ChunkSize);
if (ReadBytes == -1) {
if (errno == EINTR) continue;
return error_code(errno, posix_category());
}
Buffer.set_size(Buffer.size() + ReadBytes);
} while (ReadBytes != 0);
result.reset(getMemBufferCopy(Buffer, "<stdin>"));
return error_code::success();
}