1 //===--- MemoryBuffer.cpp - Memory Buffer implementation ------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 //  This file implements the MemoryBuffer interface.
10 //
11 //===----------------------------------------------------------------------===//
12 
13 #include "llvm/Support/MemoryBuffer.h"
14 #include "llvm/ADT/SmallString.h"
15 #include "llvm/Config/config.h"
16 #include "llvm/Support/AutoConvert.h"
17 #include "llvm/Support/Error.h"
18 #include "llvm/Support/ErrorHandling.h"
19 #include "llvm/Support/Errc.h"
20 #include "llvm/Support/FileSystem.h"
21 #include "llvm/Support/MathExtras.h"
22 #include "llvm/Support/Process.h"
23 #include "llvm/Support/Program.h"
24 #include "llvm/Support/SmallVectorMemoryBuffer.h"
25 #include <cassert>
26 #include <cstring>
27 #include <new>
28 #include <sys/types.h>
29 #include <system_error>
30 #if !defined(_MSC_VER) && !defined(__MINGW32__)
31 #include <unistd.h>
32 #else
33 #include <io.h>
34 #endif
35 using namespace llvm;
36 
37 //===----------------------------------------------------------------------===//
38 // MemoryBuffer implementation itself.
39 //===----------------------------------------------------------------------===//
40 
41 MemoryBuffer::~MemoryBuffer() { }
42 
43 /// init - Initialize this MemoryBuffer as a reference to externally allocated
44 /// memory, memory that we know is already null terminated.
45 void MemoryBuffer::init(const char *BufStart, const char *BufEnd,
46                         bool RequiresNullTerminator) {
47   assert((!RequiresNullTerminator || BufEnd[0] == 0) &&
48          "Buffer is not null terminated!");
49   BufferStart = BufStart;
50   BufferEnd = BufEnd;
51 }
52 
53 //===----------------------------------------------------------------------===//
54 // MemoryBufferMem implementation.
55 //===----------------------------------------------------------------------===//
56 
57 /// CopyStringRef - Copies contents of a StringRef into a block of memory and
58 /// null-terminates it.
59 static void CopyStringRef(char *Memory, StringRef Data) {
60   if (!Data.empty())
61     memcpy(Memory, Data.data(), Data.size());
62   Memory[Data.size()] = 0; // Null terminate string.
63 }
64 
65 namespace {
66 struct NamedBufferAlloc {
67   const Twine &Name;
68   NamedBufferAlloc(const Twine &Name) : Name(Name) {}
69 };
70 } // namespace
71 
72 void *operator new(size_t N, const NamedBufferAlloc &Alloc) {
73   SmallString<256> NameBuf;
74   StringRef NameRef = Alloc.Name.toStringRef(NameBuf);
75 
76   char *Mem = static_cast<char *>(operator new(N + NameRef.size() + 1));
77   CopyStringRef(Mem + N, NameRef);
78   return Mem;
79 }
80 
81 namespace {
82 /// MemoryBufferMem - Named MemoryBuffer pointing to a block of memory.
83 template<typename MB>
84 class MemoryBufferMem : public MB {
85 public:
86   MemoryBufferMem(StringRef InputData, bool RequiresNullTerminator) {
87     MemoryBuffer::init(InputData.begin(), InputData.end(),
88                        RequiresNullTerminator);
89   }
90 
91   /// Disable sized deallocation for MemoryBufferMem, because it has
92   /// tail-allocated data.
93   void operator delete(void *p) { ::operator delete(p); }
94 
95   StringRef getBufferIdentifier() const override {
96     // The name is stored after the class itself.
97     return StringRef(reinterpret_cast<const char *>(this + 1));
98   }
99 
100   MemoryBuffer::BufferKind getBufferKind() const override {
101     return MemoryBuffer::MemoryBuffer_Malloc;
102   }
103 };
104 } // namespace
105 
106 template <typename MB>
107 static ErrorOr<std::unique_ptr<MB>>
108 getFileAux(const Twine &Filename, uint64_t MapSize, uint64_t Offset,
109            bool IsText, bool RequiresNullTerminator, bool IsVolatile);
110 
111 std::unique_ptr<MemoryBuffer>
112 MemoryBuffer::getMemBuffer(StringRef InputData, StringRef BufferName,
113                            bool RequiresNullTerminator) {
114   auto *Ret = new (NamedBufferAlloc(BufferName))
115       MemoryBufferMem<MemoryBuffer>(InputData, RequiresNullTerminator);
116   return std::unique_ptr<MemoryBuffer>(Ret);
117 }
118 
119 std::unique_ptr<MemoryBuffer>
120 MemoryBuffer::getMemBuffer(MemoryBufferRef Ref, bool RequiresNullTerminator) {
121   return std::unique_ptr<MemoryBuffer>(getMemBuffer(
122       Ref.getBuffer(), Ref.getBufferIdentifier(), RequiresNullTerminator));
123 }
124 
125 static ErrorOr<std::unique_ptr<WritableMemoryBuffer>>
126 getMemBufferCopyImpl(StringRef InputData, const Twine &BufferName) {
127   auto Buf = WritableMemoryBuffer::getNewUninitMemBuffer(InputData.size(), BufferName);
128   if (!Buf)
129     return make_error_code(errc::not_enough_memory);
130   memcpy(Buf->getBufferStart(), InputData.data(), InputData.size());
131   return std::move(Buf);
132 }
133 
134 std::unique_ptr<MemoryBuffer>
135 MemoryBuffer::getMemBufferCopy(StringRef InputData, const Twine &BufferName) {
136   auto Buf = getMemBufferCopyImpl(InputData, BufferName);
137   if (Buf)
138     return std::move(*Buf);
139   return nullptr;
140 }
141 
142 ErrorOr<std::unique_ptr<MemoryBuffer>>
143 MemoryBuffer::getFileOrSTDIN(const Twine &Filename, bool IsText,
144                              bool RequiresNullTerminator) {
145   SmallString<256> NameBuf;
146   StringRef NameRef = Filename.toStringRef(NameBuf);
147 
148   if (NameRef == "-")
149     return getSTDIN();
150   return getFile(Filename, IsText, RequiresNullTerminator,
151                  /*IsVolatile=*/false);
152 }
153 
154 ErrorOr<std::unique_ptr<MemoryBuffer>>
155 MemoryBuffer::getFileSlice(const Twine &FilePath, uint64_t MapSize,
156                            uint64_t Offset, bool IsVolatile) {
157   return getFileAux<MemoryBuffer>(FilePath, MapSize, Offset, /*IsText=*/false,
158                                   /*RequiresNullTerminator=*/false, IsVolatile);
159 }
160 
161 //===----------------------------------------------------------------------===//
162 // MemoryBuffer::getFile implementation.
163 //===----------------------------------------------------------------------===//
164 
165 namespace {
166 
167 template <typename MB>
168 constexpr sys::fs::mapped_file_region::mapmode Mapmode =
169     sys::fs::mapped_file_region::readonly;
170 template <>
171 constexpr sys::fs::mapped_file_region::mapmode Mapmode<MemoryBuffer> =
172     sys::fs::mapped_file_region::readonly;
173 template <>
174 constexpr sys::fs::mapped_file_region::mapmode Mapmode<WritableMemoryBuffer> =
175     sys::fs::mapped_file_region::priv;
176 template <>
177 constexpr sys::fs::mapped_file_region::mapmode
178     Mapmode<WriteThroughMemoryBuffer> = sys::fs::mapped_file_region::readwrite;
179 
180 /// Memory maps a file descriptor using sys::fs::mapped_file_region.
181 ///
182 /// This handles converting the offset into a legal offset on the platform.
183 template<typename MB>
184 class MemoryBufferMMapFile : public MB {
185   sys::fs::mapped_file_region MFR;
186 
187   static uint64_t getLegalMapOffset(uint64_t Offset) {
188     return Offset & ~(sys::fs::mapped_file_region::alignment() - 1);
189   }
190 
191   static uint64_t getLegalMapSize(uint64_t Len, uint64_t Offset) {
192     return Len + (Offset - getLegalMapOffset(Offset));
193   }
194 
195   const char *getStart(uint64_t Len, uint64_t Offset) {
196     return MFR.const_data() + (Offset - getLegalMapOffset(Offset));
197   }
198 
199 public:
200   MemoryBufferMMapFile(bool RequiresNullTerminator, sys::fs::file_t FD, uint64_t Len,
201                        uint64_t Offset, std::error_code &EC)
202       : MFR(FD, Mapmode<MB>, getLegalMapSize(Len, Offset),
203             getLegalMapOffset(Offset), EC) {
204     if (!EC) {
205       const char *Start = getStart(Len, Offset);
206       MemoryBuffer::init(Start, Start + Len, RequiresNullTerminator);
207     }
208   }
209 
210   /// Disable sized deallocation for MemoryBufferMMapFile, because it has
211   /// tail-allocated data.
212   void operator delete(void *p) { ::operator delete(p); }
213 
214   StringRef getBufferIdentifier() const override {
215     // The name is stored after the class itself.
216     return StringRef(reinterpret_cast<const char *>(this + 1));
217   }
218 
219   MemoryBuffer::BufferKind getBufferKind() const override {
220     return MemoryBuffer::MemoryBuffer_MMap;
221   }
222 
223   void dontNeedIfMmap() override { MFR.dontNeed(); }
224 };
225 } // namespace
226 
227 static ErrorOr<std::unique_ptr<WritableMemoryBuffer>>
228 getMemoryBufferForStream(sys::fs::file_t FD, const Twine &BufferName) {
229   SmallString<sys::fs::DefaultReadChunkSize> Buffer;
230   if (Error E = sys::fs::readNativeFileToEOF(FD, Buffer))
231     return errorToErrorCode(std::move(E));
232   return getMemBufferCopyImpl(Buffer, BufferName);
233 }
234 
235 ErrorOr<std::unique_ptr<MemoryBuffer>>
236 MemoryBuffer::getFile(const Twine &Filename, bool IsText,
237                       bool RequiresNullTerminator, bool IsVolatile) {
238   return getFileAux<MemoryBuffer>(Filename, /*MapSize=*/-1, /*Offset=*/0,
239                                   IsText, RequiresNullTerminator, IsVolatile);
240 }
241 
242 template <typename MB>
243 static ErrorOr<std::unique_ptr<MB>>
244 getOpenFileImpl(sys::fs::file_t FD, const Twine &Filename, uint64_t FileSize,
245                 uint64_t MapSize, int64_t Offset, bool RequiresNullTerminator,
246                 bool IsVolatile);
247 
248 template <typename MB>
249 static ErrorOr<std::unique_ptr<MB>>
250 getFileAux(const Twine &Filename, uint64_t MapSize, uint64_t Offset,
251            bool IsText, bool RequiresNullTerminator, bool IsVolatile) {
252   Expected<sys::fs::file_t> FDOrErr = sys::fs::openNativeFileForRead(
253       Filename, IsText ? sys::fs::OF_TextWithCRLF : sys::fs::OF_None);
254   if (!FDOrErr)
255     return errorToErrorCode(FDOrErr.takeError());
256   sys::fs::file_t FD = *FDOrErr;
257   auto Ret = getOpenFileImpl<MB>(FD, Filename, /*FileSize=*/-1, MapSize, Offset,
258                                  RequiresNullTerminator, IsVolatile);
259   sys::fs::closeFile(FD);
260   return Ret;
261 }
262 
263 ErrorOr<std::unique_ptr<WritableMemoryBuffer>>
264 WritableMemoryBuffer::getFile(const Twine &Filename, bool IsVolatile) {
265   return getFileAux<WritableMemoryBuffer>(
266       Filename, /*MapSize=*/-1, /*Offset=*/0, /*IsText=*/false,
267       /*RequiresNullTerminator=*/false, IsVolatile);
268 }
269 
270 ErrorOr<std::unique_ptr<WritableMemoryBuffer>>
271 WritableMemoryBuffer::getFileSlice(const Twine &Filename, uint64_t MapSize,
272                                    uint64_t Offset, bool IsVolatile) {
273   return getFileAux<WritableMemoryBuffer>(
274       Filename, MapSize, Offset, /*IsText=*/false,
275       /*RequiresNullTerminator=*/false, IsVolatile);
276 }
277 
278 std::unique_ptr<WritableMemoryBuffer>
279 WritableMemoryBuffer::getNewUninitMemBuffer(size_t Size, const Twine &BufferName) {
280   using MemBuffer = MemoryBufferMem<WritableMemoryBuffer>;
281   // Allocate space for the MemoryBuffer, the data and the name. It is important
282   // that MemoryBuffer and data are aligned so PointerIntPair works with them.
283   // TODO: Is 16-byte alignment enough?  We copy small object files with large
284   // alignment expectations into this buffer.
285   SmallString<256> NameBuf;
286   StringRef NameRef = BufferName.toStringRef(NameBuf);
287   size_t AlignedStringLen = alignTo(sizeof(MemBuffer) + NameRef.size() + 1, 16);
288   size_t RealLen = AlignedStringLen + Size + 1;
289   char *Mem = static_cast<char*>(operator new(RealLen, std::nothrow));
290   if (!Mem)
291     return nullptr;
292 
293   // The name is stored after the class itself.
294   CopyStringRef(Mem + sizeof(MemBuffer), NameRef);
295 
296   // The buffer begins after the name and must be aligned.
297   char *Buf = Mem + AlignedStringLen;
298   Buf[Size] = 0; // Null terminate buffer.
299 
300   auto *Ret = new (Mem) MemBuffer(StringRef(Buf, Size), true);
301   return std::unique_ptr<WritableMemoryBuffer>(Ret);
302 }
303 
304 std::unique_ptr<WritableMemoryBuffer>
305 WritableMemoryBuffer::getNewMemBuffer(size_t Size, const Twine &BufferName) {
306   auto SB = WritableMemoryBuffer::getNewUninitMemBuffer(Size, BufferName);
307   if (!SB)
308     return nullptr;
309   memset(SB->getBufferStart(), 0, Size);
310   return SB;
311 }
312 
313 static bool shouldUseMmap(sys::fs::file_t FD,
314                           size_t FileSize,
315                           size_t MapSize,
316                           off_t Offset,
317                           bool RequiresNullTerminator,
318                           int PageSize,
319                           bool IsVolatile) {
320   // mmap may leave the buffer without null terminator if the file size changed
321   // by the time the last page is mapped in, so avoid it if the file size is
322   // likely to change.
323   if (IsVolatile && RequiresNullTerminator)
324     return false;
325 
326   // We don't use mmap for small files because this can severely fragment our
327   // address space.
328   if (MapSize < 4 * 4096 || MapSize < (unsigned)PageSize)
329     return false;
330 
331   if (!RequiresNullTerminator)
332     return true;
333 
334   // If we don't know the file size, use fstat to find out.  fstat on an open
335   // file descriptor is cheaper than stat on a random path.
336   // FIXME: this chunk of code is duplicated, but it avoids a fstat when
337   // RequiresNullTerminator = false and MapSize != -1.
338   if (FileSize == size_t(-1)) {
339     sys::fs::file_status Status;
340     if (sys::fs::status(FD, Status))
341       return false;
342     FileSize = Status.getSize();
343   }
344 
345   // If we need a null terminator and the end of the map is inside the file,
346   // we cannot use mmap.
347   size_t End = Offset + MapSize;
348   assert(End <= FileSize);
349   if (End != FileSize)
350     return false;
351 
352   // Don't try to map files that are exactly a multiple of the system page size
353   // if we need a null terminator.
354   if ((FileSize & (PageSize -1)) == 0)
355     return false;
356 
357 #if defined(__CYGWIN__)
358   // Don't try to map files that are exactly a multiple of the physical page size
359   // if we need a null terminator.
360   // FIXME: We should reorganize again getPageSize() on Win32.
361   if ((FileSize & (4096 - 1)) == 0)
362     return false;
363 #endif
364 
365   return true;
366 }
367 
368 static ErrorOr<std::unique_ptr<WriteThroughMemoryBuffer>>
369 getReadWriteFile(const Twine &Filename, uint64_t FileSize, uint64_t MapSize,
370                  uint64_t Offset) {
371   Expected<sys::fs::file_t> FDOrErr = sys::fs::openNativeFileForReadWrite(
372       Filename, sys::fs::CD_OpenExisting, sys::fs::OF_None);
373   if (!FDOrErr)
374     return errorToErrorCode(FDOrErr.takeError());
375   sys::fs::file_t FD = *FDOrErr;
376 
377   // Default is to map the full file.
378   if (MapSize == uint64_t(-1)) {
379     // If we don't know the file size, use fstat to find out.  fstat on an open
380     // file descriptor is cheaper than stat on a random path.
381     if (FileSize == uint64_t(-1)) {
382       sys::fs::file_status Status;
383       std::error_code EC = sys::fs::status(FD, Status);
384       if (EC)
385         return EC;
386 
387       // If this not a file or a block device (e.g. it's a named pipe
388       // or character device), we can't mmap it, so error out.
389       sys::fs::file_type Type = Status.type();
390       if (Type != sys::fs::file_type::regular_file &&
391           Type != sys::fs::file_type::block_file)
392         return make_error_code(errc::invalid_argument);
393 
394       FileSize = Status.getSize();
395     }
396     MapSize = FileSize;
397   }
398 
399   std::error_code EC;
400   std::unique_ptr<WriteThroughMemoryBuffer> Result(
401       new (NamedBufferAlloc(Filename))
402           MemoryBufferMMapFile<WriteThroughMemoryBuffer>(false, FD, MapSize,
403                                                          Offset, EC));
404   if (EC)
405     return EC;
406   return std::move(Result);
407 }
408 
409 ErrorOr<std::unique_ptr<WriteThroughMemoryBuffer>>
410 WriteThroughMemoryBuffer::getFile(const Twine &Filename, int64_t FileSize) {
411   return getReadWriteFile(Filename, FileSize, FileSize, 0);
412 }
413 
414 /// Map a subrange of the specified file as a WritableMemoryBuffer.
415 ErrorOr<std::unique_ptr<WriteThroughMemoryBuffer>>
416 WriteThroughMemoryBuffer::getFileSlice(const Twine &Filename, uint64_t MapSize,
417                                        uint64_t Offset) {
418   return getReadWriteFile(Filename, -1, MapSize, Offset);
419 }
420 
421 template <typename MB>
422 static ErrorOr<std::unique_ptr<MB>>
423 getOpenFileImpl(sys::fs::file_t FD, const Twine &Filename, uint64_t FileSize,
424                 uint64_t MapSize, int64_t Offset, bool RequiresNullTerminator,
425                 bool IsVolatile) {
426   static int PageSize = sys::Process::getPageSizeEstimate();
427 
428   // Default is to map the full file.
429   if (MapSize == uint64_t(-1)) {
430     // If we don't know the file size, use fstat to find out.  fstat on an open
431     // file descriptor is cheaper than stat on a random path.
432     if (FileSize == uint64_t(-1)) {
433       sys::fs::file_status Status;
434       std::error_code EC = sys::fs::status(FD, Status);
435       if (EC)
436         return EC;
437 
438       // If this not a file or a block device (e.g. it's a named pipe
439       // or character device), we can't trust the size. Create the memory
440       // buffer by copying off the stream.
441       sys::fs::file_type Type = Status.type();
442       if (Type != sys::fs::file_type::regular_file &&
443           Type != sys::fs::file_type::block_file)
444         return getMemoryBufferForStream(FD, Filename);
445 
446       FileSize = Status.getSize();
447     }
448     MapSize = FileSize;
449   }
450 
451   if (shouldUseMmap(FD, FileSize, MapSize, Offset, RequiresNullTerminator,
452                     PageSize, IsVolatile)) {
453     std::error_code EC;
454     std::unique_ptr<MB> Result(
455         new (NamedBufferAlloc(Filename)) MemoryBufferMMapFile<MB>(
456             RequiresNullTerminator, FD, MapSize, Offset, EC));
457     if (!EC)
458       return std::move(Result);
459   }
460 
461 #ifdef __MVS__
462   // Set codepage auto-conversion for z/OS.
463   if (auto EC = llvm::enableAutoConversion(FD))
464     return EC;
465 #endif
466 
467   auto Buf = WritableMemoryBuffer::getNewUninitMemBuffer(MapSize, Filename);
468   if (!Buf) {
469     // Failed to create a buffer. The only way it can fail is if
470     // new(std::nothrow) returns 0.
471     return make_error_code(errc::not_enough_memory);
472   }
473 
474   // Read until EOF, zero-initialize the rest.
475   MutableArrayRef<char> ToRead = Buf->getBuffer();
476   while (!ToRead.empty()) {
477     Expected<size_t> ReadBytes =
478         sys::fs::readNativeFileSlice(FD, ToRead, Offset);
479     if (!ReadBytes)
480       return errorToErrorCode(ReadBytes.takeError());
481     if (*ReadBytes == 0) {
482       std::memset(ToRead.data(), 0, ToRead.size());
483       break;
484     }
485     ToRead = ToRead.drop_front(*ReadBytes);
486     Offset += *ReadBytes;
487   }
488 
489   return std::move(Buf);
490 }
491 
492 ErrorOr<std::unique_ptr<MemoryBuffer>>
493 MemoryBuffer::getOpenFile(sys::fs::file_t FD, const Twine &Filename, uint64_t FileSize,
494                           bool RequiresNullTerminator, bool IsVolatile) {
495   return getOpenFileImpl<MemoryBuffer>(FD, Filename, FileSize, FileSize, 0,
496                          RequiresNullTerminator, IsVolatile);
497 }
498 
499 ErrorOr<std::unique_ptr<MemoryBuffer>>
500 MemoryBuffer::getOpenFileSlice(sys::fs::file_t FD, const Twine &Filename, uint64_t MapSize,
501                                int64_t Offset, bool IsVolatile) {
502   assert(MapSize != uint64_t(-1));
503   return getOpenFileImpl<MemoryBuffer>(FD, Filename, -1, MapSize, Offset, false,
504                                        IsVolatile);
505 }
506 
507 ErrorOr<std::unique_ptr<MemoryBuffer>> MemoryBuffer::getSTDIN() {
508   // Read in all of the data from stdin, we cannot mmap stdin.
509   //
510   // FIXME: That isn't necessarily true, we should try to mmap stdin and
511   // fallback if it fails.
512   sys::ChangeStdinMode(sys::fs::OF_Text);
513 
514   return getMemoryBufferForStream(sys::fs::getStdinHandle(), "<stdin>");
515 }
516 
517 ErrorOr<std::unique_ptr<MemoryBuffer>>
518 MemoryBuffer::getFileAsStream(const Twine &Filename) {
519   Expected<sys::fs::file_t> FDOrErr =
520       sys::fs::openNativeFileForRead(Filename, sys::fs::OF_None);
521   if (!FDOrErr)
522     return errorToErrorCode(FDOrErr.takeError());
523   sys::fs::file_t FD = *FDOrErr;
524   ErrorOr<std::unique_ptr<MemoryBuffer>> Ret =
525       getMemoryBufferForStream(FD, Filename);
526   sys::fs::closeFile(FD);
527   return Ret;
528 }
529 
530 MemoryBufferRef MemoryBuffer::getMemBufferRef() const {
531   StringRef Data = getBuffer();
532   StringRef Identifier = getBufferIdentifier();
533   return MemoryBufferRef(Data, Identifier);
534 }
535 
536 SmallVectorMemoryBuffer::~SmallVectorMemoryBuffer() {}
537