1 //===- MachOUniversalWriter.cpp - MachO universal binary writer---*- C++-*-===//
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 // Defines the Slice class and writeUniversalBinary function for writing a MachO
10 // universal binary file.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "llvm/Object/MachOUniversalWriter.h"
15 #include "llvm/ADT/Triple.h"
16 #include "llvm/Object/Archive.h"
17 #include "llvm/Object/Binary.h"
18 #include "llvm/Object/Error.h"
19 #include "llvm/Object/IRObjectFile.h"
20 #include "llvm/Object/MachO.h"
21 #include "llvm/Object/MachOUniversal.h"
22 #include "llvm/Support/FileOutputBuffer.h"
23 
24 using namespace llvm;
25 using namespace object;
26 
27 // For compatibility with cctools lipo, a file's alignment is calculated as the
28 // minimum aligment of all segments. For object files, the file's alignment is
29 // the maximum alignment of its sections.
30 static uint32_t calculateFileAlignment(const MachOObjectFile &O) {
31   uint32_t P2CurrentAlignment;
32   uint32_t P2MinAlignment = MachOUniversalBinary::MaxSectionAlignment;
33   const bool Is64Bit = O.is64Bit();
34 
35   for (const auto &LC : O.load_commands()) {
36     if (LC.C.cmd != (Is64Bit ? MachO::LC_SEGMENT_64 : MachO::LC_SEGMENT))
37       continue;
38     if (O.getHeader().filetype == MachO::MH_OBJECT) {
39       unsigned NumberOfSections =
40           (Is64Bit ? O.getSegment64LoadCommand(LC).nsects
41                    : O.getSegmentLoadCommand(LC).nsects);
42       P2CurrentAlignment = NumberOfSections ? 2 : P2MinAlignment;
43       for (unsigned SI = 0; SI < NumberOfSections; ++SI) {
44         P2CurrentAlignment = std::max(P2CurrentAlignment,
45                                       (Is64Bit ? O.getSection64(LC, SI).align
46                                                : O.getSection(LC, SI).align));
47       }
48     } else {
49       P2CurrentAlignment =
50           countTrailingZeros(Is64Bit ? O.getSegment64LoadCommand(LC).vmaddr
51                                      : O.getSegmentLoadCommand(LC).vmaddr);
52     }
53     P2MinAlignment = std::min(P2MinAlignment, P2CurrentAlignment);
54   }
55   // return a value >= 4 byte aligned, and less than MachO MaxSectionAlignment
56   return std::max(
57       static_cast<uint32_t>(2),
58       std::min(P2MinAlignment, static_cast<uint32_t>(
59                                    MachOUniversalBinary::MaxSectionAlignment)));
60 }
61 
62 static uint32_t calculateAlignment(const MachOObjectFile &ObjectFile) {
63   switch (ObjectFile.getHeader().cputype) {
64   case MachO::CPU_TYPE_I386:
65   case MachO::CPU_TYPE_X86_64:
66   case MachO::CPU_TYPE_POWERPC:
67   case MachO::CPU_TYPE_POWERPC64:
68     return 12; // log2 value of page size(4k) for x86 and PPC
69   case MachO::CPU_TYPE_ARM:
70   case MachO::CPU_TYPE_ARM64:
71   case MachO::CPU_TYPE_ARM64_32:
72     return 14; // log2 value of page size(16k) for Darwin ARM
73   default:
74     return calculateFileAlignment(ObjectFile);
75   }
76 }
77 
78 Slice::Slice(const MachOObjectFile &O, uint32_t Align)
79     : B(&O), CPUType(O.getHeader().cputype),
80       CPUSubType(O.getHeader().cpusubtype),
81       ArchName(std::string(O.getArchTriple().getArchName())),
82       P2Alignment(Align) {}
83 
84 Slice::Slice(const IRObjectFile *IRO, uint32_t CPUType, uint32_t CPUSubType,
85              std::string ArchName, uint32_t Align)
86     : B(IRO), CPUType(CPUType), CPUSubType(CPUSubType),
87       ArchName(std::move(ArchName)), P2Alignment(Align) {}
88 
89 Slice::Slice(const MachOObjectFile &O) : Slice(O, calculateAlignment(O)) {}
90 
91 using MachoCPUTy = std::pair<unsigned, unsigned>;
92 
93 static Expected<MachoCPUTy> getMachoCPUFromTriple(Triple TT) {
94   auto CPU = std::make_pair(MachO::getCPUType(TT), MachO::getCPUSubType(TT));
95   if (!CPU.first) {
96     return CPU.first.takeError();
97   }
98   if (!CPU.second) {
99     return CPU.second.takeError();
100   }
101   return std::make_pair(*CPU.first, *CPU.second);
102 }
103 
104 static Expected<MachoCPUTy> getMachoCPUFromTriple(StringRef TT) {
105   return getMachoCPUFromTriple(Triple{TT});
106 }
107 
108 Expected<Slice> Slice::create(const Archive *A, LLVMContext *LLVMCtx) {
109   Error Err = Error::success();
110   std::unique_ptr<MachOObjectFile> MFO = nullptr;
111   std::unique_ptr<IRObjectFile> IRFO = nullptr;
112   for (const Archive::Child &Child : A->children(Err)) {
113     Expected<std::unique_ptr<Binary>> ChildOrErr = Child.getAsBinary(LLVMCtx);
114     if (!ChildOrErr)
115       return createFileError(A->getFileName(), ChildOrErr.takeError());
116     Binary *Bin = ChildOrErr.get().get();
117     if (Bin->isMachOUniversalBinary())
118       return createStringError(std::errc::invalid_argument,
119                                ("archive member " + Bin->getFileName() +
120                                 " is a fat file (not allowed in an archive)")
121                                    .str()
122                                    .c_str());
123     if (Bin->isMachO()) {
124       MachOObjectFile *O = cast<MachOObjectFile>(Bin);
125       if (IRFO) {
126         return createStringError(
127             std::errc::invalid_argument,
128             "archive member %s is a MachO, while previous archive member "
129             "%s was an IR LLVM object",
130             O->getFileName().str().c_str(), IRFO->getFileName().str().c_str());
131       }
132       if (MFO &&
133           std::tie(MFO->getHeader().cputype, MFO->getHeader().cpusubtype) !=
134               std::tie(O->getHeader().cputype, O->getHeader().cpusubtype)) {
135         return createStringError(
136             std::errc::invalid_argument,
137             ("archive member " + O->getFileName() + " cputype (" +
138              Twine(O->getHeader().cputype) + ") and cpusubtype(" +
139              Twine(O->getHeader().cpusubtype) +
140              ") does not match previous archive members cputype (" +
141              Twine(MFO->getHeader().cputype) + ") and cpusubtype(" +
142              Twine(MFO->getHeader().cpusubtype) +
143              ") (all members must match) " + MFO->getFileName())
144                 .str()
145                 .c_str());
146       }
147       if (!MFO) {
148         ChildOrErr.get().release();
149         MFO.reset(O);
150       }
151     } else if (Bin->isIR()) {
152       IRObjectFile *O = cast<IRObjectFile>(Bin);
153       if (MFO) {
154         return createStringError(std::errc::invalid_argument,
155                                  "archive member '%s' is an LLVM IR object, "
156                                  "while previous archive member "
157                                  "'%s' was a MachO",
158                                  O->getFileName().str().c_str(),
159                                  MFO->getFileName().str().c_str());
160       }
161       if (IRFO) {
162         Expected<MachoCPUTy> CPUO = getMachoCPUFromTriple(O->getTargetTriple());
163         Expected<MachoCPUTy> CPUFO =
164             getMachoCPUFromTriple(IRFO->getTargetTriple());
165         if (!CPUO)
166           return CPUO.takeError();
167         if (!CPUFO)
168           return CPUFO.takeError();
169         if (*CPUO != *CPUFO) {
170           return createStringError(
171               std::errc::invalid_argument,
172               ("archive member " + O->getFileName() + " cputype (" +
173                Twine(CPUO->first) + ") and cpusubtype(" + Twine(CPUO->second) +
174                ") does not match previous archive members cputype (" +
175                Twine(CPUFO->first) + ") and cpusubtype(" +
176                Twine(CPUFO->second) + ") (all members must match) " +
177                IRFO->getFileName())
178                   .str()
179                   .c_str());
180         }
181       } else {
182         ChildOrErr.get().release();
183         IRFO.reset(O);
184       }
185     } else
186       return createStringError(std::errc::invalid_argument,
187                                ("archive member " + Bin->getFileName() +
188                                 " is neither a MachO file or an LLVM IR file "
189                                 "(not allowed in an archive)")
190                                    .str()
191                                    .c_str());
192   }
193   if (Err)
194     return createFileError(A->getFileName(), std::move(Err));
195   if (!MFO && !IRFO)
196     return createStringError(
197         std::errc::invalid_argument,
198         ("empty archive with no architecture specification: " +
199          A->getFileName() + " (can't determine architecture for it)")
200             .str()
201             .c_str());
202 
203   if (MFO) {
204     Slice ArchiveSlice(*(MFO.get()), MFO->is64Bit() ? 3 : 2);
205     ArchiveSlice.B = A;
206     return ArchiveSlice;
207   }
208 
209   // For IR objects
210   Expected<Slice> ArchiveSliceOrErr = Slice::create(IRFO.get(), 0);
211   if (!ArchiveSliceOrErr)
212     return createFileError(A->getFileName(), ArchiveSliceOrErr.takeError());
213   auto &ArchiveSlice = ArchiveSliceOrErr.get();
214   ArchiveSlice.B = A;
215   return Slice{std::move(ArchiveSlice)};
216 }
217 
218 Expected<Slice> Slice::create(const IRObjectFile *IRO, uint32_t Align) {
219   Expected<MachoCPUTy> CPUOrErr = getMachoCPUFromTriple(IRO->getTargetTriple());
220   if (!CPUOrErr)
221     return CPUOrErr.takeError();
222   unsigned CPUType, CPUSubType;
223   std::tie(CPUType, CPUSubType) = CPUOrErr.get();
224   // We don't directly use the architecture name of the target triple T, as,
225   // for instance, thumb is treated as ARM by the MachOUniversal object.
226   std::string ArchName(
227       MachOObjectFile::getArchTriple(CPUType, CPUSubType).getArchName());
228   return Slice{IRO, CPUType, CPUSubType, std::move(ArchName), Align};
229 }
230 
231 static Expected<SmallVector<MachO::fat_arch, 2>>
232 buildFatArchList(ArrayRef<Slice> Slices) {
233   SmallVector<MachO::fat_arch, 2> FatArchList;
234   uint64_t Offset =
235       sizeof(MachO::fat_header) + Slices.size() * sizeof(MachO::fat_arch);
236 
237   for (const auto &S : Slices) {
238     Offset = alignTo(Offset, 1ull << S.getP2Alignment());
239     if (Offset > UINT32_MAX)
240       return createStringError(
241           std::errc::invalid_argument,
242           ("fat file too large to be created because the offset "
243            "field in struct fat_arch is only 32-bits and the offset " +
244            Twine(Offset) + " for " + S.getBinary()->getFileName() +
245            " for architecture " + S.getArchString() + "exceeds that.")
246               .str()
247               .c_str());
248 
249     MachO::fat_arch FatArch;
250     FatArch.cputype = S.getCPUType();
251     FatArch.cpusubtype = S.getCPUSubType();
252     FatArch.offset = Offset;
253     FatArch.size = S.getBinary()->getMemoryBufferRef().getBufferSize();
254     FatArch.align = S.getP2Alignment();
255     Offset += FatArch.size;
256     FatArchList.push_back(FatArch);
257   }
258   return FatArchList;
259 }
260 
261 Error object::writeUniversalBinary(ArrayRef<Slice> Slices,
262                                    StringRef OutputFileName) {
263   MachO::fat_header FatHeader;
264   FatHeader.magic = MachO::FAT_MAGIC;
265   FatHeader.nfat_arch = Slices.size();
266 
267   Expected<SmallVector<MachO::fat_arch, 2>> FatArchListOrErr =
268       buildFatArchList(Slices);
269   if (!FatArchListOrErr)
270     return FatArchListOrErr.takeError();
271   SmallVector<MachO::fat_arch, 2> FatArchList = *FatArchListOrErr;
272 
273   const bool IsExecutable = any_of(Slices, [](Slice S) {
274     return sys::fs::can_execute(S.getBinary()->getFileName());
275   });
276   const uint64_t OutputFileSize =
277       static_cast<uint64_t>(FatArchList.back().offset) +
278       FatArchList.back().size;
279   Expected<std::unique_ptr<FileOutputBuffer>> OutFileOrError =
280       FileOutputBuffer::create(OutputFileName, OutputFileSize,
281                                IsExecutable ? FileOutputBuffer::F_executable
282                                             : 0);
283   if (!OutFileOrError)
284     return createFileError(OutputFileName, OutFileOrError.takeError());
285   std::unique_ptr<FileOutputBuffer> OutFile = std::move(OutFileOrError.get());
286   std::memset(OutFile->getBufferStart(), 0, OutputFileSize);
287 
288   if (sys::IsLittleEndianHost)
289     MachO::swapStruct(FatHeader);
290   std::memcpy(OutFile->getBufferStart(), &FatHeader, sizeof(MachO::fat_header));
291 
292   for (size_t Index = 0, Size = Slices.size(); Index < Size; ++Index) {
293     MemoryBufferRef BufferRef = Slices[Index].getBinary()->getMemoryBufferRef();
294     std::copy(BufferRef.getBufferStart(), BufferRef.getBufferEnd(),
295               OutFile->getBufferStart() + FatArchList[Index].offset);
296   }
297 
298   // FatArchs written after Slices in order to reduce the number of swaps for
299   // the LittleEndian case
300   if (sys::IsLittleEndianHost)
301     for (MachO::fat_arch &FA : FatArchList)
302       MachO::swapStruct(FA);
303   std::memcpy(OutFile->getBufferStart() + sizeof(MachO::fat_header),
304               FatArchList.begin(),
305               sizeof(MachO::fat_arch) * FatArchList.size());
306 
307   if (Error E = OutFile->commit())
308     return createFileError(OutputFileName, std::move(E));
309 
310   return Error::success();
311 }
312