1 //===- lib/ReaderWriter/MachO/ObjCPass.cpp -------------------------------===//
2 //
3 //                             The LLVM Linker
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 //===----------------------------------------------------------------------===//
11 
12 #include "ArchHandler.h"
13 #include "File.h"
14 #include "MachOPasses.h"
15 #include "lld/Core/DefinedAtom.h"
16 #include "lld/Core/File.h"
17 #include "lld/Core/LLVM.h"
18 #include "lld/Core/Reference.h"
19 #include "lld/Core/Simple.h"
20 #include "lld/ReaderWriter/MachOLinkingContext.h"
21 #include "llvm/ADT/DenseMap.h"
22 #include "llvm/ADT/STLExtras.h"
23 
24 namespace lld {
25 namespace mach_o {
26 
27 ///
28 /// ObjC Image Info Atom created by the ObjC pass.
29 ///
30 class ObjCImageInfoAtom : public SimpleDefinedAtom {
31 public:
32   ObjCImageInfoAtom(const File &file,
33                     MachOLinkingContext::ObjCConstraint objCConstraint,
34                     uint32_t swiftVersion)
35       : SimpleDefinedAtom(file) {
36 
37     Data.info.version = 0;
38 
39     switch (objCConstraint) {
40     case MachOLinkingContext::objc_unknown:
41       llvm_unreachable("Shouldn't run the objc pass without a constraint");
42     case MachOLinkingContext::objc_supports_gc:
43     case MachOLinkingContext::objc_gc_only:
44       llvm_unreachable("GC is not supported");
45     case MachOLinkingContext::objc_retainReleaseForSimulator:
46       // The retain/release for simulator flag is already the correct
47       // encoded value for the data so just set it here.
48       Data.info.flags = (uint32_t)objCConstraint;
49       break;
50     case MachOLinkingContext::objc_retainRelease:
51       // We don't need to encode this flag, so just leave the flags as 0.
52       Data.info.flags = 0;
53       break;
54     }
55 
56     Data.info.flags |= (swiftVersion << 8);
57   }
58 
59   ~ObjCImageInfoAtom() override = default;
60 
61   ContentType contentType() const override {
62     return DefinedAtom::typeObjCImageInfo;
63   }
64 
65   Alignment alignment() const override {
66     return 4;
67   }
68 
69   uint64_t size() const override {
70     return 8;
71   }
72 
73   ContentPermissions permissions() const override {
74     return DefinedAtom::permR__;
75   }
76 
77   ArrayRef<uint8_t> rawContent() const override {
78     return llvm::makeArrayRef(Data.bytes, size());
79   }
80 
81 private:
82 
83   struct objc_image_info  {
84     uint32_t	version;
85     uint32_t	flags;
86   };
87 
88   union {
89     objc_image_info info;
90     uint8_t bytes[8];
91   } Data;
92 };
93 
94 class ObjCPass : public Pass {
95 public:
96   ObjCPass(const MachOLinkingContext &context)
97       : _ctx(context),
98         _file(*_ctx.make_file<MachOFile>("<mach-o objc pass>")) {
99     _file.setOrdinal(_ctx.getNextOrdinalAndIncrement());
100   }
101 
102   llvm::Error perform(SimpleFile &mergedFile) override {
103     // Add the image info.
104     mergedFile.addAtom(*getImageInfo());
105 
106     return llvm::Error();
107   }
108 
109 private:
110 
111   const DefinedAtom* getImageInfo() {
112     return new (_file.allocator()) ObjCImageInfoAtom(_file,
113                                                      _ctx.objcConstraint(),
114                                                      _ctx.swiftVersion());
115   }
116 
117   const MachOLinkingContext   &_ctx;
118   MachOFile                   &_file;
119 };
120 
121 
122 
123 void addObjCPass(PassManager &pm, const MachOLinkingContext &ctx) {
124   pm.add(llvm::make_unique<ObjCPass>(ctx));
125 }
126 
127 } // end namespace mach_o
128 } // end namespace lld
129