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 "MachONormalizedFileBinaryUtils.h"
15 #include "MachOPasses.h"
16 #include "lld/Core/DefinedAtom.h"
17 #include "lld/Core/File.h"
18 #include "lld/Core/LLVM.h"
19 #include "lld/Core/Reference.h"
20 #include "lld/Core/Simple.h"
21 #include "lld/ReaderWriter/MachOLinkingContext.h"
22 #include "llvm/ADT/DenseMap.h"
23 #include "llvm/ADT/STLExtras.h"
24 
25 namespace lld {
26 namespace mach_o {
27 
28 ///
29 /// ObjC Image Info Atom created by the ObjC pass.
30 ///
31 class ObjCImageInfoAtom : public SimpleDefinedAtom {
32 public:
33   ObjCImageInfoAtom(const File &file, bool isBig,
34                     MachOLinkingContext::ObjCConstraint objCConstraint,
35                     uint32_t swiftVersion)
36       : SimpleDefinedAtom(file) {
37 
38     Data.info.version = 0;
39 
40     switch (objCConstraint) {
41     case MachOLinkingContext::objc_unknown:
42       llvm_unreachable("Shouldn't run the objc pass without a constraint");
43     case MachOLinkingContext::objc_supports_gc:
44     case MachOLinkingContext::objc_gc_only:
45       llvm_unreachable("GC is not supported");
46     case MachOLinkingContext::objc_retainReleaseForSimulator:
47       // The retain/release for simulator flag is already the correct
48       // encoded value for the data so just set it here.
49       Data.info.flags = (uint32_t)objCConstraint;
50       break;
51     case MachOLinkingContext::objc_retainRelease:
52       // We don't need to encode this flag, so just leave the flags as 0.
53       Data.info.flags = 0;
54       break;
55     }
56 
57     Data.info.flags |= (swiftVersion << 8);
58 
59     normalized::write32(Data.bytes + 4, Data.info.flags, isBig);
60   }
61 
62   ~ObjCImageInfoAtom() override = default;
63 
64   ContentType contentType() const override {
65     return DefinedAtom::typeObjCImageInfo;
66   }
67 
68   Alignment alignment() const override {
69     return 4;
70   }
71 
72   uint64_t size() const override {
73     return 8;
74   }
75 
76   ContentPermissions permissions() const override {
77     return DefinedAtom::permR__;
78   }
79 
80   ArrayRef<uint8_t> rawContent() const override {
81     return llvm::makeArrayRef(Data.bytes, size());
82   }
83 
84 private:
85 
86   struct objc_image_info  {
87     uint32_t	version;
88     uint32_t	flags;
89   };
90 
91   union {
92     objc_image_info info;
93     uint8_t bytes[8];
94   } Data;
95 };
96 
97 class ObjCPass : public Pass {
98 public:
99   ObjCPass(const MachOLinkingContext &context)
100       : _ctx(context),
101         _file(*_ctx.make_file<MachOFile>("<mach-o objc pass>")) {
102     _file.setOrdinal(_ctx.getNextOrdinalAndIncrement());
103   }
104 
105   llvm::Error perform(SimpleFile &mergedFile) override {
106     // Add the image info.
107     mergedFile.addAtom(*getImageInfo());
108 
109     return llvm::Error::success();
110   }
111 
112 private:
113 
114   const DefinedAtom* getImageInfo() {
115     bool IsBig = MachOLinkingContext::isBigEndian(_ctx.arch());
116     return new (_file.allocator()) ObjCImageInfoAtom(_file, IsBig,
117                                                      _ctx.objcConstraint(),
118                                                      _ctx.swiftVersion());
119   }
120 
121   const MachOLinkingContext   &_ctx;
122   MachOFile                   &_file;
123 };
124 
125 
126 
127 void addObjCPass(PassManager &pm, const MachOLinkingContext &ctx) {
128   pm.add(llvm::make_unique<ObjCPass>(ctx));
129 }
130 
131 } // end namespace mach_o
132 } // end namespace lld
133