1 //===- lib/ReaderWriter/MachO/ObjCPass.cpp -------------------------------===//
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 //===----------------------------------------------------------------------===//
10 
11 #include "ArchHandler.h"
12 #include "File.h"
13 #include "MachONormalizedFileBinaryUtils.h"
14 #include "MachOPasses.h"
15 #include "lld/Common/LLVM.h"
16 #include "lld/Core/DefinedAtom.h"
17 #include "lld/Core/File.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, bool isBig,
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     normalized::write32(Data.bytes + 4, Data.info.flags, isBig);
59   }
60 
61   ~ObjCImageInfoAtom() override = default;
62 
63   ContentType contentType() const override {
64     return DefinedAtom::typeObjCImageInfo;
65   }
66 
67   Alignment alignment() const override {
68     return 4;
69   }
70 
71   uint64_t size() const override {
72     return 8;
73   }
74 
75   ContentPermissions permissions() const override {
76     return DefinedAtom::permR__;
77   }
78 
79   ArrayRef<uint8_t> rawContent() const override {
80     return llvm::makeArrayRef(Data.bytes, size());
81   }
82 
83 private:
84 
85   struct objc_image_info  {
86     uint32_t	version;
87     uint32_t	flags;
88   };
89 
90   union {
91     objc_image_info info;
92     uint8_t bytes[8];
93   } Data;
94 };
95 
96 class ObjCPass : public Pass {
97 public:
98   ObjCPass(const MachOLinkingContext &context)
99       : _ctx(context),
100         _file(*_ctx.make_file<MachOFile>("<mach-o objc pass>")) {
101     _file.setOrdinal(_ctx.getNextOrdinalAndIncrement());
102   }
103 
104   llvm::Error perform(SimpleFile &mergedFile) override {
105     // Add the image info.
106     mergedFile.addAtom(*getImageInfo());
107 
108     return llvm::Error::success();
109   }
110 
111 private:
112 
113   const DefinedAtom* getImageInfo() {
114     bool IsBig = MachOLinkingContext::isBigEndian(_ctx.arch());
115     return new (_file.allocator()) ObjCImageInfoAtom(_file, IsBig,
116                                                      _ctx.objcConstraint(),
117                                                      _ctx.swiftVersion());
118   }
119 
120   const MachOLinkingContext   &_ctx;
121   MachOFile                   &_file;
122 };
123 
124 
125 
126 void addObjCPass(PassManager &pm, const MachOLinkingContext &ctx) {
127   pm.add(llvm::make_unique<ObjCPass>(ctx));
128 }
129 
130 } // end namespace mach_o
131 } // end namespace lld
132