1//===- Symbols.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#include "Symbols.h"
10#include "COFFLinkerContext.h"
11#include "InputFiles.h"
12#include "lld/Common/ErrorHandler.h"
13#include "lld/Common/Memory.h"
14#include "lld/Common/Strings.h"
15#include "llvm/ADT/STLExtras.h"
16#include "llvm/Demangle/Demangle.h"
17#include "llvm/Support/Debug.h"
18#include "llvm/Support/raw_ostream.h"
19
20using namespace llvm;
21using namespace llvm::object;
22
23using namespace lld::coff;
24
25namespace lld {
26
27static_assert(sizeof(SymbolUnion) <= 48,
28 "symbols should be optimized for memory usage");
29
30// Returns a symbol name for an error message.
31static std::string maybeDemangleSymbol(const COFFLinkerContext &ctx,
32 StringRef symName) {
33 if (ctx.config.demangle) {
34 std::string prefix;
35 StringRef prefixless = symName;
36 if (prefixless.consume_front(Prefix: "__imp_"))
37 prefix = "__declspec(dllimport) ";
38 StringRef demangleInput = prefixless;
39 if (ctx.config.machine == I386)
40 demangleInput.consume_front(Prefix: "_");
41 std::string demangled = demangle(MangledName: demangleInput);
42 if (demangled != demangleInput)
43 return prefix + demangled;
44 return (prefix + prefixless).str();
45 }
46 return std::string(symName);
47}
48std::string toString(const COFFLinkerContext &ctx, coff::Symbol &b) {
49 return maybeDemangleSymbol(ctx, symName: b.getName());
50}
51std::string toCOFFString(const COFFLinkerContext &ctx,
52 const Archive::Symbol &b) {
53 return maybeDemangleSymbol(ctx, symName: b.getName());
54}
55
56namespace coff {
57
58void Symbol::computeName() {
59 assert(nameData == nullptr &&
60 "should only compute the name once for DefinedCOFF symbols");
61 auto *d = cast<DefinedCOFF>(Val: this);
62 StringRef nameStr =
63 check(e: cast<ObjFile>(Val: d->file)->getCOFFObj()->getSymbolName(Symbol: d->sym));
64 nameData = nameStr.data();
65 nameSize = nameStr.size();
66 assert(nameSize == nameStr.size() && "name length truncated");
67}
68
69InputFile *Symbol::getFile() {
70 if (auto *sym = dyn_cast<DefinedCOFF>(Val: this))
71 return sym->file;
72 if (auto *sym = dyn_cast<LazyArchive>(Val: this))
73 return sym->file;
74 if (auto *sym = dyn_cast<LazyObject>(Val: this))
75 return sym->file;
76 if (auto *sym = dyn_cast<LazyDLLSymbol>(Val: this))
77 return sym->file;
78 return nullptr;
79}
80
81bool Symbol::isLive() const {
82 if (auto *r = dyn_cast<DefinedRegular>(Val: this))
83 return r->getChunk()->live;
84 if (auto *imp = dyn_cast<DefinedImportData>(Val: this))
85 return imp->file->live;
86 if (auto *imp = dyn_cast<DefinedImportThunk>(Val: this))
87 return imp->wrappedSym->file->thunkLive;
88 // Assume any other kind of symbol is live.
89 return true;
90}
91
92// MinGW specific.
93void Symbol::replaceKeepingName(Symbol *other, size_t size) {
94 StringRef origName = getName();
95 memcpy(dest: this, src: other, n: size);
96 nameData = origName.data();
97 nameSize = origName.size();
98}
99
100COFFSymbolRef DefinedCOFF::getCOFFSymbol() {
101 size_t symSize = cast<ObjFile>(Val: file)->getCOFFObj()->getSymbolTableEntrySize();
102 if (symSize == sizeof(coff_symbol16))
103 return COFFSymbolRef(reinterpret_cast<const coff_symbol16 *>(sym));
104 assert(symSize == sizeof(coff_symbol32));
105 return COFFSymbolRef(reinterpret_cast<const coff_symbol32 *>(sym));
106}
107
108uint64_t DefinedAbsolute::getRVA() { return va - ctx.config.imageBase; }
109
110static Chunk *makeImportThunk(COFFLinkerContext &ctx, DefinedImportData *s,
111 uint16_t machine) {
112 if (machine == AMD64)
113 return make<ImportThunkChunkX64>(args&: ctx, args&: s);
114 if (machine == I386)
115 return make<ImportThunkChunkX86>(args&: ctx, args&: s);
116 if (machine == ARM64)
117 return make<ImportThunkChunkARM64>(args&: ctx, args&: s);
118 assert(machine == ARMNT);
119 return make<ImportThunkChunkARM>(args&: ctx, args&: s);
120}
121
122DefinedImportThunk::DefinedImportThunk(COFFLinkerContext &ctx, StringRef name,
123 DefinedImportData *s, uint16_t machine)
124 : Defined(DefinedImportThunkKind, name), wrappedSym(s),
125 data(makeImportThunk(ctx, s, machine)) {}
126
127Defined *Undefined::getWeakAlias() {
128 // A weak alias may be a weak alias to another symbol, so check recursively.
129 for (Symbol *a = weakAlias; a; a = cast<Undefined>(Val: a)->weakAlias)
130 if (auto *d = dyn_cast<Defined>(Val: a))
131 return d;
132 return nullptr;
133}
134
135MemoryBufferRef LazyArchive::getMemberBuffer() {
136 Archive::Child c =
137 CHECK(sym.getMember(), "could not get the member for symbol " +
138 toCOFFString(file->ctx, sym));
139 return CHECK(c.getMemoryBufferRef(),
140 "could not get the buffer for the member defining symbol " +
141 toCOFFString(file->ctx, sym));
142}
143} // namespace coff
144} // namespace lld
145