1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
|
//===--------- DefineExternalSectionStartAndEndSymbols.h --------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// Utility class for recognizing external section start and end symbols and
// transforming them into defined symbols for the start and end blocks of the
// associated Section.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_EXECUTIONENGINE_JITLINK_DEFINEEXTERNALSECTIONSTARTANDENDSYMBOLS_H
#define LLVM_EXECUTIONENGINE_JITLINK_DEFINEEXTERNALSECTIONSTARTANDENDSYMBOLS_H
#include "llvm/ExecutionEngine/JITLink/JITLink.h"
#include "llvm/Support/Debug.h"
#define DEBUG_TYPE "jitlink"
namespace llvm {
namespace jitlink {
struct SectionRangeSymbolDesc {
SectionRangeSymbolDesc() = default;
SectionRangeSymbolDesc(Section &Sec, bool IsStart)
: Sec(&Sec), IsStart(IsStart) {}
Section *Sec = nullptr;
bool IsStart = false;
};
/// Pass implementation for the createDefineExternalSectionStartAndEndSymbols
/// function.
template <typename SymbolIdentifierFunction>
class DefineExternalSectionStartAndEndSymbols {
public:
DefineExternalSectionStartAndEndSymbols(SymbolIdentifierFunction F)
: F(std::move(F)) {}
Error operator()(LinkGraph &G) {
// This pass will affect the external symbols set, so copy them out into a
// vector and iterate over that.
std::vector<Symbol *> Externals(G.external_symbols().begin(),
G.external_symbols().end());
for (auto *Sym : Externals) {
SectionRangeSymbolDesc D = F(G, *Sym);
if (D.Sec) {
auto &SR = getSectionRange(*D.Sec);
if (D.IsStart) {
if (SR.empty())
G.makeAbsolute(*Sym, orc::ExecutorAddr());
else
G.makeDefined(*Sym, *SR.getFirstBlock(), 0, 0, Linkage::Strong,
Scope::Local, false);
} else {
if (SR.empty())
G.makeAbsolute(*Sym, orc::ExecutorAddr());
else
G.makeDefined(*Sym, *SR.getLastBlock(),
SR.getLastBlock()->getSize(), 0, Linkage::Strong,
Scope::Local, false);
}
}
}
return Error::success();
}
private:
SectionRange &getSectionRange(Section &Sec) {
return SectionRanges.try_emplace(&Sec, Sec).first->second;
}
DenseMap<Section *, SectionRange> SectionRanges;
SymbolIdentifierFunction F;
};
/// Returns a JITLink pass (as a function class) that uses the given symbol
/// identification function to identify external section start and end symbols
/// (and their associated Section*s) and transform the identified externals
/// into defined symbols pointing to the start of the first block in the
/// section and the end of the last (start and end symbols for empty sections
/// will be transformed into absolute symbols at address 0).
///
/// The identification function should be callable as
///
/// SectionRangeSymbolDesc (LinkGraph &G, Symbol &Sym)
///
/// If Sym is not a section range start or end symbol then a default
/// constructed SectionRangeSymbolDesc should be returned. If Sym is a start
/// symbol then SectionRangeSymbolDesc(Sec, true), where Sec is a reference to
/// the target Section. If Sym is an end symbol then
/// SectionRangeSymbolDesc(Sec, false) should be returned.
///
/// This pass should be run in the PostAllocationPass pipeline, at which point
/// all blocks should have been assigned their final addresses.
template <typename SymbolIdentifierFunction>
DefineExternalSectionStartAndEndSymbols<SymbolIdentifierFunction>
createDefineExternalSectionStartAndEndSymbolsPass(
SymbolIdentifierFunction &&F) {
return DefineExternalSectionStartAndEndSymbols<SymbolIdentifierFunction>(
std::forward<SymbolIdentifierFunction>(F));
}
/// ELF section start/end symbol detection.
inline SectionRangeSymbolDesc
identifyELFSectionStartAndEndSymbols(LinkGraph &G, Symbol &Sym) {
constexpr StringRef StartSymbolPrefix = "__start_";
constexpr StringRef EndSymbolPrefix = "__stop_";
auto SymName = Sym.getName();
if ((*SymName).starts_with(StartSymbolPrefix)) {
if (auto *Sec = G.findSectionByName(
(*SymName).drop_front(StartSymbolPrefix.size())))
return {*Sec, true};
} else if ((*SymName).starts_with(EndSymbolPrefix)) {
if (auto *Sec =
G.findSectionByName((*SymName).drop_front(EndSymbolPrefix.size())))
return {*Sec, false};
}
return {};
}
/// MachO section start/end symbol detection.
inline SectionRangeSymbolDesc
identifyMachOSectionStartAndEndSymbols(LinkGraph &G, Symbol &Sym) {
constexpr StringRef StartSymbolPrefix = "section$start$";
constexpr StringRef EndSymbolPrefix = "section$end$";
auto SymName = Sym.getName();
if ((*SymName).starts_with(StartSymbolPrefix)) {
auto [SegName, SecName] =
(*SymName).drop_front(StartSymbolPrefix.size()).split('$');
std::string SectionName = (SegName + "," + SecName).str();
if (auto *Sec = G.findSectionByName(SectionName))
return {*Sec, true};
} else if ((*SymName).starts_with(EndSymbolPrefix)) {
auto [SegName, SecName] =
(*SymName).drop_front(EndSymbolPrefix.size()).split('$');
std::string SectionName = (SegName + "," + SecName).str();
if (auto *Sec = G.findSectionByName(SectionName))
return {*Sec, false};
}
return {};
}
} // end namespace jitlink
} // end namespace llvm
#undef DEBUG_TYPE
#endif // LLVM_EXECUTIONENGINE_JITLINK_DEFINEEXTERNALSECTIONSTARTANDENDSYMBOLS_H
|
