1//===------ JITLinkGeneric.h - Generic JIT linker utilities -----*- C++ -*-===//
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// Generic JITLinker utilities. E.g. graph pruning, eh-frame parsing.
10//
11//===----------------------------------------------------------------------===//
12
13#ifndef LIB_EXECUTIONENGINE_JITLINK_JITLINKGENERIC_H
14#define LIB_EXECUTIONENGINE_JITLINK_JITLINKGENERIC_H
15
16#include "llvm/ExecutionEngine/JITLink/JITLink.h"
17
18#define DEBUG_TYPE "jitlink"
19
20namespace llvm {
21namespace jitlink {
22
23/// Base class for a JIT linker.
24///
25/// A JITLinkerBase instance links one object file into an ongoing JIT
26/// session. Symbol resolution and finalization operations are pluggable,
27/// and called using continuation passing (passing a continuation for the
28/// remaining linker work) to allow them to be performed asynchronously.
29class JITLinkerBase {
30public:
31 JITLinkerBase(std::unique_ptr<JITLinkContext> Ctx,
32 std::unique_ptr<LinkGraph> G, PassConfiguration Passes)
33 : Ctx(std::move(Ctx)), G(std::move(G)), Passes(std::move(Passes)) {
34 assert(this->Ctx && "Ctx can not be null");
35 assert(this->G && "G can not be null");
36 }
37
38 virtual ~JITLinkerBase();
39
40protected:
41 using InFlightAlloc = JITLinkMemoryManager::InFlightAlloc;
42 using AllocResult = Expected<std::unique_ptr<InFlightAlloc>>;
43 using FinalizeResult = Expected<JITLinkMemoryManager::FinalizedAlloc>;
44
45 // Returns a reference to the graph being linked.
46 LinkGraph &getGraph() { return *G; }
47
48 // Returns true if the context says that the linker should add default
49 // passes. This can be used by JITLinkerBase implementations when deciding
50 // whether they should add default passes.
51 bool shouldAddDefaultTargetPasses(const Triple &TT) {
52 return Ctx->shouldAddDefaultTargetPasses(TT);
53 }
54
55 // Returns the PassConfiguration for this instance. This can be used by
56 // JITLinkerBase implementations to add late passes that reference their
57 // own data structures (e.g. for ELF implementations to locate / construct
58 // a GOT start symbol prior to fixup).
59 PassConfiguration &getPassConfig() { return Passes; }
60
61 // Phase 1:
62 // 1.1: Run pre-prune passes
63 // 1.2: Prune graph
64 // 1.3: Run post-prune passes
65 // 1.4: Allocate memory.
66 void linkPhase1(std::unique_ptr<JITLinkerBase> Self);
67
68 // Phase 2:
69 // 2.2: Run post-allocation passes
70 // 2.3: Notify context of final assigned symbol addresses
71 // 2.4: Identify external symbols and make an async call to resolve
72 void linkPhase2(std::unique_ptr<JITLinkerBase> Self, AllocResult AR);
73
74 // Phase 3:
75 // 3.1: Apply resolution results
76 // 3.2: Run pre-fixup passes
77 // 3.3: Fix up block contents
78 // 3.4: Run post-fixup passes
79 // 3.5: Make an async call to transfer and finalize memory.
80 void linkPhase3(std::unique_ptr<JITLinkerBase> Self,
81 Expected<AsyncLookupResult> LookupResult);
82
83 // Phase 4:
84 // 4.1: Call OnFinalized callback, handing off allocation.
85 void linkPhase4(std::unique_ptr<JITLinkerBase> Self, FinalizeResult FR);
86
87private:
88 // Run all passes in the given pass list, bailing out immediately if any pass
89 // returns an error.
90 Error runPasses(LinkGraphPassList &Passes);
91
92 // Copy block contents and apply relocations.
93 // Implemented in JITLinker.
94 virtual Error fixUpBlocks(LinkGraph &G) const = 0;
95
96 JITLinkContext::LookupMap getExternalSymbolNames() const;
97 void applyLookupResult(AsyncLookupResult LR);
98 void abandonAllocAndBailOut(std::unique_ptr<JITLinkerBase> Self, Error Err);
99
100 std::unique_ptr<JITLinkContext> Ctx;
101 std::unique_ptr<LinkGraph> G;
102 PassConfiguration Passes;
103 std::unique_ptr<InFlightAlloc> Alloc;
104};
105
106template <typename LinkerImpl> class JITLinker : public JITLinkerBase {
107public:
108 using JITLinkerBase::JITLinkerBase;
109
110 /// Link constructs a LinkerImpl instance and calls linkPhase1.
111 /// Link should be called with the constructor arguments for LinkerImpl, which
112 /// will be forwarded to the constructor.
113 template <typename... ArgTs> static void link(ArgTs &&... Args) {
114 auto L = std::make_unique<LinkerImpl>(std::forward<ArgTs>(Args)...);
115
116 // Ownership of the linker is passed into the linker's doLink function to
117 // allow it to be passed on to async continuations.
118 //
119 // FIXME: Remove LTmp once we have c++17.
120 // C++17 sequencing rules guarantee that function name expressions are
121 // sequenced before arguments, so L->linkPhase1(std::move(L), ...) will be
122 // well formed.
123 auto &LTmp = *L;
124 LTmp.linkPhase1(std::move(L));
125 }
126
127private:
128 const LinkerImpl &impl() const {
129 return static_cast<const LinkerImpl &>(*this);
130 }
131
132 Error fixUpBlocks(LinkGraph &G) const override {
133 LLVM_DEBUG(dbgs() << "Fixing up blocks:\n");
134
135 for (auto &Sec : G.sections()) {
136 bool NoAllocSection = Sec.getMemLifetime() == orc::MemLifetime::NoAlloc;
137
138 for (auto *B : Sec.blocks()) {
139 LLVM_DEBUG(dbgs() << " " << *B << ":\n");
140
141 // Copy Block data and apply fixups.
142 LLVM_DEBUG(dbgs() << " Applying fixups.\n");
143 assert((!B->isZeroFill() || all_of(B->edges(),
144 [](const Edge &E) {
145 return E.getKind() ==
146 Edge::KeepAlive;
147 })) &&
148 "Non-KeepAlive edges in zero-fill block?");
149
150 // If this is a no-alloc section then copy the block content into
151 // memory allocated on the Graph's allocator (if it hasn't been
152 // already).
153 if (NoAllocSection)
154 (void)B->getMutableContent(G);
155
156 for (auto &E : B->edges()) {
157
158 // Skip non-relocation edges.
159 if (!E.isRelocation())
160 continue;
161
162 // If B is a block in a Standard or Finalize section then make sure
163 // that no edges point to symbols in NoAlloc sections.
164 assert((NoAllocSection || !E.getTarget().isDefined() ||
165 E.getTarget().getSection().getMemLifetime() !=
166 orc::MemLifetime::NoAlloc) &&
167 "Block in allocated section has edge pointing to no-alloc "
168 "section");
169
170 // Dispatch to LinkerImpl for fixup.
171 if (auto Err = impl().applyFixup(G, *B, E))
172 return Err;
173 }
174 }
175 }
176
177 return Error::success();
178 }
179};
180
181/// Removes dead symbols/blocks/addressables.
182///
183/// Finds the set of symbols and addressables reachable from any symbol
184/// initially marked live. All symbols/addressables not marked live at the end
185/// of this process are removed.
186void prune(LinkGraph &G);
187
188} // end namespace jitlink
189} // end namespace llvm
190
191#undef DEBUG_TYPE // "jitlink"
192
193#endif // LIB_EXECUTIONENGINE_JITLINK_JITLINKGENERIC_H
194