blob: b81d0a27a392f37a26a0173e5c5b32b42da1c2e6 (
plain)
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
|
//===- Passes/StubsPass.cpp - Adds stubs ----------------------------------===//
//
// The LLVM Linker
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This linker pass updates call sites which have references to shared library
// atoms to instead have a reference to a stub (PLT entry) for the specified
// symbol. The platform object does the work of creating the platform-specific
// StubAtom.
//
//===----------------------------------------------------------------------===//
#include "lld/Core/DefinedAtom.h"
#include "lld/Core/File.h"
#include "lld/Core/LLVM.h"
#include "lld/Core/Pass.h"
#include "lld/Core/Platform.h"
#include "lld/Core/Reference.h"
#include "llvm/ADT/DenseMap.h"
namespace lld {
void StubsPass::perform() {
// Skip this pass if output format uses text relocations instead of stubs.
if ( !_platform.noTextRelocs() )
return;
// Scan all references in all atoms.
for(const DefinedAtom *atom : _file.defined()) {
for (const Reference *ref : *atom) {
// Look at call-sites.
if ( _platform.isCallSite(ref->kind()) ) {
const Atom* target = ref->target();
assert(target != nullptr);
bool replaceCalleeWithStub = false;
if ( target->definition() == Atom::definitionSharedLibrary ) {
// Calls to shared libraries go through stubs.
replaceCalleeWithStub = true;
}
else if (const DefinedAtom* defTarget =
dyn_cast<DefinedAtom>(target)) {
if ( defTarget->interposable() != DefinedAtom::interposeNo ) {
// Calls to interposable functions in same linkage unit
// must also go through a stub.
assert(defTarget->scope() != DefinedAtom::scopeTranslationUnit);
replaceCalleeWithStub = true;
}
}
if ( replaceCalleeWithStub ) {
// Ask platform to make stub and other support atoms.
const DefinedAtom* stub = _platform.getStub(*target, _file);
assert(stub != nullptr);
// Switch call site to reference stub atom instead.
(const_cast<Reference*>(ref))->setTarget(stub);
}
}
}
}
// Tell platform to add all created stubs and support Atoms to file.
_platform.addStubAtoms(_file);
}
}
|
