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[mach-o] Sort GOT entries by name to make links reproducible 

The GOT slots were being laid out in a random order by the GOTPass which
caused randomness in the output file.

Note: With this change lld now bootstraps on darwin.  That is:
1) link lld using system linker to make lld.1
2) link lld using lld.1 to make lld.2
3) link lld using lld.2 to make lld.3
Now lld.2 and lld.3 are identical.

llvm-svn: 221831
This commit is contained in:
Nick Kledzik 2014-11-12 23:34:23 +00:00
parent e8356339cd
commit 8870ad2439
2 changed files with 152 additions and 5 deletions
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23
lld/lib/ReaderWriter/MachO/GOTPass.cpp
View File

@ -52,8 +52,8 @@ namespace mach_o {
//
class GOTEntryAtom : public SimpleDefinedAtom {
public:
GOTEntryAtom(const File &file, bool is64)
: SimpleDefinedAtom(file), _is64(is64) { }
GOTEntryAtom(const File &file, bool is64, StringRef name)
: SimpleDefinedAtom(file), _is64(is64), _name(name) { }
ContentType contentType() const override {
return DefinedAtom::typeGOT;
@ -77,8 +77,13 @@ public:
return llvm::makeArrayRef(zeros, size());
}
StringRef slotName() const {
return _name;
}
private:
const bool _is64;
StringRef _name;
};
@ -116,9 +121,17 @@ private:
}
}
// add all created GOT Atoms to master file
// Sort and add all created GOT Atoms to master file
std::vector<const GOTEntryAtom *> entries;
entries.reserve(_targetToGOT.size());
for (auto &it : _targetToGOT)
mergedFile->addAtom(*it.second);
entries.push_back(it.second);
std::sort(entries.begin(), entries.end(),
[](const GOTEntryAtom *left, const GOTEntryAtom *right) {
return (left->slotName().compare(right->slotName()) < 0);
});
for (const GOTEntryAtom *slot : entries)
mergedFile->addAtom(*slot);
}
bool shouldReplaceTargetWithGOTAtom(const Atom *target, bool canBypassGOT) {
@ -142,7 +155,7 @@ private:
auto pos = _targetToGOT.find(target);
if (pos == _targetToGOT.end()) {
GOTEntryAtom *gotEntry = new (_file.allocator())
GOTEntryAtom(_file, _context.is64Bit());
GOTEntryAtom(_file, _context.is64Bit(), target->name());
_targetToGOT[target] = gotEntry;
const ArchHandler::ReferenceInfo &nlInfo = _archHandler.stubInfo().
nonLazyPointerReferenceToBinder;

134
lld/test/mach-o/got-order.yaml Normal file
View File

@ -0,0 +1,134 @@
# RUN: lld -flavor darwin -arch x86_64 %s -o %t %p/Inputs/libSystem.yaml
# RUN: llvm-objdump -bind %t | FileCheck %s
#
# Test that GOT slots are sorted by name
#
--- !mach-o
arch: x86_64
file-type: MH_OBJECT
flags: [ MH_SUBSECTIONS_VIA_SYMBOLS ]
sections:
- segment: __TEXT
section: __text
type: S_REGULAR
attributes: [ S_ATTR_PURE_INSTRUCTIONS, S_ATTR_SOME_INSTRUCTIONS ]
address: 0x0000000000000000
content: [ 0x55, 0x48, 0x89, 0xE5, 0x48, 0x8B, 0x0D, 0x00,
0x00, 0x00, 0x00, 0x48, 0x8B, 0x05, 0x00, 0x00,
0x00, 0x00, 0x8B, 0x00, 0x03, 0x01, 0x48, 0x8B,
0x0D, 0x00, 0x00, 0x00, 0x00, 0x03, 0x01, 0x5D,
0xC3 ]
relocations:
- offset: 0x00000019
type: X86_64_RELOC_GOT_LOAD
length: 2
pc-rel: true
extern: true
symbol: 2
- offset: 0x0000000E
type: X86_64_RELOC_GOT_LOAD
length: 2
pc-rel: true
extern: true
symbol: 1
- offset: 0x00000007
type: X86_64_RELOC_GOT_LOAD
length: 2
pc-rel: true
extern: true
symbol: 3
global-symbols:
- name: _func
type: N_SECT
scope: [ N_EXT ]
sect: 1
value: 0x0000000000000000
undefined-symbols:
- name: _aaa
type: N_UNDF
scope: [ N_EXT ]
value: 0x0000000000000000
- name: _fff
type: N_UNDF
scope: [ N_EXT ]
value: 0x0000000000000000
- name: _zzz
type: N_UNDF
scope: [ N_EXT ]
value: 0x0000000000000000
--- !mach-o
arch: x86_64
file-type: MH_OBJECT
flags: [ MH_SUBSECTIONS_VIA_SYMBOLS ]
sections:
- segment: __TEXT
section: __text
type: S_REGULAR
attributes: [ S_ATTR_PURE_INSTRUCTIONS, S_ATTR_SOME_INSTRUCTIONS ]
address: 0x0000000000000000
content: [ 0x55, 0x48, 0x89, 0xE5, 0x48, 0x8B, 0x0D, 0x00,
0x00, 0x00, 0x00, 0x48, 0x8B, 0x05, 0x00, 0x00,
0x00, 0x00, 0x8B, 0x00, 0x03, 0x01, 0x48, 0x8B,
0x0D, 0x00, 0x00, 0x00, 0x00, 0x03, 0x01, 0x5D,
0xC3 ]
relocations:
- offset: 0x00000019
type: X86_64_RELOC_GOT_LOAD
length: 2
pc-rel: true
extern: true
symbol: 2
- offset: 0x0000000E
type: X86_64_RELOC_GOT_LOAD
length: 2
pc-rel: true
extern: true
symbol: 1
- offset: 0x00000007
type: X86_64_RELOC_GOT_LOAD
length: 2
pc-rel: true
extern: true
symbol: 3
global-symbols:
- name: _main
type: N_SECT
scope: [ N_EXT ]
sect: 1
value: 0x0000000000000000
undefined-symbols:
- name: _bar
type: N_UNDF
scope: [ N_EXT ]
value: 0x0000000000000000
- name: _foo
type: N_UNDF
scope: [ N_EXT ]
value: 0x0000000000000000
- name: _zazzle
type: N_UNDF
scope: [ N_EXT ]
value: 0x0000000000000000
--- !mach-o
arch: x86_64
file-type: MH_DYLIB
install-name: /usr/lib/libfoobar.dylib
exports:
- name: _bar
- name: _zazzle
- name: _foo
- name: _aaa
- name: _fff
- name: _zzz
...
# CHECK: __DATA __got {{[0-9a-zA-Z _]+}} pointer 0 libfoobar _aaa
# CHECK-NEXT: __DATA __got {{[0-9a-zA-Z _]+}} pointer 0 libfoobar _bar
# CHECK-NEXT: __DATA __got {{[0-9a-zA-Z _]+}} pointer 0 libfoobar _fff
# CHECK-NEXT: __DATA __got {{[0-9a-zA-Z _]+}} pointer 0 libfoobar _foo
# CHECK-NEXT: __DATA __got {{[0-9a-zA-Z _]+}} pointer 0 libfoobar _zazzle
# CHECK-NEXT: __DATA __got {{[0-9a-zA-Z _]+}} pointer 0 libfoobar _zzz