maxjhandsome
/
llvm-project
forked from OSchip/llvm-project
1
0
Fork 0
Code Issues Pull Requests Packages Releases Wiki Activity

[lld-macho] Define __mh_*_header synthetic symbols. 

Bug: https://bugs.llvm.org/show_bug.cgi?id=49290

    Differential Revision: https://reviews.llvm.org/D97007
This commit is contained in:
Vy Nguyen 2021-03-18 18:49:45 -04:00
parent 6c52d4fd4c
commit 66f340051a
14 changed files with 156 additions and 26 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
lld/MachO/Driver.cpp
View File

@ -1043,14 +1043,7 @@ bool macho::link(ArrayRef<const char *> argsArr, bool canExitEarly,
}
createSyntheticSections();
// The Itanium C++ ABI requires dylibs to pass a pointer to __cxa_atexit
// which does e.g. cleanup of static global variables. The ABI document says
// that the pointer can point to any address in one of the dylib's segments,
// but in practice ld64 seems to set it to point to the header, so that's
// what's implemented here.
symtab->addSynthetic("___dso_handle", in.header->isec, 0,
/*privateExtern=*/true, /*linkerInternal=*/true);
createSyntheticSymbols();
for (const Arg *arg : args.filtered(OPT_sectcreate)) {
StringRef segName = arg->getValue(0);

8
lld/MachO/SymbolTable.cpp
View File

@ -159,10 +159,10 @@ Symbol *SymbolTable::addLazy(StringRef name, ArchiveFile *file,
Defined *SymbolTable::addSynthetic(StringRef name, InputSection *isec,
uint32_t value, bool isPrivateExtern,
bool isLinkerInternal) {
Defined *s = addDefined(name, nullptr, isec, value, /*isWeakDef=*/false,
isPrivateExtern);
s->linkerInternal = isLinkerInternal;
bool includeInSymtab) {
Defined *s = addDefined(name, nullptr, isec, value,
/*isWeakDef=*/false, isPrivateExtern);
s->includeInSymtab = includeInSymtab;
return s;
}

4
lld/MachO/SymbolTable.h
View File

@ -9,6 +9,8 @@
#ifndef LLD_MACHO_SYMBOL_TABLE_H
#define LLD_MACHO_SYMBOL_TABLE_H
#include "Symbols.h"
#include "lld/Common/LLVM.h"
#include "llvm/ADT/CachedHashString.h"
#include "llvm/ADT/DenseMap.h"
@ -50,7 +52,7 @@ public:
const llvm::object::Archive::Symbol &sym);
Defined *addSynthetic(StringRef name, InputSection *, uint32_t value,
bool isPrivateExtern, bool isLinkerInternal);
bool isPrivateExtern, bool includeInSymtab);
ArrayRef<Symbol *> getSymbols() const { return symVector; }
Symbol *find(llvm::CachedHashStringRef name);

6
lld/MachO/Symbols.h
View File

@ -99,7 +99,7 @@ public:
bool isWeakDef, bool isExternal, bool isPrivateExtern)
: Symbol(DefinedKind, name, file), isec(isec), value(value),
overridesWeakDef(false), privateExtern(isPrivateExtern),
linkerInternal(false), weakDef(isWeakDef), external(isExternal) {}
includeInSymtab(true), weakDef(isWeakDef), external(isExternal) {}
bool isWeakDef() const override { return weakDef; }
bool isExternalWeakDef() const {
@ -124,8 +124,8 @@ public:
bool overridesWeakDef : 1;
// Whether this symbol should appear in the output binary's export trie.
bool privateExtern : 1;
// Whether this symbol should appear in the output binary's symbol table.
bool linkerInternal : 1;
// Whether this symbol should appear in the output symbol table.
bool includeInSymtab : 1;
private:
const bool weakDef : 1;

62
lld/MachO/SyntheticSections.cpp
View File

@ -53,7 +53,12 @@ SyntheticSection::SyntheticSection(const char *segname, const char *name)
// dyld3's MachOLoaded::getSlide() assumes that the __TEXT segment starts
// from the beginning of the file (i.e. the header).
MachHeaderSection::MachHeaderSection()
: SyntheticSection(segment_names::text, section_names::header) {}
: SyntheticSection(segment_names::text, section_names::header) {
// XXX: This is a hack. (See D97007)
// Setting the index to 1 to pretend that this section is the text
// section.
index = 1;
}
void MachHeaderSection::addLoadCommand(LoadCommand *lc) {
loadCommands.push_back(lc);
@ -754,7 +759,7 @@ void SymtabSection::finalizeContents() {
for (Symbol *sym : symtab->getSymbols()) {
if (auto *defined = dyn_cast<Defined>(sym)) {
if (defined->linkerInternal)
if (!defined->includeInSymtab)
continue;
assert(defined->isExternal());
addSymbol(externalSymbols, defined);
@ -993,3 +998,56 @@ void CodeSignatureSection::writeTo(uint8_t *buf) const {
memcpy(id, fileName.begin(), fileName.size());
memset(id + fileName.size(), 0, fileNamePad);
}
void macho::createSyntheticSymbols() {
auto addHeaderSymbol = [](const char *name) {
symtab->addSynthetic(name, in.header->isec, 0,
/*privateExtern=*/true,
/*includeInSymtab*/ false);
};
switch (config->outputType) {
// FIXME: Assign the right addresse value for these symbols
// (rather than 0). But we need to do that after assignAddresses().
case MH_EXECUTE:
// If linking PIE, __mh_execute_header is a defined symbol in
// __TEXT, __text)
// Otherwise, it's an absolute symbol.
if (config->isPic)
symtab->addSynthetic("__mh_execute_header", in.header->isec, 0,
/*privateExtern*/ false,
/*includeInSymbtab*/ true);
else
symtab->addSynthetic("__mh_execute_header",
/*isec*/ nullptr, 0,
/*privateExtern*/ false,
/*includeInSymbtab*/ true);
break;
// The following symbols are N_SECT symbols, even though the header is not
// part of any section and that they are private to the bundle/dylib/object
// they are part of.
case MH_BUNDLE:
addHeaderSymbol("__mh_bundle_header");
break;
case MH_DYLIB:
addHeaderSymbol("__mh_dylib_header");
break;
case MH_DYLINKER:
addHeaderSymbol("__mh_dylinker_header");
break;
case MH_OBJECT:
addHeaderSymbol("__mh_object_header");
break;
default:
llvm_unreachable("unexpected outputType");
break;
}
// The Itanium C++ ABI requires dylibs to pass a pointer to __cxa_atexit
// which does e.g. cleanup of static global variables. The ABI document
// says that the pointer can point to any address in one of the dylib's
// segments, but in practice ld64 seems to set it to point to the header,
// so that's what's implemented here.
addHeaderSymbol("___dso_handle");
}

2
lld/MachO/SyntheticSections.h
View File

@ -500,6 +500,8 @@ struct InStruct {
extern InStruct in;
extern std::vector<SyntheticSection *> syntheticSections;
void createSyntheticSymbols();
} // namespace macho
} // namespace lld

1
lld/MachO/Writer.cpp
View File

@ -751,7 +751,6 @@ static void sortSegmentsAndSections() {
// output section indices.
if (!osec->isHidden())
osec->index = ++sectionIndex;
if (!firstTLVDataSection && isThreadLocalData(osec->flags))
firstTLVDataSection = osec;

13
lld/test/MachO/export-trie.s
View File

@ -15,7 +15,9 @@
# EXPORTS-DAG: [[#%x, HELLO_WORLD_ADDR:]] {{.*}} _hello_world
# EXPORTS-DAG: [[#%x, HELLO_ITS_ME_ADDR:]] {{.*}} _hello_its_me
# EXPORTS-DAG: [[#%x, HELLO_ITS_YOU_ADDR:]] {{.*}} _hello_its_you
# EXPORTS-DAG: {{0+}} g *ABS* __mh_execute_header
# EXPORTS-LABEL: Exports trie:
# EXPORTS-DAG: 0x{{0+}} __mh_execute_header [absolute]
# EXPORTS-DAG: 0x{{0*}}[[#%X, MAIN_ADDR]] _main
# EXPORTS-DAG: 0x{{0*}}[[#%X, HELLO_ADDR]] _hello
# EXPORTS-DAG: 0x{{0*}}[[#%X, HELLO_WORLD_ADDR]] _hello_world
@ -27,13 +29,16 @@
# CHECK-LABEL: ExportTrie:
# CHECK: Name: ''
# CHECK: Name: _
# CHECK: Name: main
# CHECK: Name: hello
# CHECK-DAG: Name: _mh_execute_header
# CHECK-DAG: Name: main
# CHECK-DAG: Name: hello
# CHECK: Name: _
# CHECK: Name: world
# CHECK: Name: its_
# CHECK: Name: you
# CHECK: Name: me
# CHECK-DAG: Name: you
# CHECK-DAG: Name: me
.section __TEXT,__cstring
.globl _hello, _hello_world, _hello_its_me, _hello_its_you, _main

1
lld/test/MachO/map-file.s
View File

@ -29,6 +29,7 @@ _main:
# CHECK-NEXT: [[#%x,MAIN:]] g F __TEXT,__text _main
# CHECK-NEXT: [[#%x,NUMBER:]] g O __DATA,__common _number
# CHECK-NEXT: [[#%x,FOO:]] g O __TEXT,obj _foo
# CHECK-NEXT: {{0+}} g *ABS* __mh_execute_header
# CHECK-NEXT: # Path: {{.*}}{{/|\\}}map-file.s.tmp/test-map
# CHECK-NEXT: # Arch: x86_64

16
lld/test/MachO/mh-execute-header.s Normal file
View File

@ -0,0 +1,16 @@
# REQUIRES: x86
# RUN: rm -rf %t; mkdir %t
# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %s -o %t/test.o
# RUN: %lld -o %t/test.pie %t/test.o -pie
# RUN: llvm-objdump --macho --syms %t/test.pie | FileCheck %s --check-prefix=PIE
# RUN: %lld -o %t/test.no_pie %t/test.o -no_pie
# RUN: llvm-objdump --macho --syms %t/test.no_pie | FileCheck %s --check-prefix=NO-PIE
# PIE: 0000000100000000 g F __TEXT,__text __mh_execute_header
# NO-PIE: 0000000000000000 g *ABS* __mh_execute_header
.text
.global _main
_main:
ret

43
lld/test/MachO/mh-header-link.s Normal file
View File

@ -0,0 +1,43 @@
# REQUIRES: x86
## This tests that we can link against these synthetic symbols even
## if they are not in the symbol table.
# RUN: rm -rf %t; split-file %s %t
## Test that in a dylib, we can link against __mh_dylib_header
## (but not in other types of files)
# RUN: llvm-mc %t/dylib.s -triple=x86_64-apple-macos11.0 -filetype=obj -o %t/dylib.o
# RUN: %lld -pie -dylib %t/dylib.o -o %t/dylib.out
# RUN: llvm-objdump -m --syms %t/dylib.out | FileCheck %s --check-prefix DYLIB
# RUN: not %lld -pie -o /dev/null %t/dylib.o 2>&1 | FileCheck %s --check-prefix ERR-DYLIB
# DYLIB: SYMBOL TABLE:
# DYLIB-NEXT: {{[0-9a-f]+}} g F __TEXT,__text _main
# DYLIB-NEXT-EMPTY:
# ERR-DYLIB: error: undefined symbol: __mh_dylib_header
## Test that in an executable, we can link against __mh_execute_header
# RUN: llvm-mc %t/main.s -triple=x86_64-apple-macos11.0 -filetype=obj -o %t/exec.o
# RUN: %lld -pie %t/exec.o -o %t/exec.out
## But it would be an error trying to reference __mh_execute_header in a dylib
# RUN: not %lld -pie -o /dev/null -dylib %t/exec.o 2>&1 | FileCheck %s --check-prefix ERR-EXEC
# ERR-EXEC: error: undefined symbol: __mh_execute_header
#--- main.s
.text
.globl _main
_main:
mov __mh_execute_header@GOTPCREL(%rip), %rax
ret
#--- dylib.s
.text
.globl _main
_main:
mov __mh_dylib_header@GOTPCREL(%rip), %rax
ret

2
lld/test/MachO/objc.s
View File

@ -32,7 +32,7 @@
# NO-OBJC-EMPTY:
# NO-OBJC-NEXT: SYMBOL TABLE:
# NO-OBJC-NEXT: g F __TEXT,__text _main
# NO-OBJC-EMPTY:
# NO_OBJC-NEXT: g *ABS* __mh_execute_header
#--- has-objc-symbol.s
.globl _OBJC_CLASS_$_MyObject

1
lld/test/MachO/stabs.s
View File

@ -60,6 +60,7 @@
# CHECK-NEXT: [[#ZERO]] S _zero
# CHECK-NEXT: [[#FOO]] T _foo
# CHECK-NEXT: {{[0-9af]+}} T _no_debug
# CHECK-NEXT: {{0+}} A __mh_execute_header
# CHECK-EMPTY:
## Check that we don't attempt to emit rebase opcodes for the debug sections

14
lld/test/MachO/symtab.s
View File

@ -56,6 +56,16 @@
# CHECK-NEXT: ]
# CHECK-NEXT: Value: 0x1{{[0-9a-f]*}}
# CHECK-NEXT: }
# CHECK-NEXT: Symbol {
# CHECK-NEXT: Name: __mh_execute_header (81)
# CHECK-NEXT: Extern
# CHECK-NEXT: Type: Abs (0x2)
# CHECK-NEXT: Section: (0x0)
# CHECK-NEXT: RefType: UndefinedNonLazy (0x0)
# CHECK-NEXT: Flags [ (0x0)
# CHECK-NEXT: ]
# CHECK-NEXT: Value: 0x0
# CHECK-NEXT: }
# CHECK-NEXT: Symbol {
# CHECK-NEXT: Name: dyld_stub_binder
# CHECK-NEXT: Extern
@ -82,8 +92,8 @@
# CHECK-NEXT: ilocalsym: 0
# CHECK-NEXT: nlocalsym: 2
# CHECK-NEXT: iextdefsym: 2
# CHECK-NEXT: nextdefsym: 3
# CHECK-NEXT: iundefsym: 5
# CHECK-NEXT: nextdefsym: 4
# CHECK-NEXT: iundefsym: 6
# CHECK-NEXT: nundefsym: 2
## Verify that the first entry in the StringTable is a space, and that