[lld] 241f0e8 - [lld/mac] Add support for $ld$previous symbols with explicit symbol name
Nico Weber via llvm-commits
llvm-commits at lists.llvm.org
Thu Jul 28 17:37:31 PDT 2022
Author: Nico Weber
Date: 2022-07-28T20:35:48-04:00
New Revision: 241f0e8b76d544a4a07a7f775b8421632539be19
URL: https://github.com/llvm/llvm-project/commit/241f0e8b76d544a4a07a7f775b8421632539be19
DIFF: https://github.com/llvm/llvm-project/commit/241f0e8b76d544a4a07a7f775b8421632539be19.diff
LOG: [lld/mac] Add support for $ld$previous symbols with explicit symbol name
A symbol `$ld$previous$/Another$1.2.3$1$3.0$14.0$_xxx$` means
"pretend symbol `_xxx` is in dylib `/Another` with version `1.2.3`
if the deployment target is between `3.0` and `14.0` and we're
targeting platform `1` (ie macOS)".
This means dylibs can now inject synthetic dylibs into the link, so
DylibFile needs to grow a 3rd constructor.
The only other interesting thing is that such an injected dylib
counts as a use of the original dylib. This patch gets this mostly
right (if _only_ `$ld$previous` symbols are used from a dylib,
we don't add a dep on the dylib itself, matching ld64), but one case
where we don't match ld64 yet is that ld64 even omits the original
dylib when linking it with `-needed-l`. Lld currently still adds a load
command for the original dylib in that case. (That's for a future
patch.)
Fixes #56074.
Differential Revision: https://reviews.llvm.org/D130725
Added:
Modified:
lld/MachO/DriverUtils.cpp
lld/MachO/InputFiles.cpp
lld/MachO/InputFiles.h
lld/MachO/Writer.cpp
lld/test/MachO/special-symbol-ld-previous.s
Removed:
################################################################################
diff --git a/lld/MachO/DriverUtils.cpp b/lld/MachO/DriverUtils.cpp
index d8e474d15cfd..b91a43552443 100644
--- a/lld/MachO/DriverUtils.cpp
+++ b/lld/MachO/DriverUtils.cpp
@@ -211,7 +211,7 @@ DylibFile *macho::loadDylib(MemoryBufferRef mbref, DylibFile *umbrella,
DylibFile *&file = loadedDylibs[path];
if (file) {
if (explicitlyLinked)
- file->explicitlyLinked = explicitlyLinked;
+ file->setExplicitlyLinked();
return file;
}
diff --git a/lld/MachO/InputFiles.cpp b/lld/MachO/InputFiles.cpp
index d55d9ba40b18..1befdf480eb0 100644
--- a/lld/MachO/InputFiles.cpp
+++ b/lld/MachO/InputFiles.cpp
@@ -1978,6 +1978,14 @@ DylibFile::DylibFile(const InterfaceFile &interface, DylibFile *umbrella,
}
}
+DylibFile::DylibFile(DylibFile *umbrella)
+ : InputFile(DylibKind, MemoryBufferRef{}), refState(RefState::Unreferenced),
+ explicitlyLinked(false), isBundleLoader(false) {
+ if (umbrella == nullptr)
+ umbrella = this;
+ this->umbrella = umbrella;
+}
+
void DylibFile::parseReexports(const InterfaceFile &interface) {
const InterfaceFile *topLevel =
interface.getParent() == nullptr ? &interface : interface.getParent();
@@ -1989,6 +1997,39 @@ void DylibFile::parseReexports(const InterfaceFile &interface) {
}
}
+bool DylibFile::isExplicitlyLinked() const {
+ if (!explicitlyLinked)
+ return false;
+
+ // If this dylib was explicitly linked, but at least one of the symbols
+ // of the synthetic dylibs it created via $ld$previous symbols is
+ // referenced, then that synthetic dylib fulfils the explicit linkedness
+ // and we can deadstrip this dylib if it's unreferenced.
+ for (const auto *dylib : extraDylibs)
+ if (dylib->isReferenced())
+ return false;
+
+ return true;
+}
+
+DylibFile *DylibFile::getSyntheticDylib(StringRef installName,
+ uint32_t currentVersion,
+ uint32_t compatVersion) {
+ for (DylibFile *dylib : extraDylibs)
+ if (dylib->installName == installName) {
+ // FIXME: Check what to do if
diff erent $ld$previous symbols
+ // request the same dylib, but with
diff erent versions.
+ return dylib;
+ }
+
+ auto *dylib = make<DylibFile>(umbrella == this ? nullptr : umbrella);
+ dylib->installName = saver().save(installName);
+ dylib->currentVersion = currentVersion;
+ dylib->compatibilityVersion = compatVersion;
+ extraDylibs.push_back(dylib);
+ return dylib;
+}
+
// $ld$ symbols modify the properties/behavior of the library (e.g. its install
// name, compatibility version or hide/add symbols) for specific target
// versions.
@@ -2024,10 +2065,9 @@ void DylibFile::handleLDPreviousSymbol(StringRef name, StringRef originalName) {
std::tie(platformStr, name) = name.split('$');
std::tie(startVersion, name) = name.split('$');
std::tie(endVersion, name) = name.split('$');
- std::tie(symbolName, rest) = name.split('$');
- // TODO: ld64 contains some logic for non-empty symbolName as well.
- if (!symbolName.empty())
- return;
+ std::tie(symbolName, rest) = name.rsplit('$');
+
+ // FIXME: Does this do the right thing for zippered files?
unsigned platform;
if (platformStr.getAsInteger(10, platform) ||
platform != static_cast<unsigned>(config->platform()))
@@ -2048,8 +2088,9 @@ void DylibFile::handleLDPreviousSymbol(StringRef name, StringRef originalName) {
config->platformInfo.minimum >= end)
return;
- this->installName = saver().save(installName);
-
+ // Initialized to compatibilityVersion for the symbolName branch below.
+ uint32_t newCompatibilityVersion = compatibilityVersion;
+ uint32_t newCurrentVersionForSymbol = currentVersion;
if (!compatVersion.empty()) {
VersionTuple cVersion;
if (cVersion.tryParse(compatVersion)) {
@@ -2057,8 +2098,27 @@ void DylibFile::handleLDPreviousSymbol(StringRef name, StringRef originalName) {
"' ignored");
return;
}
- compatibilityVersion = encodeVersion(cVersion);
+ newCompatibilityVersion = encodeVersion(cVersion);
+ newCurrentVersionForSymbol = newCompatibilityVersion;
+ }
+
+ if (!symbolName.empty()) {
+ // A $ld$previous$ symbol with symbol name adds a symbol with that name to
+ // a dylib with given name and version.
+ auto *dylib = getSyntheticDylib(installName, newCurrentVersionForSymbol,
+ newCompatibilityVersion);
+
+ // Just adding the symbol to the symtab works because dylibs contain their
+ // symbols in alphabetical order, guaranteeing $ld$ symbols to precede
+ // normal symbols.
+ dylib->symbols.push_back(symtab->addDylib(
+ saver().save(symbolName), dylib, /*isWeakDef=*/false, /*isTlv=*/false));
+ return;
}
+
+ // A $ld$previous$ symbol without symbol name modifies the dylib it's in.
+ this->installName = saver().save(installName);
+ this->compatibilityVersion = newCompatibilityVersion;
}
void DylibFile::handleLDInstallNameSymbol(StringRef name,
diff --git a/lld/MachO/InputFiles.h b/lld/MachO/InputFiles.h
index ea6802814e4c..89172922a0a7 100644
--- a/lld/MachO/InputFiles.h
+++ b/lld/MachO/InputFiles.h
@@ -219,10 +219,13 @@ class DylibFile final : public InputFile {
explicit DylibFile(const llvm::MachO::InterfaceFile &interface,
DylibFile *umbrella, bool isBundleLoader,
bool explicitlyLinked);
+ explicit DylibFile(DylibFile *umbrella);
void parseLoadCommands(MemoryBufferRef mb);
void parseReexports(const llvm::MachO::InterfaceFile &interface);
bool isReferenced() const { return numReferencedSymbols > 0; }
+ bool isExplicitlyLinked() const;
+ void setExplicitlyLinked() { explicitlyLinked = true; }
static bool classof(const InputFile *f) { return f->kind() == DylibKind; }
@@ -239,14 +242,26 @@ class DylibFile final : public InputFile {
bool forceNeeded = false;
bool forceWeakImport = false;
bool deadStrippable = false;
- bool explicitlyLinked = false;
+
+private:
+ bool explicitlyLinked = false; // Access via isExplicitlyLinked().
+
+public:
// An executable can be used as a bundle loader that will load the output
// file being linked, and that contains symbols referenced, but not
// implemented in the bundle. When used like this, it is very similar
// to a dylib, so we've used the same class to represent it.
bool isBundleLoader;
+ // Synthetic Dylib objects created by $ld$previous symbols in this dylib.
+ // Usually empty. These synthetic dylibs won't have synthetic dylibs
+ // themselves.
+ SmallVector<DylibFile *, 2> extraDylibs;
+
private:
+ DylibFile *getSyntheticDylib(StringRef installName, uint32_t currentVersion,
+ uint32_t compatVersion);
+
bool handleLDSymbol(StringRef originalName);
void handleLDPreviousSymbol(StringRef name, StringRef originalName);
void handleLDInstallNameSymbol(StringRef name, StringRef originalName);
diff --git a/lld/MachO/Writer.cpp b/lld/MachO/Writer.cpp
index 7fad9f5564ce..3c44a60f4be2 100644
--- a/lld/MachO/Writer.cpp
+++ b/lld/MachO/Writer.cpp
@@ -780,70 +780,80 @@ template <class LP> void Writer::createLoadCommands() {
if (config->outputType == MH_EXECUTE)
in.header->addLoadCommand(make<LCMain>());
+ // See ld64's OutputFile::buildDylibOrdinalMapping for the corresponding
+ // library ordinal computation code in ld64.
int64_t dylibOrdinal = 1;
DenseMap<StringRef, int64_t> ordinalForInstallName;
+
+ std::vector<DylibFile *> dylibFiles;
for (InputFile *file : inputFiles) {
- if (auto *dylibFile = dyn_cast<DylibFile>(file)) {
- if (dylibFile->isBundleLoader) {
- dylibFile->ordinal = BIND_SPECIAL_DYLIB_MAIN_EXECUTABLE;
- // Shortcut since bundle-loader does not re-export the symbols.
+ if (auto *dylibFile = dyn_cast<DylibFile>(file))
+ dylibFiles.push_back(dylibFile);
+ }
+ for (size_t i = 0; i < dylibFiles.size(); ++i)
+ dylibFiles.insert(dylibFiles.end(), dylibFiles[i]->extraDylibs.begin(),
+ dylibFiles[i]->extraDylibs.end());
- dylibFile->reexport = false;
- continue;
- }
+ for (DylibFile *dylibFile : dylibFiles) {
+ if (dylibFile->isBundleLoader) {
+ dylibFile->ordinal = BIND_SPECIAL_DYLIB_MAIN_EXECUTABLE;
+ // Shortcut since bundle-loader does not re-export the symbols.
- // Don't emit load commands for a dylib that is not referenced if:
- // - it was added implicitly (via a reexport, an LC_LOAD_DYLINKER --
- // if it's on the linker command line, it's explicit)
- // - or it's marked MH_DEAD_STRIPPABLE_DYLIB
- // - or the flag -dead_strip_dylibs is used
- // FIXME: `isReferenced()` is currently computed before dead code
- // stripping, so references from dead code keep a dylib alive. This
- // matches ld64, but it's something we should do better.
- if (!dylibFile->isReferenced() && !dylibFile->forceNeeded &&
- (!dylibFile->explicitlyLinked || dylibFile->deadStrippable ||
- config->deadStripDylibs))
- continue;
+ dylibFile->reexport = false;
+ continue;
+ }
- // Several DylibFiles can have the same installName. Only emit a single
- // load command for that installName and give all these DylibFiles the
- // same ordinal.
- // This can happen in several cases:
- // - a new framework could change its installName to an older
- // framework name via an $ld$ symbol depending on platform_version
- // - symlinks (for example, libpthread.tbd is a symlink to libSystem.tbd;
- // Foo.framework/Foo.tbd is usually a symlink to
- // Foo.framework/Versions/Current/Foo.tbd, where
- // Foo.framework/Versions/Current is usually a symlink to
- // Foo.framework/Versions/A)
- // - a framework can be linked both explicitly on the linker
- // command line and implicitly as a reexport from a
diff erent
- // framework. The re-export will usually point to the tbd file
- // in Foo.framework/Versions/A/Foo.tbd, while the explicit link will
- // usually find Foo.framework/Foo.tbd. These are usually symlinks,
- // but in a --reproduce archive they will be identical but distinct
- // files.
- // In the first case, *semantically distinct* DylibFiles will have the
- // same installName.
- int64_t &ordinal = ordinalForInstallName[dylibFile->installName];
- if (ordinal) {
- dylibFile->ordinal = ordinal;
- continue;
- }
+ // Don't emit load commands for a dylib that is not referenced if:
+ // - it was added implicitly (via a reexport, an LC_LOAD_DYLINKER --
+ // if it's on the linker command line, it's explicit)
+ // - or it's marked MH_DEAD_STRIPPABLE_DYLIB
+ // - or the flag -dead_strip_dylibs is used
+ // FIXME: `isReferenced()` is currently computed before dead code
+ // stripping, so references from dead code keep a dylib alive. This
+ // matches ld64, but it's something we should do better.
+ if (!dylibFile->isReferenced() && !dylibFile->forceNeeded &&
+ (!dylibFile->isExplicitlyLinked() || dylibFile->deadStrippable ||
+ config->deadStripDylibs))
+ continue;
- ordinal = dylibFile->ordinal = dylibOrdinal++;
- LoadCommandType lcType =
- dylibFile->forceWeakImport || dylibFile->refState == RefState::Weak
- ? LC_LOAD_WEAK_DYLIB
- : LC_LOAD_DYLIB;
- in.header->addLoadCommand(make<LCDylib>(lcType, dylibFile->installName,
- dylibFile->compatibilityVersion,
- dylibFile->currentVersion));
-
- if (dylibFile->reexport)
- in.header->addLoadCommand(
- make<LCDylib>(LC_REEXPORT_DYLIB, dylibFile->installName));
+ // Several DylibFiles can have the same installName. Only emit a single
+ // load command for that installName and give all these DylibFiles the
+ // same ordinal.
+ // This can happen in several cases:
+ // - a new framework could change its installName to an older
+ // framework name via an $ld$ symbol depending on platform_version
+ // - symlinks (for example, libpthread.tbd is a symlink to libSystem.tbd;
+ // Foo.framework/Foo.tbd is usually a symlink to
+ // Foo.framework/Versions/Current/Foo.tbd, where
+ // Foo.framework/Versions/Current is usually a symlink to
+ // Foo.framework/Versions/A)
+ // - a framework can be linked both explicitly on the linker
+ // command line and implicitly as a reexport from a
diff erent
+ // framework. The re-export will usually point to the tbd file
+ // in Foo.framework/Versions/A/Foo.tbd, while the explicit link will
+ // usually find Foo.framework/Foo.tbd. These are usually symlinks,
+ // but in a --reproduce archive they will be identical but distinct
+ // files.
+ // In the first case, *semantically distinct* DylibFiles will have the
+ // same installName.
+ int64_t &ordinal = ordinalForInstallName[dylibFile->installName];
+ if (ordinal) {
+ dylibFile->ordinal = ordinal;
+ continue;
}
+
+ ordinal = dylibFile->ordinal = dylibOrdinal++;
+ LoadCommandType lcType =
+ dylibFile->forceWeakImport || dylibFile->refState == RefState::Weak
+ ? LC_LOAD_WEAK_DYLIB
+ : LC_LOAD_DYLIB;
+ in.header->addLoadCommand(make<LCDylib>(lcType, dylibFile->installName,
+ dylibFile->compatibilityVersion,
+ dylibFile->currentVersion));
+
+ if (dylibFile->reexport)
+ in.header->addLoadCommand(
+ make<LCDylib>(LC_REEXPORT_DYLIB, dylibFile->installName));
}
if (functionStartsSection)
diff --git a/lld/test/MachO/special-symbol-ld-previous.s b/lld/test/MachO/special-symbol-ld-previous.s
index db397353287f..8cdfb976dd04 100644
--- a/lld/test/MachO/special-symbol-ld-previous.s
+++ b/lld/test/MachO/special-symbol-ld-previous.s
@@ -2,52 +2,110 @@
# RUN: rm -rf %t; split-file --no-leading-lines %s %t
-# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %t/foo.s -o %t/foo.o
+# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %t/ref_xxx.s -o %t/ref_xxx.o
+# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %t/ref_ySyy.s -o %t/ref_ySyy.o
+# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %t/ref_zzz.s -o %t/ref_zzz.o
## Case 1: special symbol $ld$previous affects the install name / compatibility version
## since the specified version 11.0.0 is within the affected range [3.0, 14.0).
-# RUN: %lld -o %t/libfoo1.dylib %t/libLDPreviousInstallName.tbd %t/foo.o -dylib -platform_version macos 11.0.0 11.0.0
+# RUN: %lld -o %t/libfoo1.dylib %t/libLDPreviousInstallName.tbd %t/ref_xxx.o -dylib -platform_version macos 11.0.0 11.0.0
# RUN: llvm-objdump --macho --dylibs-used %t/libfoo1.dylib | FileCheck --check-prefix=CASE1 %s
-# CASE1: /New (compatibility version 1.2.3, current version 5.0.0)
+# CASE1: /Old (compatibility version 1.2.3, current version 5.0.0)
## Case 2: special symbol $ld$previous does not affect the install name / compatibility version
## since the specified version 2.0.0 is lower than the affected range [3.0, 14.0).
-# RUN: %lld -o %t/libfoo2.dylib %t/libLDPreviousInstallName.tbd %t/foo.o -dylib -platform_version macos 2.0.0 2.0.0
+# RUN: %lld -o %t/libfoo2.dylib %t/libLDPreviousInstallName.tbd %t/ref_xxx.o -dylib -platform_version macos 2.0.0 2.0.0
# RUN: llvm-objdump --macho --dylibs-used %t/libfoo2.dylib | FileCheck --check-prefix=CASE2 %s
-# CASE2: /Old (compatibility version 1.1.1, current version 5.0.0)
+# CASE2: /New (compatibility version 1.1.1, current version 5.0.0)
## Case 3: special symbol $ld$previous does not affect the install name / compatibility version
## since the specified version 14.0.0 is higher than the affected range [3.0, 14.0).
-# RUN: %lld -o %t/libfoo3.dylib %t/libLDPreviousInstallName.tbd %t/foo.o -dylib -platform_version macos 2.0.0 2.0.0
+# RUN: %lld -o %t/libfoo3.dylib %t/libLDPreviousInstallName.tbd %t/ref_xxx.o -dylib -platform_version macos 2.0.0 2.0.0
# RUN: llvm-objdump --macho --dylibs-used %t/libfoo3.dylib | FileCheck --check-prefix=CASE3 %s
-# CASE3: /Old (compatibility version 1.1.1, current version 5.0.0)
+# CASE3: /New (compatibility version 1.1.1, current version 5.0.0)
+
+## The remaining cases test handling when a symbol name is part of $ld$previous.
+
+## Case 4: special symbol $ld$previous affects the install name / compatibility version
+## when the specified version 11.0.0 is within the affected range [3.0, 14.0) when a symbol
+## is part of $previous$ if and only if that named symbol is referenced.
+## That is, for $ld$previous$/NewName$$3.0$14.0$_symNam$, if _symNam is
+## referenced, it refers to dylib /NewName if the deployment target is
+## in [3.0, 14.0).
+
+# RUN: %lld -o %t/libfoo4_yes.dylib %t/libLDPreviousInstallName-Symbol.tbd %t/ref_ySyy.o -dylib -platform_version macos 11.0.0 11.0.0
+# RUN: llvm-otool -L %t/libfoo4_yes.dylib | FileCheck --check-prefix=CASE4-YES --implicit-check-not=/New %s
+# CASE4-YES: /Old (compatibility version 1.2.3, current version 1.2.3)
+
+## $previous has no effect because deployment target is too new.
+# RUN: %lld -o %t/libfoo4_no.dylib %t/libLDPreviousInstallName-Symbol.tbd %t/ref_ySyy.o -dylib -platform_version macos 14.0.0 14.0.0
+# RUN: llvm-otool -L %t/libfoo4_no.dylib | FileCheck --check-prefix=CASE4-NO --implicit-check-not=/Old %s
+# CASE4-NO: /New (compatibility version 1.1.1, current version 5.0.0)
+
+## $previous has no effect because named symbol isn't referenced.
+# RUN: %lld -o %t/libfoo4_no.dylib %t/libLDPreviousInstallName-Symbol.tbd %t/ref_zzz.o -dylib -platform_version macos 11.0.0 11.0.0
+# RUN: llvm-otool -L %t/libfoo4_no.dylib | FileCheck --check-prefix=CASE4-NO %s
+
+## Case 5: Reference two symbols that add
diff erent $previous names each,
+## and one that references the "normal" dylib.
+## This should produce three
diff erent load commands.
+# RUN: %lld -o %t/libfoo5.dylib %t/libLDPreviousInstallName-Symbol.tbd %t/ref_xxx.o %t/ref_ySyy.o %t/ref_zzz.o -dylib -platform_version macos 11.0.0 11.0.0
+# RUN: llvm-otool -L %t/libfoo5.dylib | FileCheck --check-prefix=CASE5 %s
+# CASE5: /New (compatibility version 1.1.1, current version 5.0.0)
+# CASE5-DAG: /Another (compatibility version 1.1.1, current version 5.0.0)
+# CASE5-DAG: /Old (compatibility version 1.2.3, current version 1.2.3)
## Check that we emit a warning for an invalid start, end and compatibility versions.
-# RUN: %no-fatal-warnings-lld -o %t/libfoo1.dylib %t/libLDPreviousInvalid.tbd %t/foo.o -dylib \
+# RUN: %no-fatal-warnings-lld -o %t/libfoo1.dylib %t/libLDPreviousInvalid.tbd %t/ref_xxx.o -dylib \
# RUN: -platform_version macos 11.0.0 11.0.0 2>&1 | FileCheck --check-prefix=INVALID-VERSION %s
# INVALID-VERSION-DAG: failed to parse start version, symbol '$ld$previous$/New$1.2.3$1$3.a$14.0$$' ignored
# INVALID-VERSION-DAG: failed to parse end version, symbol '$ld$previous$/New$1.2.3$1$3.0$14.b$$' ignored
# INVALID-VERSION-DAG: failed to parse compatibility version, symbol '$ld$previous$/New$1.2.c$1$3.0$14.0$$' ignored
-#--- foo.s
+#--- ref_xxx.s
.long _xxx at GOTPCREL
+#--- ref_ySyy.s
+.long _y$yy at GOTPCREL
+
+#--- ref_zzz.s
+.long _zzz at GOTPCREL
+
#--- libLDPreviousInstallName.tbd
--- !tapi-tbd-v3
archs: [ x86_64 ]
uuids: [ 'x86_64: 19311019-01AB-342E-812B-73A74271A715' ]
platform: macosx
-install-name: '/Old'
+install-name: '/New'
+current-version: 5
+compatibility-version: 1.1.1
+exports:
+ - archs: [ x86_64 ]
+ symbols: [ '$ld$previous$/Old$1.2.3$1$3.0$14.0$$', _xxx ]
+...
+
+#--- libLDPreviousInstallName-Symbol.tbd
+--- !tapi-tbd-v3
+archs: [ x86_64 ]
+uuids: [ 'x86_64: 19311019-01AB-342E-812B-73A74271A715' ]
+platform: macosx
+install-name: '/New'
current-version: 5
compatibility-version: 1.1.1
exports:
- archs: [ x86_64 ]
- symbols: [ '$ld$previous$/New$1.2.3$1$3.0$14.0$$', _xxx ]
+ symbols: [
+ '$ld$previous$/Another$$1$3.0$14.0$_xxx$',
+ '$ld$previous$/Old$1.2.3$1$3.0$14.0$_y$yy$',
+ _xxx,
+ '_y$yy',
+ _zzz,
+ ]
...
#--- libLDPreviousInvalid.tbd
More information about the llvm-commits
mailing list