[ELF] Add internal InputFile (llvm#78944)

MaskRay · web-flow · commit 43b13341fbbb · 2024-01-22T09:09:46.000-08:00
Based on https://reviews.llvm.org/D45375 . Introduce a new InputFile kind `InternalKind`, use it for * `ctx.internalFile`: for linker-defined symbols and some synthesized `Undefined` * `createInternalFile`: for symbol assignments and --defsym I picked "internal" instead of "synthetic" to avoid confusion with SyntheticSection. Currently a symbol's file is one of: nullptr, ObjKind, SharedKind, BitcodeKind, BinaryKind. Now it's non-null (I plan to add an `assert(file)` to Symbol::Symbol and change `toString(const InputFile *)` separately). Debugging and error reporting gets improved. The immediate user-facing difference is more descriptive "File" column in the --cref output. This patch may unlock further simplification. Currently each symbol assignment gets its own `createInternalFile(cmd->location)`. Two symbol assignments in a linker script do not share the same file. Making the file the same would be nice, but would require non trivial code.
diff --git a/lld/ELF/Arch/ARM.cpp b/lld/ELF/Arch/ARM.cpp
@@ -1381,9 +1381,9 @@ template <typename ELFT> void elf::writeARMCmseImportLib() {
   // Copy the secure gateway entry symbols to the import library symbol table.
   for (auto &p : symtab.cmseSymMap) {
     Defined *d = cast<Defined>(p.second.sym);
-    impSymTab->addSymbol(makeDefined(nullptr, d->getName(), d->computeBinding(),
-                                     /*stOther=*/0, STT_FUNC, d->getVA(),
-                                     d->getSize(), nullptr));
+    impSymTab->addSymbol(makeDefined(
+        ctx.internalFile, d->getName(), d->computeBinding(),
+        /*stOther=*/0, STT_FUNC, d->getVA(), d->getSize(), nullptr));
   }
 
   size_t idx = 0;
diff --git a/lld/ELF/Arch/Mips.cpp b/lld/ELF/Arch/Mips.cpp
@@ -771,12 +771,11 @@ template <class ELFT> bool elf::isMipsPIC(const Defined *sym) {
   if (!sym->section)
     return false;
 
-  ObjFile<ELFT> *file =
-      cast<InputSectionBase>(sym->section)->template getFile<ELFT>();
-  if (!file)
+  InputFile *file = cast<InputSectionBase>(sym->section)->file;
+  if (!file || file->isInternal())
     return false;
 
-  return file->getObj().getHeader().e_flags & EF_MIPS_PIC;
+  return cast<ObjFile<ELFT>>(file)->getObj().getHeader().e_flags & EF_MIPS_PIC;
 }
 
 template <class ELFT> TargetInfo *elf::getMipsTargetInfo() {
diff --git a/lld/ELF/Arch/PPC64.cpp b/lld/ELF/Arch/PPC64.cpp
@@ -253,7 +253,7 @@ static bool addOptional(StringRef name, uint64_t value,
   Symbol *sym = symtab.find(name);
   if (!sym || sym->isDefined())
     return false;
-  sym->resolve(Defined{/*file=*/nullptr, StringRef(), STB_GLOBAL, STV_HIDDEN,
+  sym->resolve(Defined{ctx.internalFile, StringRef(), STB_GLOBAL, STV_HIDDEN,
                        STT_FUNC, value,
                        /*size=*/0, /*section=*/nullptr});
   defined.push_back(cast<Defined>(sym));
diff --git a/lld/ELF/Config.h b/lld/ELF/Config.h
@@ -473,6 +473,8 @@ struct Ctx {
                  std::pair<const InputFile *, const InputFile *>>
       backwardReferences;
   llvm::SmallSet<llvm::StringRef, 0> auxiliaryFiles;
+  // InputFile for linker created symbols with no source location.
+  InputFile *internalFile;
   // True if SHT_LLVM_SYMPART is used.
   std::atomic<bool> hasSympart{false};
   // True if there are TLS IE relocations. Set DF_STATIC_TLS if -shared.
diff --git a/lld/ELF/Driver.cpp b/lld/ELF/Driver.cpp
@@ -105,6 +105,7 @@ void Ctx::reset() {
   whyExtractRecords.clear();
   backwardReferences.clear();
   auxiliaryFiles.clear();
+  internalFile = nullptr;
   hasSympart.store(false, std::memory_order_relaxed);
   hasTlsIe.store(false, std::memory_order_relaxed);
   needsTlsLd.store(false, std::memory_order_relaxed);
@@ -2337,7 +2338,8 @@ static void readSymbolPartitionSection(InputSectionBase *s) {
 
 static Symbol *addUnusedUndefined(StringRef name,
                                   uint8_t binding = STB_GLOBAL) {
-  return symtab.addSymbol(Undefined{nullptr, name, binding, STV_DEFAULT, 0});
+  return symtab.addSymbol(
+      Undefined{ctx.internalFile, name, binding, STV_DEFAULT, 0});
 }
 
 static void markBuffersAsDontNeed(bool skipLinkedOutput) {
@@ -2696,6 +2698,8 @@ void LinkerDriver::link(opt::InputArgList &args) {
   for (auto *arg : args.filtered(OPT_trace_symbol))
     symtab.insert(arg->getValue())->traced = true;
 
+  ctx.internalFile = createInternalFile("<internal>");
+
   // Handle -u/--undefined before input files. If both a.a and b.so define foo,
   // -u foo a.a b.so will extract a.a.
   for (StringRef name : config->undefined)
diff --git a/lld/ELF/InputFiles.cpp b/lld/ELF/InputFiles.cpp
@@ -1785,6 +1785,10 @@ void BinaryFile::parse() {
                                       nullptr});
 }
 
+InputFile *elf::createInternalFile(StringRef name) {
+  return make<InputFile>(InputFile::InternalKind, MemoryBufferRef("", name));
+}
+
 ELFFileBase *elf::createObjFile(MemoryBufferRef mb, StringRef archiveName,
                                 bool lazy) {
   ELFFileBase *f;
diff --git a/lld/ELF/InputFiles.h b/lld/ELF/InputFiles.h
@@ -63,14 +63,17 @@ class InputFile {
     SharedKind,
     BitcodeKind,
     BinaryKind,
+    InternalKind,
   };
 
+  InputFile(Kind k, MemoryBufferRef m);
   Kind kind() const { return fileKind; }
 
   bool isElf() const {
     Kind k = kind();
     return k == ObjKind || k == SharedKind;
   }
+  bool isInternal() const { return kind() == InternalKind; }
 
   StringRef getName() const { return mb.getBufferIdentifier(); }
   MemoryBufferRef mb;
@@ -151,9 +154,6 @@ class InputFile {
   // R_PPC64_TLSLD. Disable TLS relaxation to avoid bad code generation.
   bool ppc64DisableTLSRelax = false;
 
-protected:
-  InputFile(Kind k, MemoryBufferRef m);
-
 public:
   // If not empty, this stores the name of the archive containing this file.
   // We use this string for creating error messages.
@@ -380,6 +380,7 @@ class BinaryFile : public InputFile {
   void parse();
 };
 
+InputFile *createInternalFile(StringRef name);
 ELFFileBase *createObjFile(MemoryBufferRef mb, StringRef archiveName = "",
                            bool lazy = false);
 
diff --git a/lld/ELF/InputSection.cpp b/lld/ELF/InputSection.cpp
@@ -245,6 +245,8 @@ InputSection *InputSectionBase::getLinkOrderDep() const {
 // Find a symbol that encloses a given location.
 Defined *InputSectionBase::getEnclosingSymbol(uint64_t offset,
                                               uint8_t type) const {
+  if (file->isInternal())
+    return nullptr;
   for (Symbol *b : file->getSymbols())
     if (Defined *d = dyn_cast<Defined>(b))
       if (d->section == this && d->value <= offset &&
@@ -344,7 +346,7 @@ template <class ELFT> void InputSection::copyShtGroup(uint8_t *buf) {
 }
 
 InputSectionBase *InputSection::getRelocatedSection() const {
-  if (!file || (type != SHT_RELA && type != SHT_REL))
+  if (!file || file->isInternal() || (type != SHT_RELA && type != SHT_REL))
     return nullptr;
   ArrayRef<InputSectionBase *> sections = file->getSections();
   return sections[info];
diff --git a/lld/ELF/InputSection.h b/lld/ELF/InputSection.h
@@ -9,6 +9,7 @@
 #ifndef LLD_ELF_INPUT_SECTION_H
 #define LLD_ELF_INPUT_SECTION_H
 
+#include "Config.h"
 #include "Relocations.h"
 #include "lld/Common/CommonLinkerContext.h"
 #include "lld/Common/LLVM.h"
@@ -413,7 +414,7 @@ class SyntheticSection : public InputSection {
 public:
   SyntheticSection(uint64_t flags, uint32_t type, uint32_t addralign,
                    StringRef name)
-      : InputSection(nullptr, flags, type, addralign, {}, name,
+      : InputSection(ctx.internalFile, flags, type, addralign, {}, name,
                      InputSectionBase::Synthetic) {}
 
   virtual ~SyntheticSection() = default;
diff --git a/lld/ELF/LTO.cpp b/lld/ELF/LTO.cpp
@@ -256,10 +256,12 @@ void BitcodeCompiler::add(BitcodeFile &f) {
         // Symbol section is always null for bitcode symbols, hence the check
         // for isElf(). Skip linker script defined symbols as well: they have
         // no File defined.
-        !(dr->section == nullptr && (!sym->file || sym->file->isElf()));
+        !(dr->section == nullptr &&
+          (sym->file->isInternal() || sym->file->isElf()));
 
     if (r.Prevailing)
-      Undefined(nullptr, StringRef(), STB_GLOBAL, STV_DEFAULT, sym->type)
+      Undefined(ctx.internalFile, StringRef(), STB_GLOBAL, STV_DEFAULT,
+                sym->type)
           .overwrite(*sym);
 
     // We tell LTO to not apply interprocedural optimization for wrapped
diff --git a/lld/ELF/LinkerScript.cpp b/lld/ELF/LinkerScript.cpp
@@ -233,8 +233,8 @@ void LinkerScript::addSymbol(SymbolAssignment *cmd) {
   // write expressions like this: `alignment = 16; . = ALIGN(., alignment)`.
   uint64_t symValue = value.sec ? 0 : value.getValue();
 
-  Defined newSym(nullptr, cmd->name, STB_GLOBAL, visibility, value.type,
-                 symValue, 0, sec);
+  Defined newSym(createInternalFile(cmd->location), cmd->name, STB_GLOBAL,
+                 visibility, value.type, symValue, 0, sec);
 
   Symbol *sym = symtab.insert(cmd->name);
   sym->mergeProperties(newSym);
@@ -250,8 +250,8 @@ static void declareSymbol(SymbolAssignment *cmd) {
     return;
 
   uint8_t visibility = cmd->hidden ? STV_HIDDEN : STV_DEFAULT;
-  Defined newSym(nullptr, cmd->name, STB_GLOBAL, visibility, STT_NOTYPE, 0, 0,
-                 nullptr);
+  Defined newSym(ctx.internalFile, cmd->name, STB_GLOBAL, visibility,
+                 STT_NOTYPE, 0, 0, nullptr);
 
   // If the symbol is already defined, its order is 0 (with absence indicating
   // 0); otherwise it's assigned the order of the SymbolAssignment.
diff --git a/lld/ELF/Relocations.cpp b/lld/ELF/Relocations.cpp
@@ -1757,7 +1757,7 @@ void elf::postScanRelocations() {
 
   GotSection *got = in.got.get();
   if (ctx.needsTlsLd.load(std::memory_order_relaxed) && got->addTlsIndex()) {
-    static Undefined dummy(nullptr, "", STB_LOCAL, 0, 0);
+    static Undefined dummy(ctx.internalFile, "", STB_LOCAL, 0, 0);
     if (config->shared)
       mainPart->relaDyn->addReloc(
           {target->tlsModuleIndexRel, got, got->getTlsIndexOff()});
diff --git a/lld/ELF/ScriptLexer.h b/lld/ELF/ScriptLexer.h
@@ -32,6 +32,7 @@ class ScriptLexer {
   void expect(StringRef expect);
   bool consumeLabel(StringRef tok);
   std::string getCurrentLocation();
+  MemoryBufferRef getCurrentMB();
 
   std::vector<MemoryBufferRef> mbs;
   std::vector<StringRef> tokens;
@@ -41,9 +42,6 @@ class ScriptLexer {
   size_t lastLineNumber = 0;
   size_t lastLineNumberOffset = 0;
 
-protected:
-  MemoryBufferRef getCurrentMB();
-
 private:
   void maybeSplitExpr();
   StringRef getLine();
diff --git a/lld/ELF/ScriptParser.cpp b/lld/ELF/ScriptParser.cpp
@@ -288,7 +288,8 @@ void ScriptParser::readDefsym(StringRef name) {
   Expr e = readExpr();
   if (!atEOF())
     setError("EOF expected, but got " + next());
-  auto *cmd = make<SymbolAssignment>(name, e, 0, getCurrentLocation());
+  auto *cmd = make<SymbolAssignment>(
+      name, e, 0, getCurrentMB().getBufferIdentifier().str());
   script->sectionCommands.push_back(cmd);
 }
 
diff --git a/lld/ELF/SyntheticSections.cpp b/lld/ELF/SyntheticSections.cpp
@@ -261,8 +261,8 @@ InputSection *elf::createInterpSection() {
   StringRef s = saver().save(config->dynamicLinker);
   ArrayRef<uint8_t> contents = {(const uint8_t *)s.data(), s.size() + 1};
 
-  return make<InputSection>(nullptr, SHF_ALLOC, SHT_PROGBITS, 1, contents,
-                            ".interp");
+  return make<InputSection>(ctx.internalFile, SHF_ALLOC, SHT_PROGBITS, 1,
+                            contents, ".interp");
 }
 
 Defined *elf::addSyntheticLocal(StringRef name, uint8_t type, uint64_t value,
diff --git a/lld/ELF/Target.cpp b/lld/ELF/Target.cpp
@@ -112,7 +112,7 @@ ErrorPlace elf::getErrorPlace(const uint8_t *loc) {
       std::string objLoc = isec->getLocation(loc - isecLoc);
       // Return object file location and source file location.
       // TODO: Refactor getSrcMsg not to take a variable.
-      Undefined dummy(nullptr, "", STB_LOCAL, 0, 0);
+      Undefined dummy(ctx.internalFile, "", STB_LOCAL, 0, 0);
       return {isec, objLoc + ": ",
               isec->file ? isec->getSrcMsg(dummy, loc - isecLoc) : ""};
     }
diff --git a/lld/ELF/Writer.cpp b/lld/ELF/Writer.cpp
@@ -148,23 +148,24 @@ static Defined *addOptionalRegular(StringRef name, SectionBase *sec,
   if (!s || s->isDefined() || s->isCommon())
     return nullptr;
 
-  s->resolve(Defined{nullptr, StringRef(), STB_GLOBAL, stOther, STT_NOTYPE, val,
+  s->resolve(Defined{ctx.internalFile, StringRef(), STB_GLOBAL, stOther,
+                     STT_NOTYPE, val,
                      /*size=*/0, sec});
   s->isUsedInRegularObj = true;
   return cast<Defined>(s);
 }
 
-static Defined *addAbsolute(StringRef name) {
-  Symbol *sym = symtab.addSymbol(Defined{nullptr, name, STB_GLOBAL, STV_HIDDEN,
-                                         STT_NOTYPE, 0, 0, nullptr});
-  sym->isUsedInRegularObj = true;
-  return cast<Defined>(sym);
-}
-
 // The linker is expected to define some symbols depending on
 // the linking result. This function defines such symbols.
 void elf::addReservedSymbols() {
   if (config->emachine == EM_MIPS) {
+    auto addAbsolute = [](StringRef name) {
+      Symbol *sym =
+          symtab.addSymbol(Defined{ctx.internalFile, name, STB_GLOBAL,
+                                   STV_HIDDEN, STT_NOTYPE, 0, 0, nullptr});
+      sym->isUsedInRegularObj = true;
+      return cast<Defined>(sym);
+    };
     // Define _gp for MIPS. st_value of _gp symbol will be updated by Writer
     // so that it points to an absolute address which by default is relative
     // to GOT. Default offset is 0x7ff0.
@@ -213,7 +214,7 @@ void elf::addReservedSymbols() {
     if (config->emachine == EM_PPC64)
       gotOff = 0x8000;
 
-    s->resolve(Defined{/*file=*/nullptr, StringRef(), STB_GLOBAL, STV_HIDDEN,
+    s->resolve(Defined{ctx.internalFile, StringRef(), STB_GLOBAL, STV_HIDDEN,
                        STT_NOTYPE, gotOff, /*size=*/0, Out::elfHeader});
     ElfSym::globalOffsetTable = cast<Defined>(s);
   }
@@ -280,7 +281,8 @@ static void demoteSymbolsAndComputeIsPreemptible() {
       auto *s = dyn_cast<SharedSymbol>(sym);
       if (sym->isLazy() || (s && !cast<SharedFile>(s->file)->isNeeded)) {
         uint8_t binding = sym->isLazy() ? sym->binding : uint8_t(STB_WEAK);
-        Undefined(nullptr, sym->getName(), binding, sym->stOther, sym->type)
+        Undefined(ctx.internalFile, sym->getName(), binding, sym->stOther,
+                  sym->type)
             .overwrite(*sym);
         sym->versionId = VER_NDX_GLOBAL;
       }
@@ -1922,7 +1924,7 @@ template <class ELFT> void Writer<ELFT>::finalizeSections() {
     // https://sourceware.org/ml/binutils/2002-03/msg00360.html
     if (mainPart->dynamic->parent) {
       Symbol *s = symtab.addSymbol(Defined{
-          /*file=*/nullptr, "_DYNAMIC", STB_WEAK, STV_HIDDEN, STT_NOTYPE,
+          ctx.internalFile, "_DYNAMIC", STB_WEAK, STV_HIDDEN, STT_NOTYPE,
           /*value=*/0, /*size=*/0, mainPart->dynamic.get()});
       s->isUsedInRegularObj = true;
     }
@@ -1964,7 +1966,7 @@ template <class ELFT> void Writer<ELFT>::finalizeSections() {
       // define _TLS_MODULE_BASE_ relative to the first TLS section.
       Symbol *s = symtab.find("_TLS_MODULE_BASE_");
       if (s && s->isUndefined()) {
-        s->resolve(Defined{/*file=*/nullptr, StringRef(), STB_GLOBAL,
+        s->resolve(Defined{ctx.internalFile, StringRef(), STB_GLOBAL,
                            STV_HIDDEN, STT_TLS, /*value=*/0, 0,
                            /*section=*/nullptr});
         ElfSym::tlsModuleBase = cast<Defined>(s);
@@ -2106,8 +2108,9 @@ template <class ELFT> void Writer<ELFT>::finalizeSections() {
   // With the outputSections available check for GDPLT relocations
   // and add __tls_get_addr symbol if needed.
   if (config->emachine == EM_HEXAGON && hexagonNeedsTLSSymbol(outputSections)) {
-    Symbol *sym = symtab.addSymbol(Undefined{
-        nullptr, "__tls_get_addr", STB_GLOBAL, STV_DEFAULT, STT_NOTYPE});
+    Symbol *sym =
+        symtab.addSymbol(Undefined{ctx.internalFile, "__tls_get_addr",
+                                   STB_GLOBAL, STV_DEFAULT, STT_NOTYPE});
     sym->isPreemptible = true;
     partitions[0].dynSymTab->addSymbol(sym);
   }
diff --git a/lld/test/ELF/cref.s b/lld/test/ELF/cref.s
@@ -3,11 +3,12 @@
 // RUN: echo '.global foo; foo:' | llvm-mc -filetype=obj -triple=x86_64-pc-linux - -o %t1.o
 // RUN: echo '.global foo, bar; bar:' | llvm-mc -filetype=obj -triple=x86_64-pc-linux - -o %t2.o
 // RUN: echo '.global zed; zed:' | llvm-mc -filetype=obj -triple=x86_64-pc-linux - -o %ta.o
+// RUN: echo 'abs1 = 42;' > %t.lds
 // RUN: rm -f %t.a
 // RUN: llvm-ar rcs %t.a %ta.o
 // RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t3.o
 // RUN: ld.lld -shared -o %t1.so %t1.o
-// RUN: ld.lld -o /dev/null %t1.so %t2.o %t3.o %t.a --gc-sections --cref | FileCheck -strict-whitespace %s
+// RUN: ld.lld -o /dev/null %t1.so %t2.o %t3.o %t.a %t.a %t.lds --defsym abs2=43 --gc-sections --cref | FileCheck -strict-whitespace %s
 
 /// If -Map is specified, print to the map file.
 // RUN: ld.lld -o /dev/null %t1.so %t2.o %t3.o %t.a --gc-sections -Map=%t.map --cref
@@ -26,6 +27,10 @@
 // CHECK-NEXT: baz                                               {{.*}}3.o
 // CHECK-NEXT: zed                                               {{.*}}.a({{.*}}a.o)
 // CHECK-NEXT:                                                   {{.*}}3.o
+// CHECK-NEXT: abs1                                              {{.*}}.lds:1
+// CHECK-NEXT:                                                   {{.*}}3.o
+// CHECK-NEXT: abs2                                              --defsym{{$}}
+// CHECK-NEXT:                                                   {{.*}}3.o
 // CHECK-NOT:  discarded
 
 // CHECK2:         VMA              LMA     Size Align Out     In      Symbol
@@ -46,3 +51,7 @@ baz:
 
 .section .text.a,"ax",@progbits
 discarded:
+
+.data
+.quad abs1
+.quad abs2
diff --git a/lld/test/ELF/linkerscript/symbol-ordering-file2.s b/lld/test/ELF/linkerscript/symbol-ordering-file2.s
@@ -7,10 +7,11 @@
 # RUN: echo "SECTIONS { bar = 1; }" > %t.script
 # RUN: ld.lld --symbol-ordering-file %t.ord %t.o --script %t.script \
 # RUN:   -o %t.out 2>&1 | FileCheck %s
-# CHECK: warning: <internal>: unable to order absolute symbol: bar
+# CHECK: warning: {{.*}}.script:1: unable to order absolute symbol: bar
 
 ## Check we do not crash when trying to order --defsym symbol.
 
 # RUN: echo "bar" > %t.ord
 # RUN: ld.lld --symbol-ordering-file %t.ord %t.o -defsym=bar=1 \
-# RUN:   -o %t.out 2>&1 | FileCheck %s
+# RUN:   -o %t.out 2>&1 | FileCheck %s --check-prefix=DEFSYM
+# DEFSYM: warning: --defsym: unable to order absolute symbol: bar
diff --git a/lld/test/ELF/x86-64-gotpc-no-relax-err.s b/lld/test/ELF/x86-64-gotpc-no-relax-err.s
@@ -8,7 +8,10 @@
 ## associated file or linker script line number).
 
 # CHECK:      error: {{.*}}:(.text+0x2): relocation R_X86_64_GOTPCRELX out of range: 2147483658 is not in [-2147483648, 2147483647]; references '__stop_data'
+# CHECK-NEXT: >>> defined in <internal>
+# CHECK-EMPTY:
 # CHECK-NEXT: error: {{.*}}:(.text+0x9): relocation R_X86_64_REX_GOTPCRELX out of range: 2147483651 is not in [-2147483648, 2147483647]; references '__stop_data'
+# CHECK-NEXT: >>> defined in <internal>
 
 #--- a.s
   movl __stop_data@GOTPCREL(%rip), %eax  # out of range
