[PDB] Add public symbol lookup by address

Nerixyz · Nerixyz · commit 76a14bb93bbc · 2025-09-07T22:06:58.000+02:00
diff --git a/llvm/include/llvm/DebugInfo/PDB/Native/PublicsStream.h b/llvm/include/llvm/DebugInfo/PDB/Native/PublicsStream.h
@@ -18,9 +18,13 @@ namespace llvm {
 namespace msf {
 class MappedBlockStream;
 }
+namespace codeview {
+class PublicSym32;
+}
 namespace pdb {
 struct PublicsStreamHeader;
 struct SectionOffset;
+class SymbolStream;
 
 class PublicsStream {
 public:
@@ -42,6 +46,20 @@ class PublicsStream {
     return SectionOffsets;
   }
 
+  /// Find a public symbol by a segment and offset.
+  ///
+  /// In case there is more than one symbol (for example due to ICF), the first
+  /// one is returned.
+  ///
+  /// \return If a symbol was found, the symbol at the provided address is
+  ///     returned as well as the index of this symbol in the address map. If
+  ///     the binary was linked with ICF, there might be more symbols with the
+  ///     same address after the returned one. If no symbol is found,
+  ///     `std::nullopt` is returned.
+  LLVM_ABI std::optional<std::pair<codeview::PublicSym32, size_t>>
+  findByAddress(const SymbolStream &Symbols, uint16_t Segment,
+                uint32_t Offset) const;
+
 private:
   std::unique_ptr<msf::MappedBlockStream> Stream;
   GSIHashTable PublicsTable;
diff --git a/llvm/lib/DebugInfo/PDB/Native/PublicsStream.cpp b/llvm/lib/DebugInfo/PDB/Native/PublicsStream.cpp
@@ -22,9 +22,12 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/DebugInfo/PDB/Native/PublicsStream.h"
+#include "llvm/DebugInfo/CodeView/SymbolDeserializer.h"
+#include "llvm/DebugInfo/CodeView/SymbolRecord.h"
 #include "llvm/DebugInfo/MSF/MappedBlockStream.h"
 #include "llvm/DebugInfo/PDB/Native/RawError.h"
 #include "llvm/DebugInfo/PDB/Native/RawTypes.h"
+#include "llvm/DebugInfo/PDB/Native/SymbolStream.h"
 #include "llvm/Support/BinaryStreamReader.h"
 #include "llvm/Support/Error.h"
 #include <cstdint>
@@ -96,3 +99,91 @@ Error PublicsStream::reload() {
                                 "Corrupted publics stream.");
   return Error::success();
 }
+
+static uint32_t compareSegmentOffset(uint16_t LhsSegment, uint32_t LhsOffset,
+                                     uint16_t RhsSegment, uint32_t RhsOffset) {
+  if (LhsSegment == RhsSegment)
+    return LhsOffset - RhsOffset;
+  return LhsSegment - RhsSegment;
+}
+
+static uint32_t compareSegmentOffset(uint16_t LhsSegment, uint32_t LhsOffst,
+                                     const codeview::PublicSym32 &Rhs) {
+  return compareSegmentOffset(LhsSegment, LhsOffst, Rhs.Segment, Rhs.Offset);
+}
+
+// This is a reimplementation of NearestSym:
+// https://github.com/microsoft/microsoft-pdb/blob/805655a28bd8198004be2ac27e6e0290121a5e89/PDB/dbi/gsi.cpp#L1492-L1581
+std::optional<std::pair<codeview::PublicSym32, size_t>>
+PublicsStream::findByAddress(const SymbolStream &Symbols, uint16_t Segment,
+                             uint32_t Offset) const {
+  // The address map is sorted by address, so we do binary search.
+  // Each element is an offset into the symbols for a public symbol.
+  auto Lo = AddressMap.begin();
+  auto Hi = AddressMap.end();
+  Hi -= 1;
+
+  while (Lo < Hi) {
+    auto Cur = Lo + ((Hi - Lo + 1) / 2);
+    auto Sym = Symbols.readRecord(Cur->value());
+    if (Sym.kind() != codeview::S_PUB32)
+      return std::nullopt; // this is most likely corrupted debug info
+
+    auto Psym =
+        codeview::SymbolDeserializer::deserializeAs<codeview::PublicSym32>(Sym);
+    if (!Psym) {
+      consumeError(Psym.takeError());
+      return std::nullopt;
+    }
+
+    uint32_t Cmp = compareSegmentOffset(Segment, Offset, *Psym);
+    if (Cmp < 0) {
+      Cur -= 1;
+      Hi = Cur;
+    } else if (Cmp == 0)
+      Lo = Hi = Cur;
+    else
+      Lo = Cur;
+  }
+
+  auto Sym = Symbols.readRecord(Lo->value());
+  if (Sym.kind() != codeview::S_PUB32)
+    return std::nullopt; // this is most likely corrupted debug info
+
+  auto MaybePsym =
+      codeview::SymbolDeserializer::deserializeAs<codeview::PublicSym32>(Sym);
+  if (!MaybePsym) {
+    consumeError(MaybePsym.takeError());
+    return std::nullopt;
+  }
+  codeview::PublicSym32 Psym = std::move(*MaybePsym);
+
+  uint32_t Cmp = compareSegmentOffset(Segment, Offset, Psym);
+  if (Cmp != 0)
+    return std::nullopt;
+
+  // We found a symbol. Due to ICF, multiple symbols can have the same
+  // address, so return the first one
+  while (Lo != AddressMap.begin()) {
+    --Lo;
+    Sym = Symbols.readRecord(Lo->value());
+    if (Sym.kind() != codeview::S_PUB32)
+      return std::nullopt;
+    MaybePsym =
+        codeview::SymbolDeserializer::deserializeAs<codeview::PublicSym32>(Sym);
+    if (!MaybePsym) {
+      consumeError(MaybePsym.takeError());
+      return std::nullopt;
+    }
+
+    if (MaybePsym->Segment != Segment || MaybePsym->Offset != Offset) {
+      ++Lo;
+      break;
+    }
+
+    Psym = std::move(*MaybePsym);
+  }
+
+  std::ptrdiff_t IterOffset = Lo - AddressMap.begin();
+  return std::pair{Psym, static_cast<size_t>(IterOffset)};
+}
diff --git a/llvm/unittests/DebugInfo/PDB/CMakeLists.txt b/llvm/unittests/DebugInfo/PDB/CMakeLists.txt
@@ -11,6 +11,7 @@ add_llvm_unittest_with_input_files(DebugInfoPDBTests
   StringTableBuilderTest.cpp
   PDBApiTest.cpp
   PDBVariantTest.cpp
+  PublicsStreamTest.cpp
   )
 
 target_link_libraries(DebugInfoPDBTests PRIVATE LLVMTestingSupport)
diff --git a/llvm/unittests/DebugInfo/PDB/Inputs/PublicSymbols.cpp b/llvm/unittests/DebugInfo/PDB/Inputs/PublicSymbols.cpp
@@ -0,0 +1,46 @@
+// clang-format off
+
+// Compile with
+// cl /Z7 /GR- /GS- PublicSymbols.cpp -c /Gy
+// link .\PublicSymbols.obj /DEBUG /NODEFAULTLIB /out:PublicSymbols.exe /ENTRY:main /OPT:ICF
+// llvm-pdbutil pdb2yaml --publics-stream PublicSymbols.pdb > PublicSymbols.yaml
+// llvm-pdbutil yaml2pdb PublicSymbols.yaml
+// 
+// rm PublicSymbols.exe && rm PublicSymbols.obj && rm PublicSymbols.yaml
+
+int foobar(int i){ return i + 1; }
+// these should be merged with ICF
+int dup1(int i){ return i + 2; }
+int dup2(int i){ return i + 2; }
+int dup3(int i){ return i + 2; }
+
+class AClass {
+public:
+    void AMethod(int, char*) {}
+    static bool Something(char c) {
+        return c == ' ';
+    }
+};
+
+struct Base {
+    virtual ~Base() = default;
+};
+struct Derived : public Base {};
+struct Derived2 : public Base {};
+struct Derived3 : public Derived2, public Derived {};
+
+int AGlobal;
+
+void operator delete(void *,unsigned __int64) {}
+
+int main() {
+    foobar(1);
+    dup1(1);
+    dup2(1);
+    dup3(1);
+    AClass a;
+    a.AMethod(1, nullptr);
+    AClass::Something(' ');
+    Derived3 d3;
+    return AGlobal;
+}
diff --git a/llvm/unittests/DebugInfo/PDB/Inputs/PublicSymbols.pdb b/llvm/unittests/DebugInfo/PDB/Inputs/PublicSymbols.pdb
diff --git a/llvm/unittests/DebugInfo/PDB/PublicsStreamTest.cpp b/llvm/unittests/DebugInfo/PDB/PublicsStreamTest.cpp
@@ -0,0 +1,62 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/DebugInfo/PDB/Native/PublicsStream.h"
+#include "llvm/DebugInfo/CodeView/SymbolRecord.h"
+#include "llvm/DebugInfo/PDB/Native/PDBFile.h"
+#include "llvm/Support/BinaryByteStream.h"
+#include "llvm/Support/MemoryBuffer.h"
+
+#include "llvm/Testing/Support/SupportHelpers.h"
+
+#include "gtest/gtest.h"
+
+using namespace llvm;
+using namespace llvm::pdb;
+
+extern const char *TestMainArgv0;
+
+static std::string getExePath() {
+  SmallString<128> InputsDir = unittest::getInputFileDirectory(TestMainArgv0);
+  llvm::sys::path::append(InputsDir, "PublicSymbols.pdb");
+  return std::string(InputsDir);
+}
+
+TEST(PublicsStreamTest, FindByAddress) {
+  std::string ExePath = getExePath();
+  auto Buffer = MemoryBuffer::getFile(ExePath, /*IsText=*/false,
+                                      /*RequiresNullTerminator=*/false);
+  ASSERT_TRUE(bool(Buffer));
+  auto Stream = std::make_unique<MemoryBufferByteStream>(
+      std::move(*Buffer), llvm::endianness::little);
+
+  BumpPtrAllocator Alloc;
+  PDBFile File(ExePath, std::move(Stream), Alloc);
+  ASSERT_FALSE(bool(File.parseFileHeaders()));
+  ASSERT_FALSE(bool(File.parseStreamData()));
+
+  auto Publics = File.getPDBPublicsStream();
+  ASSERT_TRUE(bool(Publics));
+  auto Symbols = File.getPDBSymbolStream();
+  ASSERT_TRUE(bool(Symbols));
+
+  auto VTableDerived = Publics->findByAddress(*Symbols, 2, 8);
+  ASSERT_TRUE(VTableDerived.has_value());
+  // both derived and derived2 have their vftables there - but derived2 is first
+  // (due to ICF)
+  ASSERT_EQ(VTableDerived->first.Name, "??_7Derived2@@6B@");
+  ASSERT_EQ(VTableDerived->second, 26);
+
+  ASSERT_FALSE(Publics->findByAddress(*Symbols, 2, 7).has_value());
+  ASSERT_FALSE(Publics->findByAddress(*Symbols, 2, 9).has_value());
+
+  auto GlobalSym = Publics->findByAddress(*Symbols, 3, 0);
+  ASSERT_TRUE(GlobalSym.has_value());
+  ASSERT_EQ(GlobalSym->first.Name, "?AGlobal@@3HA");
+  ASSERT_EQ(GlobalSym->second, 30);
+}

Original file line number	Diff line number	Diff line change
`@@ -11,6 +11,7 @@ add_llvm_unittest_with_input_files(DebugInfoPDBTests`
`11`	`11`	`StringTableBuilderTest.cpp`
`12`	`12`	`PDBApiTest.cpp`
`13`	`13`	`PDBVariantTest.cpp`
	`14`	`+ PublicsStreamTest.cpp`
`14`	`15`	`)`
`15`	`16`
`16`	`17`	`target_link_libraries(DebugInfoPDBTests PRIVATE LLVMTestingSupport)`