Revert "Add support for reading the dynamic symbol table from PT_DYNAMIC (llvm#112596)"

This reverts commit a7b2e73.

This patch broke the greendragon bot

Failed Tests (10):
  lldb-api :: python_api/sbplatform/TestLocateModuleCallback.py
  lldb-unit :: Target/./TargetTests/LocateModuleCallbackTest/GetOrCreateModuleCallbackSuccessWithModuleAndSymbol
  lldb-unit :: Target/./TargetTests/LocateModuleCallbackTest/GetOrCreateModuleCallbackSuccessWithOnlySymbol
  lldb-unit :: Target/./TargetTests/LocateModuleCallbackTest/GetOrCreateModuleCallbackSuccessWithSymbolAsModule
  lldb-unit :: Target/./TargetTests/LocateModuleCallbackTest/GetOrCreateModuleCallbackSuccessWithSymbolAsModuleAndSymbol
  lldb-unit :: Target/./TargetTests/LocateModuleCallbackTest/GetOrCreateModuleCallbackSuccessWithSymbolByPlatformUUID
  lldb-unit :: Target/./TargetTests/LocateModuleCallbackTest/GetOrCreateModuleWithCachedModuleAndSymbol
  lldb-unit :: Target/./TargetTests/ModuleCacheTest/GetAndPut
  lldb-unit :: Target/./TargetTests/ModuleCacheTest/GetAndPutStrangeHostname
  lldb-unit :: Target/./TargetTests/ModuleCacheTest/GetAndPutUuidExists

Author: rastogishubham

lldb/source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp

@@ -44,7 +44,6 @@
 #include "llvm/Support/MathExtras.h"
 #include "llvm/Support/MemoryBuffer.h"
 #include "llvm/Support/MipsABIFlags.h"
-#include "lldb/Target/Process.h"
 
 #define CASE_AND_STREAM(s, def, width)                                         \
   case def:                                                                    \
@@ -3008,10 +3007,9 @@ void ObjectFileELF::ParseSymtab(Symtab &lldb_symtab) {
   // section, nomatter if .symtab was already parsed or not. This is because
   // minidebuginfo normally removes the .symtab symbols which have their
   // matching .dynsym counterparts.
-  Section *dynsym = nullptr;
   if (!symtab ||
       GetSectionList()->FindSectionByName(ConstString(".gnu_debugdata"))) {
-    dynsym =
+    Section *dynsym =
         section_list->FindSectionByType(eSectionTypeELFDynamicSymbols, true)
             .get();
     if (dynsym) {
@@ -3021,20 +3019,6 @@ void ObjectFileELF::ParseSymtab(Symtab &lldb_symtab) {
       m_address_class_map.merge(address_class_map);
     }
   }
-  if (!dynsym) {
-    // Try and read the dynamic symbol table from the .dynamic section.
-    uint32_t num_symbols = 0;
-    std::optional<DataExtractor> symtab_data =
-        GetDynsymDataFromDynamic(num_symbols);
-    std::optional<DataExtractor> strtab_data = GetDynstrData();
-    if (symtab_data && strtab_data) {
-      auto [num_symbols_parsed, address_class_map] =
-          ParseSymbols(&lldb_symtab, symbol_id, section_list, num_symbols,
-                        symtab_data.value(), strtab_data.value());
-      symbol_id += num_symbols_parsed;
-      m_address_class_map.merge(address_class_map);
-    }
-  }
 
   // DT_JMPREL
   //      If present, this entry's d_ptr member holds the address of
@@ -3844,33 +3828,6 @@ ObjectFileELF::MapFileDataWritable(const FileSpec &file, uint64_t Size,
                                                          Offset);
 }
 
-std::optional<DataExtractor>
-ObjectFileELF::ReadDataFromDynamic(const ELFDynamic *dyn, uint64_t length,
-                                   uint64_t offset) {
-  // ELFDynamic values contain a "d_ptr" member that will be a load address if
-  // we have an ELF file read from memory, or it will be a file address if it
-  // was read from a ELF file. This function will correctly fetch data pointed
-  // to by the ELFDynamic::d_ptr, or return std::nullopt if the data isn't
-  // available.
-  const lldb::addr_t d_ptr_addr = dyn->d_ptr + offset;
-  if (ProcessSP process_sp = m_process_wp.lock()) {
-    if (DataBufferSP data_sp = ReadMemory(process_sp, d_ptr_addr, length))
-      return DataExtractor(data_sp, GetByteOrder(), GetAddressByteSize());
-  } else {
-    // We have an ELF file with no section headers or we didn't find the
-    // .dynamic section. Try and find the .dynstr section.
-    Address addr;
-    if (!addr.ResolveAddressUsingFileSections(d_ptr_addr, GetSectionList()))
-      return std::nullopt;
-    DataExtractor data;
-    addr.GetSection()->GetSectionData(data);
-    return DataExtractor(data,
-                         d_ptr_addr - addr.GetSection()->GetFileAddress(),
-                         length);
-  }
-  return std::nullopt;
-}
-
 std::optional<DataExtractor> ObjectFileELF::GetDynstrData() {
   if (SectionList *section_list = GetSectionList()) {
     // Find the SHT_DYNAMIC section.
@@ -3898,15 +3855,31 @@ std::optional<DataExtractor> ObjectFileELF::GetDynstrData() {
   // and represent the dynamic symbol tables's string table. These are needed
   // by the dynamic loader and we can read them from a process' address space.
   //
-  // When loading and ELF file from memory, only the program headers are
-  // guaranteed end up being mapped into memory, and we can find these values in
-  // the PT_DYNAMIC segment.
+  // When loading and ELF file from memory, only the program headers end up
+  // being mapped into memory, and we can find these values in the PT_DYNAMIC
+  // segment.
   const ELFDynamic *strtab = FindDynamicSymbol(DT_STRTAB);
   const ELFDynamic *strsz = FindDynamicSymbol(DT_STRSZ);
   if (strtab == nullptr || strsz == nullptr)
     return std::nullopt;
 
-  return ReadDataFromDynamic(strtab, strsz->d_val, /*offset=*/0);
+  if (ProcessSP process_sp = m_process_wp.lock()) {
+    if (DataBufferSP data_sp =
+            ReadMemory(process_sp, strtab->d_ptr, strsz->d_val))
+      return DataExtractor(data_sp, GetByteOrder(), GetAddressByteSize());
+  } else {
+    // We have an ELF file with no section headers or we didn't find the
+    // .dynamic section. Try and find the .dynstr section.
+    Address addr;
+    if (addr.ResolveAddressUsingFileSections(strtab->d_ptr, GetSectionList())) {
+      DataExtractor data;
+      addr.GetSection()->GetSectionData(data);
+      return DataExtractor(data,
+                           strtab->d_ptr - addr.GetSection()->GetFileAddress(),
+                           strsz->d_val);
+    }
+  }
+  return std::nullopt;
 }
 
 std::optional<lldb_private::DataExtractor> ObjectFileELF::GetDynamicData() {
@@ -3939,116 +3912,3 @@ std::optional<lldb_private::DataExtractor> ObjectFileELF::GetDynamicData() {
   }
   return std::nullopt;
 }
-
-std::optional<uint32_t> ObjectFileELF::GetNumSymbolsFromDynamicHash() {
-  const ELFDynamic *hash = FindDynamicSymbol(DT_HASH);
-  if (hash == nullptr)
-    return std::nullopt;
-
-  // The DT_HASH header looks like this:
-  struct DtHashHeader {
-    uint32_t nbucket;
-    uint32_t nchain;
-  };
-  if (auto data = ReadDataFromDynamic(hash, 8)) {
-    // We don't need the number of buckets value "nbucket", we just need the
-    // "nchain" value which contains the number of symbols.
-    offset_t offset = offsetof(DtHashHeader, nchain);
-    return data->GetU32(&offset);
-  }
-
-  return std::nullopt;
-}
-
-std::optional<uint32_t> ObjectFileELF::GetNumSymbolsFromDynamicGnuHash() {
-  const ELFDynamic *gnu_hash = FindDynamicSymbol(DT_GNU_HASH);
-  if (gnu_hash == nullptr)
-    return std::nullopt;
-
-  // Create a DT_GNU_HASH header
-  // https://flapenguin.me/elf-dt-gnu-hash
-  struct DtGnuHashHeader {
-    uint32_t nbuckets = 0;
-    uint32_t symoffset = 0;
-    uint32_t bloom_size = 0;
-    uint32_t bloom_shift = 0;
-  };
-  uint32_t num_symbols = 0;
-  // Read enogh data for the DT_GNU_HASH header so we can extract the values.
-  if (auto data = ReadDataFromDynamic(gnu_hash, sizeof(DtGnuHashHeader))) {
-    offset_t offset = 0;
-    DtGnuHashHeader header;
-    header.nbuckets = data->GetU32(&offset);
-    header.symoffset = data->GetU32(&offset);
-    header.bloom_size = data->GetU32(&offset);
-    header.bloom_shift = data->GetU32(&offset);
-    const size_t addr_size = GetAddressByteSize();
-    const addr_t buckets_offset =
-        sizeof(DtGnuHashHeader) + addr_size * header.bloom_size;
-    std::vector<uint32_t> buckets;
-    if (auto bucket_data = ReadDataFromDynamic(gnu_hash, header.nbuckets * 4, buckets_offset)) {
-      offset = 0;
-      for (uint32_t i = 0; i < header.nbuckets; ++i)
-        buckets.push_back(bucket_data->GetU32(&offset));
-      // Locate the chain that handles the largest index bucket.
-      uint32_t last_symbol = 0;
-      for (uint32_t bucket_value : buckets)
-        last_symbol = std::max(bucket_value, last_symbol);
-      if (last_symbol < header.symoffset) {
-        num_symbols = header.symoffset;
-      } else {
-        // Walk the bucket's chain to add the chain length to the total.
-        const addr_t chains_base_offset = buckets_offset + header.nbuckets * 4;
-        for (;;) {
-          if (auto chain_entry_data = ReadDataFromDynamic(gnu_hash, 4, chains_base_offset + (last_symbol - header.symoffset) * 4)) {
-            offset = 0;
-            uint32_t chain_entry = chain_entry_data->GetU32(&offset);
-            ++last_symbol;
-            // If the low bit is set, this entry is the end of the chain.
-            if (chain_entry & 1)
-              break;
-          } else {
-            break;
-          }
-        }
-        num_symbols = last_symbol;
-      }
-    }
-  }
-  if (num_symbols > 0)
-    return num_symbols;
-
-  return std::nullopt;
-}
-
-std::optional<DataExtractor>
-ObjectFileELF::GetDynsymDataFromDynamic(uint32_t &num_symbols) {
-  // Every ELF file which represents an executable or shared library has
-  // mandatory .dynamic entries. The DT_SYMTAB value contains a pointer to the
-  // symbol table, and DT_SYMENT contains the size of a symbol table entry.
-  // We then can use either the DT_HASH or DT_GNU_HASH to find the number of
-  // symbols in the symbol table as the symbol count is not stored in the
-  // .dynamic section as a key/value pair.
-  //
-  // When loading and ELF file from memory, only the program headers end up
-  // being mapped into memory, and we can find these values in the PT_DYNAMIC
-  // segment.
-  num_symbols = 0;
-  // Get the process in case this is an in memory ELF file.
-  ProcessSP process_sp(m_process_wp.lock());
-  const ELFDynamic *symtab = FindDynamicSymbol(DT_SYMTAB);
-  const ELFDynamic *syment = FindDynamicSymbol(DT_SYMENT);
-  // DT_SYMTAB and DT_SYMENT are mandatory.
-  if (symtab == nullptr || syment == nullptr)
-    return std::nullopt;
-
-  if (std::optional<uint32_t> syms = GetNumSymbolsFromDynamicHash())
-    num_symbols = *syms;
-  else if (std::optional<uint32_t> syms = GetNumSymbolsFromDynamicGnuHash())
-    num_symbols = *syms;
-  else
-    return std::nullopt;
-  if (num_symbols == 0)
-    return std::nullopt;
-  return ReadDataFromDynamic(symtab, syment->d_val * num_symbols);
-}

lldb/source/Plugins/ObjectFile/ELF/ObjectFileELF.h

@@ -435,47 +435,6 @@ class ObjectFileELF : public lldb_private::ObjectFile {
   /// \return The bytes that represent the string table data or \c std::nullopt
   ///         if an error occured.
   std::optional<lldb_private::DataExtractor> GetDynstrData();
-
-  /// Read the bytes pointed to by the \a dyn dynamic entry.
-  ///
-  /// ELFDynamic::d_ptr values contain file addresses if we load the ELF file
-  /// form a file on disk, or they contain load addresses if they were read
-  /// from memory. This function will correctly extract the data in both cases
-  /// if it is available.
-  ///
-  /// \param[in] dyn The dynamic entry to use to fetch the data from.
-  ///
-  /// \param[in] length The number of bytes to read.
-  ///
-  /// \param[in] offset The number of bytes to skip after the d_ptr value
-  ///                   before reading data.
-  ///
-  /// \return The bytes that represent the dynanic entries data or
-  ///         \c std::nullopt if an error occured or the data is not available.
-  std::optional<lldb_private::DataExtractor>
-  ReadDataFromDynamic(const elf::ELFDynamic *dyn, uint64_t length,
-                      uint64_t offset = 0);
-
-  /// Get the bytes that represent the dynamic symbol table from the .dynamic
-  /// section from process memory.
-  ///
-  /// This functon uses the DT_SYMTAB value from the .dynamic section to read
-  /// the symbols table data from process memory. The number of symbols in the
-  /// symbol table is calculated by looking at the DT_HASH or DT_GNU_HASH
-  /// values as the symbol count isn't stored in the .dynamic section.
-  ///
-  /// \return The bytes that represent the symbol table data from the .dynamic
-  ///         section or section headers or \c std::nullopt if an error
-  ///         occured or if there is no dynamic symbol data available.
-  std::optional<lldb_private::DataExtractor>
-  GetDynsymDataFromDynamic(uint32_t &num_symbols);
-
-  /// Get the number of symbols from the DT_HASH dynamic entry.
-  std::optional<uint32_t> GetNumSymbolsFromDynamicHash();
-
-  /// Get the number of symbols from the DT_GNU_HASH dynamic entry.
-  std::optional<uint32_t> GetNumSymbolsFromDynamicGnuHash();
-
 };
 
 #endif // LLDB_SOURCE_PLUGINS_OBJECTFILE_ELF_OBJECTFILEELF_H