[Lldb-commits] [lldb] r128550 - in /lldb/trunk/source/Plugins/ObjectFile/ELF: ObjectFileELF.cpp ObjectFileELF.h
Stephen Wilson
wilsons at start.ca
Wed Mar 30 09:07:05 PDT 2011
Author: wilsons
Date: Wed Mar 30 11:07:05 2011
New Revision: 128550
URL: http://llvm.org/viewvc/llvm-project?rev=128550&view=rev
Log:
elf: synthesize symbols for PLT entries
When populating symbol tables ObjectFileELF now generates a set of synthetic
trampoline symbols. These new symbols correspond to entries in the program
linkage table and have a (possibly mangled) name identifying the corresponding
symbol in some DSO. These symbols will be used by the DynamicLoader loader
plugin on Linux to provide thread plans when execution flows from one DSO to
another.
Modified:
lldb/trunk/source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp
lldb/trunk/source/Plugins/ObjectFile/ELF/ObjectFileELF.h
Modified: lldb/trunk/source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp
URL: http://llvm.org/viewvc/llvm-project/lldb/trunk/source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp?rev=128550&r1=128549&r2=128550&view=diff
==============================================================================
--- lldb/trunk/source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp (original)
+++ lldb/trunk/source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp Wed Mar 30 11:07:05 2011
@@ -23,6 +23,8 @@
#include "lldb/Symbol/SymbolContext.h"
#include "lldb/Host/Host.h"
+#include "llvm/ADT/PointerUnion.h"
+
#define CASE_AND_STREAM(s, def, width) \
case def: s->Printf("%-*s", width, #def); break;
@@ -31,6 +33,113 @@
using namespace elf;
using namespace llvm::ELF;
+namespace {
+//===----------------------------------------------------------------------===//
+/// @class ELFRelocation
+/// @brief Generic wrapper for ELFRel and ELFRela.
+///
+/// This helper class allows us to parse both ELFRel and ELFRela relocation
+/// entries in a generic manner.
+class ELFRelocation
+{
+public:
+
+ /// Constructs an ELFRelocation entry with a personality as given by @p
+ /// type.
+ ///
+ /// @param type Either DT_REL or DT_RELA. Any other value is invalid.
+ ELFRelocation(unsigned type);
+
+ ~ELFRelocation();
+
+ bool
+ Parse(const lldb_private::DataExtractor &data, uint32_t *offset);
+
+ static unsigned
+ RelocType32(const ELFRelocation &rel);
+
+ static unsigned
+ RelocType64(const ELFRelocation &rel);
+
+ static unsigned
+ RelocSymbol32(const ELFRelocation &rel);
+
+ static unsigned
+ RelocSymbol64(const ELFRelocation &rel);
+
+private:
+ typedef llvm::PointerUnion<ELFRel*, ELFRela*> RelocUnion;
+
+ RelocUnion reloc;
+};
+
+ELFRelocation::ELFRelocation(unsigned type)
+{
+ if (type == DT_REL)
+ reloc = new ELFRel();
+ else if (type == DT_RELA)
+ reloc = new ELFRela();
+ else {
+ assert(false && "unexpected relocation type");
+ reloc = static_cast<ELFRel*>(NULL);
+ }
+}
+
+ELFRelocation::~ELFRelocation()
+{
+ if (reloc.is<ELFRel*>())
+ delete reloc.get<ELFRel*>();
+ else
+ delete reloc.get<ELFRela*>();
+}
+
+bool
+ELFRelocation::Parse(const lldb_private::DataExtractor &data, uint32_t *offset)
+{
+ if (reloc.is<ELFRel*>())
+ return reloc.get<ELFRel*>()->Parse(data, offset);
+ else
+ return reloc.get<ELFRela*>()->Parse(data, offset);
+}
+
+unsigned
+ELFRelocation::RelocType32(const ELFRelocation &rel)
+{
+ if (rel.reloc.is<ELFRel*>())
+ return ELFRel::RelocType32(*rel.reloc.get<ELFRel*>());
+ else
+ return ELFRela::RelocType32(*rel.reloc.get<ELFRela*>());
+}
+
+unsigned
+ELFRelocation::RelocType64(const ELFRelocation &rel)
+{
+ if (rel.reloc.is<ELFRel*>())
+ return ELFRel::RelocType64(*rel.reloc.get<ELFRel*>());
+ else
+ return ELFRela::RelocType64(*rel.reloc.get<ELFRela*>());
+}
+
+unsigned
+ELFRelocation::RelocSymbol32(const ELFRelocation &rel)
+{
+ if (rel.reloc.is<ELFRel*>())
+ return ELFRel::RelocSymbol32(*rel.reloc.get<ELFRel*>());
+ else
+ return ELFRela::RelocSymbol32(*rel.reloc.get<ELFRela*>());
+}
+
+unsigned
+ELFRelocation::RelocSymbol64(const ELFRelocation &rel)
+{
+ if (rel.reloc.is<ELFRel*>())
+ return ELFRel::RelocSymbol64(*rel.reloc.get<ELFRel*>());
+ else
+ return ELFRela::RelocSymbol64(*rel.reloc.get<ELFRela*>());
+}
+
+} // end anonymous namespace
+
//------------------------------------------------------------------
// Static methods.
//------------------------------------------------------------------
@@ -195,54 +304,54 @@
return num_specs;
}
-Address
-ObjectFileELF::GetImageInfoAddress()
+user_id_t
+ObjectFileELF::GetSectionIndexByType(unsigned type)
{
if (!ParseSectionHeaders())
- return Address();
+ return 0;
- user_id_t dynsym_id = 0;
for (SectionHeaderCollIter sh_pos = m_section_headers.begin();
sh_pos != m_section_headers.end(); ++sh_pos)
{
- if (sh_pos->sh_type == SHT_DYNAMIC)
- {
- dynsym_id = SectionIndex(sh_pos);
- break;
- }
+ if (sh_pos->sh_type == type)
+ return SectionIndex(sh_pos);
}
- if (!dynsym_id)
+ return 0;
+}
+
+Address
+ObjectFileELF::GetImageInfoAddress()
+{
+ if (!ParseDynamicSymbols())
return Address();
SectionList *section_list = GetSectionList();
if (!section_list)
return Address();
- // Resolve the dynamic table entries.
+ user_id_t dynsym_id = GetSectionIndexByType(SHT_DYNAMIC);
+ if (!dynsym_id)
+ return Address();
+
+ const ELFSectionHeader *dynsym_hdr = GetSectionHeaderByIndex(dynsym_id);
+ if (!dynsym_hdr)
+ return Address();
+
Section *dynsym = section_list->FindSectionByID(dynsym_id).get();
if (!dynsym)
return Address();
-
- DataExtractor dynsym_data;
- if (dynsym->ReadSectionDataFromObjectFile(this, dynsym_data))
+
+ for (size_t i = 0; i < m_dynamic_symbols.size(); ++i)
{
- ELFDynamic symbol;
- const unsigned section_size = dynsym_data.GetByteSize();
- unsigned offset = 0;
- unsigned cursor = 0;
+ ELFDynamic &symbol = m_dynamic_symbols[i];
- // Look for a DT_DEBUG entry.
- while (cursor < section_size)
+ if (symbol.d_tag == DT_DEBUG)
{
- offset = cursor;
- if (!symbol.Parse(dynsym_data, &cursor))
- break;
-
- if (symbol.d_tag != DT_DEBUG)
- continue;
-
- return Address(dynsym, offset + sizeof(symbol.d_tag));
+ // Compute the offset as the number of previous entries plus the
+ // size of d_tag.
+ addr_t offset = i * dynsym_hdr->sh_entsize + GetAddressByteSize();
+ return Address(dynsym, offset);
}
}
@@ -476,6 +585,18 @@
return 0;
}
+const elf::ELFSectionHeader *
+ObjectFileELF::GetSectionHeaderByIndex(lldb::user_id_t id)
+{
+ if (!ParseSectionHeaders() || !id)
+ return NULL;
+
+ if (--id < m_section_headers.size())
+ return &m_section_headers[id];
+
+ return NULL;
+}
+
SectionList *
ObjectFileELF::GetSectionList()
{
@@ -548,16 +669,18 @@
return m_sections_ap.get();
}
-static void
-ParseSymbols(Symtab *symtab, SectionList *section_list,
- const ELFSectionHeader &symtab_shdr,
+static unsigned
+ParseSymbols(Symtab *symtab,
+ user_id_t start_id,
+ SectionList *section_list,
+ const ELFSectionHeader *symtab_shdr,
const DataExtractor &symtab_data,
const DataExtractor &strtab_data)
{
ELFSymbol symbol;
uint32_t offset = 0;
- const unsigned numSymbols =
- symtab_data.GetByteSize() / symtab_shdr.sh_entsize;
+ const unsigned num_symbols =
+ symtab_data.GetByteSize() / symtab_shdr->sh_entsize;
static ConstString text_section_name(".text");
static ConstString init_section_name(".init");
@@ -571,7 +694,8 @@
static ConstString data2_section_name(".data1");
static ConstString bss_section_name(".bss");
- for (unsigned i = 0; i < numSymbols; ++i)
+ unsigned i;
+ for (i = 0; i < num_symbols; ++i)
{
if (symbol.Parse(symtab_data, &offset) == false)
break;
@@ -658,7 +782,7 @@
uint32_t flags = symbol.st_other << 8 | symbol.st_info;
Symbol dc_symbol(
- i, // ID is the original symbol table index.
+ i + start_id, // ID is the original symbol table index.
symbol_name, // Symbol name.
false, // Is the symbol name mangled?
symbol_type, // Type of this symbol
@@ -672,26 +796,29 @@
flags); // Symbol flags.
symtab->AddSymbol(dc_symbol);
}
+
+ return i;
}
-void
-ObjectFileELF::ParseSymbolTable(Symtab *symbol_table,
- const ELFSectionHeader &symtab_hdr,
+unsigned
+ObjectFileELF::ParseSymbolTable(Symtab *symbol_table, user_id_t start_id,
+ const ELFSectionHeader *symtab_hdr,
user_id_t symtab_id)
{
- assert(symtab_hdr.sh_type == SHT_SYMTAB ||
- symtab_hdr.sh_type == SHT_DYNSYM);
+ assert(symtab_hdr->sh_type == SHT_SYMTAB ||
+ symtab_hdr->sh_type == SHT_DYNSYM);
// Parse in the section list if needed.
SectionList *section_list = GetSectionList();
if (!section_list)
- return;
+ return 0;
// Section ID's are ones based.
- user_id_t strtab_id = symtab_hdr.sh_link + 1;
+ user_id_t strtab_id = symtab_hdr->sh_link + 1;
Section *symtab = section_list->FindSectionByID(symtab_id).get();
Section *strtab = section_list->FindSectionByID(strtab_id).get();
+ unsigned num_symbols = 0;
if (symtab && strtab)
{
DataExtractor symtab_data;
@@ -699,10 +826,244 @@
if (symtab->ReadSectionDataFromObjectFile(this, symtab_data) &&
strtab->ReadSectionDataFromObjectFile(this, strtab_data))
{
- ParseSymbols(symbol_table, section_list, symtab_hdr,
- symtab_data, strtab_data);
+ num_symbols = ParseSymbols(symbol_table, start_id,
+ section_list, symtab_hdr,
+ symtab_data, strtab_data);
}
}
+
+ return num_symbols;
+}
+
+size_t
+ObjectFileELF::ParseDynamicSymbols()
+{
+ if (m_dynamic_symbols.size())
+ return m_dynamic_symbols.size();
+
+ user_id_t dyn_id = GetSectionIndexByType(SHT_DYNAMIC);
+ if (!dyn_id)
+ return NULL;
+
+ SectionList *section_list = GetSectionList();
+ if (!section_list)
+ return NULL;
+
+ Section *dynsym = section_list->FindSectionByID(dyn_id).get();
+ if (!dynsym)
+ return NULL;
+
+ ELFDynamic symbol;
+ DataExtractor dynsym_data;
+ if (dynsym->ReadSectionDataFromObjectFile(this, dynsym_data))
+ {
+
+ const unsigned section_size = dynsym_data.GetByteSize();
+ unsigned offset = 0;
+ unsigned cursor = 0;
+
+ while (cursor < section_size)
+ {
+ offset = cursor;
+ if (!symbol.Parse(dynsym_data, &cursor))
+ break;
+
+ m_dynamic_symbols.push_back(symbol);
+ }
+ }
+
+ return m_dynamic_symbols.size();
+}
+
+const ELFDynamic *
+ObjectFileELF::FindDynamicSymbol(unsigned tag)
+{
+ if (!ParseDynamicSymbols())
+ return NULL;
+
+ SectionList *section_list = GetSectionList();
+ if (!section_list)
+ return 0;
+
+ DynamicSymbolCollIter I = m_dynamic_symbols.begin();
+ DynamicSymbolCollIter E = m_dynamic_symbols.end();
+ for ( ; I != E; ++I)
+ {
+ ELFDynamic *symbol = &*I;
+
+ if (symbol->d_tag == tag)
+ return symbol;
+ }
+
+ return NULL;
+}
+
+Section *
+ObjectFileELF::PLTSection()
+{
+ const ELFDynamic *symbol = FindDynamicSymbol(DT_JMPREL);
+ SectionList *section_list = GetSectionList();
+
+ if (symbol && section_list)
+ {
+ addr_t addr = symbol->d_ptr;
+ return section_list->FindSectionContainingFileAddress(addr).get();
+ }
+
+ return NULL;
+}
+
+unsigned
+ObjectFileELF::PLTRelocationType()
+{
+ const ELFDynamic *symbol = FindDynamicSymbol(DT_PLTREL);
+
+ if (symbol)
+ return symbol->d_val;
+
+ return 0;
+}
+
+static unsigned
+ParsePLTRelocations(Symtab *symbol_table,
+ user_id_t start_id,
+ unsigned rel_type,
+ const ELFHeader *hdr,
+ const ELFSectionHeader *rel_hdr,
+ const ELFSectionHeader *plt_hdr,
+ const ELFSectionHeader *sym_hdr,
+ Section *plt_section,
+ DataExtractor &rel_data,
+ DataExtractor &symtab_data,
+ DataExtractor &strtab_data)
+{
+ ELFRelocation rel(rel_type);
+ ELFSymbol symbol;
+ uint32_t offset = 0;
+ const unsigned plt_entsize = plt_hdr->sh_entsize;
+ const unsigned num_relocations = rel_hdr->sh_size / rel_hdr->sh_entsize;
+
+ typedef unsigned (*reloc_info_fn)(const ELFRelocation &rel);
+ reloc_info_fn reloc_type;
+ reloc_info_fn reloc_symbol;
+
+ if (hdr->Is32Bit() == 4)
+ {
+ reloc_type = ELFRelocation::RelocType32;
+ reloc_symbol = ELFRelocation::RelocSymbol32;
+ }
+ else
+ {
+ reloc_type = ELFRelocation::RelocType64;
+ reloc_symbol = ELFRelocation::RelocSymbol64;
+ }
+
+ unsigned slot_type = hdr->GetRelocationJumpSlotType();
+ unsigned i;
+ for (i = 0; i < num_relocations; ++i)
+ {
+ if (rel.Parse(rel_data, &offset) == false)
+ break;
+
+ if (reloc_type(rel) != slot_type)
+ continue;
+
+ unsigned symbol_offset = reloc_symbol(rel) * sym_hdr->sh_entsize;
+ uint64_t plt_index = (i + 1) * plt_entsize;
+
+ if (!symbol.Parse(symtab_data, &symbol_offset))
+ break;
+
+ const char *symbol_name = strtab_data.PeekCStr(symbol.st_name);
+
+ Symbol jump_symbol(
+ i + start_id, // Symbol table index
+ symbol_name, // symbol name.
+ false, // is the symbol name mangled?
+ eSymbolTypeTrampoline, // Type of this symbol
+ false, // Is this globally visible?
+ false, // Is this symbol debug info?
+ true, // Is this symbol a trampoline?
+ true, // Is this symbol artificial?
+ plt_section, // Section in which this symbol is defined or null.
+ plt_index, // Offset in section or symbol value.
+ plt_entsize, // Size in bytes of this symbol.
+ 0); // Symbol flags.
+
+ symbol_table->AddSymbol(jump_symbol);
+ }
+
+ return i;
+}
+
+unsigned
+ObjectFileELF::ParseTrampolineSymbols(Symtab *symbol_table,
+ user_id_t start_id,
+ const ELFSectionHeader *rel_hdr,
+ user_id_t rel_id)
+{
+ assert(rel_hdr->sh_type == SHT_RELA || rel_hdr->sh_type == SHT_REL);
+
+ // The link field points to the asscoiated symbol table. The info field
+ // points to the section holding the plt.
+ user_id_t symtab_id = rel_hdr->sh_link;
+ user_id_t plt_id = rel_hdr->sh_info;
+
+ if (!symtab_id || !plt_id)
+ return 0;
+
+ // Section ID's are ones based;
+ symtab_id++;
+ plt_id++;
+
+ const ELFSectionHeader *plt_hdr = GetSectionHeaderByIndex(plt_id);
+ if (!plt_hdr)
+ return 0;
+
+ const ELFSectionHeader *sym_hdr = GetSectionHeaderByIndex(symtab_id);
+ if (!sym_hdr)
+ return 0;
+
+ SectionList *section_list = GetSectionList();
+ if (!section_list)
+ return 0;
+
+ Section *rel_section = section_list->FindSectionByID(rel_id).get();
+ if (!rel_section)
+ return 0;
+
+ Section *plt_section = section_list->FindSectionByID(plt_id).get();
+ if (!plt_section)
+ return 0;
+
+ Section *symtab = section_list->FindSectionByID(symtab_id).get();
+ if (!symtab)
+ return 0;
+
+ Section *strtab = section_list->FindSectionByID(sym_hdr->sh_link + 1).get();
+ if (!strtab)
+ return 0;
+
+ DataExtractor rel_data;
+ if (!rel_section->ReadSectionDataFromObjectFile(this, rel_data))
+ return 0;
+
+ DataExtractor symtab_data;
+ if (!symtab->ReadSectionDataFromObjectFile(this, symtab_data))
+ return 0;
+
+ DataExtractor strtab_data;
+ if (!strtab->ReadSectionDataFromObjectFile(this, strtab_data))
+ return 0;
+
+ unsigned rel_type = PLTRelocationType();
+ if (!rel_type)
+ return 0;
+
+ return ParsePLTRelocations(symbol_table, start_id, rel_type,
+ &m_header, rel_hdr, plt_hdr, sym_hdr,
+ plt_section,
+ rel_data, symtab_data, strtab_data);
}
Symtab *
@@ -714,22 +1075,35 @@
Symtab *symbol_table = new Symtab(this);
m_symtab_ap.reset(symbol_table);
- Mutex::Locker locker (symbol_table->GetMutex ());
+ Mutex::Locker locker(symbol_table->GetMutex());
if (!(ParseSectionHeaders() && GetSectionHeaderStringTable()))
return symbol_table;
// Locate and parse all linker symbol tables.
+ uint64_t symbol_id = 0;
for (SectionHeaderCollIter I = m_section_headers.begin();
I != m_section_headers.end(); ++I)
{
if (I->sh_type == SHT_SYMTAB)
{
- const ELFSectionHeader &symtab_section = *I;
+ const ELFSectionHeader &symtab_header = *I;
user_id_t section_id = SectionIndex(I);
- ParseSymbolTable (symbol_table, symtab_section, section_id);
+ symbol_id += ParseSymbolTable(symbol_table, symbol_id,
+ &symtab_header, section_id);
}
}
+
+ // Synthesize trampoline symbols to help navigate the PLT.
+ Section *reloc_section = PLTSection();
+ if (reloc_section)
+ {
+ user_id_t reloc_id = reloc_section->GetID();
+ const ELFSectionHeader *reloc_header = GetSectionHeaderByIndex(reloc_id);
+ assert(reloc_header);
+
+ ParseTrampolineSymbols(symbol_table, symbol_id, reloc_header, reloc_id);
+ }
return symbol_table;
}
Modified: lldb/trunk/source/Plugins/ObjectFile/ELF/ObjectFileELF.h
URL: http://llvm.org/viewvc/llvm-project/lldb/trunk/source/Plugins/ObjectFile/ELF/ObjectFileELF.h?rev=128550&r1=128549&r2=128550&view=diff
==============================================================================
--- lldb/trunk/source/Plugins/ObjectFile/ELF/ObjectFileELF.h (original)
+++ lldb/trunk/source/Plugins/ObjectFile/ELF/ObjectFileELF.h Wed Mar 30 11:07:05 2011
@@ -120,6 +120,10 @@
typedef SectionHeaderColl::iterator SectionHeaderCollIter;
typedef SectionHeaderColl::const_iterator SectionHeaderCollConstIter;
+ typedef std::vector<elf::ELFDynamic> DynamicSymbolColl;
+ typedef DynamicSymbolColl::iterator DynamicSymbolCollIter;
+ typedef DynamicSymbolColl::const_iterator DynamicSymbolCollConstIter;
+
/// Version of this reader common to all plugins based on this class.
static const uint32_t m_plugin_version = 1;
@@ -132,6 +136,9 @@
/// Collection of section headers.
SectionHeaderColl m_section_headers;
+ /// Collection of symbols from the dynamic table.
+ DynamicSymbolColl m_dynamic_symbols;
+
/// List of sections present in this ELF object file.
mutable std::auto_ptr<lldb_private::SectionList> m_sections_ap;
@@ -147,7 +154,7 @@
/// Cached value of the entry point for this module.
lldb_private::Address m_entry_point_address;
-
+
/// Returns a 1 based index of the given section header.
unsigned
SectionIndex(const SectionHeaderCollIter &I);
@@ -175,13 +182,29 @@
size_t
ParseDependentModules();
+ /// Parses the dynamic symbol table and populates m_dynamic_symbols. The
+ /// vector retains the order as found in the object file. Returns the
+ /// number of dynamic symbols parsed.
+ size_t
+ ParseDynamicSymbols();
+
/// Populates m_symtab_ap will all non-dynamic linker symbols. This method
/// will parse the symbols only once. Returns the number of symbols parsed.
- void
+ unsigned
ParseSymbolTable(lldb_private::Symtab *symbol_table,
- const elf::ELFSectionHeader &symtab_section,
+ lldb::user_id_t start_id,
+ const elf::ELFSectionHeader *symtab_section,
lldb::user_id_t symtab_id);
+ /// Scans the relocation entries and adds a set of artificial symbols to the
+ /// given symbol table for each PLT slot. Returns the number of symbols
+ /// added.
+ unsigned
+ ParseTrampolineSymbols(lldb_private::Symtab *symbol_table,
+ lldb::user_id_t start_id,
+ const elf::ELFSectionHeader *rela_hdr,
+ lldb::user_id_t section_id);
+
/// Loads the section name string table into m_shstr_data. Returns the
/// number of bytes constituting the table.
size_t
@@ -194,6 +217,14 @@
lldb::user_id_t
GetSectionIndexByName(const char *name);
+ // Returns the ID of the first section that has the given type.
+ lldb::user_id_t
+ GetSectionIndexByType(unsigned type);
+
+ /// Returns the section header with the given id or NULL.
+ const elf::ELFSectionHeader *
+ GetSectionHeaderByIndex(lldb::user_id_t id);
+
/// @name ELF header dump routines
//@{
static void
@@ -246,6 +277,14 @@
void
DumpDependentModules(lldb_private::Stream *s);
+ const elf::ELFDynamic *
+ FindDynamicSymbol(unsigned tag);
+
+ lldb_private::Section *
+ PLTSection();
+
+ unsigned
+ PLTRelocationType();
};
#endif // #ifndef liblldb_ObjectFileELF_h_
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