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LibELF+LibC: Split ELFDynamicObject into a Loader + Object
Separate some responsibilities: ELFDynamicLoader is responsible for loading elf binaries from disk and performing relocations, calling init functions, and eventually calling finalizer functions. ELFDynamicObject is a helper class to parse the .dynamic section of an elf binary, or the table of Elf32_Dyn entries at the _DYNAMIC symbol. ELFDynamicObject now owns the helper classes for Relocations, Symbols, Sections and the like that ELFDynamicLoader will use to perform relocations and symbol lookup. Because these new helpers are constructed from offsets into the .dynamic section within the loaded .data section of the binary, we don't need the ELFImage for nearly as much of the loading processes as we did before. Therefore we can remove most of the extra DynamicXXX classes and just keep the one that lets us find the location of _DYNAMIC in the new ELF. And finally, since we changed the name of the class that dlopen/dlsym care about, we need to compile/link and use the new ELFDynamicLoader class in LibC.
This commit is contained in:
Andrew Kaster
Andreas Kling
parent
85b95f472d
commit
767f4c7421
8 changed files with 788 additions and 634 deletions
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@ -16,13 +16,9 @@ public:
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class Section;
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class RelocationSection;
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class DynamicRelocationSection;
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class Symbol;
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class DynamicSymbol;
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class Relocation;
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class DynamicRelocation;
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class DynamicSection;
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class DynamicSectionEntry;
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class Symbol {
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public:
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@ -50,32 +46,6 @@ public:
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const unsigned m_index;
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};
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class DynamicSymbol {
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public:
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DynamicSymbol(const ELFImage& image, unsigned index, const Elf32_Sym& sym)
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: m_image(image)
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, m_sym(sym)
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, m_index(index)
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{
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}
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~DynamicSymbol() {}
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const char* name() const { return m_image.dynamic_table_string(m_sym.st_name); }
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unsigned section_index() const { return m_sym.st_shndx; }
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unsigned value() const { return m_sym.st_value; }
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unsigned size() const { return m_sym.st_size; }
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unsigned index() const { return m_index; }
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unsigned type() const { return ELF32_ST_TYPE(m_sym.st_info); }
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unsigned bind() const { return ELF32_ST_BIND(m_sym.st_info); }
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const Section section() const { return m_image.section(section_index()); }
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private:
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const ELFImage& m_image;
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const Elf32_Sym& m_sym;
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const unsigned m_index;
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};
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class ProgramHeader {
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public:
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ProgramHeader(const ELFImage& image, unsigned program_header_index)
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@ -151,38 +121,6 @@ public:
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void for_each_relocation(F) const;
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};
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class DynamicRelocationSection : public Section {
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public:
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DynamicRelocationSection(const Section& section)
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: Section(section.m_image, section.m_section_index)
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{
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}
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unsigned relocation_count() const { return entry_count(); }
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const DynamicRelocation relocation(unsigned index) const;
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template<typename F>
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void for_each_relocation(F) const;
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};
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class DynamicRelocation {
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public:
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DynamicRelocation(const ELFImage& image, const Elf32_Rel& rel)
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: m_image(image)
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, m_rel(rel)
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{
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}
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~DynamicRelocation() {}
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unsigned offset() const { return m_rel.r_offset; }
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unsigned type() const { return ELF32_R_TYPE(m_rel.r_info); }
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unsigned symbol_index() const { return ELF32_R_SYM(m_rel.r_info); }
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const DynamicSymbol symbol() const { return m_image.dynamic_symbol(symbol_index()); }
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private:
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const ELFImage& m_image;
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const Elf32_Rel& m_rel;
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};
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class Relocation {
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public:
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Relocation(const ELFImage& image, const Elf32_Rel& rel)
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@ -210,28 +148,6 @@ public:
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{
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ASSERT(type() == SHT_DYNAMIC);
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}
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template<typename F>
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void for_each_dynamic_entry(F) const;
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};
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class DynamicSectionEntry {
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public:
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DynamicSectionEntry(const ELFImage& image, const Elf32_Dyn& dyn)
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: m_image(image)
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, m_dyn(dyn)
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{
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}
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~DynamicSectionEntry() {}
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Elf32_Sword tag() const { return m_dyn.d_tag; }
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Elf32_Addr ptr() const { return m_dyn.d_un.d_ptr; }
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Elf32_Word val() const { return m_dyn.d_un.d_val; }
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private:
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const ELFImage& m_image;
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const Elf32_Dyn& m_dyn;
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};
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unsigned symbol_count() const;
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@ -240,11 +156,9 @@ public:
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unsigned program_header_count() const;
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const Symbol symbol(unsigned) const;
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const DynamicSymbol dynamic_symbol(unsigned) const;
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const Section section(unsigned) const;
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const ProgramHeader program_header(unsigned const) const;
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const DynamicSection dynamic_section() const;
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const DynamicRelocationSection dynamic_relocation_section() const;
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template<typename F>
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void for_each_section(F) const;
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@ -253,8 +167,6 @@ public:
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template<typename F>
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void for_each_symbol(F) const;
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template<typename F>
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void for_each_dynamic_symbol(F) const;
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template<typename F>
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void for_each_program_header(F) const;
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// NOTE: Returns section(0) if section with name is not found.
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@ -276,17 +188,13 @@ private:
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const char* table_string(unsigned offset) const;
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const char* section_header_table_string(unsigned offset) const;
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const char* section_index_to_string(unsigned index) const;
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const char* dynamic_table_string(unsigned offset) const;
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const u8* m_buffer { nullptr };
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HashMap<String, unsigned> m_sections;
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bool m_valid { false };
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unsigned m_symbol_table_section_index { 0 };
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unsigned m_string_table_section_index { 0 };
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unsigned m_dynamic_symbol_table_section_index { 0 }; // .dynsym
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unsigned m_dynamic_string_table_section_index { 0 }; // .dynstr
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unsigned m_dynamic_section_index { 0 }; // .dynamic
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unsigned m_dynamic_relocation_section_index { 0 }; // .rel.dyn
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unsigned m_dynamic_section_index { 0 };
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};
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template<typename F>
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@ -317,15 +225,6 @@ inline void ELFImage::RelocationSection::for_each_relocation(F func) const
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}
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}
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template<typename F>
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inline void ELFImage::DynamicRelocationSection::for_each_relocation(F func) const
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{
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for (unsigned i = 0; i < relocation_count(); ++i) {
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if (func(relocation(i)) == IterationDecision::Break)
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break;
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}
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}
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template<typename F>
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inline void ELFImage::for_each_symbol(F func) const
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{
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@ -335,31 +234,9 @@ inline void ELFImage::for_each_symbol(F func) const
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}
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}
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template<typename F>
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inline void ELFImage::for_each_dynamic_symbol(F func) const
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{
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for (unsigned i = 0; i < dynamic_symbol_count(); ++i) {
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if (func(symbol(i)) == IterationDecision::Break)
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break;
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}
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}
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template<typename F>
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inline void ELFImage::for_each_program_header(F func) const
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{
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for (unsigned i = 0; i < program_header_count(); ++i)
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func(program_header(i));
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}
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template<typename F>
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inline void ELFImage::DynamicSection::for_each_dynamic_entry(F func) const
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{
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auto* dyns = reinterpret_cast<const Elf32_Dyn*>(m_image.raw_data(offset()));
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for (unsigned i = 0;; ++i) {
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auto&& dyn = DynamicSectionEntry(m_image, dyns[i]);
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if (dyn.tag() == DT_NULL)
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break;
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if (func(dyn) == IterationDecision::Break)
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break;
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}
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}
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