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LibELF: Restore the relocation code from git history

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This is going to be very useful for implementing kernel modules.
We'll also need it for dynamic linking later on.
This commit is contained in:
Andreas Kling 2019-11-28 20:53:02 +01:00
parent 0c4f29f71f
commit c10a5ac4ad
3 changed files with 94 additions and 4 deletions
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51
Libraries/LibELF/ELFImage.h
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@ -1,8 +1,8 @@
#pragma once
#include <AK/String.h>
#include <AK/HashMap.h>
#include <AK/OwnPtr.h>
#include <AK/String.h>
#include <Kernel/VM/VirtualAddress.h>
#include <LibELF/exec_elf.h>
@ -92,6 +92,7 @@ public:
u32 address() const { return m_section_header.sh_addr; }
const char* raw_data() const { return m_image.raw_data(m_section_header.sh_offset); }
bool is_undefined() const { return m_section_index == SHN_UNDEF; }
const RelocationSection relocations() const;
u32 flags() const { return m_section_header.sh_flags; }
bool is_writable() const { return flags() & SHF_WRITE; }
bool is_executable() const { return flags() & PF_X; }
@ -103,6 +104,38 @@ public:
unsigned m_section_index;
};
class RelocationSection : public Section {
public:
RelocationSection(const Section& section)
: Section(section.m_image, section.m_section_index)
{
}
unsigned relocation_count() const { return entry_count(); }
const Relocation relocation(unsigned index) const;
template<typename F>
void for_each_relocation(F) const;
};
class Relocation {
public:
Relocation(const ELFImage& image, const Elf32_Rel& rel)
: m_image(image)
, m_rel(rel)
{
}
~Relocation() {}
unsigned offset() const { return m_rel.r_offset; }
unsigned type() const { return ELF32_R_TYPE(m_rel.r_info); }
unsigned symbol_index() const { return ELF32_R_SYM(m_rel.r_info); }
const Symbol symbol() const { return m_image.symbol(symbol_index()); }
private:
const ELFImage& m_image;
const Elf32_Rel& m_rel;
};
unsigned symbol_count() const;
unsigned section_count() const;
unsigned program_header_count() const;
@ -120,6 +153,10 @@ public:
template<typename F>
void for_each_program_header(F) const;
// NOTE: Returns section(0) if section with name is not found.
// FIXME: I don't love this API.
const Section lookup_section(const char* name) const;
bool is_executable() const { return header().e_type == ET_EXEC; }
bool is_relocatable() const { return header().e_type == ET_REL; }
@ -136,6 +173,7 @@ private:
const char* section_index_to_string(unsigned index) const;
const u8* m_buffer { nullptr };
HashMap<String, unsigned> m_sections;
bool m_valid { false };
unsigned m_symbol_table_section_index { 0 };
unsigned m_string_table_section_index { 0 };
@ -154,12 +192,21 @@ inline void ELFImage::for_each_section_of_type(unsigned type, F func) const
for (unsigned i = 0; i < section_count(); ++i) {
auto& section = this->section(i);
if (section.type() == type) {
if (!func(section))
if (func(section) == IterationDecision::Break)
break;
}
}
}
template<typename F>
inline void ELFImage::RelocationSection::for_each_relocation(F func) const
{
for (unsigned i = 0; i < relocation_count(); ++i) {
if (func(relocation(i)) == IterationDecision::Break)
break;
}
}
template<typename F>
inline void ELFImage::for_each_symbol(F func) const
{