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// Copyright (c) 2020 Johannes Stoelp
#pragma once
#include <stdint.h>
/// ----------
/// ELF Header
/// ----------
// Index into `ident`.
#define EI_MAG0 0
#define EI_MAG1 1
#define EI_MAG2 2
#define EI_MAG3 3
#define EI_CLASS 4
#define EI_DATA 5
#define EI_OSABI 7
// indent[EI_CLASS]
#define ELFCLASS32 1
#define ELFCLASS64 2
// indent[EI_CLASS]
#define ELFDATA2LSB 1
#define ELFDATA2MSB 2
// indent[EI_OSABI]
#define ELFOSABI_SYSV 0
// Objec file `type`.
#define ET_NONE 0
#define ET_DYN 3
typedef struct {
uint8_t ident[16]; // ELF identification.
uint16_t type; // Object file type.
uint16_t machine; // Machine type.
uint32_t version; // Object file version.
uint64_t entry; // Entrypoint address.
uint64_t phoff; // Program header file offset.
uint64_t shoff; // Section header file offset.
uint32_t flags; // Processor specific flags.
uint16_t ehsize; // ELF header size.
uint16_t phentsize; // Program header entry size.
uint16_t phnum; // Number of program header entries.
uint16_t shentsize; // Section header entry size.
uint16_t shnum; // Number of section header entries.
uint16_t shstrndx; // Section name string table index.
} Elf64Ehdr;
/// --------------
/// Program Header
/// --------------
#define PT_NULL 0 /* ignored */
#define PT_LOAD 1 /* Mark loadable segment (allowed p_memsz > p_filesz). */
#define PT_DYNAMIC 2 /* Location of .dynamic section */
#define PT_INTERP 3 /* Location of .interp section */
#define PT_NOTE 4 /* Location of auxiliary information */
#define PT_SHLIB 5 /* Reserved, but unspecified semantic */
#define PT_PHDR 6 /* Location & size of program headers itself */
#define PT_TLS 7 /* Thread local storage */
#define PT_GNU_EH_FRAME 0x6474e550 /* [x86-64] stack unwinding tables */
#define PT_LOPROC 0x70000000
#define PT_HIPROC 0x7fffffff
#define PF_X 0x1 /* Phdr flag eXecute flag bitmask */
#define PF_W 0x2 /* Phdr flag Write flag bitmask */
#define PF_R 0x4 /* Phdr flag Read flag bitmask */
typedef struct {
uint32_t type; // Segment kind.
uint32_t flags; // Flags describing Segment attributes like R, W, X.
uint64_t offset; // Offset into the file where the Segment starts.
uint64_t vaddr; // Virtual address of first byte of Segment in memory.
uint64_t paddr; // Physical address, ignored in our case.
uint64_t filesz; // Number of bytes of the Segment in the file image.
uint64_t memsz; // Number of bytes of the segement in memory.
uint64_t align;
} Elf64Phdr;
/// ---------------
/// Dynamic Section
/// ---------------
#define DT_NULL 0 /* [ignored] Marks end of dynamic section */
#define DT_NEEDED 1 /* [val] Name of needed library */
#define DT_PLTRELSZ 2 /* [val] Size in bytes of PLT relocs */
#define DT_PLTGOT 3 /* [ptr] Processor defined value */
#define DT_HASH 4 /* [ptr] Address of symbol hash table */
#define DT_STRTAB 5 /* [ptr] Address of string table */
#define DT_SYMTAB 6 /* [ptr] Address of symbol table */
#define DT_RELA 7 /* [ptr] Address of Rela relocs */
#define DT_RELASZ 8 /* [val] Total size of Rela relocs */
#define DT_RELAENT 9 /* [val] Size of one Rela reloc */
#define DT_STRSZ 10 /* [val] Size of string table */
#define DT_SYMENT 11 /* [val] Size of one symbol table entry */
#define DT_INIT 12 /* [ptr] Address of init function */
#define DT_FINI 13 /* [ptr] Address of termination function */
#define DT_SONAME 14 /* [val] Name of shared object */
#define DT_RPATH 15 /* [val] Library search path (deprecated) */
#define DT_SYMBOLIC 16 /* [ignored] Start symbol search here */
#define DT_REL 17 /* [ptr] Address of Rel relocs */
#define DT_RELSZ 18 /* [val] Total size of Rel relocs */
#define DT_RELENT 19 /* [val] Size of one Rel reloc */
#define DT_PLTREL 20 /* [val] Type of reloc in PLT */
#define DT_DEBUG 21 /* [ptr] For debugging; unspecified */
#define DT_TEXTREL 22 /* [ignored] Reloc might modify .text */
#define DT_JMPREL 23 /* [ptr] Address of PLT relocs */
#define DT_BIND_NOW 24 /* [ignored] Process relocations of object */
#define DT_INIT_ARRAY 25 /* [ptr] Address of array of initialization functions */
#define DT_FINI_ARRAY 26 /* [ptr] Address of array of termination functions */
#define DT_INIT_ARRAYSZ 27 /* [val] Size in bytes of the initialization array */
#define DT_FINI_ARRAYSZ 28 /* [val] Size in bytes of the termination array */
#define DT_MAX_CNT 29
typedef struct {
uint64_t tag;
union {
uint64_t val;
void* ptr;
};
} Elf64Dyn;
/// ------------
/// Symbol Entry
/// ------------
typedef struct {
uint32_t name; // Symbol name (index into string table).
uint8_t info; // Symbol Binding bits[7..4] + Symbol Type bits[3..0].
uint8_t other; // Reserved.
uint16_t shndx; // Section table index.
uint64_t value; //
uint64_t size; //
} Elf64Sym;
#define ELF64_ST_BIND(i) ((i) >> 4)
#define ELF64_ST_TYPE(i) ((i)&0xf)
// Symbold Bindings.
#define STB_GLOBAL 1 /* Global symbol, visible to all object files. */
#define STB_WEAK 2 /* Global scope, but with lower precedence than global symbols. */
// Symbol Types.
#define STT_NOTYPE 0 /* No type. */
#define STT_OBJECT 1 /* Data Object. */
#define STT_FUNC 2 /* Function entry point. */
// Special Section Indicies.
#define SHN_UNDEF 0 /* Undefined section. */
#define SHN_ABS 0xff1 /* Indicates an absolute value. */
/// -----------------
/// Relocations Entry
/// -----------------
typedef struct {
uint64_t offset; // Virtual address of the storage unit affected by the relocation.
uint64_t info; // Symbol table index + relocation type.
} Elf64Rel;
typedef struct {
uint64_t offset; // Virtual address of the storage unit affected by the relocation.
uint64_t info; // Symbol table index + relocation type.
int64_t addend; // Constant value used to compute the relocation value.
} Elf64Rela;
#define ELF64_R_SYM(i) ((i) >> 32)
#define ELF64_R_TYPE(i) ((i)&0xffffffffL)
// x86_64 relocation types.
#define R_X86_64_64 1 /* Absolute 64bit address, address affected by relocation: `base + offset` */
#define R_X86_64_COPY 5 /* Copy content from sym addr to relocation address: `base + offset` */
#define R_X86_64_GLOB_DAT 6 /* Address affected by relocation: `base + offset` */
#define R_X86_64_JUMP_SLOT 7 /* Address affected by relocation: `base + offset` */
#define R_X86_64_RELATIVE 8 /* Relative address *`base + offset` = `base + addend` */
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