elf: add ehdr, sym, reloc

1 files changed, 104 insertions, 10 deletions

diff --git a/lib/include/elf.h b/lib/include/elf.h
index a0fe6f7..4856c79 100644
--- a/lib/include/elf.h
+++ b/lib/include/elf.h
@@ -4,6 +4,51 @@
 
 #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
 /// --------------
@@ -39,16 +84,16 @@ typedef struct {
 /// 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_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 */
@@ -73,3 +118,52 @@ typedef struct {
         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_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_JUMP_SLOT 7 /* Address affected by relocation: `offset` (+ base) */