From 0358652ff40546877c63fee8ca272db76b94a37d Mon Sep 17 00:00:00 2001 From: johannst Date: Sat, 17 Apr 2021 23:43:01 +0200 Subject: elf: add ehdr, sym, reloc --- lib/include/elf.h | 114 +++++++++++++++++++++++++++++++++++++++++++++++++----- 1 file changed, 104 insertions(+), 10 deletions(-) (limited to 'lib/include/elf.h') 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 +/// ---------- +/// 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) */ -- cgit v1.2.3 From 85230524414b6d27664bf77c8584bfeced6c71cb Mon Sep 17 00:00:00 2001 From: johannst Date: Wed, 21 Apr 2021 23:41:59 +0200 Subject: add support to resolve all relocations in PLT & RELA tables; add global variable as example to libgreet.so --- lib/include/elf.h | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) (limited to 'lib/include/elf.h') diff --git a/lib/include/elf.h b/lib/include/elf.h index 4856c79..f0a0940 100644 --- a/lib/include/elf.h +++ b/lib/include/elf.h @@ -141,11 +141,12 @@ typedef struct { // 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. */ +#define SHN_UNDEF 0 /* Undefined section. */ +#define SHN_ABS 0xff1 /* Indicates an absolute value. */ /// ----------------- /// Relocations Entry @@ -166,4 +167,6 @@ typedef struct { #define ELF64_R_TYPE(i) ((i)&0xffffffffL) // x86_64 relocation types. +#define R_X86_64_COPY 5 /* Copy content from sym addr to relocation address */ +#define R_X86_64_GLOB_DAT 6 /* Address affected by relocation: `offset` (+ base) */ #define R_X86_64_JUMP_SLOT 7 /* Address affected by relocation: `offset` (+ base) */ -- cgit v1.2.3 From 05f740db6fe966d32256d4ed3b897f7b3e051fff Mon Sep 17 00:00:00 2001 From: johannst Date: Sun, 25 Apr 2021 23:38:36 +0200 Subject: added support for R_X86_64_64/R_X86_64_RELATIVE relocations + added init/fini --- lib/include/elf.h | 64 ++++++++++++++++++++++++++++++------------------------- 1 file changed, 35 insertions(+), 29 deletions(-) (limited to 'lib/include/elf.h') diff --git a/lib/include/elf.h b/lib/include/elf.h index f0a0940..7a2e597 100644 --- a/lib/include/elf.h +++ b/lib/include/elf.h @@ -84,32 +84,36 @@ 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_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_MAX_CNT 25 +#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; @@ -167,6 +171,8 @@ typedef struct { #define ELF64_R_TYPE(i) ((i)&0xffffffffL) // x86_64 relocation types. -#define R_X86_64_COPY 5 /* Copy content from sym addr to relocation address */ -#define R_X86_64_GLOB_DAT 6 /* Address affected by relocation: `offset` (+ base) */ -#define R_X86_64_JUMP_SLOT 7 /* Address affected by relocation: `offset` (+ base) */ +#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` */ -- cgit v1.2.3 From fc137e7d0263a0fe908ca1a150e34a9c8b9902d4 Mon Sep 17 00:00:00 2001 From: johannst Date: Mon, 26 Apr 2021 22:47:53 +0200 Subject: add check for PT_TLS phdr --- lib/include/elf.h | 1 + 1 file changed, 1 insertion(+) (limited to 'lib/include/elf.h') diff --git a/lib/include/elf.h b/lib/include/elf.h index 7a2e597..0317859 100644 --- a/lib/include/elf.h +++ b/lib/include/elf.h @@ -60,6 +60,7 @@ typedef struct { #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 -- cgit v1.2.3