From d2fd2046a1a67ba4b01aab0ca68c790b02f9c93c Mon Sep 17 00:00:00 2001 From: Jacob Potter Date: Fri, 5 Sep 2008 17:23:41 -0400 Subject: [PATCH] Add ELF loader. --- elfload/elf.h | 288 +++++++++++++++++++++++++++++++++++++++++++++++ elfload/loader.c | 104 +++++++++++++++++ 2 files changed, 392 insertions(+) create mode 100644 elfload/elf.h create mode 100644 elfload/loader.c diff --git a/elfload/elf.h b/elfload/elf.h new file mode 100644 index 0000000..7240b69 --- /dev/null +++ b/elfload/elf.h @@ -0,0 +1,288 @@ +/* This file defines standard ELF types, structures, and macros. + Copyright (C) 1995, 1996, 1997, 1998, 1999 Free Software Foundation, Inc. + This file is part of the GNU C Library. + Contributed by Ian Lance Taylor . + + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Library General Public License as + published by the Free Software Foundation; either version 2 of the + License, or (at your option) any later version. + + The GNU C Library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Library General Public License for more details. + + You should have received a copy of the GNU Library General Public + License along with the GNU C Library; see the file COPYING.LIB. If not, + write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, + Boston, MA 02111-1307, USA. */ + +#ifndef _ELF_H +#define _ELF_H 1 + +#include + +/* Standard ELF types. */ + +/* Type for a 16-bit quantity. */ +typedef uint16_t Elf32_Half; +typedef uint16_t Elf64_Half; + +/* Types for signed and unsigned 32-bit quantities. */ +typedef uint32_t Elf32_Word; +typedef int32_t Elf32_Sword; +typedef uint32_t Elf64_Word; +typedef int32_t Elf64_Sword; + +/* Types for signed and unsigned 64-bit quantities. */ +typedef uint64_t Elf32_Xword; +typedef int64_t Elf32_Sxword; +typedef uint64_t Elf64_Xword; +typedef int64_t Elf64_Sxword; + +/* Type of addresses. */ +typedef uint32_t Elf32_Addr; +typedef uint64_t Elf64_Addr; + +/* Type of file offsets. */ +typedef uint32_t Elf32_Off; +typedef uint64_t Elf64_Off; + +/* Type for section indices, which are 16-bit quantities. */ +typedef uint16_t Elf32_Section; +typedef uint16_t Elf64_Section; + +/* Type of symbol indices. */ +typedef uint32_t Elf32_Symndx; +typedef uint64_t Elf64_Symndx; + + +/* The ELF file header. This appears at the start of every ELF file. */ + +#define EI_NIDENT (16) + +typedef struct +{ + unsigned char e_ident[EI_NIDENT]; /** Magic number and other info */ + Elf32_Half e_type; /** Object file type */ + Elf32_Half e_machine; /** Architecture */ + Elf32_Word e_version; /** Object file version */ + Elf32_Addr e_entry; /** Entry point virtual address */ + Elf32_Off e_phoff; /** Program header table file offset */ + Elf32_Off e_shoff; /** Section header table file offset */ + Elf32_Word e_flags; /** Processor-specific flags */ + Elf32_Half e_ehsize; /** ELF header size in bytes */ + Elf32_Half e_phentsize; /** Program header table entry size */ + Elf32_Half e_phnum; /** Program header table entry count */ + Elf32_Half e_shentsize; /** Section header table entry size */ + Elf32_Half e_shnum; /** Section header table entry count */ + Elf32_Half e_shstrndx; /** Section header string table index */ +} Elf32_Ehdr; + +/* Fields in the e_ident array. The EI_* macros are indices into the + array. The macros under each EI_* macro are the values the byte + may have. */ + +#define EI_MAG0 0 /* File identification byte 0 index */ +#define ELFMAG0 0x7f /* Magic number byte 0 */ + +#define EI_MAG1 1 /* File identification byte 1 index */ +#define ELFMAG1 'E' /* Magic number byte 1 */ + +#define EI_MAG2 2 /* File identification byte 2 index */ +#define ELFMAG2 'L' /* Magic number byte 2 */ + +#define EI_MAG3 3 /* File identification byte 3 index */ +#define ELFMAG3 'F' /* Magic number byte 3 */ + +/* Conglomeration of the identification bytes, for easy testing as a word. */ +#define ELFMAG "\177ELF" +#define SELFMAG 4 + +#define EI_CLASS 4 /* File class byte index */ +#define ELFCLASSNONE 0 /* Invalid class */ +#define ELFCLASS32 1 /* 32-bit objects */ +#define ELFCLASS64 2 /* 64-bit objects */ +#define ELFCLASSNUM 3 + +#define EI_DATA 5 /* Data encoding byte index */ +#define ELFDATANONE 0 /* Invalid data encoding */ +#define ELFDATA2LSB 1 /* 2's complement, little endian */ +#define ELFDATA2MSB 2 /* 2's complement, big endian */ +#define ELFDATANUM 3 + +#define EI_VERSION 6 /* File version byte index */ + /* Value must be EV_CURRENT */ + +#define EI_OSABI 7 /* OS ABI identification */ +#define ELFOSABI_SYSV 0 /* UNIX System V ABI */ +#define ELFOSABI_HPUX 1 /* HP-UX */ +#define ELFOSABI_FREEBSD 9 /* Free BSD */ +#define ELFOSABI_ARM 97 /* ARM */ +#define ELFOSABI_STANDALONE 255 /* Standalone (embedded) application */ + +#define EI_ABIVERSION 8 /* ABI version */ + +#define EI_PAD 9 /* Byte index of padding bytes */ + +/* Legal values for e_type (object file type). */ + +#define ET_NONE 0 /* No file type */ +#define ET_REL 1 /* Relocatable file */ +#define ET_EXEC 2 /* Executable file */ +#define ET_DYN 3 /* Shared object file */ +#define ET_CORE 4 /* Core file */ +#define ET_NUM 5 /* Number of defined types */ +#define ET_LOPROC 0xff00 /* Processor-specific */ +#define ET_HIPROC 0xffff /* Processor-specific */ + +/* Legal values for e_machine (architecture). */ + +#define EM_NONE 0 /* No machine */ +#define EM_M32 1 /* AT&T WE 32100 */ +#define EM_SPARC 2 /* SUN SPARC */ +#define EM_386 3 /* Intel 80386 */ +#define EM_68K 4 /* Motorola m68k family */ +#define EM_88K 5 /* Motorola m88k family */ +#define EM_486 6 /* Intel 80486 */ +#define EM_860 7 /* Intel 80860 */ +#define EM_MIPS 8 /* MIPS R3000 big-endian */ +#define EM_S370 9 /* Amdahl */ +#define EM_MIPS_RS4_BE 10 /* MIPS R4000 big-endian */ +#define EM_RS6000 11 /* RS6000 */ + +#define EM_PARISC 15 /* HPPA */ +#define EM_nCUBE 16 /* nCUBE */ +#define EM_VPP500 17 /* Fujitsu VPP500 */ +#define EM_SPARC32PLUS 18 /* Sun's "v8plus" */ +#define EM_960 19 /* Intel 80960 */ +#define EM_PPC 20 /* PowerPC */ + +#define EM_V800 36 /* NEC V800 series */ +#define EM_FR20 37 /* Fujitsu FR20 */ +#define EM_RH32 38 /* TRW RH32 */ +#define EM_MMA 39 /* Fujitsu MMA */ +#define EM_ARM 40 /* ARM */ +#define EM_FAKE_ALPHA 41 /* Digital Alpha */ +#define EM_SH 42 /* Hitachi SH */ +#define EM_SPARCV9 43 /* SPARC v9 64-bit */ +#define EM_TRICORE 44 /* Siemens Tricore */ +#define EM_ARC 45 /* Argonaut RISC Core */ +#define EM_H8_300 46 /* Hitachi H8/300 */ +#define EM_H8_300H 47 /* Hitachi H8/300H */ +#define EM_H8S 48 /* Hitachi H8S */ +#define EM_H8_500 49 /* Hitachi H8/500 */ +#define EM_IA_64 50 /* Intel Merced */ +#define EM_MIPS_X 51 /* Stanford MIPS-X */ +#define EM_COLDFIRE 52 /* Motorola Coldfire */ +#define EM_68HC12 53 /* Motorola M68HC12 */ +#define EM_NUM 54 + +/* If it is necessary to assign new unofficial EM_* values, please + pick large random numbers (0x8523, 0xa7f2, etc.) to minimize the + chances of collision with official or non-GNU unofficial values. */ + +#define EM_ALPHA 0x9026 + +/* Legal values for e_version (version). */ + +#define EV_NONE 0 /* Invalid ELF version */ +#define EV_CURRENT 1 /* Current version */ +#define EV_NUM 2 + +/* Section header. */ + +typedef struct +{ + Elf32_Word sh_name; /** Section name (string tbl index) */ + Elf32_Word sh_type; /** Section type */ + Elf32_Word sh_flags; /** Section flags */ + Elf32_Addr sh_addr; /** Section virtual addr at execution */ + Elf32_Off sh_offset; /** Section file offset */ + Elf32_Word sh_size; /** Section size in bytes */ + Elf32_Word sh_link; /** Link to another section */ + Elf32_Word sh_info; /** Additional section information */ + Elf32_Word sh_addralign; /** Section alignment */ + Elf32_Word sh_entsize; /** Entry size if section holds table */ +} Elf32_Shdr; + +/* Special section indices. */ + +#define SHN_UNDEF 0 /* Undefined section */ +#define SHN_LORESERVE 0xff00 /* Start of reserved indices */ +#define SHN_LOPROC 0xff00 /* Start of processor-specific */ +#define SHN_HIPROC 0xff1f /* End of processor-specific */ +#define SHN_ABS 0xfff1 /* Associated symbol is absolute */ +#define SHN_COMMON 0xfff2 /* Associated symbol is common */ +#define SHN_HIRESERVE 0xffff /* End of reserved indices */ + +/* Legal values for sh_type (section type). */ + +#define SHT_NULL 0 /* Section header table entry unused */ +#define SHT_PROGBITS 1 /* Program data */ +#define SHT_SYMTAB 2 /* Symbol table */ +#define SHT_STRTAB 3 /* String table */ +#define SHT_RELA 4 /* Relocation entries with addends */ +#define SHT_HASH 5 /* Symbol hash table */ +#define SHT_DYNAMIC 6 /* Dynamic linking information */ +#define SHT_NOTE 7 /* Notes */ +#define SHT_NOBITS 8 /* Program space with no data (bss) */ +#define SHT_REL 9 /* Relocation entries, no addends */ +#define SHT_SHLIB 10 /* Reserved */ +#define SHT_DYNSYM 11 /* Dynamic linker symbol table */ +#define SHT_NUM 12 /* Number of defined types. */ +#define SHT_LOOS 0x60000000 /* Start OS-specific */ +#define SHT_LOSUNW 0x6ffffffb /* Sun-specific low bound. */ +#define SHT_SUNW_COMDAT 0x6ffffffb +#define SHT_SUNW_syminfo 0x6ffffffc +#define SHT_GNU_verdef 0x6ffffffd /* Version definition section. */ +#define SHT_GNU_verneed 0x6ffffffe /* Version needs section. */ +#define SHT_GNU_versym 0x6fffffff /* Version symbol table. */ +#define SHT_HISUNW 0x6fffffff /* Sun-specific high bound. */ +#define SHT_HIOS 0x6fffffff /* End OS-specific type */ +#define SHT_LOPROC 0x70000000 /* Start of processor-specific */ +#define SHT_HIPROC 0x7fffffff /* End of processor-specific */ +#define SHT_LOUSER 0x80000000 /* Start of application-specific */ +#define SHT_HIUSER 0x8fffffff /* End of application-specific */ + +/* Legal values for sh_flags (section flags). */ + +#define SHF_WRITE (1 << 0) /* Writable */ +#define SHF_ALLOC (1 << 1) /* Occupies memory during execution */ +#define SHF_EXECINSTR (1 << 2) /* Executable */ +#define SHF_MASKPROC 0xf0000000 /* Processor-specific */ + +/* --- Simplified ELF header --- */ +typedef struct simple_elf { + const char * e_fname; /* filename of binary */ + unsigned long e_entry; /* entry point virtual address */ + unsigned long e_txtoff; /* offset of text segment in file */ + unsigned long e_txtlen; /* length of text segment in bytes */ + unsigned long e_txtstart; /* start of text segment virtual address */ + unsigned long e_datoff; /* offset of data segment in file */ + unsigned long e_datlen; /* length of data segment in bytes */ + unsigned long e_datstart; /* start of data segment in virtual memory */ + unsigned long e_rodatoff; /* offset of rodata segment in file */ + unsigned long e_rodatlen; /* length of rodata segment in bytes */ + unsigned long e_rodatstart; /* start of rodata segment in virtual memory*/ + unsigned long e_bsslen; /* length of bss segment in bytes */ +} simple_elf_t; + + /* --- Defines --- */ +#define NMAGIC 0410 /* 0x108 */ +#define N_MAGIC(exec) ((exec).a_midmag & 0xffff) +#define N_BADMAG(x) (N_MAGIC(x) != NMAGIC) + +#define ELF_NOTELF -1 +#define ELF_SUCCESS 0 +#define NOT_PRESENT -2 + +/* + * elf function prototypes + */ +extern int getbytes( const char *filename, int offset, int size, char *buf); +extern int elf_load_helper( simple_elf_t *se_hdr, const char *fname ); +extern int elf_check_header( const char *fname ); + +#endif /* elf.h */ diff --git a/elfload/loader.c b/elfload/loader.c new file mode 100644 index 0000000..f5be3a4 --- /dev/null +++ b/elfload/loader.c @@ -0,0 +1,104 @@ +#include +#include +#include "elf.h" +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#define FATAL do { fprintf(stderr, "Error at %s:%d (%d) [%s]\n", \ + __FILE__, __LINE__, errno, strerror(errno)); exit(1); } while(0) + +#define MAP_SIZE 131072 +#define MAP_MASK (4096 - 1) + +char * snarf_file(char * fname) { + + int fd = open(fname, O_RDONLY); + if (fd < 0) FATAL; + + struct stat st; + if (fstat(fd, &st) < 0) FATAL; + + char * buf = malloc(st.st_size); + if (!buf) FATAL; + if (read(fd, buf, st.st_size) != st.st_size) FATAL; + + printf("Loaded %d bytes.\n", st.st_size); + return buf; +} + +void dump_to_ram (void * src, int target, int size) { + + printf("Copying %d bytes to 0x%08x...\n", size, target); + + int fd = open("/dev/mem", O_RDWR | O_SYNC); + if (fd < 0) FATAL; + + void * map_base = mmap(0, MAP_SIZE, PROT_READ | PROT_WRITE, + MAP_SHARED, fd, target & ~MAP_MASK); + + if (map_base == (void *) -1) FATAL; + + void * virt_addr = map_base + (target & MAP_MASK); + memcpy(virt_addr, src, size); + +} + +static const unsigned char elf_ident[4] = { 0x7F, 'E', 'L', 'F' }; + +int load_elf (char * buf) { + + Elf32_Ehdr * elf_hdr = (Elf32_Ehdr *) buf; + Elf32_Shdr * elf_sec_hdrs = (Elf32_Shdr *) (buf + elf_hdr->e_shoff); + + if (memcmp(elf_hdr->e_ident, elf_ident, sizeof(elf_ident))) FATAL; + if (elf_hdr->e_type != ET_EXEC) FATAL; + if (elf_hdr->e_machine != EM_386) FATAL; + if (elf_hdr->e_version != EV_CURRENT) FATAL; + + char * string_table = buf + elf_sec_hdrs[elf_hdr->e_shstrndx].sh_offset; + + int i; + for (i = 0; i < elf_hdr->e_shnum; i++) { + if (elf_sec_hdrs[i].sh_name == SHN_UNDEF) { + continue; + } + + char * section_name = string_table + elf_sec_hdrs[i].sh_name; + + if (!(elf_sec_hdrs[i].sh_flags & SHF_ALLOC)) { + printf("Skipping %s...\n", section_name); + continue; + } + + printf("Loading %s...\n", section_name); + + dump_to_ram(buf + elf_sec_hdrs[i].sh_offset, + elf_sec_hdrs[i].sh_addr, + elf_sec_hdrs[i].sh_size); + } + + return 0; +} + +int main(int argc, char **argv) { + if (argc != 2) { + printf("Usage: %s elffile\n", argv[0]); + return 1; + } + + printf("Loading file...\n"); + + char * buf = snarf_file(argv[1]); + load_elf(buf); + + return 0; +} + -- 2.43.0