From 6bba5dd59e8e56ed441366057beee24d6cf8ca81 Mon Sep 17 00:00:00 2001 From: "K. Lange" Date: Fri, 4 May 2018 12:36:25 +0900 Subject: [PATCH] add readelf app --- apps/readelf.c | 253 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 253 insertions(+) create mode 100644 apps/readelf.c diff --git a/apps/readelf.c b/apps/readelf.c new file mode 100644 index 00000000..87b5c3e9 --- /dev/null +++ b/apps/readelf.c @@ -0,0 +1,253 @@ +/* This file is part of ToaruOS and is released under the terms + * of the NCSA / University of Illinois License - see LICENSE.md + * Copyright (C) 2013-2014 Kevin Lange + */ +/* + * ToAruOS Miniature ELF Reader + * (C) 2011 Kevin Lange + */ + +#include +#include +#include +#include +#include + +/** + * Show usage for the readelf application. + * @param argc Argument count (unused) + * @param argv Arguments to binary + */ +void usage(int argc, char ** argv) { + /* Show usage */ + printf("%s [filename]\n", argv[0]); + printf("\tDisplays information on ELF binaries such as section names,\n"); + printf("\tlocations, sizes, and loading positions in memory.\n"); + exit(1); +} + +/** + * Application entry point. + * @returns 0 on sucess, 1 on failure + */ +int main(int argc, char ** argv) { + /* Process arguments */ + if (argc < 2) usage(argc,argv); + + FILE * binary; /**< File pointer for requested executable */ + size_t binary_size; /**< Size of the file */ + char * binary_buf; /**< Buffer to store the binary in memory */ + Elf32_Header * header; /**< ELF header */ + char * string_table = NULL; /**< The section header string table */ + char * sym_string_table = NULL; /**< The symbol string table */ + + /* Open the requested binary */ + binary = fopen(argv[1], "r"); + + /* Jump to the end so we can get the size */ + fseek(binary, 0, SEEK_END); + binary_size = ftell(binary); + fseek(binary, 0, SEEK_SET); + + /* Some sanity checks */ + if (binary_size < 4 || binary_size > 0xFFFFFFF) { + printf("Oh no! I don't quite like the size of this binary.\n"); + return 1; + } + printf("Binary is %u bytes.\n", (unsigned int)binary_size); + + /* Read the binary into a buffer */ + binary_buf = malloc(binary_size); + fread((void *)binary_buf, binary_size, 1, binary); + + /* Let's start considering this guy an elf, 'eh? */ + header = (Elf32_Header *)binary_buf; + + /* Verify the magic */ + if ( header->e_ident[0] != ELFMAG0 || + header->e_ident[1] != ELFMAG1 || + header->e_ident[2] != ELFMAG2 || + header->e_ident[3] != ELFMAG3) { + printf("Header magic is wrong!\n"); + printf("Are you sure this is a 32-bit ELF binary or object file?\n"); + return 1; + } + + /* Let's print out some of the header information, shall we? */ + printf("\033[1mELF Header\033[0m\n"); + + /* File type */ + printf("[Type %d] ", header->e_type); + switch (header->e_type) { + case ET_NONE: + printf("No file type.\n"); + break; + case ET_REL: + printf("Relocatable file.\n"); + break; + case ET_EXEC: + printf("Executable file.\n"); + break; + case ET_DYN: + printf("Shared object file.\n"); + break; + case ET_CORE: + printf("Core file.\n"); + break; + default: + printf("(Unknown file type)\n"); + break; + } + + /* Machine Type */ + switch (header->e_machine) { + case EM_386: + printf("Intel x86\n"); + break; + default: + printf("Unknown machine: %d\n", header->e_machine); + break; + } + + /* Version == EV_CURRENT? */ + if (header->e_version == EV_CURRENT) { + printf("ELF version is 1, as it should be.\n"); + } + + /* Entry point in memory */ + printf("Binary entry point in virtual memory is at 0x%x\n", (unsigned int)header->e_entry); + + /* Program header table offset */ + printf("Program header table is at +0x%x and one entry is 0x%x bytes.\n" + "There are %d total program headers.\n", + (unsigned int)header->e_phoff, (unsigned int)header->e_phentsize, (unsigned int)header->e_phnum); + + /* Section header table offset */ + printf("Section header table is at +0x%x and one entry is 0x%x bytes.\n" + "There are %d total section headers.\n", + (unsigned int)header->e_shoff, (unsigned int)header->e_shentsize, (unsigned int)header->e_shnum); + + /* Read the program headers */ + printf("\033[1mProgram Headers\033[0m\n"); + for (uint32_t x = 0; x < header->e_phentsize * header->e_phnum; x += header->e_phentsize) { + if (header->e_phoff + x > binary_size) { + printf("Tried to read beyond the end of the file.\n"); + return 1; + } + /* Grab the program header */ + Elf32_Phdr * phdr = (Elf32_Phdr *)((uintptr_t)binary_buf + (header->e_phoff + x)); + + /* Print the header type */ + switch (phdr->p_type) { + case PT_LOAD: + printf("[Loadable Segment]\n"); + break; + case PT_DYNAMIC: + printf("[Dynamic Loading Information]\n"); + break; + case PT_INTERP: + printf("[Interpreter Path]\n"); + break; + default: + printf("[Unused Segement]\n"); + break; + } + } + + uint32_t i = 0; + for (uint32_t x = 0; x < header->e_shentsize * header->e_shnum; x += header->e_shentsize) { + if (header->e_shoff + x > binary_size) { + printf("Tried to read beyond the end of the file.\n"); + return 1; + } + Elf32_Shdr * shdr = (Elf32_Shdr *)((uintptr_t)binary_buf + (header->e_shoff + x)); + if (shdr->sh_type == SHT_STRTAB) { + if (i == header->e_shstrndx) { + string_table = (char *)((uintptr_t)binary_buf + shdr->sh_offset); + printf("Found the section string table at 0x%x\n", (unsigned int)shdr->sh_offset); + } + } + i++; + } + + if (!string_table) { + printf("No string table, skipping rest of output.\n"); + return 1; + } + + /* Find the (hopefully two) string tables */ + printf("\033[1mString Tables\033[0m\n"); + for (uint32_t x = 0; x < header->e_shentsize * header->e_shnum; x += header->e_shentsize) { + if (header->e_shoff + x > binary_size) { + printf("Tried to read beyond the end of the file.\n"); + return 1; + } + Elf32_Shdr * shdr = (Elf32_Shdr *)((uintptr_t)binary_buf + (header->e_shoff + x)); + if (shdr->sh_type == SHT_STRTAB) { + if (!strcmp((char *)((uintptr_t)string_table + shdr->sh_name), ".strtab")) { + sym_string_table = (char *)((uintptr_t)binary_buf + shdr->sh_offset); + printf("Found the symbol string table at 0x%x\n", (unsigned int)shdr->sh_offset); + } + printf("Displaying string table at 0x%x\n", (unsigned int)shdr->sh_offset); + char * _string_table = (char *)((uintptr_t)binary_buf + shdr->sh_offset); + unsigned int j = 1; + int k = 0; + printf("%d\n", (unsigned int)shdr->sh_size); + while (j < shdr->sh_size) { + int t = strlen((char *)((uintptr_t)_string_table + j)); + if (t) { + printf("%d [%d] %s\n", k, j, (char *)((uintptr_t)_string_table + j)); + k++; + j += t; + } else { + j += 1; + } + } + } + } + + /* Read the section headers */ + printf("\033[1mSection Headers\033[0m\n"); + for (uint32_t x = 0; x < header->e_shentsize * header->e_shnum; x += header->e_shentsize) { + if (header->e_shoff + x > binary_size) { + printf("Tried to read beyond the end of the file.\n"); + return 1; + } + Elf32_Shdr * shdr = (Elf32_Shdr *)((uintptr_t)binary_buf + (header->e_shoff + x)); + + printf("[%d] %s\n", (unsigned int)shdr->sh_type, (char *)((uintptr_t)string_table + shdr->sh_name)); + printf("Section starts at 0x%x and is 0x%x bytes long.\n", (unsigned int)shdr->sh_offset, (unsigned int)shdr->sh_size); + if (shdr->sh_addr) { + printf("It should be loaded at 0x%x.\n", (unsigned int)shdr->sh_addr); + } + } + +#if 1 + printf("\033[1mSymbol Tables\033[0m\n"); + for (uint32_t x = 0; x < header->e_shentsize * header->e_shnum; x += header->e_shentsize) { + if (header->e_shoff + x > binary_size) { + printf("Tried to read beyond the end of the file.\n"); + return 1; + } + Elf32_Shdr * shdr = (Elf32_Shdr *)((uintptr_t)binary_buf + (header->e_shoff + x)); + + if (shdr->sh_type == SHT_SYMTAB) { + printf("Found symbol table: %s\n", (char *)((uintptr_t)string_table + shdr->sh_name)); + + Elf32_Sym * table = (Elf32_Sym *)((uintptr_t)binary_buf + (shdr->sh_offset)); + while ((uintptr_t)table - ((uintptr_t)binary_buf + shdr->sh_offset) < shdr->sh_size) { + printf("%s: 0x%x [0x%x]\n", (char *)((uintptr_t)sym_string_table + table->st_name), (unsigned int)table->st_value, (unsigned int)table->st_size); + table++; + } + } + } +#endif + + return 0; +} + +/* + * vim:noexpandtab + * vim:tabstop=4 + * vim:shiftwidth=4 + */