nex-dbg.c

#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <elf.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/mman.h>
#include <stdint.h>
#include <sys/stat.h>
#include <fcntl.h>

int main(int argc, char **argv) {
   int fd, i;
   uint8_t *mem;
   struct stat st;
   char *StringTable, *interp;
   
   Elf32_Ehdr *ehdr;
   Elf32_Phdr *phdr;
   Elf32_Shdr *shdr;

   if(argc < 2) {
      printf("Usage: %s <binary>\n", argv[0]);
      exit(0);
   }

   if((fd = open(argv[1], O_RDONLY)) < 0) {
      perror("open");
      exit(EXIT_FAILURE);
   }
   
   if(fstat(fd, &st) < 0) {
      perror("fstat");
      exit(EXIT_FAILURE);
   }
   
   mem = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
   if(mem == MAP_FAILED) {
      perror("mmap");
      exit(EXIT_FAILURE);
   }
   
   ehdr = (Elf32_Ehdr *)mem;
   phdr = (Elf32_Phdr *)&mem[ehdr->e_phoff];
   shdr = (Elf32_Shdr *)&mem[ehdr->e_shoff];
   
   if(mem[0] != 0x7f && strcmp(&mem[1], "ELF")) {
      fprintf(stderr, "%s is not an ELF file\n", argv[1]);
      exit(EXIT_FAILURE);
   }
   
   if(ehdr->e_type != ET_EXEC) {
      fprintf(stderr, "%s is not an executable\n", argv[1]);
      exit(EXIT_FAILURE);
   }

   printf("Program Entry point: 0x%x\n", ehdr->e_entry);
   
   StringTable = &mem[shdr[ehdr->e_shstrndx].sh_offset];

   printf("Section header list:\n\n");
   for(i = 1; i < ehdr->e_shnum; i++)
      printf("%s: 0x%x\n", &StringTable[shdr[i].sh_name], shdr[i].sh_addr);
   
   printf("\nProgram header list\n\n");
   for(i = 0; i < ehdr->e_phnum; i++) {   
      switch(phdr[i].p_type) {
         case PT_LOAD:
            if (phdr[i].p_offset == 0)
               printf("Text segment: 0x%x\n", phdr[i].p_vaddr);
            else
               printf("Data segment: 0x%x\n", phdr[i].p_vaddr);
         break;
         case PT_INTERP:
            interp = strdup((char *)&mem[phdr[i].p_offset]);
            printf("Interpreter: %s\n", interp);
            break;
         case PT_NOTE:
            printf("Note segment: 0x%x\n", phdr[i].p_vaddr);
            break;
         case PT_DYNAMIC:
            printf("Dynamic segment: 0x%x\n", phdr[i].p_vaddr);
            break;
         case PT_PHDR:
            printf("PHDR segment: 0x%x\n", phdr[i].p_vaddr);
            break;
      }
   }

   exit(0);
}