//Use: gcc -s -lSDL -nostartfiles -nostdlib main.c

#include <dlfcn.h>
#include <syscall.h>
#include <fcntl.h>
#include <elf.h>
#include <stdio.h>
#include <SDL/SDL.h>
#include <link.h>

//****************************************************************************************
//Some string functions for debug output.
//****************************************************************************************
long syscall3(long num, long arg1, long arg2, long arg3) {
  long __res;
  __asm__ volatile ("int $0x80":"=a"(__res):"0"(num), "b"(arg1), "c"(arg2), "d"(arg3));
  return __res;
}

void printhexstring_(unsigned int num) {
  char string[9];
  int i;
  unsigned char digit;
  for(i=0; i<8; i++) {
    digit=num&0xf;
    if(digit>9) digit+=('a'-10); else digit+='0';
    string[7-i]=digit;
    num>>=4;
  }
  string[8]='\n';

  long result=syscall3(SYS_write, 0, (long)string, 9);
}

void printstring_(long string) {
  long count=0;
  char* p=(char*)string;
  while(p[count]!='\0')
    count++;

  long result=syscall3(SYS_write, 0, string, count+1);
}

void printkeyandvalue_(long string, long value) {
  printstring_((long)string);
  printhexstring_((long)value);
}
//*****************************************************************************************


const long baseAddress=0x08048000; //base address that the executable is loaded at

struct link_map* GetLinkMap() {
  Elf32_Ehdr* ehdr=(Elf32_Ehdr*)baseAddress; //the elf header
  Elf32_Phdr* phdr=(Elf32_Phdr*)((void*)((unsigned int)ehdr+(unsigned int)ehdr->e_phoff)); //the program header

  //find the dynamic section entry in the program header
  while(phdr->p_type!=PT_DYNAMIC) {
    phdr++;
  }

  //get the dynamic section's address
  Elf32_Dyn* dyn=(Elf32_Dyn*)phdr->p_vaddr;

  //find the debug entry
  while(dyn->d_tag!=DT_DEBUG) {
    dyn++;
  }

  struct r_debug* debug=(struct r_debug*)dyn->d_un.d_ptr;
  return debug->r_map;
}

void _start() {
  struct link_map* map=GetLinkMap();

  //step through the libraries
  while(map!=0) {
    printkeyandvalue_((long)map->l_name, map->l_addr); //l_addr is the value you'd get back from 'dlopen' with this name
    map=map->l_next;
  }

  asm("int\t$0x80\n\t"::"a"(SYS_exit), "b"(0));
}