---

out.c

Go to the documentation of this file.

/*
 Copyright (c) 1992-1993 The Regents of the University of California.
 All rights reserved.  See copyright.h for copyright notice and limitation 
 of liability and disclaimer of warranty provisions.
 */

#define MAIN
#include "copyright.h"
#undef MAIN

/*
 * OUT.C
 * Looking at a.out formats.
 *
 * First task:
 * Look at mips COFF stuff:
 * Print out the contents of a file and do the following:
 *    For data, print the value and give relocation information
 *    For code, disassemble and give relocation information
 */

#include <filehdr.h>
#include <aouthdr.h>
#include <scnhdr.h>
#include <reloc.h>
#include <syms.h>
#include <stdio.h>

#define read_struct(f,s) (fread(&s,sizeof(s),1,f)==1)

#define MAXRELOCS 1000


#define MAXDATA 10000

struct data {
  long data[MAXDATA];
  struct reloc reloc[MAXRELOCS];
  int length;
  int relocs;
};

#define MAXSCNS 10
#define MAXSYMS 300
#define MAXSSPACE 20000

struct filehdr filehdr;
struct aouthdr aouthdr;
struct scnhdr scnhdr[MAXSCNS];
struct data section[MAXSCNS];
HDRR symhdr;
EXTR symbols[MAXSYMS];
char sspace[20000];

char *symbol_type[] = {
  "Nil", "Global", "Static", "Param", "Local", "Label", "Proc", "Block",
  "End", "Member", "Type", "File", "Register", "Forward", "StaticProc",
  "Constant" };

char *storage_class[] = {
  "Nil", "Text", "Data", "Bss", "Register", "Abs", "Undefined", "CdbLocal",
  "Bits", "CdbSystem", "RegImage", "Info", "UserStruct", "SData", "SBss",
  "RData", "Var", "Common", "SCommon", "VarRegister", "Variant", "SUndefined",
  "Init" };
          
main(argc,argv)
int argc;
char *argv[];
{
  char *filename = "a.out";
  FILE *f;
  int i;
  long l;
/*   EXTR filesym; */
  char buf[100];

  if (argc == 2) filename = argv[1];
  if ((f = fopen(filename,"r")) == NULL) {
    printf("out: could not open %s\n",filename);
    perror("out");
    exit(1);
  }
  if (!read_struct(f,filehdr) ||
      !read_struct(f,aouthdr) ||
      filehdr.f_magic != MIPSELMAGIC) {
    printf("out: %s is not a MIPS Little-Endian COFF object file\n",filename);
    exit(1);
  }
  if (filehdr.f_nscns > MAXSCNS) {
    printf("out: Too many COFF sections.\n");
    exit(1);
  }
  for (i=0; i < filehdr.f_nscns; ++i) {
    read_struct(f,scnhdr[i]);
    if (scnhdr[i].s_size > MAXDATA*sizeof(long) &&
        scnhdr[i].s_scnptr != 0 ||
        scnhdr[i].s_nreloc > MAXRELOCS) {
      printf("section %s is too big.\n",scnhdr[i].s_name);
      exit(1);
    }
  }
  for (i=0; i < filehdr.f_nscns; ++i) {
    if (scnhdr[i].s_scnptr != 0) {
      section[i].length = scnhdr[i].s_size/4;
      fseek(f,scnhdr[i].s_scnptr,0);
      fread(section[i].data,sizeof(long),section[i].length,f);
      section[i].relocs = scnhdr[i].s_nreloc;
      fseek(f,scnhdr[i].s_relptr,0);
      fread(section[i].reloc,sizeof(struct reloc),section[i].relocs,f);
    } else {
      section[i].length = 0;
    }
  }
  fseek(f,filehdr.f_symptr,0);
  read_struct(f,symhdr);
  if (symhdr.iextMax > MAXSYMS) {
    printf("too many symbols to store.\n");
  }
  fseek(f,symhdr.cbExtOffset,0);
  for (i=0; i < MAXSYMS && i<symhdr.iextMax; ++i) {
    read_struct(f,symbols[i]);
  }
  if (symhdr.issExtMax > MAXSSPACE) {
    printf("too large a string space.\n");
    exit(1);
  }
  fseek(f,symhdr.cbSsExtOffset,0);
  fread(sspace,1,symhdr.issExtMax,f);

  for (i=0; i<filehdr.f_nscns; ++i) {
    print_section(i);
  }

  printf("External Symbols:\nValue\t Type\t\tStorage Class\tName\n");
  for (i=0; i < MAXSYMS && i < symhdr.iextMax; ++i) {
    SYMR *sym = &symbols[i].asym;
    if (sym->sc == scUndefined) myprintf("\t ");
    else myprintf("%08x ",sym->value);
    myprintf("%s",symbol_type[sym->st]);
    mytab(25);
    myprintf("%s",storage_class[sym->sc]);
    mytab(41);
    myprintf("%s\n",&sspace[sym->iss]);
  }
  return 0;
}

static column = 1;
static FILE *outfile = stdout;

#include <varargs.h>
/*VARARGS0*/
myprintf(va_alist)
va_dcl
{
  va_list ap;
  char *form;
  char buf[100];

  va_start(ap);
  form = va_arg(ap,char *);
  vsprintf(buf,form,ap);
  va_end(ap);

  fputs(buf,outfile);

  for (form = buf; *form != '\0'; ++form) {
    if (*form == '\n') column = 1;
    else if (*form == '\t') column = ((column + 7)&~7)+1;
    else column += 1;
  }
}

mytab(n)
int n;
{
  while (column < n) {
    fputc(' ',outfile);
    ++column;
  }
  return column == n;
}  

mysetfile(f)
FILE *f;
{
  outfile = f;
}

#define printf myprintf
#include "d.c"

print_section(i)
int i;
{
  int j,k;
  int is_text;
  long pc;
  long word;
  char *s;

  printf("Section: %s\t%d/%d\n",scnhdr[i].s_name,
         scnhdr[i].s_size,section[i].relocs);
  is_text =  (strncmp(scnhdr[i].s_name,".text",5) == 0);

  for (j=0; j < section[i].length; ++j) {
    pc = scnhdr[i].s_vaddr+j*4;
    word = section[i].data[j];
    if (is_text) {
      dump_ascii(word,pc);
    } else {
      printf("%08x: %08x  ", pc,word);
      s = (char *)&word;
      for (k=0;k<4;++k) {
        if (s[k] >= ' ' && s[k] < 127) printf("%c",s[k]);
        else printf(".");
      }
      printf("\t%d",word);
    }
    print_reloc(pc,i,j);
  }
}

char *section_name[] = {
  "(null)", ".text", ".rdata", ".data", ".sdata", ".sbss", ".bss",
  ".init", ".lit8", ".lit4"
};

char *reloc_type[] = {
  "abs", "16", "32", "26", "hi16", "lo16", "gpdata", "gplit"
};

print_reloc(vaddr,i,j)
int i,j;
{
  int k;
  struct reloc *rp;
  for (k=0; k < section[i].relocs; ++k) {
    rp = &section[i].reloc[k];
    if (vaddr == rp->r_vaddr) {
      mytab(57);
      if (rp->r_extern) {
        if (rp->r_symndx >= MAXSYMS) {
          printf("sym $%d",rp->r_symndx);
        } else {
          printf("\"%s\"",&sspace[symbols[rp->r_symndx].asym.iss]);
        }
      } else {
        printf("%s",section_name[rp->r_symndx]);
      }
      printf(" %s",reloc_type[rp->r_type]);
      break;
    }
  }
  printf("\n");
}

---

The University of Southern California does not screen or control the content on this website and thus does not guarantee the accuracy, integrity, or quality of such content. All content on this website is provided by and is the sole responsibility of the person from which such content originated, and such content does not necessarily reflect the opinions of the University administration or the Board of Trustees