Added 'objdump.c' for dumping the text segment of NED a.out files as a binary blob.

[ned1] / misc / objdump.c

/*
* © 2021 Aaron Taylor <ataylor at subgeniuskitty dot com>
* See LICENSE.txt file for copyright and license details.
*/

/*
* This program dumps the text segment of a NED1 a.out format executable as a
* binary blob.
*/

#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>

#include "../common/a.out.h"

#define VERSION 1

void
print_usage(char ** argv)
{
   printf( "NED objdump v%d (www.subgeniuskitty.com)\n"
           "Usage: %s -i <file> -o <file>\n"
           "  -h                      Help (prints this message)\n"
           "  -i <file>               Specify NED a.out format input file.\n"
           "  -o <file>               Specify output filename for binary blob.\n"
           , VERSION, argv[0]
   );
}

void
die(FILE * in, FILE * out, const char * msg)
{
   fclose(in);
   fclose(out);
   fprintf(stderr, "%s\n", msg);
   exit(EXIT_FAILURE);
}

void
dump_aout_file(FILE * in_file, FILE * out_file)
{
   uint32_t read_count = 0;
   struct exec aout_exec;

   /* Read in and check the a.out header. */
   for (uint32_t i=0; i<8; i++) {
       switch (i) {
           case 0: read_count = fread(&(aout_exec.a_midmag), 4, 1, in_file); break;
           case 1: read_count = fread(&(aout_exec.a_text),   4, 1, in_file); break;
           case 2: read_count = fread(&(aout_exec.a_data),   4, 1, in_file); break;
           case 3: read_count = fread(&(aout_exec.a_bss),    4, 1, in_file); break;
           case 4: read_count = fread(&(aout_exec.a_syms),   4, 1, in_file); break;
           case 5: read_count = fread(&(aout_exec.a_entry),  4, 1, in_file); break;
           case 6: read_count = fread(&(aout_exec.a_trsize), 4, 1, in_file); break;
           case 7: read_count = fread(&(aout_exec.a_drsize), 4, 1, in_file); break;
       }
       if (read_count != 1) {
           die(in_file, out_file, "ERROR: Invalid a.out header.");
       }
   }
   if (N_BADMAG(aout_exec)) {
       die(in_file, out_file, "ERROR: Invalid magic number in a.out header.");
   } else if (N_GETMID(aout_exec) != MID_NED) {
       die(in_file, out_file, "ERROR: Executable not intended for NED Machine ID.");
   }

   /* Read in the text segment. */
   uint32_t text_segment_size = (N_DATOFF(aout_exec) - N_TXTOFF(aout_exec));
   uint8_t * text_segment = malloc(text_segment_size);
   read_count = fread(text_segment, 1, text_segment_size, in_file);
   if (read_count != text_segment_size) {
       die(in_file, out_file, "ERROR: Failed to read entire text segment.");
   }

   /* Correct the byte order. */
   for (uint32_t i=0; i < (text_segment_size / 4); i++) {
       uint8_t temp_word[4];
       for (uint8_t j=0; j<4; j++) temp_word[j] = text_segment[((i*4)+j)];
       for (uint8_t j=0; j<4; j++) text_segment[((i*4)+j)] = temp_word[(3-j)];
   }

   /* Write text segment to file. */
   uint32_t write_count = fwrite(text_segment, text_segment_size, 1, out_file);
   if (write_count != 1) {
       die(in_file, out_file, "ERROR: Unable to write to output file.");
   }

   /* Clean up and return */
   free(text_segment);
}

int
main(int argc, char ** argv)
{
   /*
    * Process command line arguments
    */
   int c;
   FILE * in_file = NULL;
   FILE * out_file = NULL;
   while ((c = getopt(argc, argv, "hi:o:")) != -1) {
       switch (c) {
           case 'i':
               if ((in_file = fopen(optarg, "r")) == NULL) {
                   fprintf(stderr, "ERROR: %s: %s\n", optarg, strerror(errno));
                   exit(EXIT_FAILURE);
               }
               break;
           case 'o':
               if ((out_file = fopen(optarg, "wx")) == NULL) {
                   fprintf(stderr, "ERROR: %s: %s\n", optarg, strerror(errno));
                   exit(EXIT_FAILURE);
               }
               break;
           case 'h':
               print_usage(argv);
               exit(EXIT_SUCCESS);
               break;
           default:
               print_usage(argv);
               exit(EXIT_FAILURE);
               break;
       }
   }
   if (in_file == NULL) {
       fprintf(stderr, "ERROR: Must specify NED1 a.out format file with -i flag.\n");
       print_usage(argv);
       exit(EXIT_FAILURE);
   }
   if (out_file == NULL) {
       fprintf(stderr, "ERROR: Must specify destination file with -o flag.\n");
       print_usage(argv);
       exit(EXIT_FAILURE);
   }

   /*
    * Perform the conversion
    */
   dump_aout_file(in_file, out_file);

   /*
    * Clean up and terminate
    */
   fclose(in_file);
   fclose(out_file);
   exit(EXIT_SUCCESS);
}