boot/addaout.c

   1 /* A small utility to append an a.out header to an arbitrary file. This allows
   2  * inclusion of arbitrary data in the boot image, so that it is magically
   3  * loaded as a RAM disk. The a.out header is structured as follows:
   4  *
   5  *      a_flags:        A_IMG to indicate this is not an executable
   6  *
   7  * Created:     April 2005, Jorrit N. Herder
   8  */
   9 #include <stdlib.h>
  10 #include <stdio.h>
  11 #include <errno.h>
  12 #include <a.out.h>
  13 #include <sys/types.h>
  14 #include <fcntl.h>
  15 #include <sys/stat.h>
  16 #include <string.h>
  17 #include <unistd.h>
  18
  19 #define INPUT_FILE      1
  20 #define OUTPUT_FILE     2
  21
  22 /* Report problems. */
  23 static void report(const char *problem, const char *message)
  24 {
  25   fprintf(stderr, "%s:\n", problem);
  26   fprintf(stderr, "   %s\n\n", message);
  27 }
  28
  29
  30 static int copy_data(int srcfd, int dstfd)
  31 {
  32     char buf[8192];
  33     ssize_t n;
  34     int total=0;
  35
  36     /** FIXME: handle error from read() */
  37
  38     /* Copy the little bytes themselves. (Source from cp.c). */
  39     while ((n= read(srcfd, buf, sizeof(buf))) > 0) {
  40         char *bp = buf;
  41         ssize_t r = 0;
  42
  43         /** FIXME: handle error from write() */
  44         while (n > 0 && (r= write(dstfd, bp, n)) > 0) {
  45             bp += r;
  46             n -= r;
  47             total += r;
  48         }
  49         if (r == 0) {
  50             fprintf(stderr, "Warning: EOF writing to output file.\n");
  51             return(-1);
  52         }
  53     }
  54     return(total);
  55 }
  56
  57
  58 /* Main program. */
  59 int main(int argc, char **argv)
  60 {
  61   struct exec aout;
  62   struct stat stin;
  63   int fdin, fdout;
  64   char * bp;
  65   int n,r;
  66   int total_size;
  67
  68   /* Check if command line arguments are present, or print usage. */
  69   if (argc!=3) {
  70         printf("Invalid arguments. Usage:\n");
  71         printf("    %s <input_file> <output_file>\n",argv[0]);
  72         return(1);
  73   }
  74
  75   /* Check if we can open the input and output file. */
  76   if (stat(argv[INPUT_FILE], &stin) != 0) {
  77         report("Couldn't get status of input file", strerror(errno));
  78         return(1);
  79   }
  80   if ((fdin = open(argv[INPUT_FILE], O_RDONLY)) < 0) {
  81         report("Couldn't open input file", strerror(errno));
  82         return(1);
  83   }
  84   if ((fdout = open(argv[OUTPUT_FILE], O_WRONLY|O_CREAT|O_TRUNC,
  85                 stin.st_mode & 0777)) < 0) {
  86         report("Couldn't open output file", strerror(errno));
  87         return(1);
  88   }
  89
  90
  91   /* Copy input file to output file, but leave space for a.out header. */
  92   lseek(fdout, sizeof(aout), SEEK_SET);
  93   total_size = copy_data(fdin, fdout);
  94   if (total_size < 0) {
  95         report("Aborted", "Output file may be truncated.");
  96         return(1);
  97   } else if (total_size == 0) {
  98         report("Aborted without prepending header", "No data in input file.");
  99         return(1);
 100   }
 101
 102
 103   /* Build a.out header and write to output file. */
 104   memset(&aout, 0, sizeof(struct exec));
 105   aout.a_magic[0] = A_MAGIC0;
 106   aout.a_magic[1] = A_MAGIC1;
 107   aout.a_flags |= A_IMG;
 108   aout.a_hdrlen = sizeof(aout);
 109   aout.a_text = 0;
 110   aout.a_data = total_size;
 111   aout.a_bss = 0;
 112   aout.a_total = aout.a_hdrlen + aout.a_data;
 113
 114   bp = (char *) &aout;
 115   n = sizeof(aout);
 116   lseek(fdout, 0L, SEEK_SET);
 117   while (n > 0 && (r= write(fdout, bp, n)) > 0) {
 118         bp += r;
 119         n -= r;
 120   }
 121
 122   printf("Prepended data file (%d bytes) with a.out header (%u bytes).\n",
 123         total_size, sizeof(aout));
 124   printf("Done.\n");
 125
 126   return(0);
 127 }
 128