addaout.c

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    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 void report(char *problem, char *message) 
   24 {
   25   fprintf(stderr, "%s:\n", problem);
   26   fprintf(stderr, "   %s\n\n", message);
   27 }
   28 
   29 
   30 int copy_data(int srcfd, int dstfd) 
   31 {
   32     char buf[8192];
   33     ssize_t n;
   34     int total=0;
   35 
   36     /* Copy the little bytes themselves. (Source from cp.c). */
   37     while ((n= read(srcfd, buf, sizeof(buf))) > 0) {
   38         char *bp = buf;
   39         ssize_t r;
   40 
   41         while (n > 0 && (r= write(dstfd, bp, n)) > 0) {
   42             bp += r;
   43             n -= r;
   44             total += r;
   45         }
   46         if (r <= 0) {
   47             if (r == 0) {
   48                 fprintf(stderr, "Warning: EOF writing to output file.\n");
   49                 return(-1);
   50             }
   51         }
   52     }
   53     return(total);
   54 }
   55 
   56 
   57 /* Main program. */
   58 int main(int argc, char **argv)
   59 {
   60   struct exec aout;
   61   struct stat stin;
   62   int fdin, fdout;
   63   char * bp;
   64   int n,r;
   65   int total_size=0;
   66   int result;
   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, 0, 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 (%u bytes) with a.out header (%u bytes).\n", 
  123         total_size, sizeof(aout));
  124   printf("Done.\n");
  125 
  126   return(0);
  127 }
  128

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FreeBSD/Linux Kernel Cross Reference sys/boot/addaout.c

FreeBSD/Linux Kernel Cross Reference
sys/boot/addaout.c