128 lines
2.9 KiB
C
128 lines
2.9 KiB
C
/* A small utility to append an a.out header to an arbitrary file. This allows
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* inclusion of arbitrary data in the boot image, so that it is magically
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* loaded as a RAM disk. The a.out header is structured as follows:
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*
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* a_flags: A_IMG to indicate this is not an executable
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*
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* Created: April 2005, Jorrit N. Herder
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*/
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#include <stdlib.h>
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#include <stdio.h>
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#include <errno.h>
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#include <a.out.h>
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#include <sys/types.h>
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#include <fcntl.h>
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#include <sys/stat.h>
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#include <string.h>
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#include <unistd.h>
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#define INPUT_FILE 1
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#define OUTPUT_FILE 2
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/* Report problems. */
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void report(char *problem, char *message)
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{
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fprintf(stderr, "%s:\n", problem);
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fprintf(stderr, " %s\n\n", message);
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}
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int copy_data(int srcfd, int dstfd)
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{
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char buf[8192];
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ssize_t n;
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int total=0;
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/* Copy the little bytes themselves. (Source from cp.c). */
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while ((n= read(srcfd, buf, sizeof(buf))) > 0) {
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char *bp = buf;
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ssize_t r;
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while (n > 0 && (r= write(dstfd, bp, n)) > 0) {
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bp += r;
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n -= r;
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total += r;
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}
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if (r <= 0) {
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if (r == 0) {
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fprintf(stderr, "Warning: EOF writing to output file.\n");
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return(-1);
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}
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}
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}
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return(total);
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}
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/* Main program. */
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int main(int argc, char **argv)
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{
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struct exec aout;
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struct stat stin;
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int fdin, fdout;
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char * bp;
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int n,r;
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int total_size=0;
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int result;
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/* Check if command line arguments are present, or print usage. */
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if (argc!=3) {
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printf("Invalid arguments. Usage:\n");
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printf(" %s <input_file> <output_file>\n",argv[0]);
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return(1);
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}
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/* Check if we can open the input and output file. */
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if (stat(argv[INPUT_FILE], &stin) != 0) {
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report("Couldn't get status of input file", strerror(errno));
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return(1);
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}
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if ((fdin = open(argv[INPUT_FILE], O_RDONLY)) < 0) {
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report("Couldn't open input file", strerror(errno));
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return(1);
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}
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if ((fdout = open(argv[OUTPUT_FILE], O_WRONLY|O_CREAT|O_TRUNC,
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stin.st_mode & 0777)) < 0) {
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report("Couldn't open output file", strerror(errno));
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return(1);
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}
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/* Copy input file to output file, but leave space for a.out header. */
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lseek(fdout, sizeof(aout), SEEK_SET);
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total_size = copy_data(fdin, fdout);
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if (total_size < 0) {
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report("Aborted", "Output file may be truncated.");
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return(1);
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} else if (total_size == 0) {
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report("Aborted without prepending header", "No data in input file.");
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return(1);
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}
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/* Build a.out header and write to output file. */
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memset(&aout, 0, sizeof(struct exec));
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aout.a_magic[0] = A_MAGIC0;
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aout.a_magic[1] = A_MAGIC1;
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aout.a_flags |= A_IMG;
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aout.a_hdrlen = sizeof(aout);
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aout.a_text = 0;
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aout.a_data = total_size;
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aout.a_bss = 0;
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aout.a_total = aout.a_hdrlen + aout.a_data;
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bp = (char *) &aout;
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n = sizeof(aout);
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lseek(fdout, 0, SEEK_SET);
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while (n > 0 && (r= write(fdout, bp, n)) > 0) {
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bp += r;
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n -= r;
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}
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printf("Prepended data file (%u bytes) with a.out header.\n", total_size);
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printf("Done.\n");
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return(0);
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}
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