minix/boot/addaout.c

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C
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2005-04-21 16:53:53 +02:00
/* A small utility to append an a.out header to an arbitrary file. This allows
* inclusion of arbitrary data in the boot image, so that it is magically
* loaded as a RAM disk. The a.out header is structured as follows:
*
* a_flags: A_IMG to indicate this is not an executable
*
* Created: April 2005, Jorrit N. Herder
*/
#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <a.out.h>
#include <sys/types.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <string.h>
#include <unistd.h>
#define INPUT_FILE 1
#define OUTPUT_FILE 2
/* Report problems. */
void report(char *problem, char *message)
{
fprintf(stderr, "%s:\n", problem);
fprintf(stderr, " %s\n\n", message);
}
int copy_data(int srcfd, int dstfd)
{
char buf[8192];
ssize_t n;
int total=0;
/* Copy the little bytes themselves. (Source from cp.c). */
while ((n= read(srcfd, buf, sizeof(buf))) > 0) {
char *bp = buf;
ssize_t r;
while (n > 0 && (r= write(dstfd, bp, n)) > 0) {
bp += r;
n -= r;
total += r;
}
if (r <= 0) {
if (r == 0) {
fprintf(stderr, "Warning: EOF writing to output file.\n");
return(-1);
}
}
}
return(total);
}
/* Main program. */
int main(int argc, char **argv)
{
struct exec aout;
struct stat stin;
int fdin, fdout;
char * bp;
int n,r;
int total_size=0;
int result;
/* Check if command line arguments are present, or print usage. */
if (argc!=3) {
printf("Invalid arguments. Usage:\n");
printf(" %s <input_file> <output_file>\n",argv[0]);
return(1);
}
/* Check if we can open the input and output file. */
if (stat(argv[INPUT_FILE], &stin) != 0) {
report("Couldn't get status of input file", strerror(errno));
return(1);
}
if ((fdin = open(argv[INPUT_FILE], O_RDONLY)) < 0) {
report("Couldn't open input file", strerror(errno));
return(1);
}
if ((fdout = open(argv[OUTPUT_FILE], O_WRONLY|O_CREAT|O_TRUNC,
stin.st_mode & 0777)) < 0) {
report("Couldn't open output file", strerror(errno));
return(1);
}
/* Copy input file to output file, but leave space for a.out header. */
lseek(fdout, sizeof(aout), SEEK_SET);
total_size = copy_data(fdin, fdout);
if (total_size < 0) {
report("Aborted", "Output file may be truncated.");
return(1);
} else if (total_size == 0) {
report("Aborted without prepending header", "No data in input file.");
return(1);
}
/* Build a.out header and write to output file. */
memset(&aout, 0, sizeof(struct exec));
aout.a_magic[0] = A_MAGIC0;
aout.a_magic[1] = A_MAGIC1;
aout.a_flags |= A_IMG;
aout.a_hdrlen = sizeof(aout);
aout.a_text = 0;
aout.a_data = total_size;
aout.a_bss = 0;
aout.a_total = aout.a_hdrlen + aout.a_data;
bp = (char *) &aout;
n = sizeof(aout);
lseek(fdout, 0, SEEK_SET);
while (n > 0 && (r= write(fdout, bp, n)) > 0) {
bp += r;
n -= r;
}
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printf("Prepended data file (%u bytes) with a.out header (%u bytes).\n",
total_size, sizeof(aout));
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printf("Done.\n");
return(0);
}