Implement "insmod -".

Also use finit_module if available. Given that "insmod -" requires
init_module, maybe this isn't a worthwhile optimization. Given that
"insmod /actual/file.ko" is the common use case, maybe it is.

Fix a bug in readfileat where *plen would be corrupted if you didn't supply
your own buffer (because ibuf is 0 in that case, not a pointer to the start
of the allocated space).

lib/lib.c

@@ -475,12 +475,12 @@ char *readfileat(int dirfd, char *name, char *ibuf, off_t *plen)
  rbuf = buf+rlen;
  len -= rlen;
  }
- *plen = len = rlen+(buf-ibuf);
+ *plen = len = rlen+(rbuf-buf);
  close(fd);
 
  if (rlen<0) {
  if (ibuf != buf) free(buf);
- buf =  0;
+ buf = 0;
  } else buf[len] = 0;
 
  return buf;

toys/other/insmod.c

@@ -16,31 +16,35 @@ config INSMOD
 #include "toys.h"
 
 #include <sys/syscall.h>
-#define init_module(mod, len, opts) syscall(__NR_init_module, mod, len, opts)
+#define finit_module(fd, opts, flags) syscall(SYS_finit_module, fd, opts, flags)
+#define init_module(mod, len, opts) syscall(SYS_init_module, mod, len, opts)
 
 void insmod_main(void)
 {
- char * buf = NULL;
- int len, res, i;
- int fd = xopen(*toys.optargs, O_RDONLY);
-
- len = fdlength(fd);
- buf = xmalloc(len);
- xreadall(fd, buf, len);
+ int fd = !strcmp(*toys.optargs, "-") ? 0 : xopen(*toys.optargs, O_RDONLY);
+ int i, rc;
 
  i = 1;
- while(toys.optargs[i] &&
+ while (toys.optargs[i] &&
  strlen(toybuf) + strlen(toys.optargs[i]) + 2 < sizeof(toybuf))
  {
  strcat(toybuf, toys.optargs[i++]);
  strcat(toybuf, " ");
  }
 
- res = init_module(buf, len, toybuf);
- if (CFG_TOYBOX_FREE) {
- if (buf != toybuf) free(buf);
- close(fd);
+ // finit_module was new in Linux 3.8, and doesn't work on stdin,
+ // so we fall back to init_module if necessary.
+ rc = finit_module(fd, toybuf, 0);
+ if (rc && (fd == 0 || errno == ENOSYS)) {
+ off_t len = 0;
+ char *path = !strcmp(*toys.optargs, "-") ? "/dev/stdin" : *toys.optargs;
+ char *buf = readfileat(AT_FDCWD, path, NULL, &len);
+
+ rc = init_module(buf, len, toybuf);
+ if (CFG_TOYBOX_FREE) free(buf);
  }
 
- if (res) perror_exit("failed to load %s", toys.optargs[0]);
+ if (rc) perror_exit("failed to load %s", toys.optargs[0]);
+
+ if (CFG_TOYBOX_FREE) close(fd);
 }