backwards_compat.c

   1 /* Simple backwards compat code to exec old version */
   2
   3 #ifndef CONFIG_NO_BACKWARDS_COMPAT
   4
   5 #include <sys/types.h>
   6 #include <sys/stat.h>
   7 #include <unistd.h>
   8 #include <stdlib.h>
   9 #include <errno.h>
  10 #include <stdio.h>
  11 #include <string.h>
  12 #include <asm/unistd.h>
  13
  14 extern long create_module(const char *, size_t);
  15
  16 #include "testing.h"
  17
  18 static void exec_old(const char *progname, char *argv[])
  19 {
  20         char *sep;
  21         pid_t pid;
  22         char ascii_pid[32];
  23         char pathname[strlen(argv[0])+1];
  24         char oldname[strlen(progname) + strlen(argv[0]) + sizeof(".old")];
  25
  26         memset(pathname, 0, strlen(argv[0])+1);
  27         sep = strrchr(argv[0], '/');
  28         if (sep)
  29                 memcpy(pathname, argv[0], sep - argv[0]+1);
  30         sprintf(oldname, "%s%s.old", pathname, progname);
  31
  32         /* Recursion detection: we need an env var since we can't
  33            change argv[0] (as older modutils uses it to determine
  34            behavior).  We *can* recurse in the case of old-style
  35            pre-install etc. commands, so make sure pid is exactly the
  36            same. */
  37         pid = getpid();
  38         snprintf(ascii_pid, sizeof(ascii_pid), "%lu", (unsigned long)pid);
  39         if (strcmp(getenv("MODULE_RECURSE") ?: "", ascii_pid) == 0) {
  40                 fprintf(stderr, "WARNING: %s: I am not the old version!\n",
  41                         oldname);
  42                 return;
  43         }
  44         setenv("MODULE_RECURSE", ascii_pid, 1);
  45
  46         execvp(oldname, argv);
  47         fprintf(stderr,
  48                 "Kernel requires old %s, but couldn't run %s: %s\n",
  49                 progname, oldname, strerror(errno));
  50         exit(2);
  51 }
  52
  53 static void try_old_version(const char *progname, char *argv[])
  54 {
  55         errno = 0;
  56         if (create_module(NULL, 0) >= 0 /* Uh oh, what have I just done? */
  57             || errno != ENOSYS)
  58                 exec_old(progname, argv);
  59 }
  60 #else /* CONFIG_NO_BACKWARDS_COMPAT */
  61 static inline void try_old_version(const char *progname, char *argv[])
  62 {
  63 }
  64 #endif /* !CONFIG_NO_BACKWARDS_COMPAT */