libvmtime.c

   1 #include <sys/time.h>
   2 #include <dlfcn.h>
   3 #include <sys/timeb.h>
   4 #include <stdlib.h>
   5 #include <stdio.h>
   6 #include <unistd.h>
   7 #include <pthread.h>
   8
   9
  10 typedef int (*gettimeofday_func_t)(struct timeval *tv, struct timezone *tz);
  11 static gettimeofday_func_t gettimeofday_orig;
  12
  13 typedef time_t (*time_func_t)(time_t *t);
  14 static time_func_t time_orig;
  15
  16 typedef int (*ftime_func_t)(struct timeb *tp);
  17 static ftime_func_t ftime_orig;
  18
  19 static time_t wayback=0;
  20
  21
  22 static int inside=0;
  23 static pthread_mutex_t inside_mutex=PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP;
  24
  25 static void enter(void)
  26 {
  27 static int done=0;
  28 void *libc_handle;
  29 char *wayback_s;
  30
  31         if (pthread_mutex_lock(&inside_mutex)) {
  32                 fprintf(stderr,"libwayback: 'inside_mutex' lock fail!\n");
  33                 _exit(1);
  34                 }
  35         if (inside<0) {
  36                 fprintf(stderr,"libwayback: 'inside' sanity fail!\n");
  37                 _exit(1);
  38                 }
  39         if (inside) {
  40                 fprintf(stderr,"libwayback: looping!\n");
  41                 _exit(1);
  42                 }
  43         inside++;
  44
  45         if (done)
  46                 return;
  47         done=1;
  48
  49         if ((wayback_s=getenv("WAYBACK")))
  50                 wayback=atol(wayback_s);
  51
  52         libc_handle=dlopen("/lib/libc.so.6",RTLD_LAZY); /* RTLD_LAZY is mandatory */
  53         gettimeofday_orig=(gettimeofday_func_t)dlsym(libc_handle,"gettimeofday");
  54         time_orig=(time_func_t)dlsym(libc_handle,"time");
  55         ftime_orig=(ftime_func_t)dlsym(libc_handle,"ftime");
  56 }
  57
  58 static void leave(void)
  59 {
  60         if (inside!=1) {
  61                 fprintf(stderr,"libwayback: 'inside' sanity fail!\n");
  62                 _exit(1);
  63                 }
  64         inside--;
  65         if (pthread_mutex_unlock(&inside_mutex)) {
  66                 fprintf(stderr,"libwayback: 'inside_mutex' unlock fail!\n");
  67                 _exit(1);
  68                 }
  69 }
  70
  71
  72 int gettimeofday(struct timeval *tv, struct timezone *tz)
  73 {
  74 int r;
  75
  76         enter();
  77
  78         r=(*gettimeofday_orig)(tv,tz);
  79         if (tv)
  80                 tv->tv_sec-=wayback;
  81
  82         leave();
  83
  84         return r;
  85 }
  86
  87
  88 time_t time(time_t *t)
  89 {
  90 time_t r;
  91
  92         enter();
  93         r=(*time_orig)(t);
  94
  95         if (t)
  96                 *t-=wayback;
  97         r-=wayback;
  98
  99         leave();
 100         return r;
 101 }
 102
 103
 104 int ftime(struct timeb *tp)
 105 {
 106 int r;
 107
 108         enter();
 109         r=(*ftime_orig)(tp);
 110
 111         if (tp)
 112                 tp->time-=wayback;
 113
 114         leave();
 115         return r;
 116 }