src/time/__tz.c

   1 #include "time_impl.h"
   2 #include <stdint.h>
   3 #include <limits.h>
   4 #include <stdlib.h>
   5 #include <string.h>
   6 #include <sys/mman.h>
   7 #include <ctype.h>
   8 #include "libc.h"
   9 #include "lock.h"
  10 #include "fork_impl.h"
  11
  12 #define malloc __libc_malloc
  13 #define calloc undef
  14 #define realloc undef
  15 #define free undef
  16
  17 long  __timezone = 0;
  18 int   __daylight = 0;
  19 char *__tzname[2] = { 0, 0 };
  20
  21 weak_alias(__timezone, timezone);
  22 weak_alias(__daylight, daylight);
  23 weak_alias(__tzname, tzname);
  24
  25 static char std_name[TZNAME_MAX+1];
  26 static char dst_name[TZNAME_MAX+1];
  27 const char __utc[] = "UTC";
  28
  29 static int dst_off;
  30 static int r0[5], r1[5];
  31
  32 static const unsigned char *zi, *trans, *index, *types, *abbrevs, *abbrevs_end;
  33 static size_t map_size;
  34
  35 static char old_tz_buf[32];
  36 static char *old_tz = old_tz_buf;
  37 static size_t old_tz_size = sizeof old_tz_buf;
  38
  39 static volatile int lock[1];
  40 volatile int *const __timezone_lockptr = lock;
  41
  42 static int getint(const char **p)
  43 {
  44         unsigned x;
  45         for (x=0; **p-'0'<10U; (*p)++) x = **p-'0' + 10*x;
  46         return x;
  47 }
  48
  49 static int getoff(const char **p)
  50 {
  51         int neg = 0;
  52         if (**p == '-') {
  53                 ++*p;
  54                 neg = 1;
  55         } else if (**p == '+') {
  56                 ++*p;
  57         }
  58         int off = 3600*getint(p);
  59         if (**p == ':') {
  60                 ++*p;
  61                 off += 60*getint(p);
  62                 if (**p == ':') {
  63                         ++*p;
  64                         off += getint(p);
  65                 }
  66         }
  67         return neg ? -off : off;
  68 }
  69
  70 static void getrule(const char **p, int rule[5])
  71 {
  72         int r = rule[0] = **p;
  73
  74         if (r!='M') {
  75                 if (r=='J') ++*p;
  76                 else rule[0] = 0;
  77                 rule[1] = getint(p);
  78         } else {
  79                 ++*p; rule[1] = getint(p);
  80                 ++*p; rule[2] = getint(p);
  81                 ++*p; rule[3] = getint(p);
  82         }
  83
  84         if (**p=='/') {
  85                 ++*p;
  86                 rule[4] = getoff(p);
  87         } else {
  88                 rule[4] = 7200;
  89         }
  90 }
  91
  92 static void getname(char *d, const char **p)
  93 {
  94         int i;
  95         if (**p == '<') {
  96                 ++*p;
  97                 for (i=0; (*p)[i] && (*p)[i]!='>'; i++)
  98                         if (i<TZNAME_MAX) d[i] = (*p)[i];
  99                 if ((*p)[i]) ++*p;
 100         } else {
 101                 for (i=0; ((*p)[i]|32)-'a'<26U; i++)
 102                         if (i<TZNAME_MAX) d[i] = (*p)[i];
 103         }
 104         *p += i;
 105         d[i<TZNAME_MAX?i:TZNAME_MAX] = 0;
 106 }
 107
 108 #define VEC(...) ((const unsigned char[]){__VA_ARGS__})
 109
 110 static uint32_t zi_read32(const unsigned char *z)
 111 {
 112         return (unsigned)z[0]<<24 | z[1]<<16 | z[2]<<8 | z[3];
 113 }
 114
 115 static size_t zi_dotprod(const unsigned char *z, const unsigned char *v, size_t n)
 116 {
 117         size_t y;
 118         uint32_t x;
 119         for (y=0; n; n--, z+=4, v++) {
 120                 x = zi_read32(z);
 121                 y += x * *v;
 122         }
 123         return y;
 124 }
 125
 126 static void do_tzset()
 127 {
 128         char buf[NAME_MAX+25], *pathname=buf+24;
 129         const char *try, *s, *p;
 130         const unsigned char *map = 0;
 131         size_t i;
 132         static const char search[] =
 133                 "/usr/share/zoneinfo/\0/share/zoneinfo/\0/etc/zoneinfo/\0";
 134
 135         s = getenv("TZ");
 136         if (!s) s = "/etc/localtime";
 137         if (!*s) s = __utc;
 138
 139         if (old_tz && !strcmp(s, old_tz)) return;
 140
 141         for (i=0; i<5; i++) r0[i] = r1[i] = 0;
 142
 143         if (zi) __munmap((void *)zi, map_size);
 144
 145         /* Cache the old value of TZ to check if it has changed. Avoid
 146          * free so as not to pull it into static programs. Growth
 147          * strategy makes it so free would have minimal benefit anyway. */
 148         i = strlen(s);
 149         if (i > PATH_MAX+1) s = __utc, i = 3;
 150         if (i >= old_tz_size) {
 151                 old_tz_size *= 2;
 152                 if (i >= old_tz_size) old_tz_size = i+1;
 153                 if (old_tz_size > PATH_MAX+2) old_tz_size = PATH_MAX+2;
 154                 old_tz = malloc(old_tz_size);
 155         }
 156         if (old_tz) memcpy(old_tz, s, i+1);
 157
 158         int posix_form = 0;
 159         if (*s != ':') {
 160                 p = s;
 161                 char dummy_name[TZNAME_MAX+1];
 162                 getname(dummy_name, &p);
 163                 if (p!=s && (*p == '+' || *p == '-' || isdigit(*p)
 164                              || !strcmp(dummy_name, "UTC")
 165                              || !strcmp(dummy_name, "GMT")))
 166                         posix_form = 1;
 167         }
 168
 169         /* Non-suid can use an absolute tzfile pathname or a relative
 170          * pathame beginning with "."; in secure mode, only the
 171          * standard path will be searched. */
 172         if (!posix_form) {
 173                 if (*s == ':') s++;
 174                 if (*s == '/' || *s == '.') {
 175                         if (!libc.secure || !strcmp(s, "/etc/localtime"))
 176                                 map = __map_file(s, &map_size);
 177                 } else {
 178                         size_t l = strlen(s);
 179                         if (l <= NAME_MAX && !strchr(s, '.')) {
 180                                 memcpy(pathname, s, l+1);
 181                                 pathname[l] = 0;
 182                                 for (try=search; !map && *try; try+=l+1) {
 183                                         l = strlen(try);
 184                                         memcpy(pathname-l, try, l);
 185                                         map = __map_file(pathname-l, &map_size);
 186                                 }
 187                         }
 188                 }
 189                 if (!map) s = __utc;
 190         }
 191         if (map && (map_size < 44 || memcmp(map, "TZif", 4))) {
 192                 __munmap((void *)map, map_size);
 193                 map = 0;
 194                 s = __utc;
 195         }
 196
 197         zi = map;
 198         if (map) {
 199                 int scale = 2;
 200                 if (map[4]!='1') {
 201                         size_t skip = zi_dotprod(zi+20, VEC(1,1,8,5,6,1), 6);
 202                         trans = zi+skip+44+44;
 203                         scale++;
 204                 } else {
 205                         trans = zi+44;
 206                 }
 207                 index = trans + (zi_read32(trans-12) << scale);
 208                 types = index + zi_read32(trans-12);
 209                 abbrevs = types + 6*zi_read32(trans-8);
 210                 abbrevs_end = abbrevs + zi_read32(trans-4);
 211                 if (zi[map_size-1] == '\n') {
 212                         for (s = (const char *)zi+map_size-2; *s!='\n'; s--);
 213                         s++;
 214                 } else {
 215                         const unsigned char *p;
 216                         __tzname[0] = __tzname[1] = 0;
 217                         __daylight = __timezone = dst_off = 0;
 218                         for (p=types; p<abbrevs; p+=6) {
 219                                 if (!p[4] && !__tzname[0]) {
 220                                         __tzname[0] = (char *)abbrevs + p[5];
 221                                         __timezone = -zi_read32(p);
 222                                 }
 223                                 if (p[4] && !__tzname[1]) {
 224                                         __tzname[1] = (char *)abbrevs + p[5];
 225                                         dst_off = -zi_read32(p);
 226                                         __daylight = 1;
 227                                 }
 228                         }
 229                         if (!__tzname[0]) __tzname[0] = __tzname[1];
 230                         if (!__tzname[0]) __tzname[0] = (char *)__utc;
 231                         if (!__daylight) {
 232                                 __tzname[1] = __tzname[0];
 233                                 dst_off = __timezone;
 234                         }
 235                         return;
 236                 }
 237         }
 238
 239         if (!s) s = __utc;
 240         getname(std_name, &s);
 241         __tzname[0] = std_name;
 242         __timezone = getoff(&s);
 243         getname(dst_name, &s);
 244         __tzname[1] = dst_name;
 245         if (dst_name[0]) {
 246                 __daylight = 1;
 247                 if (*s == '+' || *s=='-' || *s-'0'<10U)
 248                         dst_off = getoff(&s);
 249                 else
 250                         dst_off = __timezone - 3600;
 251         } else {
 252                 __daylight = 0;
 253                 dst_off = __timezone;
 254         }
 255
 256         if (*s == ',') s++, getrule(&s, r0);
 257         if (*s == ',') s++, getrule(&s, r1);
 258 }
 259
 260 /* Search zoneinfo rules to find the one that applies to the given time,
 261  * and determine alternate opposite-DST-status rule that may be needed. */
 262
 263 static size_t scan_trans(long long t, int local, size_t *alt)
 264 {
 265         int scale = 3 - (trans == zi+44);
 266         uint64_t x;
 267         int off = 0;
 268
 269         size_t a = 0, n = (index-trans)>>scale, m;
 270
 271         if (!n) {
 272                 if (alt) *alt = 0;
 273                 return 0;
 274         }
 275
 276         /* Binary search for 'most-recent rule before t'. */
 277         while (n > 1) {
 278                 m = a + n/2;
 279                 x = zi_read32(trans + (m<<scale));
 280                 if (scale == 3) x = x<<32 | zi_read32(trans + (m<<scale) + 4);
 281                 else x = (int32_t)x;
 282                 if (local) off = (int32_t)zi_read32(types + 6 * index[m-1]);
 283                 if (t - off < (int64_t)x) {
 284                         n /= 2;
 285                 } else {
 286                         a = m;
 287                         n -= n/2;
 288                 }
 289         }
 290
 291         /* First and last entry are special. First means to use lowest-index
 292          * non-DST type. Last means to apply POSIX-style rule if available. */
 293         n = (index-trans)>>scale;
 294         if (a == n-1) return -1;
 295         if (a == 0) {
 296                 x = zi_read32(trans + (a<<scale));
 297                 if (scale == 3) x = x<<32 | zi_read32(trans + (a<<scale) + 4);
 298                 else x = (int32_t)x;
 299                 if (local) off = (int32_t)zi_read32(types + 6 * index[a-1]);
 300                 if (t - off < (int64_t)x) {
 301                         for (a=0; a<(abbrevs-types)/6; a++) {
 302                                 if (types[6*a+4] != types[4]) break;
 303                         }
 304                         if (a == (abbrevs-types)/6) a = 0;
 305                         if (types[6*a+4]) {
 306                                 *alt = a;
 307                                 return 0;
 308                         } else {
 309                                 *alt = 0;
 310                                 return a;
 311                         }
 312                 }
 313         }
 314
 315         /* Try to find a neighboring opposite-DST-status rule. */
 316         if (alt) {
 317                 if (a && types[6*index[a-1]+4] != types[6*index[a]+4])
 318                         *alt = index[a-1];
 319                 else if (a+1<n && types[6*index[a+1]+4] != types[6*index[a]+4])
 320                         *alt = index[a+1];
 321                 else
 322                         *alt = index[a];
 323         }
 324
 325         return index[a];
 326 }
 327
 328 static int days_in_month(int m, int is_leap)
 329 {
 330         if (m==2) return 28+is_leap;
 331         else return 30+((0xad5>>(m-1))&1);
 332 }
 333
 334 /* Convert a POSIX DST rule plus year to seconds since epoch. */
 335
 336 static long long rule_to_secs(const int *rule, int year)
 337 {
 338         int is_leap;
 339         long long t = __year_to_secs(year, &is_leap);
 340         int x, m, n, d;
 341         if (rule[0]!='M') {
 342                 x = rule[1];
 343                 if (rule[0]=='J' && (x < 60 || !is_leap)) x--;
 344                 t += 86400 * x;
 345         } else {
 346                 m = rule[1];
 347                 n = rule[2];
 348                 d = rule[3];
 349                 t += __month_to_secs(m-1, is_leap);
 350                 int wday = (int)((t + 4*86400) % (7*86400)) / 86400;
 351                 int days = d - wday;
 352                 if (days < 0) days += 7;
 353                 if (n == 5 && days+28 >= days_in_month(m, is_leap)) n = 4;
 354                 t += 86400 * (days + 7*(n-1));
 355         }
 356         t += rule[4];
 357         return t;
 358 }
 359
 360 /* Determine the time zone in effect for a given time in seconds since the
 361  * epoch. It can be given in local or universal time. The results will
 362  * indicate whether DST is in effect at the queried time, and will give both
 363  * the GMT offset for the active zone/DST rule and the opposite DST. This
 364  * enables a caller to efficiently adjust for the case where an explicit
 365  * DST specification mismatches what would be in effect at the time. */
 366
 367 void __secs_to_zone(long long t, int local, int *isdst, long *offset, long *oppoff, const char **zonename)
 368 {
 369         LOCK(lock);
 370
 371         do_tzset();
 372
 373         if (zi) {
 374                 size_t alt, i = scan_trans(t, local, &alt);
 375                 if (i != -1) {
 376                         *isdst = types[6*i+4];
 377                         *offset = (int32_t)zi_read32(types+6*i);
 378                         *zonename = (const char *)abbrevs + types[6*i+5];
 379                         if (oppoff) *oppoff = (int32_t)zi_read32(types+6*alt);
 380                         UNLOCK(lock);
 381                         return;
 382                 }
 383         }
 384
 385         if (!__daylight) goto std;
 386
 387         /* FIXME: may be broken if DST changes right at year boundary?
 388          * Also, this could be more efficient.*/
 389         long long y = t / 31556952 + 70;
 390         while (__year_to_secs(y, 0) > t) y--;
 391         while (__year_to_secs(y+1, 0) < t) y++;
 392
 393         long long t0 = rule_to_secs(r0, y);
 394         long long t1 = rule_to_secs(r1, y);
 395
 396         if (!local) {
 397                 t0 += __timezone;
 398                 t1 += dst_off;
 399         }
 400         if (t0 < t1) {
 401                 if (t >= t0 && t < t1) goto dst;
 402                 goto std;
 403         } else {
 404                 if (t >= t1 && t < t0) goto std;
 405                 goto dst;
 406         }
 407 std:
 408         *isdst = 0;
 409         *offset = -__timezone;
 410         if (oppoff) *oppoff = -dst_off;
 411         *zonename = __tzname[0];
 412         UNLOCK(lock);
 413         return;
 414 dst:
 415         *isdst = 1;
 416         *offset = -dst_off;
 417         if (oppoff) *oppoff = -__timezone;
 418         *zonename = __tzname[1];
 419         UNLOCK(lock);
 420 }
 421
 422 static void __tzset()
 423 {
 424         LOCK(lock);
 425         do_tzset();
 426         UNLOCK(lock);
 427 }
 428
 429 weak_alias(__tzset, tzset);
 430
 431 const char *__tm_to_tzname(const struct tm *tm)
 432 {
 433         const void *p = tm->__tm_zone;
 434         LOCK(lock);
 435         do_tzset();
 436         if (p != __utc && p != __tzname[0] && p != __tzname[1] &&
 437             (!zi || (uintptr_t)p-(uintptr_t)abbrevs >= abbrevs_end - abbrevs))
 438                 p = "";
 439         UNLOCK(lock);
 440         return p;
 441 }