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