The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/kern/kern_environment.c

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    1 /*-
    2  * Copyright (c) 1998 Michael Smith
    3  * All rights reserved.
    4  *
    5  * Redistribution and use in source and binary forms, with or without
    6  * modification, are permitted provided that the following conditions
    7  * are met:
    8  * 1. Redistributions of source code must retain the above copyright
    9  *    notice, this list of conditions and the following disclaimer.
   10  * 2. Redistributions in binary form must reproduce the above copyright
   11  *    notice, this list of conditions and the following disclaimer in the
   12  *    documentation and/or other materials provided with the distribution.
   13  *
   14  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
   15  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   16  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   17  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
   18  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   19  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   20  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   21  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   22  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   23  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   24  * SUCH DAMAGE.
   25  */
   26 
   27 /*
   28  * The unified bootloader passes us a pointer to a preserved copy of
   29  * bootstrap/kernel environment variables.  We convert them to a
   30  * dynamic array of strings later when the VM subsystem is up.
   31  *
   32  * We make these available through the kenv(2) syscall for userland
   33  * and through getenv()/freeenv() setenv() unsetenv() testenv() for
   34  * the kernel.
   35  */
   36 
   37 #include <sys/cdefs.h>
   38 __FBSDID("$FreeBSD$");
   39 
   40 #include <sys/types.h>
   41 #include <sys/param.h>
   42 #include <sys/proc.h>
   43 #include <sys/queue.h>
   44 #include <sys/lock.h>
   45 #include <sys/malloc.h>
   46 #include <sys/mutex.h>
   47 #include <sys/priv.h>
   48 #include <sys/kernel.h>
   49 #include <sys/systm.h>
   50 #include <sys/sysent.h>
   51 #include <sys/sysproto.h>
   52 #include <sys/libkern.h>
   53 #include <sys/kenv.h>
   54 
   55 #include <security/mac/mac_framework.h>
   56 
   57 static MALLOC_DEFINE(M_KENV, "kenv", "kernel environment");
   58 
   59 #define KENV_SIZE       512     /* Maximum number of environment strings */
   60 
   61 /* pointer to the static environment */
   62 char            *kern_envp;
   63 static char     *kernenv_next(char *);
   64 
   65 /* dynamic environment variables */
   66 char            **kenvp;
   67 struct mtx      kenv_lock;
   68 
   69 /*
   70  * No need to protect this with a mutex since SYSINITS are single threaded.
   71  */
   72 int     dynamic_kenv = 0;
   73 
   74 #define KENV_CHECK      if (!dynamic_kenv) \
   75                             panic("%s: called before SI_SUB_KMEM", __func__)
   76 
   77 int
   78 kenv(td, uap)
   79         struct thread *td;
   80         struct kenv_args /* {
   81                 int what;
   82                 const char *name;
   83                 char *value;
   84                 int len;
   85         } */ *uap;
   86 {
   87         char *name, *value, *buffer = NULL;
   88         size_t len, done, needed, buflen;
   89         int error, i;
   90 
   91         KASSERT(dynamic_kenv, ("kenv: dynamic_kenv = 0"));
   92 
   93         error = 0;
   94         if (uap->what == KENV_DUMP) {
   95 #ifdef MAC
   96                 error = mac_kenv_check_dump(td->td_ucred);
   97                 if (error)
   98                         return (error);
   99 #endif
  100                 done = needed = 0;
  101                 buflen = uap->len;
  102                 if (buflen > KENV_SIZE * (KENV_MNAMELEN + KENV_MVALLEN + 2))
  103                         buflen = KENV_SIZE * (KENV_MNAMELEN +
  104                             KENV_MVALLEN + 2);
  105                 if (uap->len > 0 && uap->value != NULL)
  106                         buffer = malloc(buflen, M_TEMP, M_WAITOK|M_ZERO);
  107                 mtx_lock(&kenv_lock);
  108                 for (i = 0; kenvp[i] != NULL; i++) {
  109                         len = strlen(kenvp[i]) + 1;
  110                         needed += len;
  111                         len = min(len, buflen - done);
  112                         /*
  113                          * If called with a NULL or insufficiently large
  114                          * buffer, just keep computing the required size.
  115                          */
  116                         if (uap->value != NULL && buffer != NULL && len > 0) {
  117                                 bcopy(kenvp[i], buffer + done, len);
  118                                 done += len;
  119                         }
  120                 }
  121                 mtx_unlock(&kenv_lock);
  122                 if (buffer != NULL) {
  123                         error = copyout(buffer, uap->value, done);
  124                         free(buffer, M_TEMP);
  125                 }
  126                 td->td_retval[0] = ((done == needed) ? 0 : needed);
  127                 return (error);
  128         }
  129 
  130         switch (uap->what) {
  131         case KENV_SET:
  132                 error = priv_check(td, PRIV_KENV_SET);
  133                 if (error)
  134                         return (error);
  135                 break;
  136 
  137         case KENV_UNSET:
  138                 error = priv_check(td, PRIV_KENV_UNSET);
  139                 if (error)
  140                         return (error);
  141                 break;
  142         }
  143 
  144         name = malloc(KENV_MNAMELEN, M_TEMP, M_WAITOK);
  145 
  146         error = copyinstr(uap->name, name, KENV_MNAMELEN, NULL);
  147         if (error)
  148                 goto done;
  149 
  150         switch (uap->what) {
  151         case KENV_GET:
  152 #ifdef MAC
  153                 error = mac_kenv_check_get(td->td_ucred, name);
  154                 if (error)
  155                         goto done;
  156 #endif
  157                 value = getenv(name);
  158                 if (value == NULL) {
  159                         error = ENOENT;
  160                         goto done;
  161                 }
  162                 len = strlen(value) + 1;
  163                 if (len > uap->len)
  164                         len = uap->len;
  165                 error = copyout(value, uap->value, len);
  166                 freeenv(value);
  167                 if (error)
  168                         goto done;
  169                 td->td_retval[0] = len;
  170                 break;
  171         case KENV_SET:
  172                 len = uap->len;
  173                 if (len < 1) {
  174                         error = EINVAL;
  175                         goto done;
  176                 }
  177                 if (len > KENV_MVALLEN)
  178                         len = KENV_MVALLEN;
  179                 value = malloc(len, M_TEMP, M_WAITOK);
  180                 error = copyinstr(uap->value, value, len, NULL);
  181                 if (error) {
  182                         free(value, M_TEMP);
  183                         goto done;
  184                 }
  185 #ifdef MAC
  186                 error = mac_kenv_check_set(td->td_ucred, name, value);
  187                 if (error == 0)
  188 #endif
  189                         setenv(name, value);
  190                 free(value, M_TEMP);
  191                 break;
  192         case KENV_UNSET:
  193 #ifdef MAC
  194                 error = mac_kenv_check_unset(td->td_ucred, name);
  195                 if (error)
  196                         goto done;
  197 #endif
  198                 error = unsetenv(name);
  199                 if (error)
  200                         error = ENOENT;
  201                 break;
  202         default:
  203                 error = EINVAL;
  204                 break;
  205         }
  206 done:
  207         free(name, M_TEMP);
  208         return (error);
  209 }
  210 
  211 /*
  212  * Setup the dynamic kernel environment.
  213  */
  214 static void
  215 init_dynamic_kenv(void *data __unused)
  216 {
  217         char *cp;
  218         size_t len;
  219         int i;
  220 
  221         kenvp = malloc((KENV_SIZE + 1) * sizeof(char *), M_KENV,
  222                 M_WAITOK | M_ZERO);
  223         i = 0;
  224         for (cp = kern_envp; cp != NULL; cp = kernenv_next(cp)) {
  225                 len = strlen(cp) + 1;
  226                 if (len > KENV_MNAMELEN + 1 + KENV_MVALLEN + 1) {
  227                         printf("WARNING: too long kenv string, ignoring %s\n",
  228                             cp);
  229                         continue;
  230                 }
  231                 if (i < KENV_SIZE) {
  232                         kenvp[i] = malloc(len, M_KENV, M_WAITOK);
  233                         strcpy(kenvp[i++], cp);
  234                 } else
  235                         printf(
  236                             "WARNING: too many kenv strings, ignoring %s\n",
  237                             cp);
  238         }
  239         kenvp[i] = NULL;
  240 
  241         mtx_init(&kenv_lock, "kernel environment", NULL, MTX_DEF);
  242         dynamic_kenv = 1;
  243 }
  244 SYSINIT(kenv, SI_SUB_KMEM, SI_ORDER_ANY, init_dynamic_kenv, NULL);
  245 
  246 void
  247 freeenv(char *env)
  248 {
  249 
  250         if (dynamic_kenv)
  251                 free(env, M_KENV);
  252 }
  253 
  254 /*
  255  * Internal functions for string lookup.
  256  */
  257 static char *
  258 _getenv_dynamic(const char *name, int *idx)
  259 {
  260         char *cp;
  261         int len, i;
  262 
  263         mtx_assert(&kenv_lock, MA_OWNED);
  264         len = strlen(name);
  265         for (cp = kenvp[0], i = 0; cp != NULL; cp = kenvp[++i]) {
  266                 if ((strncmp(cp, name, len) == 0) &&
  267                     (cp[len] == '=')) {
  268                         if (idx != NULL)
  269                                 *idx = i;
  270                         return (cp + len + 1);
  271                 }
  272         }
  273         return (NULL);
  274 }
  275 
  276 static char *
  277 _getenv_static(const char *name)
  278 {
  279         char *cp, *ep;
  280         int len;
  281 
  282         for (cp = kern_envp; cp != NULL; cp = kernenv_next(cp)) {
  283                 for (ep = cp; (*ep != '=') && (*ep != 0); ep++)
  284                         ;
  285                 if (*ep != '=')
  286                         continue;
  287                 len = ep - cp;
  288                 ep++;
  289                 if (!strncmp(name, cp, len) && name[len] == 0)
  290                         return (ep);
  291         }
  292         return (NULL);
  293 }
  294 
  295 /*
  296  * Look up an environment variable by name.
  297  * Return a pointer to the string if found.
  298  * The pointer has to be freed with freeenv()
  299  * after use.
  300  */
  301 char *
  302 getenv(const char *name)
  303 {
  304         char buf[KENV_MNAMELEN + 1 + KENV_MVALLEN + 1];
  305         char *ret, *cp;
  306         int len;
  307 
  308         if (dynamic_kenv) {
  309                 mtx_lock(&kenv_lock);
  310                 cp = _getenv_dynamic(name, NULL);
  311                 if (cp != NULL) {
  312                         strcpy(buf, cp);
  313                         mtx_unlock(&kenv_lock);
  314                         len = strlen(buf) + 1;
  315                         ret = malloc(len, M_KENV, M_WAITOK);
  316                         strcpy(ret, buf);
  317                 } else {
  318                         mtx_unlock(&kenv_lock);
  319                         ret = NULL;
  320                 }
  321         } else
  322                 ret = _getenv_static(name);
  323         return (ret);
  324 }
  325 
  326 /*
  327  * Test if an environment variable is defined.
  328  */
  329 int
  330 testenv(const char *name)
  331 {
  332         char *cp;
  333 
  334         if (dynamic_kenv) {
  335                 mtx_lock(&kenv_lock);
  336                 cp = _getenv_dynamic(name, NULL);
  337                 mtx_unlock(&kenv_lock);
  338         } else
  339                 cp = _getenv_static(name);
  340         if (cp != NULL)
  341                 return (1);
  342         return (0);
  343 }
  344 
  345 /*
  346  * Set an environment variable by name.
  347  */
  348 int
  349 setenv(const char *name, const char *value)
  350 {
  351         char *buf, *cp, *oldenv;
  352         int namelen, vallen, i;
  353 
  354         KENV_CHECK;
  355 
  356         namelen = strlen(name) + 1;
  357         if (namelen > KENV_MNAMELEN)
  358                 return (-1);
  359         vallen = strlen(value) + 1;
  360         if (vallen > KENV_MVALLEN)
  361                 return (-1);
  362         buf = malloc(namelen + vallen, M_KENV, M_WAITOK);
  363         sprintf(buf, "%s=%s", name, value);
  364 
  365         mtx_lock(&kenv_lock);
  366         cp = _getenv_dynamic(name, &i);
  367         if (cp != NULL) {
  368                 oldenv = kenvp[i];
  369                 kenvp[i] = buf;
  370                 mtx_unlock(&kenv_lock);
  371                 free(oldenv, M_KENV);
  372         } else {
  373                 /* We add the option if it wasn't found */
  374                 for (i = 0; (cp = kenvp[i]) != NULL; i++)
  375                         ;
  376 
  377                 /* Bounds checking */
  378                 if (i < 0 || i >= KENV_SIZE) {
  379                         free(buf, M_KENV);
  380                         mtx_unlock(&kenv_lock);
  381                         return (-1);
  382                 }
  383 
  384                 kenvp[i] = buf;
  385                 kenvp[i + 1] = NULL;
  386                 mtx_unlock(&kenv_lock);
  387         }
  388         return (0);
  389 }
  390 
  391 /*
  392  * Unset an environment variable string.
  393  */
  394 int
  395 unsetenv(const char *name)
  396 {
  397         char *cp, *oldenv;
  398         int i, j;
  399 
  400         KENV_CHECK;
  401 
  402         mtx_lock(&kenv_lock);
  403         cp = _getenv_dynamic(name, &i);
  404         if (cp != NULL) {
  405                 oldenv = kenvp[i];
  406                 for (j = i + 1; kenvp[j] != NULL; j++)
  407                         kenvp[i++] = kenvp[j];
  408                 kenvp[i] = NULL;
  409                 mtx_unlock(&kenv_lock);
  410                 free(oldenv, M_KENV);
  411                 return (0);
  412         }
  413         mtx_unlock(&kenv_lock);
  414         return (-1);
  415 }
  416 
  417 /*
  418  * Return a string value from an environment variable.
  419  */
  420 int
  421 getenv_string(const char *name, char *data, int size)
  422 {
  423         char *tmp;
  424 
  425         tmp = getenv(name);
  426         if (tmp != NULL) {
  427                 strlcpy(data, tmp, size);
  428                 freeenv(tmp);
  429                 return (1);
  430         } else
  431                 return (0);
  432 }
  433 
  434 /*
  435  * Return an integer value from an environment variable.
  436  */
  437 int
  438 getenv_int(const char *name, int *data)
  439 {
  440         quad_t tmp;
  441         int rval;
  442 
  443         rval = getenv_quad(name, &tmp);
  444         if (rval)
  445                 *data = (int) tmp;
  446         return (rval);
  447 }
  448 
  449 /*
  450  * Return an unsigned integer value from an environment variable.
  451  */
  452 int
  453 getenv_uint(const char *name, unsigned int *data)
  454 {
  455         quad_t tmp;
  456         int rval;
  457 
  458         rval = getenv_quad(name, &tmp);
  459         if (rval)
  460                 *data = (unsigned int) tmp;
  461         return (rval);
  462 }
  463 
  464 /*
  465  * Return a long value from an environment variable.
  466  */
  467 int
  468 getenv_long(const char *name, long *data)
  469 {
  470         quad_t tmp;
  471         int rval;
  472 
  473         rval = getenv_quad(name, &tmp);
  474         if (rval)
  475                 *data = (long) tmp;
  476         return (rval);
  477 }
  478 
  479 /*
  480  * Return an unsigned long value from an environment variable.
  481  */
  482 int
  483 getenv_ulong(const char *name, unsigned long *data)
  484 {
  485         quad_t tmp;
  486         int rval;
  487 
  488         rval = getenv_quad(name, &tmp);
  489         if (rval)
  490                 *data = (unsigned long) tmp;
  491         return (rval);
  492 }
  493 
  494 /*
  495  * Return a quad_t value from an environment variable.
  496  */
  497 int
  498 getenv_quad(const char *name, quad_t *data)
  499 {
  500         char    *value;
  501         char    *vtp;
  502         quad_t  iv;
  503 
  504         value = getenv(name);
  505         if (value == NULL)
  506                 return (0);
  507         iv = strtoq(value, &vtp, 0);
  508         if (vtp == value || (vtp[0] != '\0' && vtp[1] != '\0')) {
  509                 freeenv(value);
  510                 return (0);
  511         }
  512         switch (vtp[0]) {
  513         case 't': case 'T':
  514                 iv *= 1024;
  515         case 'g': case 'G':
  516                 iv *= 1024;
  517         case 'm': case 'M':
  518                 iv *= 1024;
  519         case 'k': case 'K':
  520                 iv *= 1024;
  521         case '\0':
  522                 break;
  523         default:
  524                 freeenv(value);
  525                 return (0);
  526         }
  527         *data = iv;
  528         freeenv(value);
  529         return (1);
  530 }
  531 
  532 /*
  533  * Find the next entry after the one which (cp) falls within, return a
  534  * pointer to its start or NULL if there are no more.
  535  */
  536 static char *
  537 kernenv_next(char *cp)
  538 {
  539 
  540         if (cp != NULL) {
  541                 while (*cp != 0)
  542                         cp++;
  543                 cp++;
  544                 if (*cp == 0)
  545                         cp = NULL;
  546         }
  547         return (cp);
  548 }
  549 
  550 void
  551 tunable_int_init(void *data)
  552 {
  553         struct tunable_int *d = (struct tunable_int *)data;
  554 
  555         TUNABLE_INT_FETCH(d->path, d->var);
  556 }
  557 
  558 void
  559 tunable_long_init(void *data)
  560 {
  561         struct tunable_long *d = (struct tunable_long *)data;
  562 
  563         TUNABLE_LONG_FETCH(d->path, d->var);
  564 }
  565 
  566 void
  567 tunable_ulong_init(void *data)
  568 {
  569         struct tunable_ulong *d = (struct tunable_ulong *)data;
  570 
  571         TUNABLE_ULONG_FETCH(d->path, d->var);
  572 }
  573 
  574 void
  575 tunable_quad_init(void *data)
  576 {
  577         struct tunable_quad *d = (struct tunable_quad *)data;
  578 
  579         TUNABLE_QUAD_FETCH(d->path, d->var);
  580 }
  581 
  582 void
  583 tunable_str_init(void *data)
  584 {
  585         struct tunable_str *d = (struct tunable_str *)data;
  586 
  587         TUNABLE_STR_FETCH(d->path, d->var, d->size);
  588 }

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