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: releng/7.3/sys/kern/kern_environment.c 192491 2009-05-20 22:28:39Z kmacy $");
   39 
   40 #include "opt_mac.h"
   41 
   42 #include <sys/types.h>
   43 #include <sys/param.h>
   44 #include <sys/proc.h>
   45 #include <sys/queue.h>
   46 #include <sys/lock.h>
   47 #include <sys/malloc.h>
   48 #include <sys/mutex.h>
   49 #include <sys/priv.h>
   50 #include <sys/kernel.h>
   51 #include <sys/systm.h>
   52 #include <sys/sysent.h>
   53 #include <sys/sysproto.h>
   54 #include <sys/libkern.h>
   55 #include <sys/kenv.h>
   56 
   57 #include <security/mac/mac_framework.h>
   58 
   59 static MALLOC_DEFINE(M_KENV, "kenv", "kernel environment");
   60 
   61 #define KENV_SIZE       512     /* Maximum number of environment strings */
   62 
   63 /* pointer to the static environment */
   64 char            *kern_envp;
   65 static char     *kernenv_next(char *);
   66 
   67 /* dynamic environment variables */
   68 char            **kenvp;
   69 struct mtx      kenv_lock;
   70 
   71 /*
   72  * No need to protect this with a mutex since SYSINITS are single threaded.
   73  */
   74 int     dynamic_kenv = 0;
   75 
   76 #define KENV_CHECK      if (!dynamic_kenv) \
   77                             panic("%s: called before SI_SUB_KMEM", __func__)
   78 
   79 int
   80 kenv(td, uap)
   81         struct thread *td;
   82         struct kenv_args /* {
   83                 int what;
   84                 const char *name;
   85                 char *value;
   86                 int len;
   87         } */ *uap;
   88 {
   89         char *name, *value, *buffer = NULL;
   90         size_t len, done, needed, buflen;
   91         int error, i;
   92 
   93         KASSERT(dynamic_kenv, ("kenv: dynamic_kenv = 0"));
   94 
   95         error = 0;
   96         if (uap->what == KENV_DUMP) {
   97 #ifdef MAC
   98                 error = mac_check_kenv_dump(td->td_ucred);
   99                 if (error)
  100                         return (error);
  101 #endif
  102                 done = needed = 0;
  103                 buflen = uap->len;
  104                 if (buflen > KENV_SIZE * (KENV_MNAMELEN + KENV_MVALLEN + 2))
  105                         buflen = KENV_SIZE * (KENV_MNAMELEN +
  106                             KENV_MVALLEN + 2);
  107                 if (uap->len > 0 && uap->value != NULL)
  108                         buffer = malloc(buflen, M_TEMP, M_WAITOK|M_ZERO);
  109                 mtx_lock(&kenv_lock);
  110                 for (i = 0; kenvp[i] != NULL; i++) {
  111                         len = strlen(kenvp[i]) + 1;
  112                         needed += len;
  113                         len = min(len, buflen - done);
  114                         /*
  115                          * If called with a NULL or insufficiently large
  116                          * buffer, just keep computing the required size.
  117                          */
  118                         if (uap->value != NULL && buffer != NULL && len > 0) {
  119                                 bcopy(kenvp[i], buffer + done, len);
  120                                 done += len;
  121                         }
  122                 }
  123                 mtx_unlock(&kenv_lock);
  124                 if (buffer != NULL) {
  125                         error = copyout(buffer, uap->value, done);
  126                         free(buffer, M_TEMP);
  127                 }
  128                 td->td_retval[0] = ((done == needed) ? 0 : needed);
  129                 return (error);
  130         }
  131 
  132         switch (uap->what) {
  133         case KENV_SET:
  134                 error = priv_check(td, PRIV_KENV_SET);
  135                 if (error)
  136                         return (error);
  137                 break;
  138 
  139         case KENV_UNSET:
  140                 error = priv_check(td, PRIV_KENV_UNSET);
  141                 if (error)
  142                         return (error);
  143                 break;
  144         }
  145 
  146         name = malloc(KENV_MNAMELEN, M_TEMP, M_WAITOK);
  147 
  148         error = copyinstr(uap->name, name, KENV_MNAMELEN, NULL);
  149         if (error)
  150                 goto done;
  151 
  152         switch (uap->what) {
  153         case KENV_GET:
  154 #ifdef MAC
  155                 error = mac_check_kenv_get(td->td_ucred, name);
  156                 if (error)
  157                         goto done;
  158 #endif
  159                 value = getenv(name);
  160                 if (value == NULL) {
  161                         error = ENOENT;
  162                         goto done;
  163                 }
  164                 len = strlen(value) + 1;
  165                 if (len > uap->len)
  166                         len = uap->len;
  167                 error = copyout(value, uap->value, len);
  168                 freeenv(value);
  169                 if (error)
  170                         goto done;
  171                 td->td_retval[0] = len;
  172                 break;
  173         case KENV_SET:
  174                 len = uap->len;
  175                 if (len < 1) {
  176                         error = EINVAL;
  177                         goto done;
  178                 }
  179                 if (len > KENV_MVALLEN)
  180                         len = KENV_MVALLEN;
  181                 value = malloc(len, M_TEMP, M_WAITOK);
  182                 error = copyinstr(uap->value, value, len, NULL);
  183                 if (error) {
  184                         free(value, M_TEMP);
  185                         goto done;
  186                 }
  187 #ifdef MAC
  188                 error = mac_check_kenv_set(td->td_ucred, name, value);
  189                 if (error == 0)
  190 #endif
  191                         setenv(name, value);
  192                 free(value, M_TEMP);
  193                 break;
  194         case KENV_UNSET:
  195 #ifdef MAC
  196                 error = mac_check_kenv_unset(td->td_ucred, name);
  197                 if (error)
  198                         goto done;
  199 #endif
  200                 error = unsetenv(name);
  201                 if (error)
  202                         error = ENOENT;
  203                 break;
  204         default:
  205                 error = EINVAL;
  206                 break;
  207         }
  208 done:
  209         free(name, M_TEMP);
  210         return (error);
  211 }
  212 
  213 /*
  214  * Setup the dynamic kernel environment.
  215  */
  216 static void
  217 init_dynamic_kenv(void *data __unused)
  218 {
  219         char *cp;
  220         int len, i;
  221 
  222         kenvp = malloc((KENV_SIZE + 1) * sizeof(char *), M_KENV,
  223                 M_WAITOK | M_ZERO);
  224         i = 0;
  225         for (cp = kern_envp; cp != NULL; cp = kernenv_next(cp)) {
  226                 len = strlen(cp) + 1;
  227                 if (i < KENV_SIZE) {
  228                         kenvp[i] = malloc(len, M_KENV, M_WAITOK);
  229                         strcpy(kenvp[i++], cp);
  230                 } else
  231                         printf(
  232                             "WARNING: too many kenv strings, ignoring %s\n",
  233                             cp);
  234         }
  235         kenvp[i] = NULL;
  236 
  237         mtx_init(&kenv_lock, "kernel environment", NULL, MTX_DEF);
  238         dynamic_kenv = 1;
  239 }
  240 SYSINIT(kenv, SI_SUB_KMEM, SI_ORDER_ANY, init_dynamic_kenv, NULL);
  241 
  242 void
  243 freeenv(char *env)
  244 {
  245 
  246         if (dynamic_kenv)
  247                 free(env, M_KENV);
  248 }
  249 
  250 /*
  251  * Internal functions for string lookup.
  252  */
  253 static char *
  254 _getenv_dynamic(const char *name, int *idx)
  255 {
  256         char *cp;
  257         int len, i;
  258 
  259         mtx_assert(&kenv_lock, MA_OWNED);
  260         len = strlen(name);
  261         for (cp = kenvp[0], i = 0; cp != NULL; cp = kenvp[++i]) {
  262                 if ((strncmp(cp, name, len) == 0) &&
  263                     (cp[len] == '=')) {
  264                         if (idx != NULL)
  265                                 *idx = i;
  266                         return (cp + len + 1);
  267                 }
  268         }
  269         return (NULL);
  270 }
  271 
  272 static char *
  273 _getenv_static(const char *name)
  274 {
  275         char *cp, *ep;
  276         int len;
  277 
  278         for (cp = kern_envp; cp != NULL; cp = kernenv_next(cp)) {
  279                 for (ep = cp; (*ep != '=') && (*ep != 0); ep++)
  280                         ;
  281                 if (*ep != '=')
  282                         continue;
  283                 len = ep - cp;
  284                 ep++;
  285                 if (!strncmp(name, cp, len) && name[len] == 0)
  286                         return (ep);
  287         }
  288         return (NULL);
  289 }
  290 
  291 /*
  292  * Look up an environment variable by name.
  293  * Return a pointer to the string if found.
  294  * The pointer has to be freed with freeenv()
  295  * after use.
  296  */
  297 char *
  298 getenv(const char *name)
  299 {
  300         char buf[KENV_MNAMELEN + 1 + KENV_MVALLEN + 1];
  301         char *ret, *cp;
  302         int len;
  303 
  304         if (dynamic_kenv) {
  305                 mtx_lock(&kenv_lock);
  306                 cp = _getenv_dynamic(name, NULL);
  307                 if (cp != NULL) {
  308                         strcpy(buf, cp);
  309                         mtx_unlock(&kenv_lock);
  310                         len = strlen(buf) + 1;
  311                         ret = malloc(len, M_KENV, M_WAITOK);
  312                         strcpy(ret, buf);
  313                 } else {
  314                         mtx_unlock(&kenv_lock);
  315                         ret = NULL;
  316                 }
  317         } else
  318                 ret = _getenv_static(name);
  319         return (ret);
  320 }
  321 
  322 /*
  323  * Test if an environment variable is defined.
  324  */
  325 int
  326 testenv(const char *name)
  327 {
  328         char *cp;
  329 
  330         if (dynamic_kenv) {
  331                 mtx_lock(&kenv_lock);
  332                 cp = _getenv_dynamic(name, NULL);
  333                 mtx_unlock(&kenv_lock);
  334         } else
  335                 cp = _getenv_static(name);
  336         if (cp != NULL)
  337                 return (1);
  338         return (0);
  339 }
  340 
  341 /*
  342  * Set an environment variable by name.
  343  */
  344 int
  345 setenv(const char *name, const char *value)
  346 {
  347         char *buf, *cp, *oldenv;
  348         int namelen, vallen, i;
  349 
  350         KENV_CHECK;
  351 
  352         namelen = strlen(name) + 1;
  353         if (namelen > KENV_MNAMELEN)
  354                 return (-1);
  355         vallen = strlen(value) + 1;
  356         if (vallen > KENV_MVALLEN)
  357                 return (-1);
  358         buf = malloc(namelen + vallen, M_KENV, M_WAITOK);
  359         sprintf(buf, "%s=%s", name, value);
  360 
  361         mtx_lock(&kenv_lock);
  362         cp = _getenv_dynamic(name, &i);
  363         if (cp != NULL) {
  364                 oldenv = kenvp[i];
  365                 kenvp[i] = buf;
  366                 mtx_unlock(&kenv_lock);
  367                 free(oldenv, M_KENV);
  368         } else {
  369                 /* We add the option if it wasn't found */
  370                 for (i = 0; (cp = kenvp[i]) != NULL; i++)
  371                         ;
  372 
  373                 /* Bounds checking */
  374                 if (i < 0 || i >= KENV_SIZE) {
  375                         free(buf, M_KENV);
  376                         mtx_unlock(&kenv_lock);
  377                         return (-1);
  378                 }
  379 
  380                 kenvp[i] = buf;
  381                 kenvp[i + 1] = NULL;
  382                 mtx_unlock(&kenv_lock);
  383         }
  384         return (0);
  385 }
  386 
  387 /*
  388  * Unset an environment variable string.
  389  */
  390 int
  391 unsetenv(const char *name)
  392 {
  393         char *cp, *oldenv;
  394         int i, j;
  395 
  396         KENV_CHECK;
  397 
  398         mtx_lock(&kenv_lock);
  399         cp = _getenv_dynamic(name, &i);
  400         if (cp != NULL) {
  401                 oldenv = kenvp[i];
  402                 for (j = i + 1; kenvp[j] != NULL; j++)
  403                         kenvp[i++] = kenvp[j];
  404                 kenvp[i] = NULL;
  405                 mtx_unlock(&kenv_lock);
  406                 free(oldenv, M_KENV);
  407                 return (0);
  408         }
  409         mtx_unlock(&kenv_lock);
  410         return (-1);
  411 }
  412 
  413 /*
  414  * Return a string value from an environment variable.
  415  */
  416 int
  417 getenv_string(const char *name, char *data, int size)
  418 {
  419         char *tmp;
  420 
  421         tmp = getenv(name);
  422         if (tmp != NULL) {
  423                 strlcpy(data, tmp, size);
  424                 freeenv(tmp);
  425                 return (1);
  426         } else
  427                 return (0);
  428 }
  429 
  430 /*
  431  * Return an integer value from an environment variable.
  432  */
  433 int
  434 getenv_int(const char *name, int *data)
  435 {
  436         quad_t tmp;
  437         int rval;
  438 
  439         rval = getenv_quad(name, &tmp);
  440         if (rval)
  441                 *data = (int) tmp;
  442         return (rval);
  443 }
  444 
  445 /*
  446  * Return a long value from an environment variable.
  447  */
  448 long
  449 getenv_long(const char *name, long *data)
  450 {
  451         quad_t tmp;
  452         long rval;
  453 
  454         rval = getenv_quad(name, &tmp);
  455         if (rval)
  456                 *data = (long) tmp;
  457         return (rval);
  458 }
  459 
  460 /*
  461  * Return an unsigned long value from an environment variable.
  462  */
  463 unsigned long
  464 getenv_ulong(const char *name, unsigned long *data)
  465 {
  466         quad_t tmp;
  467         long rval;
  468 
  469         rval = getenv_quad(name, &tmp);
  470         if (rval)
  471                 *data = (unsigned long) tmp;
  472         return (rval);
  473 }
  474 
  475 /*
  476  * Return a quad_t value from an environment variable.
  477  */
  478 int
  479 getenv_quad(const char *name, quad_t *data)
  480 {
  481         char    *value;
  482         char    *vtp;
  483         quad_t  iv;
  484 
  485         value = getenv(name);
  486         if (value == NULL)
  487                 return (0);
  488         iv = strtoq(value, &vtp, 0);
  489         if (vtp == value || (vtp[0] != '\0' && vtp[1] != '\0')) {
  490                 freeenv(value);
  491                 return (0);
  492         }
  493         switch (vtp[0]) {
  494         case 't': case 'T':
  495                 iv *= 1024;
  496         case 'g': case 'G':
  497                 iv *= 1024;
  498         case 'm': case 'M':
  499                 iv *= 1024;
  500         case 'k': case 'K':
  501                 iv *= 1024;
  502         case '\0':
  503                 break;
  504         default:
  505                 freeenv(value);
  506                 return (0);
  507         }
  508         *data = iv;
  509         freeenv(value);
  510         return (1);
  511 }
  512 
  513 /*
  514  * Find the next entry after the one which (cp) falls within, return a
  515  * pointer to its start or NULL if there are no more.
  516  */
  517 static char *
  518 kernenv_next(char *cp)
  519 {
  520 
  521         if (cp != NULL) {
  522                 while (*cp != 0)
  523                         cp++;
  524                 cp++;
  525                 if (*cp == 0)
  526                         cp = NULL;
  527         }
  528         return (cp);
  529 }
  530 
  531 void
  532 tunable_int_init(void *data)
  533 {
  534         struct tunable_int *d = (struct tunable_int *)data;
  535 
  536         TUNABLE_INT_FETCH(d->path, d->var);
  537 }
  538 
  539 void
  540 tunable_long_init(void *data)
  541 {
  542         struct tunable_long *d = (struct tunable_long *)data;
  543 
  544         TUNABLE_LONG_FETCH(d->path, d->var);
  545 }
  546 
  547 void
  548 tunable_ulong_init(void *data)
  549 {
  550         struct tunable_ulong *d = (struct tunable_ulong *)data;
  551 
  552         TUNABLE_ULONG_FETCH(d->path, d->var);
  553 }
  554 
  555 void
  556 tunable_quad_init(void *data)
  557 {
  558         struct tunable_quad *d = (struct tunable_quad *)data;
  559 
  560         TUNABLE_QUAD_FETCH(d->path, d->var);
  561 }
  562 
  563 void
  564 tunable_str_init(void *data)
  565 {
  566         struct tunable_str *d = (struct tunable_str *)data;
  567 
  568         TUNABLE_STR_FETCH(d->path, d->var, d->size);
  569 }

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