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/5.3/sys/kern/kern_environment.c 136588 2004-10-16 08:43:07Z cvs2svn $");
   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/mac.h>
   48 #include <sys/malloc.h>
   49 #include <sys/mutex.h>
   50 #include <sys/kernel.h>
   51 #include <sys/sx.h>
   52 #include <sys/systm.h>
   53 #include <sys/sysent.h>
   54 #include <sys/sysproto.h>
   55 #include <sys/libkern.h>
   56 #include <sys/kenv.h>
   57 
   58 MALLOC_DEFINE(M_KENV, "kenv", "kernel environment");
   59 
   60 #define KENV_SIZE       512     /* Maximum number of environment strings */
   61 
   62 /* pointer to the static environment */
   63 char            *kern_envp;
   64 static char     *kernenv_next(char *);
   65 
   66 /* dynamic environment variables */
   67 char            **kenvp;
   68 struct sx       kenv_lock;
   69 
   70 /*
   71  * No need to protect this with a mutex
   72  * 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;
   90         size_t len, done, needed;
   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                 sx_slock(&kenv_lock);
  104                 for (i = 0; kenvp[i] != NULL; i++) {
  105                         len = strlen(kenvp[i]) + 1;
  106                         needed += len;
  107                         len = min(len, uap->len - done);
  108                         /*
  109                          * If called with a NULL or insufficiently large
  110                          * buffer, just keep computing the required size.
  111                          */
  112                         if (uap->value != NULL && len > 0) {
  113                                 error = copyout(kenvp[i], uap->value + done,
  114                                     len);
  115                                 if (error)
  116                                         break;
  117                                 done += len;
  118                         }
  119                 }
  120                 sx_sunlock(&kenv_lock);
  121                 td->td_retval[0] = ((done == needed) ? 0 : needed);
  122                 return (error);
  123         }
  124 
  125         if ((uap->what == KENV_SET) ||
  126             (uap->what == KENV_UNSET)) {
  127                 error = suser(td);
  128                 if (error)
  129                         return (error);
  130         }
  131 
  132         name = malloc(KENV_MNAMELEN, M_TEMP, M_WAITOK);
  133 
  134         error = copyinstr(uap->name, name, KENV_MNAMELEN, NULL);
  135         if (error)
  136                 goto done;
  137 
  138         switch (uap->what) {
  139         case KENV_GET:
  140 #ifdef MAC
  141                 error = mac_check_kenv_get(td->td_ucred, name);
  142                 if (error)
  143                         goto done;
  144 #endif
  145                 value = getenv(name);
  146                 if (value == NULL) {
  147                         error = ENOENT;
  148                         goto done;
  149                 }
  150                 len = strlen(value) + 1;
  151                 if (len > uap->len)
  152                         len = uap->len;
  153                 error = copyout(value, uap->value, len);
  154                 freeenv(value);
  155                 if (error)
  156                         goto done;
  157                 td->td_retval[0] = len;
  158                 break;
  159         case KENV_SET:
  160                 len = uap->len;
  161                 if (len < 1) {
  162                         error = EINVAL;
  163                         goto done;
  164                 }
  165                 if (len > KENV_MVALLEN)
  166                         len = KENV_MVALLEN;
  167                 value = malloc(len, M_TEMP, M_WAITOK);
  168                 error = copyinstr(uap->value, value, len, NULL);
  169                 if (error) {
  170                         free(value, M_TEMP);
  171                         goto done;
  172                 }
  173 #ifdef MAC
  174                 error = mac_check_kenv_set(td->td_ucred, name, value);
  175                 if (error == 0)
  176 #endif
  177                         setenv(name, value);
  178                 free(value, M_TEMP);
  179                 break;
  180         case KENV_UNSET:
  181 #ifdef MAC
  182                 error = mac_check_kenv_unset(td->td_ucred, name);
  183                 if (error)
  184                         goto done;
  185 #endif
  186                 error = unsetenv(name);
  187                 if (error)
  188                         error = ENOENT;
  189                 break;
  190         default:
  191                 error = EINVAL;
  192                 break;
  193         }
  194 done:
  195         free(name, M_TEMP);
  196         return (error);
  197 }
  198 
  199 /*
  200  * Setup the dynamic kernel environment.
  201  */
  202 static void
  203 init_dynamic_kenv(void *data __unused)
  204 {
  205         char *cp;
  206         int len, i;
  207 
  208         kenvp = malloc(KENV_SIZE * sizeof(char *), M_KENV, M_WAITOK | M_ZERO);
  209         i = 0;
  210         for (cp = kern_envp; cp != NULL; cp = kernenv_next(cp)) {
  211                 len = strlen(cp) + 1;
  212                 kenvp[i] = malloc(len, M_KENV, M_WAITOK);
  213                 strcpy(kenvp[i++], cp);
  214         }
  215         kenvp[i] = NULL;
  216 
  217         sx_init(&kenv_lock, "kernel environment");
  218         dynamic_kenv = 1;
  219 }
  220 SYSINIT(kenv, SI_SUB_KMEM, SI_ORDER_ANY, init_dynamic_kenv, NULL);
  221 
  222 void
  223 freeenv(char *env)
  224 {
  225 
  226         if (dynamic_kenv)
  227                 free(env, M_KENV);
  228 }
  229 
  230 /*
  231  * Internal functions for string lookup.
  232  */
  233 static char *
  234 _getenv_dynamic(const char *name, int *idx)
  235 {
  236         char *cp;
  237         int len, i;
  238 
  239         sx_assert(&kenv_lock, SX_LOCKED);
  240         len = strlen(name);
  241         for (cp = kenvp[0], i = 0; cp != NULL; cp = kenvp[++i]) {
  242                 if ((cp[len] == '=') &&
  243                     (strncmp(cp, name, len) == 0)) {
  244                         if (idx != NULL)
  245                                 *idx = i;
  246                         return (cp + len + 1);
  247                 }
  248         }
  249         return (NULL);
  250 }
  251 
  252 static char *
  253 _getenv_static(const char *name)
  254 {
  255         char *cp, *ep;
  256         int len;
  257 
  258         for (cp = kern_envp; cp != NULL; cp = kernenv_next(cp)) {
  259                 for (ep = cp; (*ep != '=') && (*ep != 0); ep++)
  260                         ;
  261                 if (*ep != '=')
  262                         continue;
  263                 len = ep - cp;
  264                 ep++;
  265                 if (!strncmp(name, cp, len) && name[len] == 0)
  266                         return (ep);
  267         }
  268         return (NULL);
  269 }
  270 
  271 /*
  272  * Look up an environment variable by name.
  273  * Return a pointer to the string if found.
  274  * The pointer has to be freed with freeenv()
  275  * after use.
  276  */
  277 char *
  278 getenv(const char *name)
  279 {
  280         char buf[KENV_MNAMELEN + 1 + KENV_MVALLEN + 1];
  281         char *ret, *cp;
  282         int len;
  283 
  284         if (dynamic_kenv) {
  285                 sx_slock(&kenv_lock);
  286                 cp = _getenv_dynamic(name, NULL);
  287                 if (cp != NULL) {
  288                         strcpy(buf, cp);
  289                         sx_sunlock(&kenv_lock);
  290                         len = strlen(buf) + 1;
  291                         ret = malloc(len, M_KENV, M_WAITOK);
  292                         strcpy(ret, buf);
  293                 } else {
  294                         sx_sunlock(&kenv_lock);
  295                         ret = NULL;
  296                 }
  297         } else
  298                 ret = _getenv_static(name);
  299         return (ret);
  300 }
  301 
  302 /*
  303  * Test if an environment variable is defined.
  304  */
  305 int
  306 testenv(const char *name)
  307 {
  308         char *cp;
  309 
  310         if (dynamic_kenv) {
  311                 sx_slock(&kenv_lock);
  312                 cp = _getenv_dynamic(name, NULL);
  313                 sx_sunlock(&kenv_lock);
  314         } else
  315                 cp = _getenv_static(name);
  316         if (cp != NULL)
  317                 return (1);
  318         return (0);
  319 }
  320 
  321 /*
  322  * Set an environment variable by name.
  323  */
  324 int
  325 setenv(const char *name, const char *value)
  326 {
  327         char *buf, *cp, *oldenv;
  328         int namelen, vallen, i;
  329 
  330         KENV_CHECK;
  331 
  332         namelen = strlen(name) + 1;
  333         if (namelen > KENV_MNAMELEN)
  334                 return (-1);
  335         vallen = strlen(value) + 1;
  336         if (vallen > KENV_MVALLEN)
  337                 return (-1);
  338         buf = malloc(namelen + vallen, M_KENV, M_WAITOK);
  339         sprintf(buf, "%s=%s", name, value);
  340 
  341         sx_xlock(&kenv_lock);
  342         cp = _getenv_dynamic(name, &i);
  343         if (cp != NULL) {
  344                 oldenv = kenvp[i];
  345                 kenvp[i] = buf;
  346                 sx_xunlock(&kenv_lock);
  347                 free(oldenv, M_KENV);
  348         } else {
  349                 /* We add the option if it wasn't found */
  350                 for (i = 0; (cp = kenvp[i]) != NULL; i++)
  351                         ;
  352                 kenvp[i] = buf;
  353                 kenvp[i + 1] = NULL;
  354                 sx_xunlock(&kenv_lock);
  355         }
  356         return (0);
  357 }
  358 
  359 /*
  360  * Unset an environment variable string.
  361  */
  362 int
  363 unsetenv(const char *name)
  364 {
  365         char *cp, *oldenv;
  366         int i, j;
  367 
  368         KENV_CHECK;
  369 
  370         sx_xlock(&kenv_lock);
  371         cp = _getenv_dynamic(name, &i);
  372         if (cp != NULL) {
  373                 oldenv = kenvp[i];
  374                 for (j = i + 1; kenvp[j] != NULL; j++)
  375                         kenvp[i++] = kenvp[j];
  376                 kenvp[i] = NULL;
  377                 sx_xunlock(&kenv_lock);
  378                 free(oldenv, M_KENV);
  379                 return (0);
  380         }
  381         sx_xunlock(&kenv_lock);
  382         return (-1);
  383 }
  384 
  385 /*
  386  * Return a string value from an environment variable.
  387  */
  388 int
  389 getenv_string(const char *name, char *data, int size)
  390 {
  391         char *tmp;
  392 
  393         tmp = getenv(name);
  394         if (tmp != NULL) {
  395                 strlcpy(data, tmp, size);
  396                 freeenv(tmp);
  397                 return (1);
  398         } else
  399                 return (0);
  400 }
  401 
  402 /*
  403  * Return an integer value from an environment variable.
  404  */
  405 int
  406 getenv_int(const char *name, int *data)
  407 {
  408         quad_t tmp;
  409         int rval;
  410 
  411         rval = getenv_quad(name, &tmp);
  412         if (rval)
  413                 *data = (int) tmp;
  414         return (rval);
  415 }
  416 
  417 /*
  418  * Return a quad_t value from an environment variable.
  419  */
  420 int
  421 getenv_quad(const char *name, quad_t *data)
  422 {
  423         char    *value;
  424         char    *vtp;
  425         quad_t  iv;
  426 
  427         value = getenv(name);
  428         if (value == NULL)
  429                 return (0);
  430         iv = strtoq(value, &vtp, 0);
  431         if ((vtp == value) || (*vtp != '\0')) {
  432                 freeenv(value);
  433                 return (0);
  434         }
  435         freeenv(value);
  436         *data = iv;
  437         return (1);
  438 }
  439 
  440 /*
  441  * Find the next entry after the one which (cp) falls within, return a
  442  * pointer to its start or NULL if there are no more.
  443  */
  444 static char *
  445 kernenv_next(char *cp)
  446 {
  447 
  448         if (cp != NULL) {
  449                 while (*cp != 0)
  450                         cp++;
  451                 cp++;
  452                 if (*cp == 0)
  453                         cp = NULL;
  454         }
  455         return (cp);
  456 }
  457 
  458 void
  459 tunable_int_init(void *data)
  460 {
  461         struct tunable_int *d = (struct tunable_int *)data;
  462 
  463         TUNABLE_INT_FETCH(d->path, d->var);
  464 }
  465 
  466 void
  467 tunable_quad_init(void *data)
  468 {
  469         struct tunable_quad *d = (struct tunable_quad *)data;
  470 
  471         TUNABLE_QUAD_FETCH(d->path, d->var);
  472 }
  473 
  474 void
  475 tunable_str_init(void *data)
  476 {
  477         struct tunable_str *d = (struct tunable_str *)data;
  478 
  479         TUNABLE_STR_FETCH(d->path, d->var, d->size);
  480 }

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