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  * $FreeBSD: releng/5.1/sys/kern/kern_environment.c 111119 2003-02-19 05:47:46Z imp $
   27  */
   28 
   29 /*
   30  * The unified bootloader passes us a pointer to a preserved copy of
   31  * bootstrap/kernel environment variables.  We convert them to a
   32  * dynamic array of strings later when the VM subsystem is up.
   33  *
   34  * We make these available through the kenv(2) syscall for userland
   35  * and through getenv()/freeenv() setenv() unsetenv() testenv() for
   36  * the kernel.
   37  */
   38 
   39 #include "opt_mac.h"
   40 
   41 #include <sys/types.h>
   42 #include <sys/param.h>
   43 #include <sys/proc.h>
   44 #include <sys/queue.h>
   45 #include <sys/lock.h>
   46 #include <sys/mac.h>
   47 #include <sys/malloc.h>
   48 #include <sys/mutex.h>
   49 #include <sys/kernel.h>
   50 #include <sys/sx.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 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 sx       kenv_lock;
   68 
   69 /*
   70  * No need to protect this with a mutex
   71  * since SYSINITS are single threaded.
   72  */
   73 int     dynamic_kenv = 0;
   74 
   75 #define KENV_CHECK      if (!dynamic_kenv) \
   76                             panic("%s: called before SI_SUB_KMEM", __func__)
   77 
   78 int
   79 kenv(td, uap)
   80         struct thread *td;
   81         struct kenv_args /* {
   82                 int what;
   83                 const char *name;
   84                 char *value;
   85                 int len;
   86         } */ *uap;
   87 {
   88         char *name, *value;
   89         size_t len, done;
   90         int error, i;
   91 
   92         KASSERT(dynamic_kenv, ("kenv: dynamic_kenv = 0"));
   93 
   94         error = 0;
   95         if (uap->what == KENV_DUMP) {
   96 #ifdef MAC
   97                 error = mac_check_kenv_dump(td->td_ucred);
   98                 if (error)
   99                         return (error);
  100 #endif
  101                 len = 0;
  102                 /* Return the size if called with a NULL buffer */
  103                 if (uap->value == NULL) {
  104                         sx_slock(&kenv_lock);
  105                         for (i = 0; kenvp[i] != NULL; i++)
  106                                 len += strlen(kenvp[i]) + 1;
  107                         sx_sunlock(&kenv_lock);
  108                         td->td_retval[0] = len;
  109                         return (0);
  110                 }
  111                 done = 0;
  112                 sx_slock(&kenv_lock);
  113                 for (i = 0; kenvp[i] != NULL && done < uap->len; i++) {
  114                         len = min(strlen(kenvp[i]) + 1, uap->len - done);
  115                         error = copyout(kenvp[i], uap->value + done,
  116                             len);
  117                         if (error) {
  118                                 sx_sunlock(&kenv_lock);
  119                                 return (error);
  120                         }
  121                         done += len;
  122                 }
  123                 sx_sunlock(&kenv_lock);
  124                 return (0);
  125         }
  126 
  127         if ((uap->what == KENV_SET) ||
  128             (uap->what == KENV_UNSET)) {
  129                 error = suser(td);
  130                 if (error)
  131                         return (error);
  132         }
  133 
  134         name = malloc(KENV_MNAMELEN, M_TEMP, M_WAITOK);
  135 
  136         error = copyinstr(uap->name, name, KENV_MNAMELEN, NULL);
  137         if (error)
  138                 goto done;
  139 
  140         switch (uap->what) {
  141         case KENV_GET:
  142 #ifdef MAC
  143                 error = mac_check_kenv_get(td->td_ucred, name);
  144                 if (error)
  145                         goto done;
  146 #endif
  147                 value = getenv(name);
  148                 if (value == NULL) {
  149                         error = ENOENT;
  150                         goto done;
  151                 }
  152                 len = strlen(value) + 1;
  153                 if (len > uap->len)
  154                         len = uap->len;
  155                 error = copyout(value, uap->value, len);
  156                 freeenv(value);
  157                 if (error)
  158                         goto done;
  159                 td->td_retval[0] = len;
  160                 break;
  161         case KENV_SET:
  162                 len = uap->len;
  163                 if (len < 1) {
  164                         error = EINVAL;
  165                         goto done;
  166                 }
  167                 if (len > KENV_MVALLEN)
  168                         len = KENV_MVALLEN;
  169                 value = malloc(len, M_TEMP, M_WAITOK);
  170                 error = copyinstr(uap->value, value, len, NULL);
  171                 if (error) {
  172                         free(value, M_TEMP);
  173                         goto done;
  174                 }
  175 #ifdef MAC
  176                 error = mac_check_kenv_set(td->td_ucred, name, value);
  177                 if (error == 0)
  178 #endif
  179                         setenv(name, value);
  180                 free(value, M_TEMP);
  181                 break;
  182         case KENV_UNSET:
  183 #ifdef MAC
  184                 error = mac_check_kenv_unset(td->td_ucred, name);
  185                 if (error)
  186                         goto done;
  187 #endif
  188                 error = unsetenv(name);
  189                 if (error)
  190                         error = ENOENT;
  191                 break;
  192         default:
  193                 error = EINVAL;
  194                 break;
  195         }
  196 done:
  197         free(name, M_TEMP);
  198         return (error);
  199 }
  200 
  201 /*
  202  * Setup the dynamic kernel environment.
  203  */
  204 static void
  205 init_dynamic_kenv(void *data __unused)
  206 {
  207         char *cp;
  208         int len, i;
  209 
  210         kenvp = malloc(KENV_SIZE * sizeof(char *), M_KENV, M_WAITOK | M_ZERO);
  211         i = 0;
  212         for (cp = kern_envp; cp != NULL; cp = kernenv_next(cp)) {
  213                 len = strlen(cp) + 1;
  214                 kenvp[i] = malloc(len, M_KENV, M_WAITOK);
  215                 strcpy(kenvp[i++], cp);
  216         }
  217         kenvp[i] = NULL;
  218 
  219         sx_init(&kenv_lock, "kernel environment");
  220         dynamic_kenv = 1;
  221 }
  222 SYSINIT(kenv, SI_SUB_KMEM, SI_ORDER_ANY, init_dynamic_kenv, NULL);
  223 
  224 void
  225 freeenv(char *env)
  226 {
  227 
  228         if (dynamic_kenv)
  229                 free(env, M_KENV);
  230 }
  231 
  232 /*
  233  * Internal functions for string lookup.
  234  */
  235 static char *
  236 _getenv_dynamic(const char *name, int *idx)
  237 {
  238         char *cp;
  239         int len, i;
  240 
  241         sx_assert(&kenv_lock, SX_LOCKED);
  242         len = strlen(name);
  243         for (cp = kenvp[0], i = 0; cp != NULL; cp = kenvp[++i]) {
  244                 if ((cp[len] == '=') &&
  245                     (strncmp(cp, name, len) == 0)) {
  246                         if (idx != NULL)
  247                                 *idx = i;
  248                         return (cp + len + 1);
  249                 }
  250         }
  251         return (NULL);
  252 }
  253 
  254 static char *
  255 _getenv_static(const char *name)
  256 {
  257         char *cp, *ep;
  258         int len;
  259 
  260         for (cp = kern_envp; cp != NULL; cp = kernenv_next(cp)) {
  261                 for (ep = cp; (*ep != '=') && (*ep != 0); ep++)
  262                         ;
  263                 if (*ep != '=')
  264                         continue;
  265                 len = ep - cp;
  266                 ep++;
  267                 if (!strncmp(name, cp, len) && name[len] == 0)
  268                         return (ep);
  269         }
  270         return (NULL);
  271 }
  272 
  273 /*
  274  * Look up an environment variable by name.
  275  * Return a pointer to the string if found.
  276  * The pointer has to be freed with freeenv()
  277  * after use.
  278  */
  279 char *
  280 getenv(const char *name)
  281 {
  282         char buf[KENV_MNAMELEN + 1 + KENV_MVALLEN + 1];
  283         char *ret, *cp;
  284         int len;
  285 
  286         if (dynamic_kenv) {
  287                 sx_slock(&kenv_lock);
  288                 cp = _getenv_dynamic(name, NULL);
  289                 if (cp != NULL) {
  290                         strcpy(buf, cp);
  291                         sx_sunlock(&kenv_lock);
  292                         len = strlen(buf) + 1;
  293                         ret = malloc(len, M_KENV, M_WAITOK);
  294                         strcpy(ret, buf);
  295                 } else {
  296                         sx_sunlock(&kenv_lock);
  297                         ret = NULL;
  298                 }
  299         } else
  300                 ret = _getenv_static(name);
  301         return (ret);
  302 }
  303 
  304 /*
  305  * Test if an environment variable is defined.
  306  */
  307 int
  308 testenv(const char *name)
  309 {
  310         char *cp;
  311 
  312         if (dynamic_kenv) {
  313                 sx_slock(&kenv_lock);
  314                 cp = _getenv_dynamic(name, NULL);
  315                 sx_sunlock(&kenv_lock);
  316         } else
  317                 cp = _getenv_static(name);
  318         if (cp != NULL)
  319                 return (1);
  320         return (0);
  321 }
  322 
  323 /*
  324  * Set an environment variable by name.
  325  */
  326 int
  327 setenv(const char *name, const char *value)
  328 {
  329         char *buf, *cp, *oldenv;
  330         int namelen, vallen, i;
  331 
  332         KENV_CHECK;
  333 
  334         namelen = strlen(name) + 1;
  335         if (namelen > KENV_MNAMELEN)
  336                 return (-1);
  337         vallen = strlen(value) + 1;
  338         if (vallen > KENV_MVALLEN)
  339                 return (-1);
  340         buf = malloc(namelen + vallen, M_KENV, M_WAITOK);
  341         sprintf(buf, "%s=%s", name, value);
  342 
  343         sx_xlock(&kenv_lock);
  344         cp = _getenv_dynamic(name, &i);
  345         if (cp != NULL) {
  346                 oldenv = kenvp[i];
  347                 kenvp[i] = buf;
  348                 sx_xunlock(&kenv_lock);
  349                 free(oldenv, M_KENV);
  350         } else {
  351                 /* We add the option if it wasn't found */
  352                 for (i = 0; (cp = kenvp[i]) != NULL; i++)
  353                         ;
  354                 kenvp[i] = buf;
  355                 kenvp[i + 1] = NULL;
  356                 sx_xunlock(&kenv_lock);
  357         }
  358         return (0);
  359 }
  360 
  361 /*
  362  * Unset an environment variable string.
  363  */
  364 int
  365 unsetenv(const char *name)
  366 {
  367         char *cp, *oldenv;
  368         int i, j;
  369 
  370         KENV_CHECK;
  371 
  372         sx_xlock(&kenv_lock);
  373         cp = _getenv_dynamic(name, &i);
  374         if (cp != NULL) {
  375                 oldenv = kenvp[i];
  376                 for (j = i + 1; kenvp[j] != NULL; j++)
  377                         kenvp[i++] = kenvp[j];
  378                 kenvp[i] = NULL;
  379                 sx_xunlock(&kenv_lock);
  380                 free(oldenv, M_KENV);
  381                 return (0);
  382         }
  383         sx_xunlock(&kenv_lock);
  384         return (-1);
  385 }
  386 
  387 /*
  388  * Return a string value from an environment variable.
  389  */
  390 int
  391 getenv_string(const char *name, char *data, int size)
  392 {
  393         char *tmp;
  394 
  395         tmp = getenv(name);
  396         if (tmp != NULL) {
  397                 strlcpy(data, tmp, size);
  398                 freeenv(tmp);
  399                 return (1);
  400         } else
  401                 return (0);
  402 }
  403 
  404 /*
  405  * Return an integer value from an environment variable.
  406  */
  407 int
  408 getenv_int(const char *name, int *data)
  409 {
  410         quad_t tmp;
  411         int rval;
  412 
  413         rval = getenv_quad(name, &tmp);
  414         if (rval)
  415                 *data = (int) tmp;
  416         return (rval);
  417 }
  418 
  419 /*
  420  * Return a quad_t value from an environment variable.
  421  */
  422 int
  423 getenv_quad(const char *name, quad_t *data)
  424 {
  425         char    *value;
  426         char    *vtp;
  427         quad_t  iv;
  428 
  429         value = getenv(name);
  430         if (value == NULL)
  431                 return (0);
  432         iv = strtoq(value, &vtp, 0);
  433         if ((vtp == value) || (*vtp != '\0')) {
  434                 freeenv(value);
  435                 return (0);
  436         }
  437         freeenv(value);
  438         *data = iv;
  439         return (1);
  440 }
  441 
  442 /*
  443  * Find the next entry after the one which (cp) falls within, return a
  444  * pointer to its start or NULL if there are no more.
  445  */
  446 static char *
  447 kernenv_next(char *cp)
  448 {
  449 
  450         if (cp != NULL) {
  451                 while (*cp != 0)
  452                         cp++;
  453                 cp++;
  454                 if (*cp == 0)
  455                         cp = NULL;
  456         }
  457         return (cp);
  458 }
  459 
  460 void
  461 tunable_int_init(void *data)
  462 {
  463         struct tunable_int *d = (struct tunable_int *)data;
  464 
  465         TUNABLE_INT_FETCH(d->path, d->var);
  466 }
  467 
  468 void
  469 tunable_quad_init(void *data)
  470 {
  471         struct tunable_quad *d = (struct tunable_quad *)data;
  472 
  473         TUNABLE_QUAD_FETCH(d->path, d->var);
  474 }
  475 
  476 void
  477 tunable_str_init(void *data)
  478 {
  479         struct tunable_str *d = (struct tunable_str *)data;
  480 
  481         TUNABLE_STR_FETCH(d->path, d->var, d->size);
  482 }

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