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 "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         size_t len;
  221         int i;
  222 
  223         kenvp = malloc((KENV_SIZE + 1) * sizeof(char *), M_KENV,
  224                 M_WAITOK | M_ZERO);
  225         i = 0;
  226         for (cp = kern_envp; cp != NULL; cp = kernenv_next(cp)) {
  227                 len = strlen(cp) + 1;
  228                 if (len > KENV_MNAMELEN + 1 + KENV_MVALLEN + 1) {
  229                         printf("WARNING: too long kenv string, ignoring %s\n",
  230                             cp);
  231                         continue;
  232                 }
  233                 if (i < KENV_SIZE) {
  234                         kenvp[i] = malloc(len, M_KENV, M_WAITOK);
  235                         strcpy(kenvp[i++], cp);
  236                 } else
  237                         printf(
  238                             "WARNING: too many kenv strings, ignoring %s\n",
  239                             cp);
  240         }
  241         kenvp[i] = NULL;
  242 
  243         mtx_init(&kenv_lock, "kernel environment", NULL, MTX_DEF);
  244         dynamic_kenv = 1;
  245 }
  246 SYSINIT(kenv, SI_SUB_KMEM, SI_ORDER_ANY, init_dynamic_kenv, NULL);
  247 
  248 void
  249 freeenv(char *env)
  250 {
  251 
  252         if (dynamic_kenv)
  253                 free(env, M_KENV);
  254 }
  255 
  256 /*
  257  * Internal functions for string lookup.
  258  */
  259 static char *
  260 _getenv_dynamic(const char *name, int *idx)
  261 {
  262         char *cp;
  263         int len, i;
  264 
  265         mtx_assert(&kenv_lock, MA_OWNED);
  266         len = strlen(name);
  267         for (cp = kenvp[0], i = 0; cp != NULL; cp = kenvp[++i]) {
  268                 if ((strncmp(cp, name, len) == 0) &&
  269                     (cp[len] == '=')) {
  270                         if (idx != NULL)
  271                                 *idx = i;
  272                         return (cp + len + 1);
  273                 }
  274         }
  275         return (NULL);
  276 }
  277 
  278 static char *
  279 _getenv_static(const char *name)
  280 {
  281         char *cp, *ep;
  282         int len;
  283 
  284         for (cp = kern_envp; cp != NULL; cp = kernenv_next(cp)) {
  285                 for (ep = cp; (*ep != '=') && (*ep != 0); ep++)
  286                         ;
  287                 if (*ep != '=')
  288                         continue;
  289                 len = ep - cp;
  290                 ep++;
  291                 if (!strncmp(name, cp, len) && name[len] == 0)
  292                         return (ep);
  293         }
  294         return (NULL);
  295 }
  296 
  297 /*
  298  * Look up an environment variable by name.
  299  * Return a pointer to the string if found.
  300  * The pointer has to be freed with freeenv()
  301  * after use.
  302  */
  303 char *
  304 getenv(const char *name)
  305 {
  306         char buf[KENV_MNAMELEN + 1 + KENV_MVALLEN + 1];
  307         char *ret, *cp;
  308         int len;
  309 
  310         if (dynamic_kenv) {
  311                 mtx_lock(&kenv_lock);
  312                 cp = _getenv_dynamic(name, NULL);
  313                 if (cp != NULL) {
  314                         strcpy(buf, cp);
  315                         mtx_unlock(&kenv_lock);
  316                         len = strlen(buf) + 1;
  317                         ret = malloc(len, M_KENV, M_WAITOK);
  318                         strcpy(ret, buf);
  319                 } else {
  320                         mtx_unlock(&kenv_lock);
  321                         ret = NULL;
  322                 }
  323         } else
  324                 ret = _getenv_static(name);
  325         return (ret);
  326 }
  327 
  328 /*
  329  * Test if an environment variable is defined.
  330  */
  331 int
  332 testenv(const char *name)
  333 {
  334         char *cp;
  335 
  336         if (dynamic_kenv) {
  337                 mtx_lock(&kenv_lock);
  338                 cp = _getenv_dynamic(name, NULL);
  339                 mtx_unlock(&kenv_lock);
  340         } else
  341                 cp = _getenv_static(name);
  342         if (cp != NULL)
  343                 return (1);
  344         return (0);
  345 }
  346 
  347 /*
  348  * Set an environment variable by name.
  349  */
  350 int
  351 setenv(const char *name, const char *value)
  352 {
  353         char *buf, *cp, *oldenv;
  354         int namelen, vallen, i;
  355 
  356         KENV_CHECK;
  357 
  358         namelen = strlen(name) + 1;
  359         if (namelen > KENV_MNAMELEN)
  360                 return (-1);
  361         vallen = strlen(value) + 1;
  362         if (vallen > KENV_MVALLEN)
  363                 return (-1);
  364         buf = malloc(namelen + vallen, M_KENV, M_WAITOK);
  365         sprintf(buf, "%s=%s", name, value);
  366 
  367         mtx_lock(&kenv_lock);
  368         cp = _getenv_dynamic(name, &i);
  369         if (cp != NULL) {
  370                 oldenv = kenvp[i];
  371                 kenvp[i] = buf;
  372                 mtx_unlock(&kenv_lock);
  373                 free(oldenv, M_KENV);
  374         } else {
  375                 /* We add the option if it wasn't found */
  376                 for (i = 0; (cp = kenvp[i]) != NULL; i++)
  377                         ;
  378 
  379                 /* Bounds checking */
  380                 if (i < 0 || i >= KENV_SIZE) {
  381                         free(buf, M_KENV);
  382                         mtx_unlock(&kenv_lock);
  383                         return (-1);
  384                 }
  385 
  386                 kenvp[i] = buf;
  387                 kenvp[i + 1] = NULL;
  388                 mtx_unlock(&kenv_lock);
  389         }
  390         return (0);
  391 }
  392 
  393 /*
  394  * Unset an environment variable string.
  395  */
  396 int
  397 unsetenv(const char *name)
  398 {
  399         char *cp, *oldenv;
  400         int i, j;
  401 
  402         KENV_CHECK;
  403 
  404         mtx_lock(&kenv_lock);
  405         cp = _getenv_dynamic(name, &i);
  406         if (cp != NULL) {
  407                 oldenv = kenvp[i];
  408                 for (j = i + 1; kenvp[j] != NULL; j++)
  409                         kenvp[i++] = kenvp[j];
  410                 kenvp[i] = NULL;
  411                 mtx_unlock(&kenv_lock);
  412                 free(oldenv, M_KENV);
  413                 return (0);
  414         }
  415         mtx_unlock(&kenv_lock);
  416         return (-1);
  417 }
  418 
  419 /*
  420  * Return a string value from an environment variable.
  421  */
  422 int
  423 getenv_string(const char *name, char *data, int size)
  424 {
  425         char *tmp;
  426 
  427         tmp = getenv(name);
  428         if (tmp != NULL) {
  429                 strlcpy(data, tmp, size);
  430                 freeenv(tmp);
  431                 return (1);
  432         } else
  433                 return (0);
  434 }
  435 
  436 /*
  437  * Return an integer value from an environment variable.
  438  */
  439 int
  440 getenv_int(const char *name, int *data)
  441 {
  442         quad_t tmp;
  443         int rval;
  444 
  445         rval = getenv_quad(name, &tmp);
  446         if (rval)
  447                 *data = (int) tmp;
  448         return (rval);
  449 }
  450 
  451 /*
  452  * Return a long value from an environment variable.
  453  */
  454 long
  455 getenv_long(const char *name, long *data)
  456 {
  457         quad_t tmp;
  458         long rval;
  459 
  460         rval = getenv_quad(name, &tmp);
  461         if (rval)
  462                 *data = (long) tmp;
  463         return (rval);
  464 }
  465 
  466 /*
  467  * Return an unsigned long value from an environment variable.
  468  */
  469 unsigned long
  470 getenv_ulong(const char *name, unsigned long *data)
  471 {
  472         quad_t tmp;
  473         long rval;
  474 
  475         rval = getenv_quad(name, &tmp);
  476         if (rval)
  477                 *data = (unsigned long) tmp;
  478         return (rval);
  479 }
  480 
  481 /*
  482  * Return a quad_t value from an environment variable.
  483  */
  484 int
  485 getenv_quad(const char *name, quad_t *data)
  486 {
  487         char    *value;
  488         char    *vtp;
  489         quad_t  iv;
  490 
  491         value = getenv(name);
  492         if (value == NULL)
  493                 return (0);
  494         iv = strtoq(value, &vtp, 0);
  495         if (vtp == value || (vtp[0] != '\0' && vtp[1] != '\0')) {
  496                 freeenv(value);
  497                 return (0);
  498         }
  499         switch (vtp[0]) {
  500         case 't': case 'T':
  501                 iv *= 1024;
  502         case 'g': case 'G':
  503                 iv *= 1024;
  504         case 'm': case 'M':
  505                 iv *= 1024;
  506         case 'k': case 'K':
  507                 iv *= 1024;
  508         case '\0':
  509                 break;
  510         default:
  511                 freeenv(value);
  512                 return (0);
  513         }
  514         *data = iv;
  515         freeenv(value);
  516         return (1);
  517 }
  518 
  519 /*
  520  * Find the next entry after the one which (cp) falls within, return a
  521  * pointer to its start or NULL if there are no more.
  522  */
  523 static char *
  524 kernenv_next(char *cp)
  525 {
  526 
  527         if (cp != NULL) {
  528                 while (*cp != 0)
  529                         cp++;
  530                 cp++;
  531                 if (*cp == 0)
  532                         cp = NULL;
  533         }
  534         return (cp);
  535 }
  536 
  537 void
  538 tunable_int_init(void *data)
  539 {
  540         struct tunable_int *d = (struct tunable_int *)data;
  541 
  542         TUNABLE_INT_FETCH(d->path, d->var);
  543 }
  544 
  545 void
  546 tunable_long_init(void *data)
  547 {
  548         struct tunable_long *d = (struct tunable_long *)data;
  549 
  550         TUNABLE_LONG_FETCH(d->path, d->var);
  551 }
  552 
  553 void
  554 tunable_ulong_init(void *data)
  555 {
  556         struct tunable_ulong *d = (struct tunable_ulong *)data;
  557 
  558         TUNABLE_ULONG_FETCH(d->path, d->var);
  559 }
  560 
  561 void
  562 tunable_quad_init(void *data)
  563 {
  564         struct tunable_quad *d = (struct tunable_quad *)data;
  565 
  566         TUNABLE_QUAD_FETCH(d->path, d->var);
  567 }
  568 
  569 void
  570 tunable_str_init(void *data)
  571 {
  572         struct tunable_str *d = (struct tunable_str *)data;
  573 
  574         TUNABLE_STR_FETCH(d->path, d->var, d->size);
  575 }

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