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: stable/10/sys/kern/kern_environment.c 294683 2016-01-24 21:04:06Z ian $");
   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 int      env_len;
   64 static int      env_pos;
   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 sys_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_kenv_check_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 + 1, M_TEMP, M_WAITOK);
  147 
  148         error = copyinstr(uap->name, name, KENV_MNAMELEN + 1, NULL);
  149         if (error)
  150                 goto done;
  151 
  152         switch (uap->what) {
  153         case KENV_GET:
  154 #ifdef MAC
  155                 error = mac_kenv_check_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 + 1)
  180                         len = KENV_MVALLEN + 1;
  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_kenv_check_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_kenv_check_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  * Populate the initial kernel environment.
  215  *
  216  * This is called very early in MD startup, either to provide a copy of the
  217  * environment obtained from a boot loader, or to provide an empty buffer into
  218  * which MD code can store an initial environment using kern_setenv() calls.
  219  *
  220  * If the global envmode is 1, the environment is initialized from the global
  221  * static_env[], regardless of the arguments passed.  This implements the env
  222  * keyword described in config(5).  In this case env_pos is set to env_len,
  223  * causing kern_setenv() to return -1 (if len > 0) or panic (if len == 0) until
  224  * the dynamic environment is available.  The envmode and static_env variables
  225  * are defined in env.c which is generated by config(8).
  226  *
  227  * If len is non-zero, the caller is providing an empty buffer.  The caller will
  228  * subsequently use kern_setenv() to add up to len bytes of initial environment
  229  * before the dynamic environment is available.
  230  *
  231  * If len is zero, the caller is providing a pre-loaded buffer containing
  232  * environment strings.  Additional strings cannot be added until the dynamic
  233  * environment is available.  The memory pointed to must remain stable at least
  234  * until sysinit runs init_dynamic_kenv().  If no initial environment is
  235  * available from the boot loader, passing a NULL pointer allows the static_env
  236  * to be installed if it is configured.
  237  */
  238 void
  239 init_static_kenv(char *buf, size_t len)
  240 {
  241 
  242         if (envmode == 1) {
  243                 kern_envp = static_env;
  244                 env_len = len;
  245                 env_pos = len;
  246         } else {
  247                 kern_envp = buf;
  248                 env_len = len;
  249                 env_pos = 0;
  250         }
  251 }
  252 
  253 /*
  254  * Setup the dynamic kernel environment.
  255  */
  256 static void
  257 init_dynamic_kenv(void *data __unused)
  258 {
  259         char *cp;
  260         size_t len;
  261         int i;
  262 
  263         kenvp = malloc((KENV_SIZE + 1) * sizeof(char *), M_KENV,
  264                 M_WAITOK | M_ZERO);
  265         i = 0;
  266         if (kern_envp && *kern_envp != '\0') {
  267                 for (cp = kern_envp; cp != NULL; cp = kernenv_next(cp)) {
  268                         len = strlen(cp) + 1;
  269                         if (len > KENV_MNAMELEN + 1 + KENV_MVALLEN + 1) {
  270                                 printf(
  271                                 "WARNING: too long kenv string, ignoring %s\n",
  272                                     cp);
  273                                 continue;
  274                         }
  275                         if (i < KENV_SIZE) {
  276                                 kenvp[i] = malloc(len, M_KENV, M_WAITOK);
  277                                 strcpy(kenvp[i++], cp);
  278                         } else
  279                                 printf(
  280                                 "WARNING: too many kenv strings, ignoring %s\n",
  281                                     cp);
  282                 }
  283         }
  284         kenvp[i] = NULL;
  285 
  286         mtx_init(&kenv_lock, "kernel environment", NULL, MTX_DEF);
  287         dynamic_kenv = 1;
  288 }
  289 SYSINIT(kenv, SI_SUB_KMEM, SI_ORDER_ANY, init_dynamic_kenv, NULL);
  290 
  291 void
  292 freeenv(char *env)
  293 {
  294 
  295         if (dynamic_kenv)
  296                 free(env, M_KENV);
  297 }
  298 
  299 /*
  300  * Internal functions for string lookup.
  301  */
  302 static char *
  303 _getenv_dynamic(const char *name, int *idx)
  304 {
  305         char *cp;
  306         int len, i;
  307 
  308         mtx_assert(&kenv_lock, MA_OWNED);
  309         len = strlen(name);
  310         for (cp = kenvp[0], i = 0; cp != NULL; cp = kenvp[++i]) {
  311                 if ((strncmp(cp, name, len) == 0) &&
  312                     (cp[len] == '=')) {
  313                         if (idx != NULL)
  314                                 *idx = i;
  315                         return (cp + len + 1);
  316                 }
  317         }
  318         return (NULL);
  319 }
  320 
  321 static char *
  322 _getenv_static(const char *name)
  323 {
  324         char *cp, *ep;
  325         int len;
  326 
  327         for (cp = kern_envp; cp != NULL; cp = kernenv_next(cp)) {
  328                 for (ep = cp; (*ep != '=') && (*ep != 0); ep++)
  329                         ;
  330                 if (*ep != '=')
  331                         continue;
  332                 len = ep - cp;
  333                 ep++;
  334                 if (!strncmp(name, cp, len) && name[len] == 0)
  335                         return (ep);
  336         }
  337         return (NULL);
  338 }
  339 
  340 /*
  341  * Look up an environment variable by name.
  342  * Return a pointer to the string if found.
  343  * The pointer has to be freed with freeenv()
  344  * after use.
  345  */
  346 char *
  347 getenv(const char *name)
  348 {
  349         char buf[KENV_MNAMELEN + 1 + KENV_MVALLEN + 1];
  350         char *ret;
  351 
  352         if (dynamic_kenv) {
  353                 if (getenv_string(name, buf, sizeof(buf))) {
  354                         ret = strdup(buf, M_KENV);
  355                 } else {
  356                         ret = NULL;
  357                         WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL,
  358                             "getenv");
  359                 }
  360         } else
  361                 ret = _getenv_static(name);
  362         return (ret);
  363 }
  364 
  365 /*
  366  * Test if an environment variable is defined.
  367  */
  368 int
  369 testenv(const char *name)
  370 {
  371         char *cp;
  372 
  373         if (dynamic_kenv) {
  374                 mtx_lock(&kenv_lock);
  375                 cp = _getenv_dynamic(name, NULL);
  376                 mtx_unlock(&kenv_lock);
  377         } else
  378                 cp = _getenv_static(name);
  379         if (cp != NULL)
  380                 return (1);
  381         return (0);
  382 }
  383 
  384 static int
  385 setenv_static(const char *name, const char *value)
  386 {
  387         int len;
  388 
  389         if (env_pos >= env_len)
  390                 return (-1);
  391 
  392         /* Check space for x=y and two nuls */
  393         len = strlen(name) + strlen(value);
  394         if (len + 3 < env_len - env_pos) {
  395                 len = sprintf(&kern_envp[env_pos], "%s=%s", name, value);
  396                 env_pos += len+1;
  397                 kern_envp[env_pos] = '\0';
  398                 return (0);
  399         } else
  400                 return (-1);
  401 
  402 }
  403 
  404 /*
  405  * Set an environment variable by name.
  406  */
  407 int
  408 setenv(const char *name, const char *value)
  409 {
  410         char *buf, *cp, *oldenv;
  411         int namelen, vallen, i;
  412 
  413         if (dynamic_kenv == 0 && env_len > 0)
  414                 return (setenv_static(name, value));
  415 
  416         KENV_CHECK;
  417 
  418         namelen = strlen(name) + 1;
  419         if (namelen > KENV_MNAMELEN + 1)
  420                 return (-1);
  421         vallen = strlen(value) + 1;
  422         if (vallen > KENV_MVALLEN + 1)
  423                 return (-1);
  424         buf = malloc(namelen + vallen, M_KENV, M_WAITOK);
  425         sprintf(buf, "%s=%s", name, value);
  426 
  427         mtx_lock(&kenv_lock);
  428         cp = _getenv_dynamic(name, &i);
  429         if (cp != NULL) {
  430                 oldenv = kenvp[i];
  431                 kenvp[i] = buf;
  432                 mtx_unlock(&kenv_lock);
  433                 free(oldenv, M_KENV);
  434         } else {
  435                 /* We add the option if it wasn't found */
  436                 for (i = 0; (cp = kenvp[i]) != NULL; i++)
  437                         ;
  438 
  439                 /* Bounds checking */
  440                 if (i < 0 || i >= KENV_SIZE) {
  441                         free(buf, M_KENV);
  442                         mtx_unlock(&kenv_lock);
  443                         return (-1);
  444                 }
  445 
  446                 kenvp[i] = buf;
  447                 kenvp[i + 1] = NULL;
  448                 mtx_unlock(&kenv_lock);
  449         }
  450         return (0);
  451 }
  452 
  453 /*
  454  * Unset an environment variable string.
  455  */
  456 int
  457 unsetenv(const char *name)
  458 {
  459         char *cp, *oldenv;
  460         int i, j;
  461 
  462         KENV_CHECK;
  463 
  464         mtx_lock(&kenv_lock);
  465         cp = _getenv_dynamic(name, &i);
  466         if (cp != NULL) {
  467                 oldenv = kenvp[i];
  468                 for (j = i + 1; kenvp[j] != NULL; j++)
  469                         kenvp[i++] = kenvp[j];
  470                 kenvp[i] = NULL;
  471                 mtx_unlock(&kenv_lock);
  472                 free(oldenv, M_KENV);
  473                 return (0);
  474         }
  475         mtx_unlock(&kenv_lock);
  476         return (-1);
  477 }
  478 
  479 /*
  480  * Return a string value from an environment variable.
  481  */
  482 int
  483 getenv_string(const char *name, char *data, int size)
  484 {
  485         char *cp;
  486 
  487         if (dynamic_kenv) {
  488                 mtx_lock(&kenv_lock);
  489                 cp = _getenv_dynamic(name, NULL);
  490                 if (cp != NULL)
  491                         strlcpy(data, cp, size);
  492                 mtx_unlock(&kenv_lock);
  493         } else {
  494                 cp = _getenv_static(name);
  495                 if (cp != NULL)
  496                         strlcpy(data, cp, size);
  497         }
  498         return (cp != NULL);
  499 }
  500 
  501 /*
  502  * Return an integer value from an environment variable.
  503  */
  504 int
  505 getenv_int(const char *name, int *data)
  506 {
  507         quad_t tmp;
  508         int rval;
  509 
  510         rval = getenv_quad(name, &tmp);
  511         if (rval)
  512                 *data = (int) tmp;
  513         return (rval);
  514 }
  515 
  516 /*
  517  * Return an unsigned integer value from an environment variable.
  518  */
  519 int
  520 getenv_uint(const char *name, unsigned int *data)
  521 {
  522         quad_t tmp;
  523         int rval;
  524 
  525         rval = getenv_quad(name, &tmp);
  526         if (rval)
  527                 *data = (unsigned int) tmp;
  528         return (rval);
  529 }
  530 
  531 /*
  532  * Return a long value from an environment variable.
  533  */
  534 int
  535 getenv_long(const char *name, long *data)
  536 {
  537         quad_t tmp;
  538         int rval;
  539 
  540         rval = getenv_quad(name, &tmp);
  541         if (rval)
  542                 *data = (long) tmp;
  543         return (rval);
  544 }
  545 
  546 /*
  547  * Return an unsigned long value from an environment variable.
  548  */
  549 int
  550 getenv_ulong(const char *name, unsigned long *data)
  551 {
  552         quad_t tmp;
  553         int rval;
  554 
  555         rval = getenv_quad(name, &tmp);
  556         if (rval)
  557                 *data = (unsigned long) tmp;
  558         return (rval);
  559 }
  560 
  561 /*
  562  * Return a quad_t value from an environment variable.
  563  */
  564 int
  565 getenv_quad(const char *name, quad_t *data)
  566 {
  567         char    value[KENV_MNAMELEN + 1 + KENV_MVALLEN + 1];
  568         char    *vtp;
  569         quad_t  iv;
  570 
  571         if (!getenv_string(name, value, sizeof(value)))
  572                 return (0);
  573         iv = strtoq(value, &vtp, 0);
  574         if (vtp == value || (vtp[0] != '\0' && vtp[1] != '\0'))
  575                 return (0);
  576         switch (vtp[0]) {
  577         case 't': case 'T':
  578                 iv *= 1024;
  579         case 'g': case 'G':
  580                 iv *= 1024;
  581         case 'm': case 'M':
  582                 iv *= 1024;
  583         case 'k': case 'K':
  584                 iv *= 1024;
  585         case '\0':
  586                 break;
  587         default:
  588                 return (0);
  589         }
  590         *data = iv;
  591         return (1);
  592 }
  593 
  594 /*
  595  * Find the next entry after the one which (cp) falls within, return a
  596  * pointer to its start or NULL if there are no more.
  597  */
  598 static char *
  599 kernenv_next(char *cp)
  600 {
  601 
  602         if (cp != NULL) {
  603                 while (*cp != 0)
  604                         cp++;
  605                 cp++;
  606                 if (*cp == 0)
  607                         cp = NULL;
  608         }
  609         return (cp);
  610 }
  611 
  612 void
  613 tunable_int_init(void *data)
  614 {
  615         struct tunable_int *d = (struct tunable_int *)data;
  616 
  617         TUNABLE_INT_FETCH(d->path, d->var);
  618 }
  619 
  620 void
  621 tunable_long_init(void *data)
  622 {
  623         struct tunable_long *d = (struct tunable_long *)data;
  624 
  625         TUNABLE_LONG_FETCH(d->path, d->var);
  626 }
  627 
  628 void
  629 tunable_ulong_init(void *data)
  630 {
  631         struct tunable_ulong *d = (struct tunable_ulong *)data;
  632 
  633         TUNABLE_ULONG_FETCH(d->path, d->var);
  634 }
  635 
  636 void
  637 tunable_quad_init(void *data)
  638 {
  639         struct tunable_quad *d = (struct tunable_quad *)data;
  640 
  641         TUNABLE_QUAD_FETCH(d->path, d->var);
  642 }
  643 
  644 void
  645 tunable_str_init(void *data)
  646 {
  647         struct tunable_str *d = (struct tunable_str *)data;
  648 
  649         TUNABLE_STR_FETCH(d->path, d->var, d->size);
  650 }

Cache object: 13246157b41b1735a4ec9d3d9b204d28


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