kern_environment.c

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/*-
 * Copyright (c) 1998 Michael Smith
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

/*
 * The unified bootloader passes us a pointer to a preserved copy of
 * bootstrap/kernel environment variables.  We convert them to a
 * dynamic array of strings later when the VM subsystem is up.
 *
 * We make these available through the kenv(2) syscall for userland
 * and through getenv()/freeenv() setenv() unsetenv() testenv() for
 * the kernel.
 */

#include <sys/cdefs.h>
__FBSDID("$BSDSUniX$");

#include <sys/types.h>
#include <sys/param.h>
#include <sys/proc.h>
#include <sys/queue.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mutex.h>
#include <sys/priv.h>
#include <sys/kernel.h>
#include <sys/systm.h>
#include <sys/sysent.h>
#include <sys/sysproto.h>
#include <sys/libkern.h>
#include <sys/kenv.h>

#include <security/mac/mac_framework.h>

static MALLOC_DEFINE(M_KENV, "kenv", "kernel environment");

#define KENV_SIZE       512     /* Maximum number of environment strings */

/* pointer to the static environment */
char            *kern_envp;
static int      env_len;
static int      env_pos;
static char     *kernenv_next(char *);

/* dynamic environment variables */
char            **kenvp;
struct mtx      kenv_lock;

/*
 * No need to protect this with a mutex since SYSINITS are single threaded.
 */
int     dynamic_kenv = 0;

#define KENV_CHECK      if (!dynamic_kenv) \
                            panic("%s: called before SI_SUB_KMEM", __func__)

int
sys_kenv(td, uap)
        struct thread *td;
        struct kenv_args /* {
                int what;
                const char *name;
                char *value;
                int len;
        } */ *uap;
{
        char *name, *value, *buffer = NULL;
        size_t len, done, needed, buflen;
        int error, i;

        KASSERT(dynamic_kenv, ("kenv: dynamic_kenv = 0"));

        error = 0;
        if (uap->what == KENV_DUMP) {
#ifdef MAC
                error = mac_kenv_check_dump(td->td_ucred);
                if (error)
                        return (error);
#endif
                done = needed = 0;
                buflen = uap->len;
                if (buflen > KENV_SIZE * (KENV_MNAMELEN + KENV_MVALLEN + 2))
                        buflen = KENV_SIZE * (KENV_MNAMELEN +
                            KENV_MVALLEN + 2);
                if (uap->len > 0 && uap->value != NULL)
                        buffer = malloc(buflen, M_TEMP, M_WAITOK|M_ZERO);
                mtx_lock(&kenv_lock);
                for (i = 0; kenvp[i] != NULL; i++) {
                        len = strlen(kenvp[i]) + 1;
                        needed += len;
                        len = min(len, buflen - done);
                        /*
                         * If called with a NULL or insufficiently large
                         * buffer, just keep computing the required size.
                         */
                        if (uap->value != NULL && buffer != NULL && len > 0) {
                                bcopy(kenvp[i], buffer + done, len);
                                done += len;
                        }
                }
                mtx_unlock(&kenv_lock);
                if (buffer != NULL) {
                        error = copyout(buffer, uap->value, done);
                        free(buffer, M_TEMP);
                }
                td->td_retval[0] = ((done == needed) ? 0 : needed);
                return (error);
        }

        switch (uap->what) {
        case KENV_SET:
                error = priv_check(td, PRIV_KENV_SET);
                if (error)
                        return (error);
                break;

        case KENV_UNSET:
                error = priv_check(td, PRIV_KENV_UNSET);
                if (error)
                        return (error);
                break;
        }

        name = malloc(KENV_MNAMELEN + 1, M_TEMP, M_WAITOK);

        error = copyinstr(uap->name, name, KENV_MNAMELEN + 1, NULL);
        if (error)
                goto done;

        switch (uap->what) {
        case KENV_GET:
#ifdef MAC
                error = mac_kenv_check_get(td->td_ucred, name);
                if (error)
                        goto done;
#endif
                value = getenv(name);
                if (value == NULL) {
                        error = ENOENT;
                        goto done;
                }
                len = strlen(value) + 1;
                if (len > uap->len)
                        len = uap->len;
                error = copyout(value, uap->value, len);
                freeenv(value);
                if (error)
                        goto done;
                td->td_retval[0] = len;
                break;
        case KENV_SET:
                len = uap->len;
                if (len < 1) {
                        error = EINVAL;
                        goto done;
                }
                if (len > KENV_MVALLEN + 1)
                        len = KENV_MVALLEN + 1;
                value = malloc(len, M_TEMP, M_WAITOK);
                error = copyinstr(uap->value, value, len, NULL);
                if (error) {
                        free(value, M_TEMP);
                        goto done;
                }
#ifdef MAC
                error = mac_kenv_check_set(td->td_ucred, name, value);
                if (error == 0)
#endif
                        setenv(name, value);
                free(value, M_TEMP);
                break;
        case KENV_UNSET:
#ifdef MAC
                error = mac_kenv_check_unset(td->td_ucred, name);
                if (error)
                        goto done;
#endif
                error = unsetenv(name);
                if (error)
                        error = ENOENT;
                break;
        default:
                error = EINVAL;
                break;
        }
done:
        free(name, M_TEMP);
        return (error);
}

void
init_static_kenv(char *buf, size_t len)
{
        kern_envp = buf;
        env_len = len;
        env_pos = 0;
}

/*
 * Setup the dynamic kernel environment.
 */
static void
init_dynamic_kenv(void *data __unused)
{
        char *cp;
        size_t len;
        int i;

        kenvp = malloc((KENV_SIZE + 1) * sizeof(char *), M_KENV,
                M_WAITOK | M_ZERO);
        i = 0;
        for (cp = kern_envp; cp != NULL; cp = kernenv_next(cp)) {
                len = strlen(cp) + 1;
                if (len > KENV_MNAMELEN + 1 + KENV_MVALLEN + 1) {
                        printf("WARNING: too long kenv string, ignoring %s\n",
                            cp);
                        continue;
                }
                if (i < KENV_SIZE) {
                        kenvp[i] = malloc(len, M_KENV, M_WAITOK);
                        strcpy(kenvp[i++], cp);
                } else
                        printf(
                            "WARNING: too many kenv strings, ignoring %s\n",
                            cp);
        }
        kenvp[i] = NULL;

        mtx_init(&kenv_lock, "kernel environment", NULL, MTX_DEF);
        dynamic_kenv = 1;
}
SYSINIT(kenv, SI_SUB_KMEM, SI_ORDER_ANY, init_dynamic_kenv, NULL);

void
freeenv(char *env)
{

        if (dynamic_kenv)
                free(env, M_KENV);
}

/*
 * Internal functions for string lookup.
 */
static char *
_getenv_dynamic(const char *name, int *idx)
{
        char *cp;
        int len, i;

        mtx_assert(&kenv_lock, MA_OWNED);
        len = strlen(name);
        for (cp = kenvp[0], i = 0; cp != NULL; cp = kenvp[++i]) {
                if ((strncmp(cp, name, len) == 0) &&
                    (cp[len] == '=')) {
                        if (idx != NULL)
                                *idx = i;
                        return (cp + len + 1);
                }
        }
        return (NULL);
}

static char *
_getenv_static(const char *name)
{
        char *cp, *ep;
        int len;

        for (cp = kern_envp; cp != NULL; cp = kernenv_next(cp)) {
                for (ep = cp; (*ep != '=') && (*ep != 0); ep++)
                        ;
                if (*ep != '=')
                        continue;
                len = ep - cp;
                ep++;
                if (!strncmp(name, cp, len) && name[len] == 0)
                        return (ep);
        }
        return (NULL);
}

/*
 * Look up an environment variable by name.
 * Return a pointer to the string if found.
 * The pointer has to be freed with freeenv()
 * after use.
 */
char *
getenv(const char *name)
{
        char buf[KENV_MNAMELEN + 1 + KENV_MVALLEN + 1];
        char *ret, *cp;
        int len;

        if (dynamic_kenv) {
                mtx_lock(&kenv_lock);
                cp = _getenv_dynamic(name, NULL);
                if (cp != NULL) {
                        strcpy(buf, cp);
                        mtx_unlock(&kenv_lock);
                        len = strlen(buf) + 1;
                        ret = malloc(len, M_KENV, M_WAITOK);
                        strcpy(ret, buf);
                } else {
                        mtx_unlock(&kenv_lock);
                        ret = NULL;
                        WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL,
                            "getenv");
                }
        } else
                ret = _getenv_static(name);
        return (ret);
}

/*
 * Test if an environment variable is defined.
 */
int
testenv(const char *name)
{
        char *cp;

        if (dynamic_kenv) {
                mtx_lock(&kenv_lock);
                cp = _getenv_dynamic(name, NULL);
                mtx_unlock(&kenv_lock);
        } else
                cp = _getenv_static(name);
        if (cp != NULL)
                return (1);
        return (0);
}

static int
setenv_static(const char *name, const char *value)
{
        int len;

        if (env_pos >= env_len)
                return (-1);

        /* Check space for x=y and two nuls */
        len = strlen(name) + strlen(value);
        if (len + 3 < env_len - env_pos) {
                len = sprintf(&kern_envp[env_pos], "%s=%s", name, value);
                env_pos += len+1;
                kern_envp[env_pos] = '\0';
                return (0);
        } else
                return (-1);

}

/*
 * Set an environment variable by name.
 */
int
setenv(const char *name, const char *value)
{
        char *buf, *cp, *oldenv;
        int namelen, vallen, i;

        if (dynamic_kenv == 0 && env_len > 0)
                return (setenv_static(name, value));

        KENV_CHECK;

        namelen = strlen(name) + 1;
        if (namelen > KENV_MNAMELEN + 1)
                return (-1);
        vallen = strlen(value) + 1;
        if (vallen > KENV_MVALLEN + 1)
                return (-1);
        buf = malloc(namelen + vallen, M_KENV, M_WAITOK);
        sprintf(buf, "%s=%s", name, value);

        mtx_lock(&kenv_lock);
        cp = _getenv_dynamic(name, &i);
        if (cp != NULL) {
                oldenv = kenvp[i];
                kenvp[i] = buf;
                mtx_unlock(&kenv_lock);
                free(oldenv, M_KENV);
        } else {
                /* We add the option if it wasn't found */
                for (i = 0; (cp = kenvp[i]) != NULL; i++)
                        ;

                /* Bounds checking */
                if (i < 0 || i >= KENV_SIZE) {
                        free(buf, M_KENV);
                        mtx_unlock(&kenv_lock);
                        return (-1);
                }

                kenvp[i] = buf;
                kenvp[i + 1] = NULL;
                mtx_unlock(&kenv_lock);
        }
        return (0);
}

/*
 * Unset an environment variable string.
 */
int
unsetenv(const char *name)
{
        char *cp, *oldenv;
        int i, j;

        KENV_CHECK;

        mtx_lock(&kenv_lock);
        cp = _getenv_dynamic(name, &i);
        if (cp != NULL) {
                oldenv = kenvp[i];
                for (j = i + 1; kenvp[j] != NULL; j++)
                        kenvp[i++] = kenvp[j];
                kenvp[i] = NULL;
                mtx_unlock(&kenv_lock);
                free(oldenv, M_KENV);
                return (0);
        }
        mtx_unlock(&kenv_lock);
        return (-1);
}

/*
 * Return a string value from an environment variable.
 */
int
getenv_string(const char *name, char *data, int size)
{
        char *tmp;

        tmp = getenv(name);
        if (tmp != NULL) {
                strlcpy(data, tmp, size);
                freeenv(tmp);
                return (1);
        } else
                return (0);
}

/*
 * Return an integer value from an environment variable.
 */
int
getenv_int(const char *name, int *data)
{
        quad_t tmp;
        int rval;

        rval = getenv_quad(name, &tmp);
        if (rval)
                *data = (int) tmp;
        return (rval);
}

/*
 * Return an unsigned integer value from an environment variable.
 */
int
getenv_uint(const char *name, unsigned int *data)
{
        quad_t tmp;
        int rval;

        rval = getenv_quad(name, &tmp);
        if (rval)
                *data = (unsigned int) tmp;
        return (rval);
}

/*
 * Return a long value from an environment variable.
 */
int
getenv_long(const char *name, long *data)
{
        quad_t tmp;
        int rval;

        rval = getenv_quad(name, &tmp);
        if (rval)
                *data = (long) tmp;
        return (rval);
}

/*
 * Return an unsigned long value from an environment variable.
 */
int
getenv_ulong(const char *name, unsigned long *data)
{
        quad_t tmp;
        int rval;

        rval = getenv_quad(name, &tmp);
        if (rval)
                *data = (unsigned long) tmp;
        return (rval);
}

/*
 * Return a quad_t value from an environment variable.
 */
int
getenv_quad(const char *name, quad_t *data)
{
        char    *value;
        char    *vtp;
        quad_t  iv;

        value = getenv(name);
        if (value == NULL)
                return (0);
        iv = strtoq(value, &vtp, 0);
        if (vtp == value || (vtp[0] != '\0' && vtp[1] != '\0')) {
                freeenv(value);
                return (0);
        }
        switch (vtp[0]) {
        case 't': case 'T':
                iv *= 1024;
        case 'g': case 'G':
                iv *= 1024;
        case 'm': case 'M':
                iv *= 1024;
        case 'k': case 'K':
                iv *= 1024;
        case '\0':
                break;
        default:
                freeenv(value);
                return (0);
        }
        *data = iv;
        freeenv(value);
        return (1);
}

/*
 * Find the next entry after the one which (cp) falls within, return a
 * pointer to its start or NULL if there are no more.
 */
static char *
kernenv_next(char *cp)
{

        if (cp != NULL) {
                while (*cp != 0)
                        cp++;
                cp++;
                if (*cp == 0)
                        cp = NULL;
        }
        return (cp);
}

void
tunable_int_init(void *data)
{
        struct tunable_int *d = (struct tunable_int *)data;

        TUNABLE_INT_FETCH(d->path, d->var);
}

void
tunable_long_init(void *data)
{
        struct tunable_long *d = (struct tunable_long *)data;

        TUNABLE_LONG_FETCH(d->path, d->var);
}

void
tunable_ulong_init(void *data)
{
        struct tunable_ulong *d = (struct tunable_ulong *)data;

        TUNABLE_ULONG_FETCH(d->path, d->var);
}

void
tunable_quad_init(void *data)
{
        struct tunable_quad *d = (struct tunable_quad *)data;

        TUNABLE_QUAD_FETCH(d->path, d->var);
}

void
tunable_str_init(void *data)
{
        struct tunable_str *d = (struct tunable_str *)data;

        TUNABLE_STR_FETCH(d->path, d->var, d->size);
}