FreeBSD/Linux Kernel Cross Reference
sys/kern/subr_hints.c

     /*-
      * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
      *
      * Copyright (c) 2000,2001 Peter Wemm <peter@FreeBSD.org>
      * 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.
     */
    
    #include <sys/cdefs.h>
    __FBSDID("$FreeBSD$");
    
    #include <sys/param.h>
    #include <sys/lock.h>
    #include <sys/kenv.h>
    #include <sys/kernel.h>
    #include <sys/malloc.h>
    #include <sys/mutex.h>
    #include <sys/sysctl.h>
    #include <sys/systm.h>
    #include <sys/bus.h>
    
    #define FBACK_MDENV     0       /* MD env (e.g. loader.conf) */
    #define FBACK_STENV     1       /* Static env */
    #define FBACK_STATIC    2       /* static_hints */
    
    /*
     * We'll use hintenv_merged to indicate that the dynamic environment has been
     * properly prepared for hint usage.  This implies that the dynamic environment
     * has already been setup (dynamic_kenv) and that we have added any supplied
     * static_hints to the dynamic environment.
     */
    static bool     hintenv_merged;
    /* Static environment and static hints cannot change, so we'll skip known bad */
    static bool     stenv_skip;
    static bool     sthints_skip;
    /*
     * Access functions for device resources.
     */
    
    static void
    static_hints_to_env(void *data __unused)
    {
            const char *cp;
            char *line, *eq;
            int eqidx, i;
    
            cp = static_hints;
            while (cp && *cp != '\0') {
                    eq = strchr(cp, '=');
                    if (eq == NULL)
                            /* Bad hint value */
                            continue;
                    eqidx = eq - cp;
    
                    i = strlen(cp);
                    line = malloc(i + 1, M_TEMP, M_WAITOK);
                    strcpy(line, cp);
                    line[eqidx] = line[i] = '\0';
                    /*
                     * Before adding a hint to the dynamic environment, check if
                     * another value for said hint has already been added.  This is
                     * needed because static environment overrides static hints and
                     * dynamic environment overrides all.
                     */
                    if (testenv(line) == 0)
                            kern_setenv(line, line + eqidx + 1);
                    free(line, M_TEMP);
                    cp += i + 1;
            }
            hintenv_merged = true;
    }
    
    /* Any time after dynamic env is setup */
    SYSINIT(hintenv, SI_SUB_KMEM + 1, SI_ORDER_SECOND, static_hints_to_env, NULL);
    
    /*
     * Checks the environment to see if we even have any hints.  If it has no hints,
     * then res_find can take the hint that there's no point in searching it and
     * either move on to the next environment or fail early.
    */
   static bool
   _res_checkenv(char *envp)
   {
           char *cp;
   
           cp = envp;
           while (cp) {
                   if (strncmp(cp, "hint.", 5) == 0)
                           return (true);
                   while (*cp != '\0')
                           cp++;
                   cp++;
                   if (*cp == '\0')
                           break;
           }
           return (false);
   }
   
   /*
    * Evil wildcarding resource string lookup.
    * This walks the supplied env string table and returns a match.
    * The start point can be remembered for incremental searches.
    */
   static int
   res_find(char **hintp_cookie, int *line, int *startln,
       const char *name, int *unit, const char *resname, const char *value,
       const char **ret_name, int *ret_namelen, int *ret_unit,
       const char **ret_resname, int *ret_resnamelen, const char **ret_value)
   {
           int fbacklvl = FBACK_MDENV, i = 0, n = 0, namelen;
           char r_name[32];
           int r_unit;
           char r_resname[32];
           char r_value[128];
           const char *s, *cp;
           char *hintp, *p;
           bool dyn_used = false;
   
           /*
            * We are expecting that the caller will pass us a hintp_cookie that
            * they are tracking.  Upon entry, if *hintp_cookie is *not* set, this
            * indicates to us that we should be figuring out based on the current
            * environment where to search.  This keeps us sane throughout the
            * entirety of a single search.
            */
           if (*hintp_cookie == NULL) {
                   hintp = NULL;
                   if (hintenv_merged) {
                           /*
                            * static_hints, if it was previously used, has
                            * already been folded in to the environment
                            * by this point.
                            */
                           mtx_lock(&kenv_lock);
                           cp = kenvp[0];
                           for (i = 0; cp != NULL; cp = kenvp[++i]) {
                                   if (!strncmp(cp, "hint.", 5)) {
                                           hintp = kenvp[0];
                                           break;
                                   }
                           }
                           mtx_unlock(&kenv_lock);
                           dyn_used = true;
                   } else {
                           /*
                            * We'll have a chance to keep coming back here until
                            * we've actually exhausted all of our possibilities.
                            * We might have chosen the MD/Static env because it
                            * had some kind of hints, but perhaps it didn't have
                            * the hint we are looking for.  We don't provide any
                            * fallback when searching the dynamic environment.
                            */
   fallback:
                           if (dyn_used || fbacklvl >= FBACK_STATIC)
                                   return (ENOENT);
   
                           switch (fbacklvl) {
                           case FBACK_MDENV:
                                   fbacklvl++;
                                   if (_res_checkenv(md_envp)) {
                                           hintp = md_envp;
                                           break;
                                   }
   
                                   /* FALLTHROUGH */
                           case FBACK_STENV:
                                   fbacklvl++;
                                   if (!stenv_skip && _res_checkenv(kern_envp)) {
                                           hintp = kern_envp;
                                           break;
                                   } else
                                           stenv_skip = true;
   
                                   /* FALLTHROUGH */
                           case FBACK_STATIC:
                                   fbacklvl++;
                                   /* We'll fallback to static_hints if needed/can */
                                   if (!sthints_skip &&
                                       _res_checkenv(static_hints))
                                           hintp = static_hints;
                                   else
                                           sthints_skip = true;
   
                                   break;
                           default:
                                   return (ENOENT);
                           }
                   }
   
                   if (hintp == NULL)
                           return (ENOENT);
                   *hintp_cookie = hintp;
           } else {
                   hintp = *hintp_cookie;
                   if (hintenv_merged && hintp == kenvp[0])
                           dyn_used = true;
                   else
                           /*
                            * If we aren't using the dynamic environment, we need
                            * to run through the proper fallback procedure again.
                            * This is so that we do continuations right if we're
                            * working with *line and *startln.
                            */
                           goto fallback;
           }
   
           if (dyn_used) {
                   mtx_lock(&kenv_lock);
                   i = 0;
           }
   
           if (name)
                   namelen = strlen(name);
           cp = hintp;
           while (cp) {
                   (*line)++;
                   if (strncmp(cp, "hint.", 5) != 0)
                           goto nexthint;
                   if (name && strncmp(cp + 5, name, namelen) != 0)
                           goto nexthint;
                   n = sscanf(cp + 5, "%32[^.].%d.%32[^=]=%127s", r_name, &r_unit,
                       r_resname, r_value);
                   if (n != 4) {
                           printf("CONFIG: invalid hint '%s'\n", cp);
                           p = strchr(cp, 'h');
                           *p = 'H';
                           goto nexthint;
                   }
                   if (startln && *startln >= 0 && *line < *startln)
                           goto nexthint;
                   if (name && strcmp(name, r_name) != 0)
                           goto nexthint;
                   if (unit && *unit != r_unit)
                           goto nexthint;
                   if (resname && strcmp(resname, r_resname) != 0)
                           goto nexthint;
                   if (value && strcmp(value, r_value) != 0)
                           goto nexthint;
                   /* Successfully found a hint matching all criteria */
                   break;
   nexthint:
                   if (dyn_used) {
                           cp = kenvp[++i];
                           if (cp == NULL)
                                   break;
                   } else {
                           while (*cp != '\0')
                                   cp++;
                           cp++;
                           if (*cp == '\0') {
                                   cp = NULL;
                                   break;
                           }
                   }
           }
           if (dyn_used)
                   mtx_unlock(&kenv_lock);
           if (cp == NULL)
                   goto fallback;
   
           s = cp;
           /* This is a bit of a hack, but at least is reentrant */
           /* Note that it returns some !unterminated! strings. */
           s = strchr(s, '.') + 1;         /* start of device */
           if (ret_name)
                   *ret_name = s;
           s = strchr(s, '.') + 1;         /* start of unit */
           if (ret_namelen && ret_name)
                   *ret_namelen = s - *ret_name - 1; /* device length */
           if (ret_unit)
                   *ret_unit = r_unit;
           s = strchr(s, '.') + 1;         /* start of resname */
           if (ret_resname)
                   *ret_resname = s;
           s = strchr(s, '=') + 1;         /* start of value */
           if (ret_resnamelen && ret_resname)
                   *ret_resnamelen = s - *ret_resname - 1; /* value len */
           if (ret_value)
                   *ret_value = s;
           if (startln)                    /* line number for anchor */
                   *startln = *line + 1;
           return 0;
   }
   
   /*
    * Search all the data sources for matches to our query.  We look for
    * dynamic hints first as overrides for static or fallback hints.
    */
   static int
   resource_find(int *line, int *startln,
       const char *name, int *unit, const char *resname, const char *value,
       const char **ret_name, int *ret_namelen, int *ret_unit,
       const char **ret_resname, int *ret_resnamelen, const char **ret_value)
   {
           int i;
           int un;
           char *hintp;
   
           *line = 0;
           hintp = NULL;
   
           /* Search for exact unit matches first */
           i = res_find(&hintp, line, startln, name, unit, resname, value,
               ret_name, ret_namelen, ret_unit, ret_resname, ret_resnamelen,
               ret_value);
           if (i == 0)
                   return 0;
           if (unit == NULL)
                   return ENOENT;
           /* If we are still here, search for wildcard matches */
           un = -1;
           i = res_find(&hintp, line, startln, name, &un, resname, value,
               ret_name, ret_namelen, ret_unit, ret_resname, ret_resnamelen,
               ret_value);
           if (i == 0)
                   return 0;
           return ENOENT;
   }
   
   int
   resource_int_value(const char *name, int unit, const char *resname, int *result)
   {
           int error;
           const char *str;
           char *op;
           unsigned long val;
           int line;
   
           line = 0;
           error = resource_find(&line, NULL, name, &unit, resname, NULL,
               NULL, NULL, NULL, NULL, NULL, &str);
           if (error)
                   return error;
           if (*str == '\0') 
                   return EFTYPE;
           val = strtoul(str, &op, 0);
           if (*op != '\0') 
                   return EFTYPE;
           *result = val;
           return 0;
   }
   
   int
   resource_long_value(const char *name, int unit, const char *resname,
       long *result)
   {
           int error;
           const char *str;
           char *op;
           unsigned long val;
           int line;
   
           line = 0;
           error = resource_find(&line, NULL, name, &unit, resname, NULL,
               NULL, NULL, NULL, NULL, NULL, &str);
           if (error)
                   return error;
           if (*str == '\0') 
                   return EFTYPE;
           val = strtoul(str, &op, 0);
           if (*op != '\0') 
                   return EFTYPE;
           *result = val;
           return 0;
   }
   
   int
   resource_string_value(const char *name, int unit, const char *resname,
       const char **result)
   {
           int error;
           const char *str;
           int line;
   
           line = 0;
           error = resource_find(&line, NULL, name, &unit, resname, NULL,
               NULL, NULL, NULL, NULL, NULL, &str);
           if (error)
                   return error;
           *result = str;
           return 0;
   }
   
   /*
    * This is a bit nasty, but allows us to not modify the env strings.
    */
   static const char *
   resource_string_copy(const char *s, int len)
   {
           static char stringbuf[256];
           static int offset = 0;
           const char *ret;
   
           if (len == 0)
                   len = strlen(s);
           if (len > 255)
                   return NULL;
           if ((offset + len + 1) > 255)
                   offset = 0;
           bcopy(s, &stringbuf[offset], len);
           stringbuf[offset + len] = '\0';
           ret = &stringbuf[offset];
           offset += len + 1;
           return ret;
   }
   
   /*
    * err = resource_find_match(&anchor, &name, &unit, resname, value)
    * Iteratively fetch a list of devices wired "at" something
    * res and value are restrictions.  eg: "at", "scbus0".
    * For practical purposes, res = required, value = optional.
    * *name and *unit are set.
    * set *anchor to zero before starting.
    */
   int
   resource_find_match(int *anchor, const char **name, int *unit,
       const char *resname, const char *value)
   {
           const char *found_name;
           int found_namelen;
           int found_unit;
           int ret;
           int newln;
   
           newln = *anchor;
           ret = resource_find(anchor, &newln, NULL, NULL, resname, value,
               &found_name, &found_namelen, &found_unit, NULL, NULL, NULL);
           if (ret == 0) {
                   *name = resource_string_copy(found_name, found_namelen);
                   *unit = found_unit;
           }
           *anchor = newln;
           return ret;
   }
   
   /*
    * err = resource_find_dev(&anchor, name, &unit, res, value);
    * Iterate through a list of devices, returning their unit numbers.
    * res and value are optional restrictions.  eg: "at", "scbus0".
    * *unit is set to the value.
    * set *anchor to zero before starting.
    */
   int
   resource_find_dev(int *anchor, const char *name, int *unit,
       const char *resname, const char *value)
   {
           int found_unit;
           int newln;
           int ret;
   
           newln = *anchor;
           ret = resource_find(anchor, &newln, name, NULL, resname, value,
               NULL, NULL, &found_unit, NULL, NULL, NULL);
           if (ret == 0) {
                   *unit = found_unit;
           }
           *anchor = newln;
           return ret;
   }
   
   /*
    * Check to see if a device is disabled via a disabled hint.
    */
   int
   resource_disabled(const char *name, int unit)
   {
           int error, value;
   
           error = resource_int_value(name, unit, "disabled", &value);
           if (error)
                  return (0);
           return (value);
   }
   
   /*
    * Clear a value associated with a device by removing it from
    * the kernel environment.  This only removes a hint for an
    * exact unit.
    */
   int
   resource_unset_value(const char *name, int unit, const char *resname)
   {
           char varname[128];
           const char *retname, *retvalue;
           int error, line;
           size_t len;
   
           line = 0;
           error = resource_find(&line, NULL, name, &unit, resname, NULL,
               &retname, NULL, NULL, NULL, NULL, &retvalue);
           if (error)
                   return (error);
   
           retname -= strlen("hint.");
           len = retvalue - retname - 1;
           if (len > sizeof(varname) - 1)
                   return (ENAMETOOLONG);
           memcpy(varname, retname, len);
           varname[len] = '\0';
           return (kern_unsetenv(varname));
   }

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