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  1. /*
  2.  * Copyright (c) 2008 Jakub Jermar
  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.  *
  9.  * - Redistributions of source code must retain the above copyright
  10.  *   notice, this list of conditions and the following disclaimer.
  11.  * - Redistributions in binary form must reproduce the above copyright
  12.  *   notice, this list of conditions and the following disclaimer in the
  13.  *   documentation and/or other materials provided with the distribution.
  14.  * - The name of the author may not be used to endorse or promote products
  15.  *   derived from this software without specific prior written permission.
  16.  *
  17.  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  18.  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  19.  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  20.  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  21.  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  22.  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  23.  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  24.  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  25.  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  26.  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  27.  */
  28.  
  29. /** @addtogroup fs
  30.  * @{
  31.  */
  32.  
  33. /**
  34.  * @file    vfs_lookup.c
  35.  * @brief
  36.  */
  37.  
  38. #include "vfs.h"
  39. #include <ipc/ipc.h>
  40. #include <async.h>
  41. #include <errno.h>
  42. #include <string.h>
  43. #include <stdarg.h>
  44. #include <bool.h>
  45. #include <futex.h>
  46. #include <libadt/list.h>
  47. #include <atomic.h>
  48. #include <vfs/canonify.h>
  49.  
  50. #define min(a, b)   ((a) < (b) ? (a) : (b))
  51.  
  52. atomic_t plb_futex = FUTEX_INITIALIZER;
  53. link_t plb_head;    /**< PLB entry ring buffer. */
  54. uint8_t *plb = NULL;
  55.  
  56. /** Perform a path lookup.
  57.  *
  58.  * @param path      Path to be resolved; it must be a NULL-terminated
  59.  *          string.
  60.  * @param lflag     Flags to be used during lookup.
  61.  * @param result    Empty structure where the lookup result will be stored.
  62.  *          Can be NULL.
  63.  * @param altroot   If non-empty, will be used instead of rootfs as the root
  64.  *          of the whole VFS tree.
  65.  *
  66.  * @return      EOK on success or an error code from errno.h.
  67.  */
  68. int vfs_lookup_internal(char *path, int lflag, vfs_lookup_res_t *result,
  69.     vfs_pair_t *altroot, ...)
  70. {
  71.     vfs_pair_t *root;
  72.  
  73.     if (altroot)
  74.         root = altroot;
  75.     else
  76.         root = (vfs_pair_t *) &rootfs;
  77.  
  78.     if (!root->fs_handle)
  79.         return ENOENT;
  80.    
  81.     size_t len;
  82.     path = canonify(path, &len);
  83.     if (!path)
  84.         return EINVAL;
  85.    
  86.     unsigned long index = 0;
  87.     if (lflag & L_LINK) {
  88.         va_list ap;
  89.  
  90.         va_start(ap, altroot);
  91.         index = va_arg(ap, unsigned long);
  92.         va_end(ap);
  93.     }
  94.    
  95.     futex_down(&plb_futex);
  96.  
  97.     plb_entry_t entry;
  98.     link_initialize(&entry.plb_link);
  99.     entry.len = len;
  100.  
  101.     off_t first;    /* the first free index */
  102.     off_t last; /* the last free index */
  103.  
  104.     if (list_empty(&plb_head)) {
  105.         first = 0;
  106.         last = PLB_SIZE - 1;
  107.     } else {
  108.         plb_entry_t *oldest = list_get_instance(plb_head.next,
  109.             plb_entry_t, plb_link);
  110.         plb_entry_t *newest = list_get_instance(plb_head.prev,
  111.             plb_entry_t, plb_link);
  112.  
  113.         first = (newest->index + newest->len) % PLB_SIZE;
  114.         last = (oldest->index - 1) % PLB_SIZE;
  115.     }
  116.  
  117.     if (first <= last) {
  118.         if ((last - first) + 1 < len) {
  119.             /*
  120.              * The buffer cannot absorb the path.
  121.              */
  122.             futex_up(&plb_futex);
  123.             return ELIMIT;
  124.         }
  125.     } else {
  126.         if (PLB_SIZE - ((first - last) + 1) < len) {
  127.             /*
  128.              * The buffer cannot absorb the path.
  129.              */
  130.             futex_up(&plb_futex);
  131.             return ELIMIT;
  132.         }
  133.     }
  134.  
  135.     /*
  136.      * We know the first free index in PLB and we also know that there is
  137.      * enough space in the buffer to hold our path.
  138.      */
  139.  
  140.     entry.index = first;
  141.     entry.len = len;
  142.  
  143.     /*
  144.      * Claim PLB space by inserting the entry into the PLB entry ring
  145.      * buffer.
  146.      */
  147.     list_append(&entry.plb_link, &plb_head);
  148.    
  149.     futex_up(&plb_futex);
  150.  
  151.     /*
  152.      * Copy the path into PLB.
  153.      */
  154.     size_t cnt1 = min(len, (PLB_SIZE - first) + 1);
  155.     size_t cnt2 = len - cnt1;
  156.    
  157.     memcpy(&plb[first], path, cnt1);
  158.     memcpy(plb, &path[cnt1], cnt2);
  159.  
  160.     ipc_call_t answer;
  161.     int phone = vfs_grab_phone(root->fs_handle);
  162.     aid_t req = async_send_5(phone, VFS_LOOKUP, (ipcarg_t) first,
  163.         (ipcarg_t) (first + len - 1) % PLB_SIZE,
  164.         (ipcarg_t) root->dev_handle, (ipcarg_t) lflag, (ipcarg_t) index,
  165.         &answer);
  166.     vfs_release_phone(phone);
  167.  
  168.     ipcarg_t rc;
  169.     async_wait_for(req, &rc);
  170.  
  171.     futex_down(&plb_futex);
  172.     list_remove(&entry.plb_link);
  173.     /*
  174.      * Erasing the path from PLB will come handy for debugging purposes.
  175.      */
  176.     memset(&plb[first], 0, cnt1);
  177.     memset(plb, 0, cnt2);
  178.     futex_up(&plb_futex);
  179.  
  180.     if ((rc == EOK) && result) {
  181.         result->triplet.fs_handle = (int) IPC_GET_ARG1(answer);
  182.         result->triplet.dev_handle = (int) IPC_GET_ARG2(answer);
  183.         result->triplet.index = (int) IPC_GET_ARG3(answer);
  184.         result->size = (size_t) IPC_GET_ARG4(answer);
  185.         result->lnkcnt = (unsigned) IPC_GET_ARG5(answer);
  186.     }
  187.  
  188.     return rc;
  189. }
  190.  
  191. /**
  192.  * @}
  193.  */
  194.