WebSVN – HelenOS – Diff – /trunk/uspace/srv/vfs/vfs_lookup.c

 /*
  * Copyright (c) 2008 Jakub Jermar
  * All rights reserved.
+ *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
+ *
  * - Redistributions of source code must retain the above copyright
  *   notice, this list of conditions and the following disclaimer.
  * - 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.
  * - The name of the author may not be used to endorse or promote products
  *   derived from this software without specific prior written permission.
+ *
  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 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.
  */
 /** @addtogroup fs
  * @{
  */
 /**
  * @file    vfs_lookup.c
  * @brief
  */
 #include <ipc/ipc.h>
 #include <async.h>
 #include <errno.h>
 #include <string.h>
+#include <stdlib.h>
 #include <bool.h>
 #include <futex.h>
 #include <libadt/list.h>
 #include <atomic.h>
 #include "vfs.h"
 #define min(a, b)   ((a) < (b) ? (a) : (b))
+/* Forward static declarations. */
+static char *canonify(char *path);
 atomic_t plb_futex = FUTEX_INITIALIZER;
 link_t plb_head;    /**< PLB entry ring buffer. */
 uint8_t *plb = NULL;
 /** Perform a path lookup.
+ *
  * @param path      Path to be resolved; it needn't be an ASCIIZ string.
  * @param len       Number of path characters pointed by path.
  * @param lflag     Flags to be used during lookup.
  * @param result    Empty structure where the lookup result will be stored.
  *          Can be NULL.
  * @param altroot   If non-empty, will be used instead of rootfs as the root
  *          of the whole VFS tree.
+ *
  * @return      EOK on success or an error code from errno.h.
  */
 int vfs_lookup_internal(char *path, size_t len, int lflag,
     vfs_lookup_res_t *result, vfs_pair_t *altroot)
+{
     vfs_pair_t *root;
     if (!len)
         return EINVAL;
     if (altroot)
         root = altroot;
     else
         root = (vfs_pair_t *) &rootfs;
     if (!root->fs_handle)
         return ENOENT;
     futex_down(&plb_futex);
     plb_entry_t entry;
     link_initialize(&entry.plb_link);
     entry.len = len;
     off_t first;    /* the first free index */
     off_t last; /* the last free index */
     if (list_empty(&plb_head)) {
         first = 0;
         last = PLB_SIZE - 1;
     } else {
         plb_entry_t *oldest = list_get_instance(plb_head.next,
             plb_entry_t, plb_link);
         plb_entry_t *newest = list_get_instance(plb_head.prev,
             plb_entry_t, plb_link);
         first = (newest->index + newest->len) % PLB_SIZE;
         last = (oldest->index - 1) % PLB_SIZE;
+    }
     if (first <= last) {
         if ((last - first) + 1 < len) {
             /*
              * The buffer cannot absorb the path.
              */
             futex_up(&plb_futex);
             return ELIMIT;
+        }
     } else {
         if (PLB_SIZE - ((first - last) + 1) < len) {
             /*
              * The buffer cannot absorb the path.
              */
             futex_up(&plb_futex);
             return ELIMIT;
+        }
+    }
     /*
      * We know the first free index in PLB and we also know that there is
      * enough space in the buffer to hold our path.
      */
     entry.index = first;
     entry.len = len;
     /*
      * Claim PLB space by inserting the entry into the PLB entry ring
      * buffer.
      */
     list_append(&entry.plb_link, &plb_head);
     futex_up(&plb_futex);
     /*
      * Copy the path into PLB.
      */
     size_t cnt1 = min(len, (PLB_SIZE - first) + 1);
     size_t cnt2 = len - cnt1;
     memcpy(&plb[first], path, cnt1);
     memcpy(plb, &path[cnt1], cnt2);
     ipc_call_t answer;
     int phone = vfs_grab_phone(root->fs_handle);
     aid_t req = async_send_4(phone, VFS_LOOKUP, (ipcarg_t) first,
         (ipcarg_t) (first + len - 1) % PLB_SIZE,
         (ipcarg_t) root->dev_handle, (ipcarg_t) lflag, &answer);
     vfs_release_phone(phone);
     ipcarg_t rc;
     async_wait_for(req, &rc);
     futex_down(&plb_futex);
     list_remove(&entry.plb_link);
     /*
      * Erasing the path from PLB will come handy for debugging purposes.
      */
     memset(&plb[first], 0, cnt1);
     memset(plb, 0, cnt2);
     futex_up(&plb_futex);
     if ((rc == EOK) && result) {
         result->triplet.fs_handle = (int) IPC_GET_ARG1(answer);
         result->triplet.dev_handle = (int) IPC_GET_ARG2(answer);
         result->triplet.index = (int) IPC_GET_ARG3(answer);
         result->size = (size_t) IPC_GET_ARG4(answer);
         result->lnkcnt = (unsigned) IPC_GET_ARG5(answer);
+    }
     return rc;
+}
+/** Token types used for tokenization of path. */
+typedef enum {
+    TK_INVALID,
+    TK_SLASH,
+    TK_DOT,
+    TK_DOTDOT,
+    TK_COMP,
+    TK_NUL
+} tokval_t;
+typedef struct {
+    tokval_t kind;
+    char *start;
+    char *stop;
+} token_t;
+/** Fake up the TK_SLASH token. */
+static token_t slash_token(char *start)
+{
+    token_t ret;
+    ret.kind = TK_SLASH;
+    ret.start = start;
+    ret.stop = start;
+    return ret;
+}
+/** Given a token, return the next token. */
+static token_t next_token(token_t *cur)
+{
+    token_t ret;
+    if (cur->stop[1] == '\0') {
+        ret.kind = TK_NUL;
+        ret.start = cur->stop + 1;
+        ret.stop = ret.start;
+        return ret;
+    }
+    if (cur->stop[1] == '/') {
+        ret.kind = TK_SLASH;
+        ret.start = cur->stop + 1;
+        ret.stop = ret.start;
+        return ret;
+    }
+    if (cur->stop[1] == '.' && (!cur->stop[2] || cur->stop[2] == '/')) {
+        ret.kind = TK_DOT;
+        ret.start = cur->stop + 1;
+        ret.stop = ret.start;
+        return ret;
+    }
+    if (cur->stop[1] == '.' && cur->stop[2] == '.' &&
+        (!cur->stop[3] || cur->stop[3] == '/')) {
+        ret.kind = TK_DOTDOT;
+        ret.start = cur->stop + 1;
+        ret.stop = cur->stop + 2;
+        return ret;
+    }
+    unsigned i;
+    for (i = 1; cur->stop[i] && cur->stop[i] != '/'; i++)
+        ;
+    ret.kind = TK_COMP;
+    ret.start = &cur->stop[1];
+    ret.stop = &cur->stop[i - 1];
+    return ret;
+}
+/** States used by canonify(). */
+typedef enum {
+    S_INI,
+    S_A,
+    S_B,
+    S_C,
+    S_ACCEPT,
+    S_RESTART,
+    S_REJECT
+} state_t;
+typedef struct {
+    state_t s;
+    void (* f)(token_t *, token_t *, token_t *);
+} change_state_t;
+/*
+ * Actions that can be performed when transitioning from one
+ * state of canonify() to another.
+ */
+static void set_first_slash(token_t *t, token_t *tfsl, token_t *tlcomp)
+{
+    *tfsl = *t;
+}
+static void save_component(token_t *t, token_t *tfsl, token_t *tlcomp)
+{
+    *tlcomp = *t;
+}
+static void terminate_slash(token_t *t, token_t *tfsl, token_t *tlcomp)
+{
+    tfsl->stop[1] = '\0';
+}
+static void remove_trailing_slash(token_t *t, token_t *tfsl, token_t *tlcomp)
+{
+    t->start[-1] = '\0';
+}
+/** Eat the extra '/'..
+ *
+ * @param t     The current TK_SLASH token.
+ */
+static void shift_slash(token_t *t, token_t *tfsl, token_t *tlcomp)
+{
+    char *p = t->start;
+    char *q = t->stop + 1;
+    while ((*p++ = *q++))
+        ;
+}
+/** Eat the extra '.'.
+ *
+ * @param t     The current TK_DOT token.
+ */
+static void shift_dot(token_t *t, token_t *tfsl, token_t *tlcomp)
+{
+    char *p = t->start;
+    char *q = t->stop + 1;
+    while ((*p++ = *q++))
+        ;
+}
+/** Collapse the TK_COMP TK_SLASH TK_DOTDOT pattern.
+ *
+ * @param t     The current TK_DOTDOT token.
+ * @param tlcomp    The last TK_COMP token.
+ */
+static void shift_dotdot(token_t *t, token_t *tfsl, token_t *tlcomp)
+{
+    char *p = tlcomp->start;
+    char *q = t->stop + 1;
+    while ((*p++ = *q++))
+        ;
+}
+/** Transition function for canonify(). */
+static change_state_t trans[4][6] = {
+    [S_INI] = {
+        [TK_SLASH] = {
+            .s = S_A,
+            .f = set_first_slash,
+        },
+        [TK_DOT] = {
+            .s = S_REJECT,
+            .f = NULL,
+        },
+        [TK_DOTDOT] = {
+            .s = S_REJECT,
+            .f = NULL,
+        },
+        [TK_COMP] = {
+            .s = S_REJECT,
+            .f = NULL,
+        },
+        [TK_NUL] = {
+            .s = S_REJECT,
+            .f = NULL,
+        },
+        [TK_INVALID] = {
+            .s = S_REJECT,
+            .f = NULL,
+        },
+    },
+    [S_A] = {
+        [TK_SLASH] = {
+            .s = S_A,
+            .f = set_first_slash,
+        },
+        [TK_DOT] = {
+            .s = S_A,
+            .f = NULL,
+        },
+        [TK_DOTDOT] = {
+            .s = S_A,
+            .f = NULL,
+        },
+        [TK_COMP] = {
+            .s = S_B,
+            .f = save_component,
+        },
+        [TK_NUL] = {
+            .s = S_ACCEPT,
+            .f = terminate_slash,
+        },
+        [TK_INVALID] = {
+            .s = S_REJECT,
+            .f = NULL,
+        },
+    },
+    [S_B] = {
+        [TK_SLASH] = {
+            .s = S_C,
+            .f = NULL,
+        },
+        [TK_DOT] = {
+            .s = S_REJECT,
+            .f = NULL,
+        },
+        [TK_DOTDOT] = {
+            .s = S_REJECT,
+            .f = NULL,
+        },
+        [TK_COMP] = {
+            .s = S_REJECT,
+            .f = NULL,
+        },
+        [TK_NUL] = {
+            .s = S_ACCEPT,
+            .f = NULL,
+        },
+        [TK_INVALID] = {
+            .s = S_REJECT,
+            .f = NULL,
+        },
+    },
+    [S_C] = {
+        [TK_SLASH] = {
+            .s = S_RESTART,
+            .f = shift_slash,
+        },
+        [TK_DOT] = {
+            .s = S_RESTART,
+            .f = shift_dot,
+        },
+        [TK_DOTDOT] = {
+            .s = S_RESTART,
+            .f = shift_dotdot,
+        },
+        [TK_COMP] = {
+            .s = S_B,
+            .f = save_component,
+        },
+        [TK_NUL] = {
+            .s = S_ACCEPT,
+            .f = remove_trailing_slash,
+        },
+        [TK_INVALID] = {
+            .s = S_REJECT,
+            .f = NULL,
+        },
+    }
+};
+/** Canonify a file system path.
+ *
+ * A file system path is canonical, if the following holds:
+ * 1) the path is absolute (i.e. a/b/c is not canonical)
+ * 2) there is no trailing slash in the path (i.e. /a/b/c is not canonical)
+ * 3) there is no extra slash in the path (i.e. /a//b/c is not canonical)
+ * 4) there is no '.' component in the path (i.e. /a/./b/c is not canonical)
+ * 5) there is no '..' component in the path (i.e. /a/b/../c is not canonical)
+ *
+ * This function makes a potentially non-canonical file system path canonical.
+ * It works in-place and requires a NULL-terminated input string.
+ *
+ * @param       Path to be canonified.
+ *
+ * @return      Canonified path or NULL on failure.
+ */
+char *canonify(char *path)
+{
+    state_t state;
+    token_t t;
+    token_t tfsl;       /* first slash */
+    token_t tlcomp;     /* last component */
+    if (*path != '/')
+        return NULL;
+    tfsl = slash_token(path);
+restart:
+    state = S_INI;
+    t = tfsl;
+    while (state != S_ACCEPT && state != S_RESTART && state != S_REJECT) {
+        if (trans[state][t.kind].f)
+            trans[state][t.kind].f(&t, &tfsl, &tlcomp);
+        state = trans[state][t.kind].s;
+        t = next_token(&t);
+    }
+    switch (state) {
+    case S_RESTART:
+        goto restart;
+    case S_REJECT:
+        return NULL;
+    case S_ACCEPT:
+        return tfsl.start;
+    default:
+        abort();
+    }
+}
 /**
  * @}
  */

Subversion Repositories HelenOS

(root)/trunk/uspace/srv/vfs/vfs_lookup.c @ 2769 – Rev 2730 → 2751