core/fs_mgr/fs_mgr_fstab.c

/*
 * Copyright (C) 2014 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include <ctype.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/mount.h>

#include "fs_mgr_priv.h"

struct fs_mgr_flag_values {
    char *key_loc;
    long long part_length;
    char *label;
    int partnum;
    int swap_prio;
    unsigned int zram_size;
};

struct flag_list {
    const char *name;
    unsigned flag;
};

static struct flag_list mount_flags[] = {
    { "noatime",    MS_NOATIME },
    { "noexec",     MS_NOEXEC },
    { "nosuid",     MS_NOSUID },
    { "nodev",      MS_NODEV },
    { "nodiratime", MS_NODIRATIME },
    { "ro",         MS_RDONLY },
    { "rw",         0 },
    { "remount",    MS_REMOUNT },
    { "bind",       MS_BIND },
    { "rec",        MS_REC },
    { "unbindable", MS_UNBINDABLE },
    { "private",    MS_PRIVATE },
    { "slave",      MS_SLAVE },
    { "shared",     MS_SHARED },
    { "defaults",   0 },
    { 0,            0 },
};

static struct flag_list fs_mgr_flags[] = {
    { "wait",        MF_WAIT },
    { "check",       MF_CHECK },
    { "encryptable=",MF_CRYPT },
    { "forceencrypt=",MF_FORCECRYPT },
    { "nonremovable",MF_NONREMOVABLE },
    { "voldmanaged=",MF_VOLDMANAGED},
    { "length=",     MF_LENGTH },
    { "recoveryonly",MF_RECOVERYONLY },
    { "swapprio=",   MF_SWAPPRIO },
    { "zramsize=",   MF_ZRAMSIZE },
    { "verify",      MF_VERIFY },
    { "noemulatedsd", MF_NOEMULATEDSD },
    { "formattable", MF_FORMATTABLE },
    { "defaults",    0 },
    { 0,             0 },
};

static int parse_flags(char *flags, struct flag_list *fl,
                       struct fs_mgr_flag_values *flag_vals,
                       char *fs_options, int fs_options_len)
{
    int f = 0;
    int i;
    char *p;
    char *savep;

    /* initialize flag values.  If we find a relevant flag, we'll
     * update the value */
    if (flag_vals) {
        memset(flag_vals, 0, sizeof(*flag_vals));
        flag_vals->partnum = -1;
        flag_vals->swap_prio = -1; /* negative means it wasn't specified. */
    }

    /* initialize fs_options to the null string */
    if (fs_options && (fs_options_len > 0)) {
        fs_options[0] = '\0';
    }

    p = strtok_r(flags, ",", &savep);
    while (p) {
        /* Look for the flag "p" in the flag list "fl"
         * If not found, the loop exits with fl[i].name being null.
         */
        for (i = 0; fl[i].name; i++) {
            if (!strncmp(p, fl[i].name, strlen(fl[i].name))) {
                f |= fl[i].flag;
                if ((fl[i].flag == MF_CRYPT) && flag_vals) {
                    /* The encryptable flag is followed by an = and the
                     * location of the keys.  Get it and return it.
                     */
                    flag_vals->key_loc = strdup(strchr(p, '=') + 1);
                } else if ((fl[i].flag == MF_FORCECRYPT) && flag_vals) {
                    /* The forceencrypt flag is followed by an = and the
                     * location of the keys.  Get it and return it.
                     */
                    flag_vals->key_loc = strdup(strchr(p, '=') + 1);
                } else if ((fl[i].flag == MF_LENGTH) && flag_vals) {
                    /* The length flag is followed by an = and the
                     * size of the partition.  Get it and return it.
                     */
                    flag_vals->part_length = strtoll(strchr(p, '=') + 1, NULL, 0);
                } else if ((fl[i].flag == MF_VOLDMANAGED) && flag_vals) {
                    /* The voldmanaged flag is followed by an = and the
                     * label, a colon and the partition number or the
                     * word "auto", e.g.
                     *   voldmanaged=sdcard:3
                     * Get and return them.
                     */
                    char *label_start;
                    char *label_end;
                    char *part_start;

                    label_start = strchr(p, '=') + 1;
                    label_end = strchr(p, ':');
                    if (label_end) {
                        flag_vals->label = strndup(label_start,
                                                   (int) (label_end - label_start));
                        part_start = strchr(p, ':') + 1;
                        if (!strcmp(part_start, "auto")) {
                            flag_vals->partnum = -1;
                        } else {
                            flag_vals->partnum = strtol(part_start, NULL, 0);
                        }
                    } else {
                        ERROR("Warning: voldmanaged= flag malformed\n");
                    }
                } else if ((fl[i].flag == MF_SWAPPRIO) && flag_vals) {
                    flag_vals->swap_prio = strtoll(strchr(p, '=') + 1, NULL, 0);
                } else if ((fl[i].flag == MF_ZRAMSIZE) && flag_vals) {
                    flag_vals->zram_size = strtoll(strchr(p, '=') + 1, NULL, 0);
                }
                break;
            }
        }

        if (!fl[i].name) {
            if (fs_options) {
                /* It's not a known flag, so it must be a filesystem specific
                 * option.  Add it to fs_options if it was passed in.
                 */
                strlcat(fs_options, p, fs_options_len);
                strlcat(fs_options, ",", fs_options_len);
            } else {
                /* fs_options was not passed in, so if the flag is unknown
                 * it's an error.
                 */
                ERROR("Warning: unknown flag %s\n", p);
            }
        }
        p = strtok_r(NULL, ",", &savep);
    }

    if (fs_options && fs_options[0]) {
        /* remove the last trailing comma from the list of options */
        fs_options[strlen(fs_options) - 1] = '\0';
    }

    return f;
}

struct fstab *fs_mgr_read_fstab(const char *fstab_path)
{
    FILE *fstab_file;
    int cnt, entries;
    ssize_t len;
    size_t alloc_len = 0;
    char *line = NULL;
    const char *delim = " \t";
    char *save_ptr, *p;
    struct fstab *fstab = NULL;
    struct fs_mgr_flag_values flag_vals;
#define FS_OPTIONS_LEN 1024
    char tmp_fs_options[FS_OPTIONS_LEN];

    fstab_file = fopen(fstab_path, "r");
    if (!fstab_file) {
        ERROR("Cannot open file %s\n", fstab_path);
        return 0;
    }

    entries = 0;
    while ((len = getline(&line, &alloc_len, fstab_file)) != -1) {
        /* if the last character is a newline, shorten the string by 1 byte */
        if (line[len - 1] == '\n') {
            line[len - 1] = '\0';
        }
        /* Skip any leading whitespace */
        p = line;
        while (isspace(*p)) {
            p++;
        }
        /* ignore comments or empty lines */
        if (*p == '#' || *p == '\0')
            continue;
        entries++;
    }

    if (!entries) {
        ERROR("No entries found in fstab\n");
        goto err;
    }

    /* Allocate and init the fstab structure */
    fstab = calloc(1, sizeof(struct fstab));
    fstab->num_entries = entries;
    fstab->fstab_filename = strdup(fstab_path);
    fstab->recs = calloc(fstab->num_entries, sizeof(struct fstab_rec));

    fseek(fstab_file, 0, SEEK_SET);

    cnt = 0;
    while ((len = getline(&line, &alloc_len, fstab_file)) != -1) {
        /* if the last character is a newline, shorten the string by 1 byte */
        if (line[len - 1] == '\n') {
            line[len - 1] = '\0';
        }

        /* Skip any leading whitespace */
        p = line;
        while (isspace(*p)) {
            p++;
        }
        /* ignore comments or empty lines */
        if (*p == '#' || *p == '\0')
            continue;

        /* If a non-comment entry is greater than the size we allocated, give an
         * error and quit.  This can happen in the unlikely case the file changes
         * between the two reads.
         */
        if (cnt >= entries) {
            ERROR("Tried to process more entries than counted\n");
            break;
        }

        if (!(p = strtok_r(line, delim, &save_ptr))) {
            ERROR("Error parsing mount source\n");
            goto err;
        }
        fstab->recs[cnt].blk_device = strdup(p);

        if (!(p = strtok_r(NULL, delim, &save_ptr))) {
            ERROR("Error parsing mount_point\n");
            goto err;
        }
        fstab->recs[cnt].mount_point = strdup(p);

        if (!(p = strtok_r(NULL, delim, &save_ptr))) {
            ERROR("Error parsing fs_type\n");
            goto err;
        }
        fstab->recs[cnt].fs_type = strdup(p);

        if (!(p = strtok_r(NULL, delim, &save_ptr))) {
            ERROR("Error parsing mount_flags\n");
            goto err;
        }
        tmp_fs_options[0] = '\0';
        fstab->recs[cnt].flags = parse_flags(p, mount_flags, NULL,
                                       tmp_fs_options, FS_OPTIONS_LEN);

        /* fs_options are optional */
        if (tmp_fs_options[0]) {
            fstab->recs[cnt].fs_options = strdup(tmp_fs_options);
        } else {
            fstab->recs[cnt].fs_options = NULL;
        }

        if (!(p = strtok_r(NULL, delim, &save_ptr))) {
            ERROR("Error parsing fs_mgr_options\n");
            goto err;
        }
        fstab->recs[cnt].fs_mgr_flags = parse_flags(p, fs_mgr_flags,
                                                    &flag_vals, NULL, 0);
        fstab->recs[cnt].key_loc = flag_vals.key_loc;
        fstab->recs[cnt].length = flag_vals.part_length;
        fstab->recs[cnt].label = flag_vals.label;
        fstab->recs[cnt].partnum = flag_vals.partnum;
        fstab->recs[cnt].swap_prio = flag_vals.swap_prio;
        fstab->recs[cnt].zram_size = flag_vals.zram_size;
        cnt++;
    }
    fclose(fstab_file);
    free(line);
    return fstab;

err:
    fclose(fstab_file);
    free(line);
    if (fstab)
        fs_mgr_free_fstab(fstab);
    return NULL;
}

void fs_mgr_free_fstab(struct fstab *fstab)
{
    int i;

    if (!fstab) {
        return;
    }

    for (i = 0; i < fstab->num_entries; i++) {
        /* Free the pointers return by strdup(3) */
        free(fstab->recs[i].blk_device);
        free(fstab->recs[i].mount_point);
        free(fstab->recs[i].fs_type);
        free(fstab->recs[i].fs_options);
        free(fstab->recs[i].key_loc);
        free(fstab->recs[i].label);
    }

    /* Free the fstab_recs array created by calloc(3) */
    free(fstab->recs);

    /* Free the fstab filename */
    free(fstab->fstab_filename);

    /* Free fstab */
    free(fstab);
}

/* Add an entry to the fstab, and return 0 on success or -1 on error */
int fs_mgr_add_entry(struct fstab *fstab,
                     const char *mount_point, const char *fs_type,
                     const char *blk_device)
{
    struct fstab_rec *new_fstab_recs;
    int n = fstab->num_entries;

    new_fstab_recs = (struct fstab_rec *)
                     realloc(fstab->recs, sizeof(struct fstab_rec) * (n + 1));

    if (!new_fstab_recs) {
        return -1;
    }

    /* A new entry was added, so initialize it */
     memset(&new_fstab_recs[n], 0, sizeof(struct fstab_rec));
     new_fstab_recs[n].mount_point = strdup(mount_point);
     new_fstab_recs[n].fs_type = strdup(fs_type);
     new_fstab_recs[n].blk_device = strdup(blk_device);
     new_fstab_recs[n].length = 0;

     /* Update the fstab struct */
     fstab->recs = new_fstab_recs;
     fstab->num_entries++;

     return 0;
}

/*
 * Returns the 1st matching fstab_rec that follows the start_rec.
 * start_rec is the result of a previous search or NULL.
 */
struct fstab_rec *fs_mgr_get_entry_for_mount_point_after(struct fstab_rec *start_rec, struct fstab *fstab, const char *path)
{
    int i;
    if (!fstab) {
        return NULL;
    }

    if (start_rec) {
        for (i = 0; i < fstab->num_entries; i++) {
            if (&fstab->recs[i] == start_rec) {
                i++;
                break;
            }
        }
    } else {
        i = 0;
    }
    for (; i < fstab->num_entries; i++) {
        int len = strlen(fstab->recs[i].mount_point);
        if (strncmp(path, fstab->recs[i].mount_point, len) == 0 &&
            (path[len] == '\0' || path[len] == '/')) {
            return &fstab->recs[i];
        }
    }
    return NULL;
}

/*
 * Returns the 1st matching mount point.
 * There might be more. To look for others, use fs_mgr_get_entry_for_mount_point_after()
 * and give the fstab_rec from the previous search.
 */
struct fstab_rec *fs_mgr_get_entry_for_mount_point(struct fstab *fstab, const char *path)
{
    return fs_mgr_get_entry_for_mount_point_after(NULL, fstab, path);
}

int fs_mgr_is_voldmanaged(struct fstab_rec *fstab)
{
    return fstab->fs_mgr_flags & MF_VOLDMANAGED;
}

int fs_mgr_is_nonremovable(struct fstab_rec *fstab)
{
    return fstab->fs_mgr_flags & MF_NONREMOVABLE;
}

int fs_mgr_is_verified(struct fstab_rec *fstab)
{
    return fstab->fs_mgr_flags & MF_VERIFY;
}

int fs_mgr_is_encryptable(struct fstab_rec *fstab)
{
    return fstab->fs_mgr_flags & (MF_CRYPT | MF_FORCECRYPT);
}

int fs_mgr_is_noemulatedsd(struct fstab_rec *fstab)
{
    return fstab->fs_mgr_flags & MF_NOEMULATEDSD;
}

int fs_mgr_is_formattable(struct fstab_rec *fstab)
{
    return fstab->fs_mgr_flags & (MF_FORMATTABLE);
}