/* -*- mode:c; c-file-style:"k&r"; c-basic-offset: 4; tab-width:4; indent-tabs-mode:nil; mode:auto-fill; fill-column:78; -*- */
/* vim: set ts=4 sw=4 et tw=78 fo=cqt wm=0: */

/* Copyright (C) 2014 OSCAR lab, Stony Brook University
   This file is part of Graphene Library OS.

   Graphene Library OS is free software: you can redistribute it and/or
   modify it under the terms of the GNU General Public License
   as published by the Free Software Foundation, either version 3 of the
   License, or (at your option) any later version.

   Graphene Library OS is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */

/*
 * fs.c
 *
 * This file contains codes for implementation of 'dev' filesystem.
 */

#include <shim_internal.h>
#include <shim_handle.h>
#include <shim_fs.h>
#include <shim_utils.h>
#include <shim_profile.h>

#include <pal.h>
#include <pal_error.h>

#include <errno.h>

#include <linux/stat.h>
#include <linux/fcntl.h>

#include <asm/fcntl.h>
#include <asm/mman.h>
#include <asm/unistd.h>
#include <asm/prctl.h>

#define EMPTY_DEV_OPS                       \
    {                                       \
        .open       = NULL,                 \
        .close      = NULL,                 \
        .read       = NULL,                 \
        .write      = NULL,                 \
        .flush      = NULL,                 \
        .seek       = NULL,                 \
        .truncate   = NULL,                 \
        .mode       = NULL,                 \
        .stat       = NULL,                 \
        .hstat      = NULL,                 \
    }

#define DEV_INO_BASE   1025

static int dev_null_read (struct shim_handle * hdl, void * buf,
                          size_t count)
{
    return 0;
}

static int dev_zero_read (struct shim_handle * hdl, void * buf,
                          size_t count)
{
    memset(buf, 0, count);
    return count;
}

static int dev_null_write (struct shim_handle * hdl, const void * buf,
                           size_t count)
{
    return count;
}

static int dev_null_mode (const char * name, mode_t * mode)
{
    *mode = 0666|S_IFCHR;
    return 0;
}

static int dev_null_stat (const char * name, struct stat * stat)
{
    stat->st_mode = 0666|S_IFCHR;
    stat->st_uid = 0;
    stat->st_gid = 0;
    stat->st_size = 0;
    stat->st_blksize = 0;
    return 0;
}

static int dev_null_hstat (struct shim_handle * hdl, struct stat * stat)
{
    stat->st_mode = 0666|S_IFCHR;
    stat->st_uid = 0;
    stat->st_gid = 0;
    stat->st_size = 0;
    stat->st_blksize = 0;
    return 0;
}

static int dev_null_truncate (struct shim_handle * hdl, int size)
{
    return 0;
}

static int dev_random_mode (const char * name, mode_t * mode)
{
    *mode = 0666|S_IFCHR;
    return 0;
}

static int dev_random_read (struct shim_handle * hdl, void * buf,
                             size_t count)
{
    int rv;
    rv = DkRandomBitsRead(buf, count);
    return rv;
}

static int dev_urandom_read (struct shim_handle * hdl, void * buf,
                             size_t count)
{
    int rv;
    rv = getrand(buf, count);
    return rv;
}

static int dev_random_stat (const char * name, struct stat * stat)
{
    stat->st_mode = 0666|S_IFCHR;
    stat->st_uid = 0;
    stat->st_gid = 0;
    stat->st_size = 0;
    stat->st_blksize = 0;
    return 0;
}

static int dev_random_hstat (struct shim_handle * hdl, struct stat * stat)
{
    stat->st_mode = 0444|S_IFCHR;
    stat->st_uid = 0;
    stat->st_gid = 0;
    stat->st_size = 0;
    stat->st_blksize = 0;
    return 0;
}

static int search_dev_driver (const char * name, struct shim_dev_ops * ops)
{
    if (!memcmp(name, "null", 5) || !memcmp(name, "tty", 4)) {
        if (ops)
            ops->read   = &dev_null_read;
null_dev:
        if (ops) {
            ops->write  = &dev_null_write;
            ops->truncate = &dev_null_truncate;
            ops->mode   = &dev_null_mode;
            ops->stat   = &dev_null_stat;
            ops->hstat  = &dev_null_hstat;
        }
        return 0;
    }

    if (!memcmp(name, "zero", 5)) {
        if (ops)
            ops->read   = &dev_zero_read;
        goto null_dev;
    }

    if (!memcmp(name, "random", 7)) {
        if (ops)
            ops->read   = &dev_random_read;
random_dev:
        if (ops) {
            ops->mode   = &dev_random_mode;
            ops->stat   = &dev_random_stat;
            ops->hstat  = &dev_random_hstat;
        }
        return 0;
    }

    if (!memcmp(name, "urandom", 8)) {
        if (ops)
            ops->read   = &dev_urandom_read;
        goto random_dev;
    }

    if (!memcmp(name, "stdin", 6) || !memcmp(name, "stdout", 7) ||
        !memcmp(name, "stderr", 7))
        return -EISLINK;

    return -ENOENT;
}

static int dev_mount (const char * uri, const char * root, void ** mount_data)
{
    /* do nothing */
    return 0;
}

static int dev_unmount (void * mount_data)
{
    /* do nothing */
    return 0;
}

static int dev_open (struct shim_handle * hdl, struct shim_dentry * dent,
                     int flags)
{
    struct shim_dev_ops ops_buf = EMPTY_DEV_OPS;
    int ret = search_dev_driver(qstrgetstr(&dent->rel_path), &ops_buf);

    if (ret < 0)
        return ret;

    hdl->type     = TYPE_DEV;
    hdl->flags    = flags & ~O_ACCMODE;
    hdl->acc_mode = ACC_MODE(flags & O_ACCMODE);

    memcpy(&hdl->info.dev.dev_ops, &ops_buf,
           sizeof(struct shim_dev_ops));

    if (!ops_buf.read && (hdl->acc_mode & MAY_READ))
        return -EACCES;

    if (!ops_buf.write && (hdl->acc_mode & MAY_WRITE))
        return -EACCES;

    if (ops_buf.open)
        return ops_buf.open(hdl, qstrgetstr(&dent->rel_path), flags);

    return 0;
}

static int dev_lookup (struct shim_dentry * dent, bool force)
{
    if (qstrempty(&dent->rel_path)) {
        dent->ino = DEV_INO_BASE;
        return 0;
    }

    /* we don't care about forced or not */
    return search_dev_driver(qstrgetstr(&dent->rel_path), NULL);
}

static int dev_mode (struct shim_dentry * dent, mode_t * mode, bool force)
{
    if (qstrempty(&dent->rel_path)) {
        dent->ino = DEV_INO_BASE;
        *mode = 0555|S_IFDIR;
        return 0;
    }

    /* we don't care about forced or not */
    struct shim_dev_ops ops_buf = EMPTY_DEV_OPS;
    int ret = search_dev_driver(qstrgetstr(&dent->rel_path), &ops_buf);

    if (ret < 0)
        return ret;

    return ops_buf.mode(qstrgetstr(&dent->rel_path), mode);
}

static int dev_flush (struct shim_handle * hdl)
{
    if (!hdl->info.dev.dev_ops.flush)
        return 0;

    return hdl->info.dev.dev_ops.flush(hdl);
}

static int dev_close (struct shim_handle * hdl)
{
    if (!hdl->info.dev.dev_ops.close)
        return 0;

    return hdl->info.dev.dev_ops.close(hdl);
}

static int dev_read (struct shim_handle * hdl, void * buf,
                     size_t count)
{
    if (!hdl->info.dev.dev_ops.read)
        return -EACCES;

    return hdl->info.dev.dev_ops.read(hdl, buf, count);
}

static int dev_write (struct shim_handle * hdl, const void * buf,
                     size_t count)
{
    if (!hdl->info.dev.dev_ops.write)
        return -EACCES;

    return hdl->info.dev.dev_ops.write(hdl, buf, count);
}

static int dev_seek (struct shim_handle * hdl, off_t offset, int wence)
{
    if (!hdl->info.dev.dev_ops.seek)
        return -EACCES;

    return hdl->info.dev.dev_ops.seek(hdl, offset, wence);
}

static int dev_truncate (struct shim_handle * hdl, int len)
{
    if (!hdl->info.dev.dev_ops.truncate)
        return -EACCES;

    return hdl->info.dev.dev_ops.truncate(hdl, len);
}

static int dev_readdir (struct shim_dentry * dent, struct shim_dirent ** dirent)
{
    if (!qstrempty(&dent->rel_path)) {
        struct shim_dev_ops ops_buf = EMPTY_DEV_OPS;
        int ret = search_dev_driver(qstrgetstr(&dent->rel_path), &ops_buf);

        if (ret < 0 && ret != -EISLINK)
            return ret;

        return -ENOTDIR;
    }

    struct shim_dirent * buf, * ptr;
    int buf_size = MAX_PATH;

retry:
    buf = malloc(buf_size);
    *dirent = ptr = buf;
    struct shim_dirent ** last = dirent;

#define copy_entry(devname, devtype)                                \
    do {                                                            \
        int name_len = strlen(devname);                             \
                                                                    \
        if ((void *) (ptr + 1) + name_len + 1 >                     \
            (void *) buf + buf_size)                                \
            goto nomem;                                             \
                                                                    \
        ptr->next = (void *) (ptr + 1) + name_len + 1;              \
        ptr->ino = 1;                                               \
        ptr->type = (devtype);                                      \
        memcpy(ptr->name, (devname), name_len + 1);                 \
        last = &ptr->next;                                          \
        ptr = ptr->next;                                            \
    } while (0)

    copy_entry("null",   LINUX_DT_CHR);
    copy_entry("zero",   LINUX_DT_CHR);
    copy_entry("stdin",  LINUX_DT_LNK);
    copy_entry("stdout", LINUX_DT_LNK);
    copy_entry("stderr", LINUX_DT_LNK);

    *last = NULL;
    return 0;

nomem:
    buf_size *= 2;
    free(buf);
    goto retry;
}

static int dev_stat (struct shim_dentry * dent, struct stat * buf)
{
    if (qstrempty(&dent->rel_path)) {
        buf->st_dev     = DEV_INO_BASE;
        buf->st_ino     = DEV_INO_BASE;
        buf->st_mode    = 0777|S_IFDIR;
        buf->st_size    = 4096;
        buf->st_blksize = 4096;
        return 0;
    }

    struct shim_dev_ops ops_buf = EMPTY_DEV_OPS;
    int ret = search_dev_driver(qstrgetstr(&dent->rel_path), &ops_buf);

    if (ret < 0 && ret != -EISLINK)
        return ret;

    if (ret == -EISLINK) {
        buf->st_dev     = DEV_INO_BASE;
        buf->st_ino     = DEV_INO_BASE;
        buf->st_mode    = 0777|S_IFLNK;
        buf->st_size    = 0;
        buf->st_blksize = 0;
        return 0;
    }

    buf->st_dev     = DEV_INO_BASE;
    buf->st_ino     = DEV_INO_BASE;

    return ops_buf.stat ? ops_buf.stat(qstrgetstr(&dent->rel_path), buf) :
           -EACCES;
}

static int dev_hstat (struct shim_handle * hdl, struct stat * buf)
{
    if (!hdl->info.dev.dev_ops.hstat)
        return -EACCES;

    return hdl->info.dev.dev_ops.hstat(hdl, buf);
}

static int dev_poll (struct shim_handle * hdl, int poll_type)
{
    if (poll_type == FS_POLL_SZ)
        return 0;

    int ret = 0;
    if ((poll_type & FS_POLL_RD) && hdl->info.dev.dev_ops.read)
        ret |= FS_POLL_RD;
    if ((poll_type & FS_POLL_WR) && hdl->info.dev.dev_ops.write)
        ret |= FS_POLL_WR;

    return ret;
}

static int dev_follow_link (struct shim_dentry * dent, struct shim_qstr * link)
{
    const char * name = qstrgetstr(&dent->rel_path);

    if (!memcmp(name, "stdin", 6))
        qstrsetstr(link, "/proc/self/0", 13);
    else if (!memcmp(name, "stdout", 7))
        qstrsetstr(link, "/proc/self/1", 13);
    else if (!memcmp(name, "stderr", 7))
        qstrsetstr(link, "/proc/self/2", 13);
    else if (!memcmp(name, "null", 5) || !memcmp(name, "zero", 5))
        return -ENOTLINK;

    return -ENOENT;
}

struct shim_fs_ops dev_fs_ops = {
        .mount          = &dev_mount,
        .unmount        = &dev_unmount,
        .flush          = &dev_flush,
        .close          = &dev_close,
        .read           = &dev_read,
        .write          = &dev_write,
        .seek           = &dev_seek,
        .hstat          = &dev_hstat,
        .poll           = &dev_poll,
        .truncate       = &dev_truncate,
    };

struct shim_d_ops dev_d_ops = {
        .open           = &dev_open,
        .lookup         = &dev_lookup,
        .mode           = &dev_mode,
        .readdir        = &dev_readdir,
        .stat           = &dev_stat,
        .follow_link    = &dev_follow_link,
    };