qemu

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/*
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 * Copyright (c) 2019, Mellanox Technologies. All rights reserved.
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 * Copyright (C) 2023 Intel Corporation.
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 *
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 * This software is available to you under a choice of one of two
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 * licenses.  You may choose to be licensed under the terms of the GNU
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 * General Public License (GPL) Version 2, available from the file
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 * COPYING in the main directory of this source tree, or the
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 * OpenIB.org BSD license below:
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 *
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 *      Redistribution and use in source and binary forms, with or
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 *      without modification, are permitted provided that the following
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 *      conditions are met:
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 *
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 *      - Redistributions of source code must retain the above
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 *        copyright notice, this list of conditions and the following
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 *        disclaimer.
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 *
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 *      - Redistributions in binary form must reproduce the above
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 *        copyright notice, this list of conditions and the following
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 *        disclaimer in the documentation and/or other materials
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 *        provided with the distribution.
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 *
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 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
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 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
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 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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 * SOFTWARE.
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 *
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 * Authors: Yi Liu <yi.l.liu@intel.com>
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 *
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 * Copied from
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 * https://github.com/linux-rdma/rdma-core/blob/master/util/open_cdev.c
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 *
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 */
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#include "qemu/osdep.h"
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#include "qemu/chardev_open.h"
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static int open_cdev_internal(const char *path, dev_t cdev)
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{
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    struct stat st;
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    int fd;
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    fd = qemu_open_old(path, O_RDWR);
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    if (fd == -1) {
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        return -1;
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    }
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    if (fstat(fd, &st) || !S_ISCHR(st.st_mode) ||
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        (cdev != 0 && st.st_rdev != cdev)) {
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        close(fd);
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        return -1;
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    }
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    return fd;
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}
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static int open_cdev_robust(dev_t cdev)
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{
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    g_autofree char *devpath = NULL;
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    /*
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     * This assumes that udev is being used and is creating the /dev/char/
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     * symlinks.
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     */
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    devpath = g_strdup_printf("/dev/char/%u:%u", major(cdev), minor(cdev));
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    return open_cdev_internal(devpath, cdev);
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}
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int open_cdev(const char *devpath, dev_t cdev)
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{
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    int fd;
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    fd = open_cdev_internal(devpath, cdev);
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    if (fd == -1 && cdev != 0) {
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        return open_cdev_robust(cdev);
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    }
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    return fd;
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}
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