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      1 /*	$NetBSD: fopsmapper.c,v 1.3 2024/04/17 18:10:27 riastradh Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 2020 The NetBSD Foundation, Inc.
      5  * All rights reserved.
      6  *
      7  * Redistribution and use in source and binary forms, with or without
      8  * modification, are permitted provided that the following conditions
      9  * are met:
     10  * 1. Redistributions of source code must retain the above copyright
     11  *    notice, this list of conditions and the following disclaimer.
     12  * 2. Redistributions in binary form must reproduce the above copyright
     13  *    notice, this list of conditions and the following disclaimer in the
     14  *    documentation and/or other materials provided with the distribution.
     15  *
     16  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     17  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     18  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     19  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     20  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     21  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     22  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     23  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     24  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     25  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     26  * POSSIBILITY OF SUCH DAMAGE.
     27  */
     28 
     29 #include <sys/cdefs.h>
     30 __KERNEL_RCSID(0, "$NetBSD: fopsmapper.c,v 1.3 2024/04/17 18:10:27 riastradh Exp $");
     31 
     32 #include <sys/types.h>
     33 
     34 #include <sys/conf.h>
     35 #include <sys/file.h>
     36 #include <sys/filedesc.h>
     37 #include <sys/kernel.h>
     38 #include <sys/kmem.h>
     39 #include <sys/mman.h>
     40 #include <sys/module.h>
     41 #include <sys/mutex.h>
     42 #include <sys/param.h>
     43 #include <sys/systm.h>
     44 
     45 #include <uvm/uvm_extern.h>
     46 
     47 /*
     48  * To use this module you need to:
     49  *
     50  * mknod /dev/fopsmapper c 351 0
     51  */
     52 
     53 dev_open_t fopsmapper_open;
     54 
     55 const struct cdevsw fopsmapper_cdevsw = {
     56 	.d_open = fopsmapper_open,
     57 	.d_close = noclose,
     58 	.d_read = noread,
     59 	.d_write = nowrite,
     60 	.d_ioctl = noioctl,
     61 	.d_stop = nostop,
     62 	.d_tty = notty,
     63 	.d_poll = nopoll,
     64 	.d_mmap = nommap,
     65 	.d_kqfilter = nokqfilter,
     66 	.d_discard = nodiscard,
     67 	.d_flag = D_OTHER
     68 };
     69 
     70 static int fopsmapper_mmap(struct file *, off_t *, size_t, int, int *, int *,
     71     struct uvm_object **, int *);
     72 static int fopsmapper_close(struct file *);
     73 
     74 const struct fileops mapper_fileops = {
     75 	.fo_read = fbadop_read,
     76 	.fo_write = fbadop_write,
     77 	.fo_ioctl = fbadop_ioctl,
     78 	.fo_fcntl = fnullop_fcntl,
     79 	.fo_poll = fnullop_poll,
     80 	.fo_stat = fbadop_stat,
     81 	.fo_close = fopsmapper_close,
     82 	.fo_kqfilter = fnullop_kqfilter,
     83 	.fo_restart = fnullop_restart,
     84 	.fo_mmap = fopsmapper_mmap,
     85 };
     86 
     87 struct fopsmapper_softc {
     88 	char *buf;
     89 	struct uvm_object *uobj;
     90 	size_t bufsize;
     91 };
     92 
     93 int
     94 fopsmapper_open(dev_t dev, int flag, int mode, struct lwp *l)
     95 {
     96 	struct fopsmapper_softc *fo;
     97 	struct file *fp;
     98 	int fd, error;
     99 
    100 	if ((error = fd_allocfile(&fp, &fd)) != 0)
    101 		return error;
    102 
    103 	fo = kmem_zalloc(sizeof(*fo), KM_SLEEP);
    104 
    105 	return fd_clone(fp, fd, flag, &mapper_fileops, fo);
    106 }
    107 
    108 int
    109 fopsmapper_mmap(struct file *fp, off_t *offp, size_t size, int prot,
    110     int *flagsp, int *advicep, struct uvm_object **uobjp, int *maxprotp)
    111 {
    112 	struct fopsmapper_softc *fo;
    113 	vaddr_t va;
    114 	int error;
    115 
    116 	if (prot & PROT_EXEC)
    117 		return EACCES;
    118 
    119 	if (size != (size_t)PAGE_SIZE)
    120 		return EINVAL;
    121 
    122 	if ((fo = fp->f_data) == NULL)
    123 		return ENXIO;
    124 
    125 	fo->bufsize = size;
    126 	fo->uobj = uao_create(size, 0);
    127 
    128 	fo->buf = NULL;
    129 
    130 	/*
    131 	 * Map the uvm object into kernel.  Consumes our reference to
    132 	 * uobj on success.
    133 	 */
    134 	error =	uvm_map(kernel_map, &va, fo->bufsize, fo->uobj, 0, 0,
    135 	    UVM_MAPFLAG(UVM_PROT_RW, UVM_PROT_RW,
    136 		UVM_INH_SHARE, UVM_ADV_RANDOM, 0));
    137 	if (error) {
    138 		uao_detach(fo->uobj);
    139 		goto out;
    140 	}
    141 	fo->buf = (char *)va;
    142 	snprintf(fo->buf, 13, "Hey There!");
    143 
    144 	/* Get the reference of uobj */
    145 	uao_reference(fo->uobj);
    146 	*uobjp = fo->uobj;
    147 	*maxprotp = prot;
    148 	*advicep = UVM_ADV_RANDOM;
    149 	error = 0;
    150 
    151 out:	return error;
    152 }
    153 
    154 int
    155 fopsmapper_close(struct file *fp)
    156 {
    157 	struct fopsmapper_softc *fo;
    158 
    159 	fo = fp->f_data;
    160 	KASSERT(fo != NULL);
    161 
    162 	if (fo->buf != NULL)
    163 		uvm_deallocate(kernel_map, (vaddr_t)fo->buf, fo->bufsize);
    164 
    165 	kmem_free(fo, sizeof(*fo));
    166 
    167 	return 0;
    168 }
    169 
    170 MODULE(MODULE_CLASS_MISC, fopsmapper, NULL);
    171 
    172 static int
    173 fopsmapper_modcmd(modcmd_t cmd, void *arg __unused)
    174 {
    175 	int cmajor = 351, bmajor = -1;
    176 
    177 	switch (cmd) {
    178 	case MODULE_CMD_INIT:
    179 		if (devsw_attach("fopsmapper", NULL, &bmajor,
    180 			&fopsmapper_cdevsw, &cmajor))
    181 			return ENXIO;
    182 		return 0;
    183 	case MODULE_CMD_FINI:
    184 		return EBUSY;
    185 	default:
    186 		return ENOTTY;
    187 	}
    188 }
    189