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fopsmapper.c revision 1.2.4.2 
      1 /*	$NetBSD: fopsmapper.c,v 1.2.4.2 2020/04/13 08:05:11 martin 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 1.2.4.2 2020/04/13 08:05:11 martin Exp $");
     31 
     32 #include <sys/module.h>
     33 #include <sys/param.h>
     34 #include <sys/systm.h>
     35 #include <sys/kernel.h>
     36 
     37 #include <sys/conf.h>
     38 #include <sys/file.h>
     39 #include <sys/filedesc.h>
     40 #include <sys/kmem.h>
     41 #include <sys/mman.h>
     42 #include <sys/mutex.h>
     43 #include <uvm/uvm_extern.h>
     44 
     45 /*
     46  * To use this module you need to:
     47  *
     48  * mknod /dev/fopsmapper c 351 0
     49  *
     50  */
     51 
     52 dev_type_open(fopsmapper_open);
     53 
     54 const struct cdevsw fopsmapper_cdevsw = {
     55 	.d_open = fopsmapper_open,
     56 	.d_close = noclose,
     57 	.d_read = noread,
     58 	.d_write = nowrite,
     59 	.d_ioctl = noioctl,
     60 	.d_stop = nostop,
     61 	.d_tty = notty,
     62 	.d_poll = nopoll,
     63 	.d_mmap = nommap,
     64 	.d_kqfilter = nokqfilter,
     65 	.d_discard = nodiscard,
     66 	.d_flag = D_OTHER
     67 };
     68 
     69 static int fopsmapper_mmap(file_t *, off_t *, size_t,
     70 	       	int, int *, int *,struct uvm_object **, int *);
     71 static int fopsmapper_close(file_t *);
     72 
     73 const struct fileops mapper_fileops = {
     74 	.fo_read = fbadop_read,
     75 	.fo_write = fbadop_write,
     76 	.fo_ioctl = fbadop_ioctl,
     77 	.fo_fcntl = fnullop_fcntl,
     78 	.fo_poll = fnullop_poll,
     79 	.fo_stat = fbadop_stat,
     80 	.fo_close = fopsmapper_close,
     81 	.fo_kqfilter = fnullop_kqfilter,
     82 	.fo_restart = fnullop_restart,
     83 	.fo_mmap = fopsmapper_mmap,
     84 };
     85 
     86 typedef struct fopsmapper_softc {
     87 	char *buf;
     88 	struct uvm_object *uobj;
     89 	size_t bufsize;
     90 } fops_t;
     91 
     92 int
     93 fopsmapper_open(dev_t dev, int flag, int mode, struct lwp *l)
     94 {
     95 	fops_t *fo;
     96 	struct file *fp;
     97 	int fd, error;
     98 
     99 	if ((error = fd_allocfile(&fp, &fd)) != 0)
    100 		return error;
    101 
    102 	fo = kmem_zalloc(sizeof(*fo), KM_SLEEP);
    103 
    104 	return fd_clone(fp, fd, flag, &mapper_fileops, fo);
    105 }
    106 
    107 int
    108 fopsmapper_mmap(file_t * fp, off_t * offp, size_t size, int prot,
    109 		int *flagsp, int *advicep, struct uvm_object **uobjp,
    110 		int *maxprotp)
    111 {
    112 	fops_t *fo;
    113 	int error;
    114 
    115 	if (prot & PROT_EXEC)
    116 		return EACCES;
    117 
    118 	if (size != (size_t)PAGE_SIZE)
    119 		return EINVAL;
    120 
    121 	if ((fo = fp->f_data) == NULL)
    122 		return ENXIO;
    123 
    124 	fo->bufsize = size;
    125 	fo->uobj = uao_create(size, 0);
    126 
    127 	fo->buf = NULL;
    128 	/* Map the uvm object into kernel */
    129 	error =	uvm_map(kernel_map, (vaddr_t *) &fo->buf, fo->bufsize,
    130 	                fo->uobj, 0, 0,
    131 	                UVM_MAPFLAG(UVM_PROT_RW, UVM_PROT_RW,
    132 	                            UVM_INH_SHARE,UVM_ADV_RANDOM, 0));
    133 
    134 	if (error) {
    135 		uao_detach(fo->uobj);
    136 		return error;
    137 	}
    138 	snprintf(fo->buf, 13, "Hey There!");
    139 
    140 	/* Get the reference of uobj */
    141 	uao_reference(fo->uobj);
    142 
    143 	*uobjp = fo->uobj;
    144 	*maxprotp = prot;
    145 	*advicep = UVM_ADV_RANDOM;
    146 
    147 	return 0;
    148 }
    149 
    150 int
    151 fopsmapper_close(file_t * fp)
    152 {
    153 	fops_t *fo;
    154 
    155 	fo = fp->f_data;
    156 	KASSERT(fo != NULL);
    157 
    158 	if (fo->buf != NULL)
    159 		uvm_deallocate(kernel_map, (vaddr_t)fo->buf, fo->bufsize);
    160 
    161 	kmem_free(fo, sizeof(*fo));
    162 
    163 	return 0;
    164 }
    165 
    166 MODULE(MODULE_CLASS_MISC, fopsmapper, NULL);
    167 
    168 static int
    169 fopsmapper_modcmd(modcmd_t cmd, void *arg __unused)
    170 {
    171 	int cmajor = 351, bmajor = -1;
    172 
    173 	switch (cmd) {
    174 	case MODULE_CMD_INIT:
    175 		if (devsw_attach("fopsmapper", NULL, &bmajor,
    176 		    &fopsmapper_cdevsw, &cmajor))
    177 			return ENXIO;
    178 		return 0;
    179 	case MODULE_CMD_FINI:
    180 		return EBUSY;
    181 	default:
    182 		return ENOTTY;
    183 	}
    184 }
    185