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/*-
* SPDX-License-Identifier: BSD-2-Clause
*
* Copyright (c) 2005 Pawel Jakub Dawidek <pjd@FreeBSD.org>
* All rights reserved.
* Copyright (c) 2025 Mateusz Piotrowski <0mp@FreeBSD.org>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <sys/param.h>
#include <sys/bio.h>
#include <sys/kernel.h>
#include <sys/limits.h>
#include <sys/malloc.h>
#include <sys/queue.h>
#include <sys/sysctl.h>
#include <sys/systm.h>
#include <sys/uio.h>
#include <sys/types.h>
#include <geom/geom.h>
#define G_ZERO_CLASS_NAME "ZERO"
static int g_zero_byte_sysctl(SYSCTL_HANDLER_ARGS);
SYSCTL_DECL(_kern_geom);
static SYSCTL_NODE(_kern_geom, OID_AUTO, zero, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
"GEOM_ZERO stuff");
static int g_zero_clear = 1;
SYSCTL_INT(_kern_geom_zero, OID_AUTO, clear,
CTLFLAG_RWTUN, &g_zero_clear, 0,
"Clear read data buffer");
static int g_zero_byte = 0;
static uint8_t g_zero_buffer[PAGE_SIZE];
SYSCTL_PROC(_kern_geom_zero, OID_AUTO, byte,
CTLTYPE_INT | CTLFLAG_RWTUN | CTLFLAG_MPSAFE, &g_zero_byte, 0,
g_zero_byte_sysctl, "I",
"Byte (octet) value to clear the buffers with");
static struct g_provider *gpp;
static int
g_zero_byte_sysctl(SYSCTL_HANDLER_ARGS)
{
int error;
// XXX: Confirm that this is called on module load as well.
// XXX: Shouldn't we lock here to avoid changing the byte value if the
// driver is in the process of handling I/O?
error = sysctl_handle_int(oidp, &g_zero_byte, 0, req);
if (error != 0 || req->newptr == NULL)
return (error);
memset(g_zero_buffer, g_zero_byte, PAGE_SIZE);
return (0);
}
static void
g_zero_fill_pages(struct bio *bp)
{
struct iovec aiovec;
struct uio auio;
size_t length;
vm_offset_t offset;
aiovec.iov_base = g_zero_buffer;
aiovec.iov_len = PAGE_SIZE;
auio.uio_iov = &aiovec;
auio.uio_iovcnt = 1;
auio.uio_offset = 0;
auio.uio_segflg = UIO_SYSSPACE;
auio.uio_rw = UIO_WRITE;
auio.uio_td = curthread;
/*
* To handle the unmapped I/O request, we need to fill the pages in the
* bp->bio_ma array with the g_zero_byte value. However, instead of
* setting every byte individually, we use uiomove_fromphys() to fill a
* page at a time with g_zero_buffer.
*/
bp->bio_resid = bp->bio_length;
offset = bp->bio_ma_offset & PAGE_MASK;
for (int i = 0; i < bp->bio_ma_n && bp->bio_resid > 0; i++) {
length = MIN(PAGE_SIZE - offset, bp->bio_resid);
auio.uio_resid = length;
(void)uiomove_fromphys(&bp->bio_ma[i], offset, length, &auio);
offset = 0;
bp->bio_resid -= length;
}
}
static void
g_zero_start(struct bio *bp)
{
int error;
switch (bp->bio_cmd) {
case BIO_READ:
if (g_zero_clear) {
if ((bp->bio_flags & BIO_UNMAPPED) != 0)
g_zero_fill_pages(bp);
else
memset(bp->bio_data, g_zero_byte,
bp->bio_length);
}
/* FALLTHROUGH */
case BIO_DELETE:
case BIO_WRITE:
bp->bio_completed = bp->bio_length;
error = 0;
break;
case BIO_GETATTR:
default:
error = EOPNOTSUPP;
break;
}
g_io_deliver(bp, error);
}
static void
g_zero_init(struct g_class *mp)
{
struct g_geom *gp;
struct g_provider *pp;
g_topology_assert();
gp = g_new_geom(mp, "gzero");
gp->start = g_zero_start;
gp->access = g_std_access;
gpp = pp = g_new_providerf(gp, "%s", gp->name);
pp->flags |= G_PF_ACCEPT_UNMAPPED | G_PF_DIRECT_SEND |
G_PF_DIRECT_RECEIVE;
pp->mediasize = 1152921504606846976LLU;
pp->sectorsize = 512;
g_error_provider(pp, 0);
}
static int
g_zero_destroy_geom(struct gctl_req *req __unused, struct g_class *mp __unused,
struct g_geom *gp)
{
struct g_provider *pp;
g_topology_assert();
if (gp == NULL)
return (0);
pp = LIST_FIRST(&gp->provider);
if (pp == NULL)
return (0);
if (pp->acr > 0 || pp->acw > 0 || pp->ace > 0)
return (EBUSY);
gpp = NULL;
g_wither_geom(gp, ENXIO);
return (0);
}
static struct g_class g_zero_class = {
.name = G_ZERO_CLASS_NAME,
.version = G_VERSION,
.init = g_zero_init,
.destroy_geom = g_zero_destroy_geom
};
DECLARE_GEOM_CLASS(g_zero_class, g_zero);
MODULE_VERSION(geom_zero, 0);
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