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Extensively rework the geom_bsd method, put a lot of comments in, betting

Browse Source 
that this will make people use this for their future copy&paste operations.

Rework the detection of raw-disk offsets in disklabels.  This actually
unearthed a number of bugs in the (now) previous version.

Also accept labels which don't have a magic RAW_PART, provided they don't
confuse us too much.

Change the order of our sanity-checks on labels found on disks to be more
robust.

Check against MAXPARTITIONS in our sanity-check and reject disklabels
we cannot cope with.

Create new g_bsd_modify() function to implment disklabel modifying
ioctls.

Implement DIOCSDINFO and DIOCWDINFO with the provision that the latter
still not writes your change back to disk.  I didn't have the nerves
for that yet.

In the start routine, use g_call_me() for complex ioctls to prevent
sleeping.

Sponsored by:   DARPA & NAI Labs.
This commit is contained in:
Poul-Henning Kamp 2002-09-27 21:54:37 +00:00
parent 5a6baf5457
commit 3d3816e633
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=104065
1 changed files with 424 additions and 104 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

528
sys/geom/geom_bsd.c
View File

@ -33,9 +33,12 @@
* SUCH DAMAGE.
*
* $FreeBSD$
*
* This is the method for dealing with BSD disklabels. It has been
* extensively (by my standards at least) commented, in the vain hope that
* it will server as the source in future copy&paste operations.
*/
#include <sys/param.h>
#ifndef _KERNEL
#include <stdio.h>
@ -60,12 +63,26 @@
#define BSD_CLASS_NAME "BSD"
/*
* Our private data about one instance. All the rest is handled by the
* slice code and stored in the its softc, so this is just the stuff
* specific to BSD disklabels.
*/
struct g_bsd_softc {
off_t labeloffset;
off_t rawoffset;
struct disklabel ondisk;
struct disklabel inram;
};
/*
* The next 4 functions isolate us from how the compiler lays out and pads
* "struct disklabel". We treat what we read from disk as a bytestream and
* explicitly convert it into a struct disklabel. This makes us compiler-
* endianes- and wordsize- agnostic.
* For now we only have little-endian formats to deal with.
*/
static void
g_bsd_ledec_partition(u_char *ptr, struct partition *d)
{
@ -181,28 +198,203 @@ g_bsd_leenc_disklabel(u_char *ptr, struct disklabel *d)
#endif
/*
* For reasons which were valid and just in their days, FreeBSD/i386 uses
* absolute disk-addresses in disklabels. The way it works is that the
* p_offset field of all partitions have the first sector number of the
* disk slice added to them. This was hidden kernel-magic, userland did
* not see these offsets. These two functions subtract and add them
* while converting from the "ondisk" to the "inram" labels and vice
* versa.
*/
static void
ondisk2inram(struct g_bsd_softc *sc)
{
struct partition *ppp;
unsigned offset;
struct disklabel *dl;
int i;
sc->inram = sc->ondisk;
offset = sc->inram.d_partitions[RAW_PART].p_offset;
for (i = 0; i < 8; i++) {
ppp = &sc->inram.d_partitions[i];
if (ppp->p_offset >= offset)
ppp->p_offset -= offset;
dl= &sc->inram;
/* Basic sanity-check needed to avoid mistakes */
if (dl->d_magic != DISKMAGIC || dl->d_magic2 != DISKMAGIC)
return;
if (dl->d_npartitions > MAXPARTITIONS)
return;
sc->rawoffset = dl->d_partitions[RAW_PART].p_offset;
for (i = 0; i < dl->d_npartitions; i++) {
ppp = &dl->d_partitions[i];
if (ppp->p_size != 0 && ppp->p_offset < sc->rawoffset)
sc->rawoffset = 0;
}
sc->inram.d_checksum = 0;
sc->inram.d_checksum = dkcksum(&sc->inram);
if (sc->rawoffset > 0) {
if (dl->d_partitions[RAW_PART].p_size +
sc->rawoffset == dl->d_secperunit) {
}
for (i = 0; i < dl->d_npartitions; i++) {
ppp = &dl->d_partitions[i];
ppp->p_offset -= sc->rawoffset;
}
}
dl->d_checksum = 0;
dl->d_checksum = dkcksum(&sc->inram);
}
static void
inram2ondisk(struct g_bsd_softc *sc)
{
struct partition *ppp;
int i;
sc->ondisk = sc->inram;
if (sc->rawoffset != 0) {
for (i = 0; i < sc->inram.d_npartitions; i++) {
ppp = &sc->ondisk.d_partitions[i];
ppp->p_offset += sc->rawoffset;
}
}
sc->ondisk.d_checksum = 0;
sc->ondisk.d_checksum = dkcksum(&sc->ondisk);
}
/*
* It is rather fortunate that this checksum only covers up to the
* actual end of actual data, otherwise the pointer-screwup in
* alpha architectures would have been much harder to handle.
* Check that this looks like a valid disklabel, but be prepared
* to get any kind of junk. The checksum must be checked only
* after this function returns success to prevent a bogus d_npartitions
* value from tripping us up.
*/
static int
g_bsd_checklabel(struct disklabel *dl)
{
struct partition *ppp;
int i;
if (dl->d_magic != DISKMAGIC || dl->d_magic2 != DISKMAGIC)
return(EINVAL);
/*
* If the label specifies more partitions than we can handle
* we have to reject it: If people updated the label they would
* trash it, and that would break the checksum.
*/
if (dl->d_npartitions > MAXPARTITIONS)
return(EINVAL);
for (i = 0; i < dl->d_npartitions; i++) {
ppp = &dl->d_partitions[i];
/* Cannot extend past unit */
if (ppp->p_size != 0 &&
ppp->p_offset + ppp->p_size > dl->d_secperunit) {
return(EINVAL);
}
}
return(0);
}
/*
* Modify our slicer to match proposed disklabel, if possible.
* First carry out all the simple checks, then lock topology
* and check that no open providers are affected negatively
* then carry out all the changes.
*
* NB: Returns with topology held only if successful return.
*/
static int
g_bsd_modify(struct g_geom *gp, struct disklabel *dl)
{
int i, error;
struct partition *ppp;
struct g_slicer *gsp;
struct g_consumer *cp;
u_int secsize;
off_t mediasize;
/* Basic check that this is indeed a disklabel */
error = g_bsd_checklabel(dl);
if (error)
return(error);
/* Make sure the checksum is OK */
if (dkcksum(dl) != 0)
return(EINVAL);
/* Get dimensions of our device */
cp = LIST_FIRST(&gp->consumer);
error = g_getattr("GEOM::sectorsize", cp, &secsize);
if (error)
return(error);
error = g_getattr("GEOM::mediasize", cp, &mediasize);
if (error)
return(error);
#ifdef nolonger
/*
* The raw-partition must start at zero. We do not check that the
* size == mediasize because this is overly restrictive. We have
* already tested in g_bsd_checklabel() that it is not longer.
* XXX: RAW_PART is archaic anyway, and we should drop it.
*/
if (dl->d_partitions[RAW_PART].p_offset != 0)
return (EINVAL);
#endif
#ifdef notyet
/*
* Indications are that the d_secperunit is not correctly
* initialized in many cases, and since we don't need it
* for anything, we dont strictly need this test.
* Preemptive action to avoid confusing people in disklabel(8)
* may be in order.
*/
/* The label cannot claim a larger size than the media */
if ((off_t)dl->d_secperunit * dl->d_secsize > mediasize)
return (EINVAL);
#endif
/* ... or a smaller sector size */
if (dl->d_secsize < secsize)
return (EINVAL);
/* ... or a non-multiple sector size */
if (dl->d_secsize % secsize != 0)
return (EINVAL);
g_topology_lock();
/* Don't munge open parititions */
gsp = gp->softc;
for (i = 0; i < dl->d_npartitions; i++) {
ppp = &dl->d_partitions[i];
error = g_slice_config(gp, i, G_SLICE_CONFIG_CHECK,
(off_t)ppp->p_offset * dl->d_secsize,
(off_t)ppp->p_size * dl->d_secsize,
"%s%c", gp->name, 'a' + i);
if (error) {
g_topology_unlock();
return (error);
}
}
/* Look good, go for it... */
for (i = 0; i < gsp->nslice; i++) {
ppp = &dl->d_partitions[i];
g_slice_config(gp, i, G_SLICE_CONFIG_SET,
(off_t)ppp->p_offset * dl->d_secsize,
(off_t)ppp->p_size * dl->d_secsize,
"%s%c", gp->name, 'a' + i);
}
return (0);
}
/*
* Calculate a disklabel checksum for a little-endian byte-stream.
* We need access to the decoded disklabel because the checksum only
* covers the partition data for the first d_npartitions.
*/
static int
g_bsd_lesum(struct disklabel *dl, u_char *p)
@ -219,6 +411,13 @@ g_bsd_lesum(struct disklabel *dl, u_char *p)
return (sum);
}
/*
* This is an internal helper function, called multiple times from the taste
* function to try to locate a disklabel on the disk. More civilized formats
* will not need this, as there is only one possible place on disk to look
* for the magic spot.
*/
static int
g_bsd_try(struct g_slicer *gsp, struct g_consumer *cp, int secsize, struct g_bsd_softc *ms, off_t offset)
{
@ -227,26 +426,100 @@ g_bsd_try(struct g_slicer *gsp, struct g_consumer *cp, int secsize, struct g_bsd
struct disklabel *dl;
off_t secoff;
dl = &ms->ondisk;
/*
* We need to read entire aligned sectors, and we assume that the
* disklabel does not span sectors, so one sector is enough.
*/
error = 0;
secoff = offset % secsize;
buf = g_read_data(cp, offset - secoff, secsize, &error);
if (buf == NULL || error != 0)
return(ENOENT);
/* Decode into our native format */
dl = &ms->ondisk;
g_bsd_ledec_disklabel(buf + secoff, dl);
if (dl->d_magic == DISKMAGIC &&
dl->d_magic2 == DISKMAGIC &&
g_bsd_lesum(dl, buf + secoff) == 0)
error = 0;
else
ondisk2inram(ms);
dl = &ms->inram;
/* Does it look like a label at all ? */
if (g_bsd_checklabel(dl))
error = ENOENT;
/* ... and does the raw data have a good checksum ? */
if (error == 0 && g_bsd_lesum(dl, buf + secoff) != 0)
error = ENOENT;
/* Remember to free the buffer g_read_data() gave us */
g_free(buf);
/* If we had a label, record it properly */
if (error == 0) {
gsp->frontstuff = 16 * secsize;
gsp->frontstuff = 16 * secsize; /* XXX */
ms->labeloffset = offset;
}
return(error);
}
/*
* Implement certain ioctls to modify disklabels with. This function
* is called by the event handler thread with topology locked as result
* of the g_call_me() in g_bsd_start(). It is not necessary to keep
* topology locked all the time but make sure to return with topology
* locked as well.
*/
static void
g_bsd_ioctl(void *arg)
{
struct bio *bp;
struct g_geom *gp;
struct g_slicer *gsp;
struct g_bsd_softc *ms;
struct disklabel *dl;
struct g_ioctl *gio;
/* We don't need topology for now */
g_topology_unlock();
/* Get hold of the interesting bits from the bio */
bp = arg;
gp = bp->bio_to->geom;
gsp = gp->softc;
ms = gsp->softc;
gio = (struct g_ioctl *)bp->bio_data;
/* The disklabel to set is the ioctl argument */
dl = gio->data;
/* Validate and modify our slice instance to match */
bp->bio_error = g_bsd_modify(gp, dl); /* picks up topology lock */
if (bp->bio_error != 0) {
g_topology_lock();
g_io_deliver(bp);
return;
}
/* Update our copy of the disklabel */
ms->inram = *dl;
inram2ondisk(ms);
/* XXX: DIOCWDINFO write to disk */
/* return the request */
g_io_deliver(bp);
}
/*-
* This start routine is only called for non-trivial requests, all the
* trivial ones are handled autonomously by the slice code.
* For requests we handle here, we must call the g_io_deliver() on the
* bio, and return non-zero to indicate to the slice code that we did so.
* This code executes in the "DOWN" I/O path, this means:
* * No sleeping.
* * Don't grab the topology lock.
* * Don't call biowait, g_getattr(), g_setattr() or g_read_data()
*/
static int
g_bsd_start(struct bio *bp)
{
@ -254,26 +527,55 @@ g_bsd_start(struct bio *bp)
struct g_bsd_softc *ms;
struct g_slicer *gsp;
struct g_ioctl *gio;
int error;
gp = bp->bio_to->geom;
gsp = gp->softc;
ms = gsp->softc;
/* We only handle ioctl(2) requests of the right format. */
if (strcmp(bp->bio_attribute, "GEOM::ioctl"))
return(0);
else if (bp->bio_length != sizeof *gio)
return(0);
/* Get hold of the ioctl parameters */
gio = (struct g_ioctl *)bp->bio_data;
if (gio->cmd == DIOCGDINFO) {
switch(gio->cmd) {
case DIOCGDINFO:
/* Return a copy of the disklabel to userland */
bcopy(&ms->inram, gio->data, sizeof ms->inram);
bp->bio_error = 0;
g_io_deliver(bp);
return (1);
case DIOCSDINFO:
case DIOCWDINFO:
/*
* These we cannot do without the topology lock and some
* some I/O requests. Ask the event-handler to schedule
* us in a less restricted environment.
*/
error = g_call_me(g_bsd_ioctl, bp);
if (error)
g_io_fail(bp, error);
/*
* We must return non-zero to indicate that we will deal
* with this bio, even though we have not done so yet.
*/
return (1);
default:
return (0);
}
return (0);
}
/*
* Dump configuration information in XML format.
* Notice that the function is called once for the geom and once for each
* consumer and provider. We let g_slice_dumpconf() do most of the work.
*/
static void
g_bsd_dumpconf(struct sbuf *sb, char *indent, struct g_geom *gp, struct g_consumer *cp __unused, struct g_provider *pp)
g_bsd_dumpconf(struct sbuf *sb, char *indent, struct g_geom *gp, struct g_consumer *cp, struct g_provider *pp)
{
struct g_bsd_softc *ms;
struct g_slicer *gsp;
@ -287,125 +589,143 @@ g_bsd_dumpconf(struct sbuf *sb, char *indent, struct g_geom *gp, struct g_consum
g_slice_dumpconf(sb, indent, gp, cp, pp);
}
/*
* The taste function is called from the event-handler, with the topology
* lock already held and a provider to examine. The flags are unused.
*
* If flags == G_TF_NORMAL, the idea is to take a bite of the provider and
* if we find valid, consistent magic on it, build a geom on it.
* any magic bits which indicate that we should automatically put a BSD
* geom on it.
*
* There may be cases where the operator would like to put a BSD-geom on
* providers which do not meet all of the requirements. This can be done
* by instead passing the G_TF_INSIST flag, which will override these
* checks.
*
* The final flags value is G_TF_TRANSPARENT, which instructs the method
* to put a geom on top of the provider and configure it to be as transparent
* as possible. This is not really relevant to the BSD method and therefore
* not implemented here.
*/
static struct g_geom *
g_bsd_taste(struct g_class *mp, struct g_provider *pp, int flags)
{
struct g_geom *gp;
struct g_consumer *cp;
struct g_provider *pp2;
int error, i, j, npart;
int error, i;
struct g_bsd_softc *ms;
struct disklabel *dl;
u_int secsize;
u_int fwsectors, fwheads;
off_t mediasize;
struct partition *ppp, *ppr;
struct g_slicer *gsp;
g_trace(G_T_TOPOLOGY, "bsd_taste(%s,%s)", mp->name, pp->name);
g_topology_assert();
/* We don't implement transparent inserts */
if (flags == G_TF_TRANSPARENT)
return (NULL);
/*
* The BSD-method will not automatically configure itself recursively
* Note that it is legal to examine the class-name of our provider,
* nothing else should ever be examined inside the provider.
*/
if (flags == G_TF_NORMAL &&
!strcmp(pp->geom->class->name, BSD_CLASS_NAME))
return (NULL);
gp = g_slice_new(mp, 8, pp, &cp, &ms, sizeof *ms, g_bsd_start);
/*
* BSD labels are a subclass of the general "slicing" topology so
* a lot of the work can be done by the common "slice" code.
* Create a geom with space for MAXPARTITIONS providers, one consumer
* and a softc structure for us. Specify the provider to attach
* the consumer to and our "start" routine for special requests.
* The provider is opened with mode (1,0,0) so we can do reads
* from it.
*/
gp = g_slice_new(mp, MAXPARTITIONS, pp, &cp, &ms,
sizeof *ms, g_bsd_start);
if (gp == NULL)
return (NULL);
gsp = gp->softc;
/*
* Now that we have attached to and opened our provider, we do
* not need the topology lock until we change the topology again
* next time.
*/
g_topology_unlock();
/*
* Fill in the optional details, in our case we have a dumpconf
* routine which the "slice" code should call at the right time
*/
gp->dumpconf = g_bsd_dumpconf;
npart = 0;
while (1) { /* a trick to allow us to use break */
/* Get the geom_slicer softc from the geom */
gsp = gp->softc;
/*
* The do...while loop here allows us to have multiple escapes
* using a simple "break". This improves code clarity without
* ending up in deep nesting and without using goto or come from.
*/
do {
/*
* If the provider is an MBR we will only auto attach
* to type 165 slices in the G_TF_NORMAL case. We will
* attach to any other type (BSD was handles above)
*/
error = g_getattr("MBR::type", cp, &i);
if (!error && i != 165 && flags == G_TF_NORMAL)
break;
/* Get sector size, we need it to read data. */
error = g_getattr("GEOM::sectorsize", cp, &secsize);
if (error) {
secsize = 512;
printf("g_bsd_taste: error %d Sectors are %d bytes\n",
error, secsize);
}
error = g_getattr("GEOM::mediasize", cp, &mediasize);
if (error) {
mediasize = 0;
printf("g_error %d Mediasize is %lld bytes\n",
error, (long long)mediasize);
}
if (error || secsize < 512)
break;
/* First look for a label at the start of the second sector */
error = g_bsd_try(gsp, cp, secsize, ms, secsize);
/* Next, loot for it 64 bytes into the first sector */
if (error)
error = g_bsd_try(gsp, cp, secsize, ms, 64);
/* If we didn't find a label, punt */
if (error)
break;
dl = &ms->ondisk;
if (bootverbose)
g_hexdump(dl, sizeof(*dl));
if (dl->d_secsize < secsize)
break;
if (dl->d_secsize > secsize)
secsize = dl->d_secsize;
ppr = &dl->d_partitions[2];
for (i = 0; i < 8; i++) {
ppp = &dl->d_partitions[i];
if (ppp->p_size == 0)
continue;
npart++;
g_topology_lock();
pp2 = g_slice_addslice(gp, i,
((off_t)(ppp->p_offset - ppr->p_offset)) << 9ULL,
((off_t)ppp->p_size) << 9ULL,
"%s%c", pp->name, 'a' + i);
/*
* Proccess the found disklabel, and modify our "slice"
* instance to match it, if possible.
*/
dl = &ms->inram;
error = g_bsd_modify(gp, dl); /* picks up topology lock */
if (!error)
g_topology_unlock();
g_error_provider(pp2, 0);
}
ondisk2inram(ms);
break;
}
if (npart == 0 && (
(flags == G_TF_INSIST && mediasize != 0) ||
(flags == G_TF_TRANSPARENT))) {
dl = &ms->ondisk;
bzero(dl, sizeof *dl);
dl->d_magic = DISKMAGIC;
dl->d_magic2 = DISKMAGIC;
ppp = &dl->d_partitions[RAW_PART];
ppp->p_offset = 0;
ppp->p_size = mediasize / secsize;
dl->d_npartitions = MAXPARTITIONS;
dl->d_interleave = 1;
dl->d_secsize = secsize;
dl->d_rpm = 3600;
j = sizeof fwsectors;
error = g_io_getattr("GEOM::fwsectors", cp, &j, &fwsectors);
if (error)
dl->d_nsectors = 32;
else
dl->d_nsectors = fwsectors;
error = g_io_getattr("GEOM::fwheads", cp, &j, &fwheads);
if (error)
dl->d_ntracks = 64;
else
dl->d_ntracks = fwheads;
dl->d_secpercyl = dl->d_nsectors * dl->d_ntracks;
dl->d_ncylinders = ppp->p_size / dl->d_secpercyl;
dl->d_secperunit = ppp->p_size;
dl->d_checksum = 0;
dl->d_checksum = dkcksum(dl);
ms->inram = ms->ondisk;
g_topology_lock();
pp2 = g_slice_addslice(gp, RAW_PART,
0, mediasize, "%s%c", pp->name, 'a' + RAW_PART);
g_topology_unlock();
g_error_provider(pp2, 0);
npart = 1;
}
} while (0);
/* Success of failure, we can close our provider now */
g_topology_lock();
error = g_access_rel(cp, -1, 0, 0);
if (npart > 0)
/* If we have configured any providers, return the new geom. */
if (gsp->nprovider > 0)
return (gp);
/*
* ...else push the "self-destruct" button, by spoiling our own
* consumer. This triggers a call to g_std_spoiled which will
* dismantle what was setup.
*/
g_std_spoiled(cp);
return (NULL);
}
static struct g_class g_bsd_class = {
/* Finally, register with GEOM infrastructure. */
static struct g_class g_bsd_class = {
BSD_CLASS_NAME,
g_bsd_taste,
NULL,