devsd.c

在x86平台上运行不可信任代码的sandbox。

/*
 * Storage Device.
 */
#include "u.h"
#include "lib.h"
#include "mem.h"
#include "dat.h"
#include "fns.h"
#include "io.h"
#include "ureg.h"
#include "error.h"

#include "sd.h"

extern Dev sddevtab;
extern SDifc* sdifc[];

static char Echange[] = "media or partition has changed";

static char devletters[] = "0123456789"
	"abcdefghijklmnopqrstuvwxyz"
	"ABCDEFGHIJKLMNOPQRSTUVWXYZ";

static SDev *devs[sizeof devletters-1];
static QLock devslock;

enum {
	Rawcmd,
	Rawdata,
	Rawstatus,
};

enum {
	Qtopdir		= 1,		/* top level directory */
	Qtopbase,
	Qtopctl		 = Qtopbase,

	Qunitdir,			/* directory per unit */
	Qunitbase,
	Qctl		= Qunitbase,
	Qraw,
	Qpart,

	TypeLOG		= 4,
	NType		= (1<<TypeLOG),
	TypeMASK	= (NType-1),
	TypeSHIFT	= 0,

	PartLOG		= 8,
	NPart		= (1<<PartLOG),
	PartMASK	= (NPart-1),
	PartSHIFT	= TypeLOG,

	UnitLOG		= 8,
	NUnit		= (1<<UnitLOG),
	UnitMASK	= (NUnit-1),
	UnitSHIFT	= (PartLOG+TypeLOG),

	DevLOG		= 8,
	NDev		= (1 << DevLOG),
	DevMASK		= (NDev-1),
	DevSHIFT	 = (UnitLOG+PartLOG+TypeLOG),

	Ncmd = 20,
};

#define TYPE(q)		((((ulong)(q).path)>>TypeSHIFT) & TypeMASK)
#define PART(q)		((((ulong)(q).path)>>PartSHIFT) & PartMASK)
#define UNIT(q)		((((ulong)(q).path)>>UnitSHIFT) & UnitMASK)
#define DEV(q)		((((ulong)(q).path)>>DevSHIFT) & DevMASK)
#define QID(d,u, p, t)	(((d)<<DevSHIFT)|((u)<<UnitSHIFT)|\
					 ((p)<<PartSHIFT)|((t)<<TypeSHIFT))


static void
sdaddpart(SDunit* unit, char* name, uvlong start, uvlong end)
{
	SDpart *pp;
	int i, partno;

	/*
	 * Check name not already used
	 * and look for a free slot.
	 */
	if(unit->part != nil){
		partno = -1;
		for(i = 0; i < unit->npart; i++){
			pp = &unit->part[i];
			if(!pp->valid){
				if(partno == -1)
					partno = i;
				break;
			}
			if(strcmp(name, pp->perm.name) == 0){
				if(pp->start == start && pp->end == end)
					return;
				error(Ebadctl);
			}
		}
	}
	else{
		if((unit->part = malloc(sizeof(SDpart)*SDnpart)) == nil)
			error(Enomem);
		unit->npart = SDnpart;
		partno = 0;
	}

	/*
	 * If no free slot found then increase the
	 * array size (can't get here with unit->part == nil).
	 */
	if(partno == -1){
		if(unit->npart >= NPart)
			error(Enomem);
		if((pp = malloc(sizeof(SDpart)*(unit->npart+SDnpart))) == nil)
			error(Enomem);
		memmove(pp, unit->part, sizeof(SDpart)*unit->npart);
		free(unit->part);
		unit->part = pp;
		partno = unit->npart;
		unit->npart += SDnpart;
	}

	/*
	 * Check size and extent are valid.
	 */
	if(start > end || end > unit->sectors)
		error(Eio);
	pp = &unit->part[partno];
	pp->start = start;
	pp->end = end;
	kstrdup(&pp->perm.name, name);
	kstrdup(&pp->perm.user, eve);
	pp->perm.perm = 0640;
	pp->valid = 1;
}

static void
sddelpart(SDunit* unit, char* name)
{
	int i;
	SDpart *pp;

	/*
	 * Look for the partition to delete.
	 * Can't delete if someone still has it open.
	 */
	pp = unit->part;
	for(i = 0; i < unit->npart; i++){
		if(strcmp(name, pp->perm.name) == 0)
			break;
		pp++;
	}
	if(i >= unit->npart)
		error(Ebadctl);
	if(strcmp(up->user, pp->perm.user) && !iseve())
		error(Eperm);
	pp->valid = 0;
	pp->vers++;
}

static void
sdincvers(SDunit *unit)
{
	int i;

	unit->vers++;
	if(unit->part){
		for(i = 0; i < unit->npart; i++){
			unit->part[i].valid = 0;
			unit->part[i].vers++;
		}
	}
}

static int
sdinitpart(SDunit* unit)
{
	if(unit->sectors > 0){
		unit->sectors = unit->secsize = 0;
		sdincvers(unit);
	}

	if(unit->inquiry[0] & 0xC0)
		return 0;
	switch(unit->inquiry[0] & 0x1F){
	case 0x00:			/* DA */
	case 0x04:			/* WORM */
	case 0x05:			/* CD-ROM */
	case 0x07:			/* MO */
		break;
	default:
		return 0;
	}

	if(unit->dev->ifc->online)
		unit->dev->ifc->online(unit);
	if(unit->sectors){
		sdincvers(unit);
		sdaddpart(unit, "data", 0, unit->sectors);
#if 0
		/*
		 * Use partitions passed from boot program,
		 * e.g.
		 *	sdC0part=dos 63 123123/plan9 123123 456456
		 * This happens before /boot sets hostname so the
		 * partitions will have the null-string for user.
		 * The gen functions patch it up.
		 */
		snprint(buf, sizeof buf, "%spart", unit->perm.name);
		for(p = getconf(buf); p != nil; p = q){
			if(q = strchr(p, '/'))
				*q++ = '\0';
			nf = tokenize(p, f, nelem(f));
			if(nf < 3)
				continue;

			start = strtoull(f[1], 0, 0);
			end = strtoull(f[2], 0, 0);
			if(!waserror()){
				sdaddpart(unit, f[0], start, end);
				poperror();
			}
		}
#endif
	}

	return 1;
}

static int
sdindex(int idno)
{
	char *p;

	p = strchr(devletters, idno);
	if(p == nil)
		return -1;
	return p-devletters;
}

static SDev*
sdgetdev(int idno)
{
	SDev *sdev;
	int i;

	if((i = sdindex(idno)) < 0)
		return nil;

	qlock(&devslock);
	if((sdev = devs[i]))
		incref(&sdev->r);
	qunlock(&devslock);
	return sdev;
}

static SDunit*
sdgetunit(SDev* sdev, int subno)
{
	SDunit *unit;
	char buf[32];

	/*
	 * Associate a unit with a given device and sub-unit
	 * number on that device.
	 * The device will be probed if it has not already been
	 * successfully accessed.
	 */
	qlock(&sdev->unitlock);
	if(subno > sdev->nunit){
		qunlock(&sdev->unitlock);
		return nil;
	}

	unit = sdev->unit[subno];
	if(unit == nil){
		/*
		 * Probe the unit only once. This decision
		 * may be a little severe and reviewed later.
		 */
		if(sdev->unitflg[subno]){
			qunlock(&sdev->unitlock);
			return nil;
		}
		if((unit = malloc(sizeof(SDunit))) == nil){
			qunlock(&sdev->unitlock);
			return nil;
		}
		sdev->unitflg[subno] = 1;

		snprint(buf, sizeof(buf), "%s%d", sdev->name, subno);
		kstrdup(&unit->perm.name, buf);
		kstrdup(&unit->perm.user, eve);
		unit->perm.perm = 0555;
		unit->subno = subno;
		unit->dev = sdev;

		if(sdev->enabled == 0 && sdev->ifc->enable)
			sdev->ifc->enable(sdev);
		sdev->enabled = 1;

		/*
		 * No need to lock anything here as this is only
		 * called before the unit is made available in the
		 * sdunit[] array.
		 */
		if(unit->dev->ifc->verify(unit) == 0){
			qunlock(&sdev->unitlock);
			free(unit);
			return nil;
		}
		sdev->unit[subno] = unit;
	}
	qunlock(&sdev->unitlock);
	return unit;
}

static void
sdreset(void)
{
	int i;
	SDev *sdev;

	/*
	 * Probe all known controller types and register any devices found.
	 */
	for(i = 0; sdifc[i] != nil; i++){
		if(sdifc[i]->pnp == nil || (sdev = sdifc[i]->pnp()) == nil)
			continue;
		sdadddevs(sdev);
	}
}

void
sdadddevs(SDev *sdev)
{
	int i, j, id;
	SDev *next;

	for(; sdev; sdev=next){
		next = sdev->next;

		sdev->unit = (SDunit**)malloc(sdev->nunit * sizeof(SDunit*));
		sdev->unitflg = (int*)malloc(sdev->nunit * sizeof(int));
		if(sdev->unit == nil || sdev->unitflg == nil){
			print("sdadddevs: out of memory\n");
		giveup:
			free(sdev->unit);
			free(sdev->unitflg);
			if(sdev->ifc->clear)
				sdev->ifc->clear(sdev);
			free(sdev);
			continue;
		}
		id = sdindex(sdev->idno);
		if(id == -1){
			print("sdadddevs: bad id number %d (%C)\n", id, id);
			goto giveup;
		}
		qlock(&devslock);
		for(i=0; i<nelem(devs); i++){
			if(devs[j = (id+i)%nelem(devs)] == nil){
				sdev->idno = devletters[j];
				devs[j] = sdev;
				snprint(sdev->name, sizeof sdev->name, "sd%c", devletters[j]);
				break;
			}
		}
		qunlock(&devslock);
		if(i == nelem(devs)){
			print("sdadddevs: out of device letters\n");
			goto giveup;
		}
	}
}

// void
// sdrmdevs(SDev *sdev)
// {
// 	char buf[2];
//
// 	snprint(buf, sizeof buf, "%c", sdev->idno);
// 	unconfigure(buf);
// }

static int
sd2gen(Chan* c, int i, Dir* dp)
{
	Qid q;
	uvlong l;
	SDpart *pp;
	SDperm *perm;
	SDunit *unit;
	SDev *sdev;
	int rv;

	sdev = sdgetdev(DEV(c->qid));
	assert(sdev);
	unit = sdev->unit[UNIT(c->qid)];

	rv = -1;
	switch(i){
	case Qctl:
		mkqid(&q, QID(DEV(c->qid), UNIT(c->qid), PART(c->qid), Qctl),
			unit->vers, QTFILE);
		perm = &unit->ctlperm;
		if(emptystr(perm->user)){
			kstrdup(&perm->user, eve);
			perm->perm = 0640;
		}
		devdir(c, q, "ctl", 0, perm->user, perm->perm, dp);
		rv = 1;
		break;

	case Qraw:
		mkqid(&q, QID(DEV(c->qid), UNIT(c->qid), PART(c->qid), Qraw),
			unit->vers, QTFILE);
		perm = &unit->rawperm;
		if(emptystr(perm->user)){
			kstrdup(&perm->user, eve);
			perm->perm = DMEXCL|0600;
		}
		devdir(c, q, "raw", 0, perm->user, perm->perm, dp);
		rv = 1;
		break;

	case Qpart:
		pp = &unit->part[PART(c->qid)];
		l = (pp->end - pp->start) * unit->secsize;
		mkqid(&q, QID(DEV(c->qid), UNIT(c->qid), PART(c->qid), Qpart),
			unit->vers+pp->vers, QTFILE);
		if(emptystr(pp->perm.user))
			kstrdup(&pp->perm.user, eve);
		devdir(c, q, pp->perm.name, l, pp->perm.user, pp->perm.perm, dp);
		rv = 1;
		break;
	}

	decref(&sdev->r);
	return rv;
}

static int
sd1gen(Chan* c, int i, Dir* dp)
{
	Qid q;

	switch(i){
	case Qtopctl:
		mkqid(&q, QID(0, 0, 0, Qtopctl), 0, QTFILE);
		devdir(c, q, "sdctl", 0, eve, 0640, dp);
		return 1;
	}
	return -1;
}

static int
sdgen(Chan* c, char *name, Dirtab *dt, int j, int s, Dir* dp)
{
	Qid q;
	uvlong l;
	int i, r;
	SDpart *pp;
	SDunit *unit;
	SDev *sdev;

	switch(TYPE(c->qid)){
	case Qtopdir:
		if(s == DEVDOTDOT){
			mkqid(&q, QID(0, 0, 0, Qtopdir), 0, QTDIR);
			sprint(up->genbuf, "#%C", sddevtab.dc);
			devdir(c, q, up->genbuf, 0, eve, 0555, dp);
			return 1;
		}

		if(s+Qtopbase < Qunitdir)
			return sd1gen(c, s+Qtopbase, dp);
		s -= (Qunitdir-Qtopbase);

		qlock(&devslock);
		for(i=0; i<nelem(devs); i++){
			if(devs[i]){
				if(s < devs[i]->nunit)
					break;
				s -= devs[i]->nunit;
			}
		}

		if(i == nelem(devs)){
			/* Run off the end of the list */
			qunlock(&devslock);
			return -1;
		}

		if((sdev = devs[i]) == nil){
			qunlock(&devslock);
			return 0;
		}

		incref(&sdev->r);
		qunlock(&devslock);

		if((unit = sdev->unit[s]) == nil)
			if((unit = sdgetunit(sdev, s)) == nil){
				decref(&sdev->r);
				return 0;
			}

		mkqid(&q, QID(sdev->idno, s, 0, Qunitdir), 0, QTDIR);
		if(emptystr(unit->perm.user))
			kstrdup(&unit->perm.user, eve);
		devdir(c, q, unit->perm.name, 0, unit->perm.user, unit->perm.perm, dp);
		decref(&sdev->r);
		return 1;

	case Qunitdir:
		if(s == DEVDOTDOT){
			mkqid(&q, QID(0, 0, 0, Qtopdir), 0, QTDIR);
			sprint(up->genbuf, "#%C", sddevtab.dc);
			devdir(c, q, up->genbuf, 0, eve, 0555, dp);
			return 1;
		}

		if((sdev = sdgetdev(DEV(c->qid))) == nil){
			devdir(c, c->qid, "unavailable", 0, eve, 0, dp);
			return 1;
		}

		unit = sdev->unit[UNIT(c->qid)];
		qlock(&unit->ctl);

		/*
		 * Check for media change.
		 * If one has already been detected, sectors will be zero.
		 * If there is one waiting to be detected, online
		 * will return > 1.
		 * Online is a bit of a large hammer but does the job.
		 */
		if(unit->sectors == 0
		|| (unit->dev->ifc->online && unit->dev->ifc->online(unit) > 1))
			sdinitpart(unit);

		i = s+Qunitbase;
		if(i < Qpart){
			r = sd2gen(c, i, dp);
			qunlock(&unit->ctl);
			decref(&sdev->r);