ref: 229d7bb35315ade6f25d96071adfd6933a50015d
dir: /kern/dev.c/
#include "u.h"
#include "lib.h"
#include "dat.h"
#include "fns.h"
#include "error.h"
extern ulong kerndate;
void
mkqid(Qid *q, vlong path, ulong vers, int type)
{
q->type = type;
q->vers = vers;
q->path = path;
}
int
devno(int c, int user)
{
int i;
for(i = 0; devtab[i] != nil; i++) {
if(devtab[i]->dc == c)
return i;
}
if(user == 0)
panic("devno %C %#ux", c, c);
return -1;
}
void
devdir(Chan *c, Qid qid, char *n, vlong length, char *user, long perm, Dir *db)
{
db->name = n;
if(c->flag&CMSG)
qid.type |= QTMOUNT;
db->qid = qid;
db->type = devtab[c->type]->dc;
db->dev = c->dev;
db->mode = perm;
db->mode |= qid.type << 24;
db->atime = seconds();
db->mtime = kerndate;
db->length = length;
db->uid = user;
db->gid = eve;
db->muid = user;
}
/*
* (here, Devgen is the prototype; devgen is the function in dev.c.)
*
* a Devgen is expected to return the directory entry for ".."
* if you pass it s==DEVDOTDOT (-1). otherwise...
*
* there are two contradictory rules.
*
* (i) if c is a directory, a Devgen is expected to list its children
* as you iterate s.
*
* (ii) whether or not c is a directory, a Devgen is expected to list
* its siblings as you iterate s.
*
* devgen always returns the list of children in the root
* directory. thus it follows (i) when c is the root and (ii) otherwise.
* many other Devgens follow (i) when c is a directory and (ii) otherwise.
*
* devwalk assumes (i). it knows that devgen breaks (i)
* for children that are themselves directories, and explicitly catches them.
*
* devstat assumes (ii). if the Devgen in question follows (i)
* for this particular c, devstat will not find the necessary info.
* with our particular Devgen functions, this happens only for
* directories, so devstat makes something up, assuming
* c->name, c->qid, eve, DMDIR|0555.
*
* devdirread assumes (i). the callers have to make sure
* that the Devgen satisfies (i) for the chan being read.
*/
/*
* the zeroth element of the table MUST be the directory itself for ..
*/
int
devgen(Chan *c, char *name, Dirtab *tab, int ntab, int i, Dir *dp)
{
if(tab == 0)
return -1;
if(i == DEVDOTDOT){
/* nothing */
}else if(name){
for(i=1; i<ntab; i++)
if(strcmp(tab[i].name, name) == 0)
break;
if(i==ntab)
return -1;
tab += i;
}else{
/* skip over the first element, that for . itself */
i++;
if(i >= ntab)
return -1;
tab += i;
}
devdir(c, tab->qid, tab->name, tab->length, eve, tab->perm, dp);
return 1;
}
void
devreset(void)
{
}
void
devinit(void)
{
}
void
devshutdown(void)
{
}
Chan*
devattach(int tc, char *spec)
{
int n;
Chan *c;
char *buf;
c = newchan();
mkqid(&c->qid, 0, 0, QTDIR);
c->type = devno(tc, 0);
if(spec == nil)
spec = "";
n = 1+UTFmax+strlen(spec)+1;
buf = smalloc(n);
snprint(buf, n, "#%C%s", tc, spec);
c->path = newpath(buf);
free(buf);
return c;
}
Chan*
devclone(Chan *c)
{
Chan *nc;
if(c->flag & COPEN)
panic("clone of open file type %C", devtab[c->type]->dc);
nc = newchan();
nc->type = c->type;
nc->dev = c->dev;
nc->mode = c->mode;
nc->qid = c->qid;
nc->offset = c->offset;
nc->umh = nil;
nc->aux = c->aux;
nc->mqid = c->mqid;
return nc;
}
Walkqid*
devwalk(Chan *c, Chan *nc, char **name, int nname, Dirtab *tab, int ntab, Devgen *gen)
{
int i, j, alloc;
Walkqid *wq;
char *n;
Dir dir;
if(nname > 0)
isdir(c);
alloc = (nc == nil);
wq = smalloc(sizeof(Walkqid)+(nname-1)*sizeof(Qid));
if(waserror()){
if(alloc && wq->clone != nil)
cclose(wq->clone);
free(wq);
return nil;
}
if(alloc){
nc = devclone(c);
nc->type = 0; /* device doesn't know about this channel yet */
}
wq->clone = nc;
for(j=0; j<nname; j++){
if(!(nc->qid.type&QTDIR)){
if(j==0)
error(Enotdir);
goto Done;
}
n = name[j];
if(strcmp(n, ".") == 0){
Accept:
wq->qid[wq->nqid++] = nc->qid;
continue;
}
if(strcmp(n, "..") == 0){
if((*gen)(nc, nil, tab, ntab, DEVDOTDOT, &dir) != 1){
print("devgen walk .. in dev%s %llux broken\n",
devtab[nc->type]->name, nc->qid.path);
error("broken devgen");
}
nc->qid = dir.qid;
goto Accept;
}
/*
* Ugly problem: If we're using devgen, make sure we're
* walking the directory itself, represented by the first
* entry in the table, and not trying to step into a sub-
* directory of the table, e.g. /net/net. Devgen itself
* should take care of the problem, but it doesn't have
* the necessary information (that we're doing a walk).
*/
if(gen==devgen && nc->qid.path!=tab[0].qid.path)
goto Notfound;
for(i=0;; i++) {
switch((*gen)(nc, n, tab, ntab, i, &dir)){
case -1:
Notfound:
if(j == 0)
error(Enonexist);
kstrcpy(up->errstr, Enonexist, ERRMAX);
goto Done;
case 0:
continue;
case 1:
if(strcmp(n, dir.name) == 0){
nc->qid = dir.qid;
goto Accept;
}
continue;
}
}
}
/*
* We processed at least one name, so will return some data.
* If we didn't process all nname entries succesfully, we drop
* the cloned channel and return just the Qids of the walks.
*/
Done:
poperror();
if(wq->nqid < nname){
if(alloc)
cclose(wq->clone);
wq->clone = nil;
}else if(wq->clone != nil){
/* attach cloned channel to same device */
wq->clone->type = c->type;
}
return wq;
}
int
devstat(Chan *c, uchar *db, int n, Dirtab *tab, int ntab, Devgen *gen)
{
int i;
Dir dir;
char *p, *elem;
for(i=0;; i++){
switch((*gen)(c, nil, tab, ntab, i, &dir)){
case -1:
if(c->qid.type & QTDIR){
if(c->path == nil)
elem = "???";
else if(strcmp(c->path->s, "/") == 0)
elem = "/";
else
for(elem=p=c->path->s; *p; p++)
if(*p == '/')
elem = p+1;
devdir(c, c->qid, elem, 0, eve, DMDIR|0555, &dir);
n = convD2M(&dir, db, n);
if(n == 0)
error(Ebadarg);
return n;
}
error(Enonexist);
case 0:
break;
case 1:
if(c->qid.path == dir.qid.path) {
if(c->flag&CMSG)
dir.mode |= DMMOUNT;
n = convD2M(&dir, db, n);
if(n == 0)
error(Ebadarg);
return n;
}
break;
}
}
}
long
devdirread(Chan *c, char *d, long n, Dirtab *tab, int ntab, Devgen *gen)
{
long m, dsz;
Dir dir;
for(m=0; m<n; c->dri++) {
switch((*gen)(c, nil, tab, ntab, c->dri, &dir)){
case -1:
return m;
case 0:
break;
case 1:
dsz = convD2M(&dir, (uchar*)d, n-m);
if(dsz <= BIT16SZ){ /* <= not < because this isn't stat; read is stuck */
if(m == 0)
error(Eshort);
return m;
}
m += dsz;
d += dsz;
break;
}
}
return m;
}
/*
* error(Eperm) if open permission not granted for up->user.
*/
void
devpermcheck(char *fileuid, ulong perm, int omode)
{
ulong t;
static int access[] = { 0400, 0200, 0600, 0100 };
if(strcmp(up->user, fileuid) == 0)
perm <<= 0;
else
if(strcmp(up->user, eve) == 0)
perm <<= 3;
else
perm <<= 6;
t = access[omode&3];
if((t&perm) != t)
error(Eperm);
}
Chan*
devopen(Chan *c, int omode, Dirtab *tab, int ntab, Devgen *gen)
{
int i;
Dir dir;
for(i=0;; i++) {
switch((*gen)(c, nil, tab, ntab, i, &dir)){
case -1:
goto Return;
case 0:
break;
case 1:
if(c->qid.path == dir.qid.path) {
devpermcheck(dir.uid, dir.mode, omode);
goto Return;
}
break;
}
}
Return:
c->offset = 0;
if((c->qid.type&QTDIR) && omode!=OREAD)
error(Eperm);
c->mode = openmode(omode);
c->flag |= COPEN;
return c;
}
Chan*
devcreate(Chan *c, char *name, int mode, ulong perm)
{
USED(c);
USED(name);
USED(mode);
USED(perm);
error(Eperm);
return 0;
}
Block*
devbread(Chan *c, long n, ulong offset)
{
Block *bp;
bp = allocb(n);
if(bp == 0)
error(Enomem);
if(waserror()) {
freeb(bp);
nexterror();
}
bp->wp += devtab[c->type]->read(c, bp->wp, n, offset);
poperror();
return bp;
}
long
devbwrite(Chan *c, Block *bp, ulong offset)
{
long n;
if(waserror()) {
freeb(bp);
nexterror();
}
n = devtab[c->type]->write(c, bp->rp, BLEN(bp), offset);
poperror();
freeb(bp);
return n;
}
void
devremove(Chan *c)
{
USED(c);
error(Eperm);
}
int
devwstat(Chan *c, uchar *a, int n)
{
USED(c);
USED(a);
USED(n);
error(Eperm);
return 0;
}
void
devpower(int a)
{
USED(a);
error(Eperm);
}
int
devconfig(int a, char *b, DevConf *c)
{
USED(a);
USED(b);
USED(c);
error(Eperm);
return 0;
}