ref: a85fefcc920f837ce3a8e0010cfd09cf0b3523ce
dir: /kern/devcons.c/
#include "u.h"
#include "lib.h"
#include "dat.h"
#include "fns.h"
#include "error.h"
#include "keyboard.h"
void (*consdebug)(void) = 0;
void (*screenputs)(char*, int) = 0;
Queue* kbdq; /* unprocessed console input */
Queue* lineq; /* processed console input */
Queue* serialoq; /* serial console output */
Queue* kprintoq; /* console output, for /dev/kprint */
long kprintinuse; /* test and set whether /dev/kprint is open */
int iprintscreenputs = 0;
int panicking;
struct
{
int exiting;
int machs;
} active;
static struct
{
QLock lk;
int raw; /* true if we shouldn't process input */
int ctl; /* number of opens to the control file */
int x; /* index into line */
char line[1024]; /* current input line */
int count;
int ctlpoff;
/* a place to save up characters at interrupt time before dumping them in the queue */
Lock lockputc;
char istage[1024];
char *iw;
char *ir;
char *ie;
} kbd = {
{ 0 },
0,
0,
0,
{ 0 },
0,
0,
{ 0 },
{ 0 },
kbd.istage,
kbd.istage,
kbd.istage + sizeof(kbd.istage),
};
char *sysname;
vlong fasthz;
static int readtime(ulong, char*, int);
static int readbintime(char*, int);
static int writetime(char*, int);
static int writebintime(char*, int);
enum
{
CMreboot,
CMpanic,
};
Cmdtab rebootmsg[] =
{
CMreboot, "reboot", 0,
CMpanic, "panic", 0,
};
int
return0(void *v)
{
return 0;
}
void
printinit(void)
{
lineq = qopen(2*1024, 0, 0, nil);
if(lineq == nil)
panic("printinit");
qnoblock(lineq, 1);
kbdq = qopen(4*1024, 0, 0, 0);
if(kbdq == nil)
panic("kbdinit");
qnoblock(kbdq, 1);
}
int
consactive(void)
{
if(serialoq)
return qlen(serialoq) > 0;
return 0;
}
void
prflush(void)
{
/*
ulong now;
now = m->ticks;
while(consactive())
if(m->ticks - now >= HZ)
break;
*/
}
/*
* Print a string on the console. Convert \n to \r\n for serial
* line consoles. Locking of the queues is left up to the screen
* or uart code. Multi-line messages to serial consoles may get
* interspersed with other messages.
*/
static void
putstrn0(char *str, int n, int usewrite)
{
/*
* if someone is reading /dev/kprint,
* put the message there.
* if not and there's an attached bit mapped display,
* put the message there.
*
* if there's a serial line being used as a console,
* put the message there.
*/
if(kprintoq != nil && !qisclosed(kprintoq)){
if(usewrite)
qwrite(kprintoq, str, n);
else
qiwrite(kprintoq, str, n);
}else if(screenputs != 0)
screenputs(str, n);
}
void
putstrn(char *str, int n)
{
putstrn0(str, n, 0);
}
int noprint;
int
print(char *fmt, ...)
{
int n;
va_list arg;
char buf[PRINTSIZE];
if(noprint)
return -1;
va_start(arg, fmt);
n = vseprint(buf, buf+sizeof(buf), fmt, arg) - buf;
va_end(arg);
putstrn(buf, n);
return n;
}
void
panic(char *fmt, ...)
{
int n;
va_list arg;
char buf[PRINTSIZE];
kprintoq = nil; /* don't try to write to /dev/kprint */
if(panicking)
for(;;);
panicking = 1;
splhi();
strcpy(buf, "panic: ");
va_start(arg, fmt);
n = vseprint(buf+strlen(buf), buf+sizeof(buf), fmt, arg) - buf;
va_end(arg);
buf[n] = '\n';
uartputs(buf, n+1);
if(consdebug)
(*consdebug)();
spllo();
prflush();
putstrn(buf, n+1);
dumpstack();
exit(1);
}
int
pprint(char *fmt, ...)
{
int n;
Chan *c;
va_list arg;
char buf[2*PRINTSIZE];
if(up == nil || up->fgrp == nil)
return 0;
c = up->fgrp->fd[2];
if(c==0 || (c->mode!=OWRITE && c->mode!=ORDWR))
return 0;
n = sprint(buf, "%s %lud: ", up->text, up->pid);
va_start(arg, fmt);
n = vseprint(buf+n, buf+sizeof(buf), fmt, arg) - buf;
va_end(arg);
if(waserror())
return 0;
devtab[c->type]->write(c, buf, n, c->offset);
poperror();
lock(&c->ref.lk);
c->offset += n;
unlock(&c->ref.lk);
return n;
}
static void
echoscreen(char *buf, int n)
{
char *e, *p;
char ebuf[128];
int x;
p = ebuf;
e = ebuf + sizeof(ebuf) - 4;
while(n-- > 0){
if(p >= e){
screenputs(ebuf, p - ebuf);
p = ebuf;
}
x = *buf++;
if(x == 0x15){
*p++ = '^';
*p++ = 'U';
*p++ = '\n';
} else
*p++ = x;
}
if(p != ebuf)
screenputs(ebuf, p - ebuf);
}
static void
echoserialoq(char *buf, int n)
{
char *e, *p;
char ebuf[128];
int x;
p = ebuf;
e = ebuf + sizeof(ebuf) - 4;
while(n-- > 0){
if(p >= e){
qiwrite(serialoq, ebuf, p - ebuf);
p = ebuf;
}
x = *buf++;
if(x == '\n'){
*p++ = '\r';
*p++ = '\n';
} else if(x == 0x15){
*p++ = '^';
*p++ = 'U';
*p++ = '\n';
} else
*p++ = x;
}
if(p != ebuf)
qiwrite(serialoq, ebuf, p - ebuf);
}
static void
echo(char *buf, int n)
{
static int ctrlt;
int x;
char *e, *p;
e = buf+n;
for(p = buf; p < e; p++){
switch(*p){
case 0x10: /* ^P */
if(cpuserver && !kbd.ctlpoff){
active.exiting = 1;
return;
}
break;
case 0x14: /* ^T */
ctrlt++;
if(ctrlt > 2)
ctrlt = 2;
continue;
}
if(ctrlt != 2)
continue;
/* ^T escapes */
ctrlt = 0;
switch(*p){
case 'S':
x = splhi();
dumpstack();
procdump();
splx(x);
return;
case 's':
dumpstack();
return;
case 'x':
xsummary();
ixsummary();
mallocsummary();
pagersummary();
return;
case 'd':
if(consdebug == 0)
consdebug = rdb;
else
consdebug = 0;
print("consdebug now 0x%p\n", consdebug);
return;
case 'D':
if(consdebug == 0)
consdebug = rdb;
consdebug();
return;
case 'p':
x = spllo();
procdump();
splx(x);
return;
case 'q':
scheddump();
return;
case 'k':
killbig();
return;
case 'r':
exit(0);
return;
}
}
qproduce(kbdq, buf, n);
if(kbd.raw)
return;
if(screenputs != 0)
echoscreen(buf, n);
if(serialoq)
echoserialoq(buf, n);
}
/*
* Called by a uart interrupt for console input.
*
* turn '\r' into '\n' before putting it into the queue.
*/
int
kbdcr2nl(Queue *q, int ch)
{
char *next;
USED(q);
ilock(&kbd.lockputc); /* just a mutex */
if(ch == '\r' && !kbd.raw)
ch = '\n';
next = kbd.iw+1;
if(next >= kbd.ie)
next = kbd.istage;
if(next != kbd.ir){
*kbd.iw = ch;
kbd.iw = next;
}
iunlock(&kbd.lockputc);
return 0;
}
static
void
_kbdputc(int c)
{
Rune r;
char buf[UTFmax];
int n;
r = c;
n = runetochar(buf, &r);
if(n == 0)
return;
echo(buf, n);
// kbd.c = r;
// qproduce(kbdq, buf, n);
}
/* _kbdputc, but with compose translation */
int
kbdputc(Queue *q, int c)
{
int i;
static int collecting, nk;
static Rune kc[5];
if(c == Kalt){
collecting = 1;
nk = 0;
return 0;
}
if(!collecting){
_kbdputc(c);
return 0;
}
kc[nk++] = c;
c = latin1(kc, nk);
if(c < -1) /* need more keystrokes */
return 0;
if(c != -1) /* valid sequence */
_kbdputc(c);
else
for(i=0; i<nk; i++)
_kbdputc(kc[i]);
nk = 0;
collecting = 0;
return 0;
}
enum{
Qdir,
Qbintime,
Qcons,
Qconsctl,
Qcpunote,
Qcputime,
Qdrivers,
Qkprint,
Qhostdomain,
Qhostowner,
Qnull,
Qosversion,
Qpgrpid,
Qpid,
Qppid,
Qrandom,
Qreboot,
Qsecstore,
Qshowfile,
Qsnarf,
Qswap,
Qsysname,
Qsysstat,
Qtime,
Quser,
Qzero,
};
enum
{
VLNUMSIZE= 22,
};
static Dirtab consdir[]={
".", {Qdir, 0, QTDIR}, 0, DMDIR|0555,
"bintime", {Qbintime}, 24, 0664,
"cons", {Qcons}, 0, 0660,
"consctl", {Qconsctl}, 0, 0220,
"cpunote", {Qcpunote}, 0, 0444,
"cputime", {Qcputime}, 6*NUMSIZE, 0444,
"drivers", {Qdrivers}, 0, 0444,
"hostdomain", {Qhostdomain}, DOMLEN, 0664,
"hostowner", {Qhostowner}, 0, 0664,
"kprint", {Qkprint, 0, QTEXCL}, 0, DMEXCL|0440,
"null", {Qnull}, 0, 0666,
"osversion", {Qosversion}, 0, 0444,
"pgrpid", {Qpgrpid}, NUMSIZE, 0444,
"pid", {Qpid}, NUMSIZE, 0444,
"ppid", {Qppid}, NUMSIZE, 0444,
"random", {Qrandom}, 0, 0444,
"reboot", {Qreboot}, 0, 0664,
"secstore", {Qsecstore}, 0, 0666,
"showfile", {Qshowfile}, 0, 0220,
"snarf", {Qsnarf}, 0, 0666,
"swap", {Qswap}, 0, 0664,
"sysname", {Qsysname}, 0, 0664,
"sysstat", {Qsysstat}, 0, 0666,
"time", {Qtime}, NUMSIZE+3*VLNUMSIZE, 0664,
"user", {Quser}, 0, 0666,
"zero", {Qzero}, 0, 0444,
};
char secstorebuf[65536];
Dirtab *secstoretab = &consdir[Qsecstore];
Dirtab *snarftab = &consdir[Qsnarf];
int
readnum(ulong off, char *buf, ulong n, ulong val, int size)
{
char tmp[64];
snprint(tmp, sizeof(tmp), "%*.0lud", size-1, val);
tmp[size-1] = ' ';
if(off >= size)
return 0;
if(off+n > size)
n = size-off;
memmove(buf, tmp+off, n);
return n;
}
int
readstr(ulong off, char *buf, ulong n, char *str)
{
int size;
size = strlen(str);
if(off >= size)
return 0;
if(off+n > size)
n = size-off;
memmove(buf, str+off, n);
return n;
}
static void
consinit(void)
{
todinit();
randominit();
/*
* at 115200 baud, the 1024 char buffer takes 56 ms to process,
* processing it every 22 ms should be fine
*/
/* addclock0link(kbdputcclock, 22); */
}
static Chan*
consattach(char *spec)
{
return devattach('c', spec);
}
static Walkqid*
conswalk(Chan *c, Chan *nc, char **name, int nname)
{
return devwalk(c, nc, name,nname, consdir, nelem(consdir), devgen);
}
static int
consstat(Chan *c, uchar *dp, int n)
{
return devstat(c, dp, n, consdir, nelem(consdir), devgen);
}
static Chan*
consopen(Chan *c, int omode)
{
c->aux = nil;
c = devopen(c, omode, consdir, nelem(consdir), devgen);
switch((ulong)c->qid.path){
case Qconsctl:
qlock(&kbd.lk);
kbd.ctl++;
qunlock(&kbd.lk);
break;
case Qkprint:
if(tas(&kprintinuse) != 0){
c->flag &= ~COPEN;
error(Einuse);
}
if(kprintoq == nil){
kprintoq = qopen(8*1024, Qcoalesce, 0, 0);
if(kprintoq == nil){
c->flag &= ~COPEN;
error(Enomem);
}
qnoblock(kprintoq, 1);
}else
qreopen(kprintoq);
c->iounit = qiomaxatomic;
break;
case Qsecstore:
if(omode == ORDWR)
error(Eperm);
if(omode != OREAD)
memset(secstorebuf, 0, sizeof secstorebuf);
break;
case Qsnarf:
if(omode == ORDWR)
error(Eperm);
if(omode == OREAD)
c->aux = strdup("");
else
c->aux = mallocz(SnarfSize, 1);
break;
}
return c;
}
static void
consclose(Chan *c)
{
switch((ulong)c->qid.path){
/* last close of control file turns off raw */
case Qconsctl:
if(c->flag&COPEN){
qlock(&kbd.lk);
if(--kbd.ctl == 0)
kbd.raw = 0;
qunlock(&kbd.lk);
}
break;
/* close of kprint allows other opens */
case Qkprint:
if(c->flag & COPEN){
kprintinuse = 0;
qhangup(kprintoq, nil);
}
break;
case Qsnarf:
if(c->mode == OWRITE)
clipwrite(c->aux);
free(c->aux);
break;
}
}
static long
consread(Chan *c, void *buf, long n, vlong off)
{
char *b;
char tmp[128]; /* must be >= 6*NUMSIZE */
char *cbuf = buf;
int ch, i, eol;
vlong offset = off;
if(n <= 0)
return n;
switch((ulong)c->qid.path){
case Qdir:
return devdirread(c, buf, n, consdir, nelem(consdir), devgen);
case Qcons:
qlock(&kbd.lk);
if(waserror()) {
qunlock(&kbd.lk);
nexterror();
}
if(kbd.raw) {
if(qcanread(lineq))
n = qread(lineq, buf, n);
else {
/* read as much as possible */
do {
i = qread(kbdq, cbuf, n);
cbuf += i;
n -= i;
} while (n>0 && qcanread(kbdq));
n = cbuf - (char*)buf;
}
} else {
while(!qcanread(lineq)) {
qread(kbdq, &kbd.line[kbd.x], 1);
ch = kbd.line[kbd.x];
eol = 0;
switch(ch){
case '\b':
if(kbd.x)
kbd.x--;
break;
case 0x15:
kbd.x = 0;
break;
case '\n':
case 0x04:
eol = 1;
default:
kbd.line[kbd.x++] = ch;
break;
}
if(kbd.x == sizeof(kbd.line) || eol){
if(ch == 0x04)
kbd.x--;
qwrite(lineq, kbd.line, kbd.x);
kbd.x = 0;
}
}
n = qread(lineq, buf, n);
}
qunlock(&kbd.lk);
poperror();
return n;
case Qcpunote:
sleep(&up->sleep, return0, nil);
case Qcputime:
return 0;
case Qkprint:
return qread(kprintoq, buf, n);
case Qpgrpid:
return readnum((ulong)offset, buf, n, up->pgrp->pgrpid, NUMSIZE);
case Qpid:
return readnum((ulong)offset, buf, n, up->pid, NUMSIZE);
case Qppid:
return readnum((ulong)offset, buf, n, up->parentpid, NUMSIZE);
case Qtime:
return readtime((ulong)offset, buf, n);
case Qbintime:
return readbintime(buf, n);
case Qhostowner:
return readstr((ulong)offset, buf, n, eve);
case Qhostdomain:
return readstr((ulong)offset, buf, n, hostdomain);
case Quser:
return readstr((ulong)offset, buf, n, up->user);
case Qnull:
return 0;
case Qsnarf:
if(offset == 0){
free(c->aux);
c->aux = clipread();
}
if(c->aux == nil)
return 0;
return readstr(offset, buf, n, c->aux);
case Qsecstore:
return readstr(offset, buf, n, secstorebuf);
case Qsysstat:
return 0;
case Qswap:
return 0;
case Qsysname:
if(sysname == nil)
return 0;
return readstr((ulong)offset, buf, n, sysname);
case Qrandom:
return randomread(buf, n);
case Qdrivers:
b = malloc(READSTR);
if(b == nil)
error(Enomem);
n = 0;
for(i = 0; devtab[i] != nil; i++)
n += snprint(b+n, READSTR-n, "#%C %s\n", devtab[i]->dc, devtab[i]->name);
if(waserror()){
free(b);
nexterror();
}
n = readstr((ulong)offset, buf, n, b);
free(b);
poperror();
return n;
case Qzero:
memset(buf, 0, n);
return n;
case Qosversion:
snprint(tmp, sizeof tmp, "2000");
n = readstr((ulong)offset, buf, n, tmp);
return n;
default:
print("consread 0x%llux\n", c->qid.path);
error(Egreg);
}
return -1; /* never reached */
}
static long
conswrite(Chan *c, void *va, long n, vlong off)
{
char buf[256];
long l, bp;
char *a = va;
int fd;
Chan *swc;
ulong offset = off;
Cmdbuf *cb;
Cmdtab *ct;
switch((ulong)c->qid.path){
case Qcons:
/*
* Can't page fault in putstrn, so copy the data locally.
*/
l = n;
while(l > 0){
bp = l;
if(bp > sizeof buf)
bp = sizeof buf;
memmove(buf, a, bp);
putstrn0(buf, bp, 1);
a += bp;
l -= bp;
}
break;
case Qconsctl:
if(n >= sizeof(buf))
n = sizeof(buf)-1;
strncpy(buf, a, n);
buf[n] = 0;
for(a = buf; a;){
if(strncmp(a, "rawon", 5) == 0){
qlock(&kbd.lk);
if(kbd.x){
qwrite(kbdq, kbd.line, kbd.x);
kbd.x = 0;
}
kbd.raw = 1;
qunlock(&kbd.lk);
} else if(strncmp(a, "rawoff", 6) == 0){
qlock(&kbd.lk);
kbd.raw = 0;
kbd.x = 0;
qunlock(&kbd.lk);
} else if(strncmp(a, "ctlpon", 6) == 0){
kbd.ctlpoff = 0;
} else if(strncmp(a, "ctlpoff", 7) == 0){
kbd.ctlpoff = 1;
}
if((a = strchr(a, ' ')))
a++;
}
break;
case Qtime:
if(!iseve())
error(Eperm);
return writetime(a, n);
case Qbintime:
if(!iseve())
error(Eperm);
return writebintime(a, n);
case Qhostowner:
return hostownerwrite(a, n);
case Qhostdomain:
return hostdomainwrite(a, n);
case Quser:
return userwrite(a, n);
case Qnull:
break;
case Qreboot:
if(!iseve())
error(Eperm);
cb = parsecmd(a, n);
if(waserror()) {
free(cb);
nexterror();
}
ct = lookupcmd(cb, rebootmsg, nelem(rebootmsg));
switch(ct->index) {
case CMreboot:
rebootcmd(cb->nf-1, cb->f+1);
break;
case CMpanic:
panic("/dev/reboot");
}
poperror();
free(cb);
break;
case Qsecstore:
if(offset >= sizeof secstorebuf || offset+n+1 >= sizeof secstorebuf)
error(Etoobig);
secstoretab->qid.vers++;
memmove(secstorebuf+offset, va, n);
return n;
case Qshowfile:
return showfilewrite(a, n);
case Qsnarf:
if(offset >= SnarfSize || offset+n >= SnarfSize)
error(Etoobig);
snarftab->qid.vers++;
memmove((uchar*)c->aux+offset, va, n);
return n;
case Qsysstat:
n = 0;
break;
case Qswap:
if(n >= sizeof buf)
error(Egreg);
memmove(buf, va, n); /* so we can NUL-terminate */
buf[n] = 0;
/* start a pager if not already started */
if(strncmp(buf, "start", 5) == 0){
kickpager();
break;
}
if(cpuserver && !iseve())
error(Eperm);
if(buf[0]<'0' || '9'<buf[0])
error(Ebadarg);
fd = strtoul(buf, 0, 0);
swc = fdtochan(fd, -1, 1, 1);
setswapchan(swc);
break;
case Qsysname:
if(offset != 0)
error(Ebadarg);
if(n <= 0 || n >= sizeof buf)
error(Ebadarg);
strncpy(buf, a, n);
buf[n] = 0;
if(buf[n-1] == '\n')
buf[n-1] = 0;
kstrdup(&sysname, buf);
break;
default:
print("conswrite: 0x%llux\n", c->qid.path);
error(Egreg);
}
return n;
}
Dev consdevtab = {
'c',
"cons",
devreset,
consinit,
devshutdown,
consattach,
conswalk,
consstat,
consopen,
devcreate,
consclose,
consread,
devbread,
conswrite,
devbwrite,
devremove,
devwstat,
};
static uvlong uvorder = (uvlong) 0x0001020304050607ULL;
static uchar*
le2vlong(vlong *to, uchar *f)
{
uchar *t, *o;
int i;
t = (uchar*)to;
o = (uchar*)&uvorder;
for(i = 0; i < sizeof(vlong); i++)
t[o[i]] = f[i];
return f+sizeof(vlong);
}
static uchar*
vlong2le(uchar *t, vlong from)
{
uchar *f, *o;
int i;
f = (uchar*)&from;
o = (uchar*)&uvorder;
for(i = 0; i < sizeof(vlong); i++)
t[i] = f[o[i]];
return t+sizeof(vlong);
}
static long order = 0x00010203;
static uchar*
le2long(long *to, uchar *f)
{
uchar *t, *o;
int i;
t = (uchar*)to;
o = (uchar*)ℴ
for(i = 0; i < sizeof(long); i++)
t[o[i]] = f[i];
return f+sizeof(long);
}
/*
static uchar*
long2le(uchar *t, long from)
{
uchar *f, *o;
int i;
f = (uchar*)&from;
o = (uchar*)ℴ
for(i = 0; i < sizeof(long); i++)
t[i] = f[o[i]];
return t+sizeof(long);
}
*/
char *Ebadtimectl = "bad time control";
/*
* like the old #c/time but with added info. Return
*
* secs nanosecs fastticks fasthz
*/
static int
readtime(ulong off, char *buf, int n)
{
vlong nsec, ticks;
long sec;
char str[7*NUMSIZE];
nsec = todget(&ticks);
if(fasthz == (vlong)0)
fastticks((uvlong*)&fasthz);
sec = nsec/((uvlong) 1000000000);
snprint(str, sizeof(str), "%*.0lud %*.0llud %*.0llud %*.0llud ",
NUMSIZE-1, sec,
VLNUMSIZE-1, nsec,
VLNUMSIZE-1, ticks,
VLNUMSIZE-1, fasthz);
return readstr(off, buf, n, str);
}
/*
* set the time in seconds
*/
static int
writetime(char *buf, int n)
{
char b[13];
long i;
vlong now;
if(n >= sizeof(b))
error(Ebadtimectl);
strncpy(b, buf, n);
b[n] = 0;
i = strtol(b, 0, 0);
if(i <= 0)
error(Ebadtimectl);
now = i*((vlong) 1000000000);
todset(now, 0, 0);
return n;
}
/*
* read binary time info. all numbers are little endian.
* ticks and nsec are syncronized.
*/
static int
readbintime(char *buf, int n)
{
int i;
vlong nsec, ticks;
uchar *b = (uchar*)buf;
i = 0;
if(fasthz == (vlong)0)
fastticks((uvlong*)&fasthz);
nsec = todget(&ticks);
if(n >= 3*sizeof(uvlong)){
vlong2le(b+2*sizeof(uvlong), fasthz);
i += sizeof(uvlong);
}
if(n >= 2*sizeof(uvlong)){
vlong2le(b+sizeof(uvlong), ticks);
i += sizeof(uvlong);
}
if(n >= 8){
vlong2le(b, nsec);
i += sizeof(vlong);
}
return i;
}
/*
* set any of the following
* - time in nsec
* - nsec trim applied over some seconds
* - clock frequency
*/
static int
writebintime(char *buf, int n)
{
uchar *p;
vlong delta;
long period;
n--;
p = (uchar*)buf + 1;
switch(*buf){
case 'n':
if(n < sizeof(vlong))
error(Ebadtimectl);
le2vlong(&delta, p);
todset(delta, 0, 0);
break;
case 'd':
if(n < sizeof(vlong)+sizeof(long))
error(Ebadtimectl);
p = le2vlong(&delta, p);
le2long(&period, p);
todset(-1, delta, period);
break;
case 'f':
if(n < sizeof(uvlong))
error(Ebadtimectl);
le2vlong(&fasthz, p);
todsetfreq(fasthz);
break;
}
return n;
}
int
iprint(char *fmt, ...)
{
int n, s;
va_list arg;
char buf[PRINTSIZE];
s = splhi();
va_start(arg, fmt);
n = vseprint(buf, buf+sizeof(buf), fmt, arg) - buf;
va_end(arg);
if(screenputs != 0 && iprintscreenputs)
screenputs(buf, n);
#undef write
write(2, buf, n);
splx(s);
return n;
}