--- /n/sources/plan9/sys/src/cmd/unix/u9fs/fcallconv.c	Fri Jan 25 10:50:05 2013
+++ /sys/src/cmd/unix/u9fs/fcallconv.c	Thu Jun 25 00:00:00 2026
@@ -4,8 +4,8 @@
 
 extern int old9p;
 
-static uint dumpsome(char*, char*, long);
-static void fdirconv(char*, Dir*);
+static uint dumpsome(char*, char*, char*, long);
+static void fdirconv(char*, char*, Dir*);
 static char *qidtype(char*, uchar);
 
 #define	QIDFMT	"(%.16llux %lud %s)"
@@ -14,133 +14,133 @@ int
 fcallconv(va_list *arg, Fconv *f1)
 {
 	Fcall *f;
-	int fid, type, tag, n, i;
+	int fid, type, tag, i;
 	char buf[512], tmp[200];
-	Dir *d;
+	char *p, *e;
+	Dir d;
 	Qid *q;
 
+	e = buf+sizeof(buf);
 	f = va_arg(*arg, Fcall*);
 	type = f->type;
 	fid = f->fid;
 	tag = f->tag;
 	switch(type){
 	case Tversion:	/* 100 */
-		sprint(buf, "Tversion tag %ud msize %ud version '%s'", tag, f->msize, f->version);
+		seprint(buf, e, "Tversion tag %ud msize %ud version '%s'", tag, f->msize, f->version);
 		break;
 	case Rversion:
-		sprint(buf, "Rversion tag %ud msize %ud version '%s'", tag, f->msize, f->version);
+		seprint(buf, e, "Rversion tag %ud msize %ud version '%s'", tag, f->msize, f->version);
 		break;
 	case Tauth:	/* 102 */
-		sprint(buf, "Tauth tag %ud afid %d uname %s aname %s", tag,
+		seprint(buf, e, "Tauth tag %ud afid %d uname %s aname %s", tag,
 			f->afid, f->uname, f->aname);
 		break;
 	case Rauth:
-		sprint(buf, "Rauth tag %ud qid " QIDFMT, tag,
+		seprint(buf, e, "Rauth tag %ud qid " QIDFMT, tag,
 			f->aqid.path, f->aqid.vers, qidtype(tmp, f->aqid.type));
 		break;
 	case Tattach:	/* 104 */
-		sprint(buf, "Tattach tag %ud fid %d afid %d uname %s aname %s", tag,
+		seprint(buf, e, "Tattach tag %ud fid %d afid %d uname %s aname %s", tag,
 			fid, f->afid, f->uname, f->aname);
 		break;
 	case Rattach:
-		sprint(buf, "Rattach tag %ud qid " QIDFMT, tag,
+		seprint(buf, e, "Rattach tag %ud qid " QIDFMT, tag,
 			f->qid.path, f->qid.vers, qidtype(tmp, f->qid.type));
 		break;
 	case Rerror:	/* 107; 106 (Terror) illegal */
-		sprint(buf, "Rerror tag %ud ename %s", tag, f->ename);
+		seprint(buf, e, "Rerror tag %ud ename %s", tag, f->ename);
 		break;
 	case Tflush:	/* 108 */
-		sprint(buf, "Tflush tag %ud oldtag %ud", tag, f->oldtag);
+		seprint(buf, e, "Tflush tag %ud oldtag %ud", tag, f->oldtag);
 		break;
 	case Rflush:
-		sprint(buf, "Rflush tag %ud", tag);
+		seprint(buf, e, "Rflush tag %ud", tag);
 		break;
 	case Twalk:	/* 110 */
-		n = sprint(buf, "Twalk tag %ud fid %d newfid %d nwname %d ", tag, fid, f->newfid, f->nwname);
+		p = seprint(buf, e, "Twalk tag %ud fid %d newfid %d nwname %d ", tag, fid, f->newfid, f->nwname);
+		if(f->nwname <= MAXWELEM)
 			for(i=0; i<f->nwname; i++)
-				n += sprint(buf+n, "%d:%s ", i, f->wname[i]);
+				p = seprint(p, e, "%d:%s ", i, f->wname[i]);
 		break;
 	case Rwalk:
-		n = sprint(buf, "Rwalk tag %ud nwqid %ud ", tag, f->nwqid);
-		for(i=0; i<f->nwqid; i++){
-			q = &f->wqid[i];
-			n += sprint(buf+n, "%d:" QIDFMT " ", i,
-				q->path, q->vers, qidtype(tmp, q->type));
-		}
+		p = seprint(buf, e, "Rwalk tag %ud nwqid %ud ", tag, f->nwqid);
+		if(f->nwqid <= MAXWELEM)
+			for(i=0; i<f->nwqid; i++){
+				q = &f->wqid[i];
+				p = seprint(p, e, "%d:" QIDFMT " ", i,
+					q->path, q->vers, qidtype(tmp, q->type));
+			}
 		break;
 	case Topen:	/* 112 */
-		sprint(buf, "Topen tag %ud fid %ud mode %d", tag, fid, f->mode);
+		seprint(buf, e, "Topen tag %ud fid %ud mode %d", tag, fid, f->mode);
 		break;
 	case Ropen:
-		sprint(buf, "Ropen tag %ud qid " QIDFMT " iounit %ud ", tag,
+		seprint(buf, e, "Ropen tag %ud qid " QIDFMT " iounit %ud ", tag,
 			f->qid.path, f->qid.vers, qidtype(tmp, f->qid.type), f->iounit);
 		break;
 	case Tcreate:	/* 114 */
-		sprint(buf, "Tcreate tag %ud fid %ud name %s perm %M mode %d",
+		seprint(buf, e, "Tcreate tag %ud fid %ud name %s perm %M mode %d",
 			tag, fid, f->name, (ulong)f->perm, f->mode);
 		break;
 	case Rcreate:
-		sprint(buf, "Rcreate tag %ud qid " QIDFMT " iounit %ud ", tag,
+		seprint(buf, e, "Rcreate tag %ud qid " QIDFMT " iounit %ud ", tag,
 			f->qid.path, f->qid.vers, qidtype(tmp, f->qid.type), f->iounit);
 		break;
 	case Tread:	/* 116 */
-		sprint(buf, "Tread tag %ud fid %d offset %lld count %ud",
+		seprint(buf, e, "Tread tag %ud fid %d offset %lld count %ud",
 			tag, fid, f->offset, f->count);
 		break;
 	case Rread:
-		n = sprint(buf, "Rread tag %ud count %ud ", tag, f->count);
-			dumpsome(buf+n, f->data, f->count);
+		p = seprint(buf, e, "Rread tag %ud count %ud ", tag, f->count);
+			dumpsome(p, e, f->data, f->count);
 		break;
 	case Twrite:	/* 118 */
-		n = sprint(buf, "Twrite tag %ud fid %d offset %lld count %ud ",
+		p = seprint(buf, e, "Twrite tag %ud fid %d offset %lld count %ud ",
 			tag, fid, f->offset, f->count);
-		dumpsome(buf+n, f->data, f->count);
+		dumpsome(p, e, f->data, f->count);
 		break;
 	case Rwrite:
-		sprint(buf, "Rwrite tag %ud count %ud", tag, f->count);
+		seprint(buf, e, "Rwrite tag %ud count %ud", tag, f->count);
 		break;
 	case Tclunk:	/* 120 */
-		sprint(buf, "Tclunk tag %ud fid %ud", tag, fid);
+		seprint(buf, e, "Tclunk tag %ud fid %ud", tag, fid);
 		break;
 	case Rclunk:
-		sprint(buf, "Rclunk tag %ud", tag);
+		seprint(buf, e, "Rclunk tag %ud", tag);
 		break;
 	case Tremove:	/* 122 */
-		sprint(buf, "Tremove tag %ud fid %ud", tag, fid);
+		seprint(buf, e, "Tremove tag %ud fid %ud", tag, fid);
 		break;
 	case Rremove:
-		sprint(buf, "Rremove tag %ud", tag);
+		seprint(buf, e, "Rremove tag %ud", tag);
 		break;
 	case Tstat:	/* 124 */
-		sprint(buf, "Tstat tag %ud fid %ud", tag, fid);
+		seprint(buf, e, "Tstat tag %ud fid %ud", tag, fid);
 		break;
 	case Rstat:
-		n = sprint(buf, "Rstat tag %ud ", tag);
-		if(f->nstat > sizeof tmp)
-			sprint(buf+n, " stat(%d bytes)", f->nstat);
+		p = seprint(buf, e, "Rstat tag %ud ", tag);
+		if(f->nstat > sizeof tmp || (old9p?convM2Dold:convM2D)(f->stat, f->nstat, &d, tmp) == 0)
+			seprint(p, e, " stat(%d bytes)", f->nstat);
 		else{
-			d = (Dir*)tmp;
-			(old9p?convM2Dold:convM2D)(f->stat, f->nstat, d, (char*)(d+1));
-			sprint(buf+n, " stat ");
-			fdirconv(buf+n+6, d);
+			seprint(p, e, " stat ");
+			fdirconv(p+6, e, &d);
 		}
 		break;
 	case Twstat:	/* 126 */
-		n = sprint(buf, "Twstat tag %ud fid %ud", tag, fid);
-		if(f->nstat > sizeof tmp)
-			sprint(buf+n, " stat(%d bytes)", f->nstat);
+		p = seprint(buf, e, "Twstat tag %ud fid %ud", tag, fid);
+		if(f->nstat > sizeof tmp || (old9p?convM2Dold:convM2D)(f->stat, f->nstat, &d, tmp) == 0)
+			seprint(p, e, " stat(%d bytes)", f->nstat);
 		else{
-			d = (Dir*)tmp;
-			(old9p?convM2Dold:convM2D)(f->stat, f->nstat, d, (char*)(d+1));
-			sprint(buf+n, " stat ");
-			fdirconv(buf+n+6, d);
+			seprint(p, e, " stat ");
+			fdirconv(p+6, e, &d);
 		}
 		break;
 	case Rwstat:
-		sprint(buf, "Rwstat tag %ud", tag);
+		seprint(buf, e, "Rwstat tag %ud", tag);
 		break;
 	default:
-		sprint(buf,  "unknown type %d", type);
+		seprint(buf, e,  "unknown type %d", type);
 	}
 	strconv(buf, f1);
 	return(sizeof(Fcall*));
@@ -171,17 +171,17 @@ dirconv(va_list *arg, Fconv *f)
 {
 	char buf[160];
 
-	fdirconv(buf, va_arg(*arg, Dir*));
+	fdirconv(buf, buf+sizeof buf, va_arg(*arg, Dir*));
 	strconv(buf, f);
 	return(sizeof(Dir*));
 }
 
 static void
-fdirconv(char *buf, Dir *d)
+fdirconv(char *buf, char *e, Dir *d)
 {
 	char tmp[16];
 
-	sprint(buf, "'%s' '%s' '%s' '%s' "
+	seprint(buf, e, "'%s' '%s' '%s' '%s' "
 		"q " QIDFMT " m %#luo "
 		"at %ld mt %ld l %lld "
 		"t %d d %d",
@@ -199,11 +199,15 @@ fdirconv(char *buf, Dir *d)
 #define DUMPL 64
 
 static uint
-dumpsome(char *ans, char *buf, long count)
+dumpsome(char *ans, char *e, char *buf, long count)
 {
 	int i, printable;
 	char *p;
 
+	if(buf == nil){
+		seprint(ans, e, "<no data>");
+		return strlen(ans);
+	}
 	printable = 1;
 	if(count > DUMPL)
 		count = DUMPL;
@@ -213,9 +217,13 @@ dumpsome(char *ans, char *buf, long coun
 	p = ans;
 	*p++ = '\'';
 	if(printable){
+		if(count > e-p-2)
+			count = e-p-2;
 		memmove(p, buf, count);
 		p += count;
 	}else{
+		if(2*count > e-p-2)
+			count = (e-p-2)/2;
 		for(i=0; i<count; i++){
 			if(i>0 && i%4==0)
 				*p++ = ' ';