commit - e63025d09486aea0f644578b5e05a093c130b7d2
commit + cd5a73785d8f7533f1438a955daf23159d09a352
blob - 87673cdb075735d448eef823b3bdd1b41fffecae
blob + 07ce503a22184efb8e4b69555f2e8bcb3bf7223d
--- src/cmd/acme/acme.c
+++ src/cmd/acme/acme.c
@@ -28,6 +28,7 @@ Reffont	*reffonts[2];
 int		snarffd = -1;
 int		mainpid;
 int		swapscrollbuttons = FALSE;
+char		*mtpt;
 
 enum{
 	NSnarf = 1000	/* less than 1024, I/O buffer size */
@@ -104,6 +105,11 @@ threadmain(int argc, char *argv[])
 	case 'l':
 		loadfile = ARGF();
 		if(loadfile == nil)
+			goto Usage;
+		break;
+	case 'm':
+		mtpt = ARGF();
+		if(mtpt == nil)
 			goto Usage;
 		break;
 	case 'r':
@@ -1055,4 +1061,14 @@ acmegetsnarf(void)
 	bufinsert(&snarfbuf, 0, r, nr);
 	free(r);
 	free(s);
+}
+
+int
+ismtpt(char *file)
+{
+	int n;
+
+	/* This is not foolproof, but it will stop a lot of them. */
+	n = strlen(mtpt);
+	return strncmp(file, mtpt, n) == 0 && ((n > 0 && mtpt[n-1] == '/') || file[n] == '/' || file[n] == 0);
 }
blob - a0d5cef372aa85bddf12cc66646d9cfec62e48d3
blob + 93af258db9ac1bc1288059fad892cb0cfb7b96d0
--- src/cmd/acme/dat.h
+++ src/cmd/acme/dat.h
@@ -542,6 +542,7 @@ int			erroutfd;
 int			messagesize;		/* negotiated in 9P version setup */
 int			globalautoindent;
 int			dodollarsigns;
+char*		mtpt;
 
 enum
 {
blob - 34d561c5cb32bd753a2be9c17afd793ebceef92b
blob + c714175f12d5c9292a4170c1ee17801b5d594ecb
--- src/cmd/acme/fns.h
+++ src/cmd/acme/fns.h
@@ -102,3 +102,5 @@ int	abbrevenv(Rune**, uint*);
 #define	runemalloc(a)		(Rune*)emalloc((a)*sizeof(Rune))
 #define	runerealloc(a, b)	(Rune*)erealloc((a), (b)*sizeof(Rune))
 #define	runemove(a, b, c)	memmove((a), (b), (c)*sizeof(Rune))
+
+int	ismtpt(char*);
blob - 9a7dbd10650a866adf7be5b4018edabf4fd423d3
blob + b5ed8d6ca19f21cf2623434a5a164794c4f88c6f
--- src/cmd/acme/fsys.c
+++ src/cmd/acme/fsys.c
@@ -121,7 +121,7 @@ fsysinit(void)
 	initfcall();
 	if(pipe(p) < 0)
 		error("can't create pipe");
-	if(post9pservice(p[0], "acme") < 0)
+	if(post9pservice(p[0], "acme", mtpt) < 0)
 		error("can't post service");
 	sfd = p[1];
 	fmtinstall('F', fcallfmt);
blob - 66c6c66403d388d2a71174c12cf07a2f15c36777
blob + 2ca2061deee3bdcf162378fca5bbaecc038a73f4
--- src/cmd/acme/look.c
+++ src/cmd/acme/look.c
@@ -620,7 +620,7 @@ expandfile(Text *t, uint q0, uint q1, Expand *e)
 	if(w != nil)
 		goto Isfile;
 	/* if it's the name of a file, it's a file */
-	if(access(e->bname, 0) < 0){
+	if(ismtpt(e->bname) || access(e->bname, 0) < 0){
 		free(e->bname);
 		e->bname = nil;
 		goto Isntfile;
blob - ddb3527a2eaf801a23380d073623ac9ecb77d37f
blob + f972b6abefde15d437d8b3ea04d616ccf7b597af
--- src/cmd/acme/text.c
+++ src/cmd/acme/text.c
@@ -198,6 +198,10 @@ textload(Text *t, uint q0, char *file, int setqid)
 		error("text.load");
 	if(t->w->isdir && t->file->nname==0){
 		warning(nil, "empty directory name");
+		return 0;
+	}
+	if(ismtpt(file)){
+		warning(nil, "will not open self mount point %s\n", file);
 		return 0;
 	}
 	fd = open(file, OREAD);