netbsd-bugs: port-hpcmips/36666: [dM] hpcfb space optimization code clears incorrectly

Subject: port-hpcmips/36666: [dM] hpcfb space optimization code clears incorrectly
To: None <port-hpcmips-maintainer@netbsd.org, gnats-admin@netbsd.org,>
From: der Mouse <mouse@Rodents.Montreal.QC.CA>
List: netbsd-bugs
Date: 07/19/2007 05:10:00
>Number:         36666
>Category:       port-hpcmips
>Synopsis:       [dM] dev/hpc/hpcfb.c space optimization code incorrectly clears areas sometimes
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    port-hpcmips-maintainer
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Thu Jul 19 05:10:00 +0000 2007
>Originator:     der Mouse
>Release:        NetBSD 3.1
>Organization:
	Dis-
>Environment:
System: NetBSD Darkstar.Rodents.Montreal.QC.CA 3.1 NetBSD 3.1 (DARKSTAR) #11: Wed Jul 18 23:07:02 EDT 2007 mouse@Darkstar.Rodents.Montreal.QC.CA:/usr/src/sys/arch/hpcmips/compile/DARKSTAR hpcmips
Architecture: mipsel
Machine: hpcmips
hpcfb.c,v 1.31.2.1
>Description:
	Under some circumstances, the code in hpcfb.c that attempts to
	avoid rewriting stuff unnecessarily (mostly, the stuff using
	maxcol/spacecol) clears character cells incorrectly.
>How-To-Repeat:
	I've constructed files to demonstrate the bug.  This was
	observed with a text editor, on a file which I am not prepared
	to disclose the exact contents of, but it turns out that this
	obfuscated version works equally well to demonstrate the bug.

	$ uudecode -p > setup-stuff << \END
	begin 644 foo
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	`
	end
	END
	$ uudecode -p > show-bug << \END
	begin 644 foo
	$&ULQ30``
	`
	end
	END

	Then, on a 106x36 hpcfb-driven display using "sun" emulation
	(in my case, a z50 display with a 6x13 font - a suitable font
	is enclosed below), "cat setup-stuff" will display a screenful
	of text.  Note the line near the middle reading
	"InfibulateTheGonkulator(1);".

	Then "cat setup-stuff show-bug".  As you can see by looking at
	it with (eg) hexdump, show-bug just scrolls the screen by one
	line.  Note that everything after the "The" on the line I
	pointed out above gets erased (incorrectly) by the scroll.

	Here's that 6x13 font, in the form of a (bzip2ed) .h file
	suitable for dropping into dev/wsfont/ (with suitable edits to
	wsfont.c and the kernel config, of course).

	begin 644 fixed6x13.h.bz2
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	`
	end

>Fix:
	The best I can offer right now is the hpcfb.c I'm using.  It
	actually has a number of changes:

	- Fixes this problem.  I've just ripped out all the whitespace
	   optimization code; it impairs speed, but I prefer slow to
	   broken.

	- Uses RI_CENTER, in case the font size does not divide the
	   screen size exactly (I'd rather have it centred than smushed
	   into the upper left).

	- Fixes a bug that prevents RI_CENTER from working right (see
	   the change "@@ -853,7 +852,9 @@" below).

	- Makes clearing the framebuffer clear the whole framebuffer,
	   even if some of it doesn't correspond to character
	   positions.

	I realize that this is not the most useful fix, but at the
	moment it's all I have to offer.  I've been meaning to write
	something better; if I do, I'll add it to this PR.

	In the meantime, the hpcfb.c I mentioned above is at
	ftp.rodents.montreal.qc.ca:/mouse/misc/hpcfb/interim-hpcfb.c.
	Enclosed here is a diff from hpcfb.c,v 1.31.2.1:

	--- hpcfb.c.stock	2007-07-18 23:02:14.000000000 -0400
	+++ hpcfb.c.mouse	2007-05-05 16:02:57.000000000 -0400
	@@ -109,8 +109,6 @@
	 };
	 
	 struct hpcfb_tvrow {
	-	int maxcol;
	-	int spacecol;
	 	struct hpcfb_vchar col[HPCFB_MAX_COLUMN];
	 };
	 
	@@ -448,6 +446,7 @@
	 #else
	 	ri->ri_flg = RI_CURSOR;
	 #endif
	+	ri->ri_flg |= RI_CENTER;
	 	switch (ri->ri_depth) {
	 	case 8:
	 		if (32 <= fbconf->hf_pack_width &&
	@@ -853,7 +852,9 @@
	 	/* switch screen to new one */
	 	dc->dc_state |= HPCFB_DC_CURRENT;
	 	dc->dc_state &= ~HPCFB_DC_ABORT;
	+	/* XXX not until "too dangerous" setting 6 lines above is enabled
	 	dc->dc_rinfo.ri_bits = dc->dc_fbaddr;
	+	*/
	 	sc->sc_dc = dc;
	 
	 	/* redraw screen image */
	@@ -965,7 +966,6 @@
	 {
	 	struct hpcfb_tvrow *vscn = dc->dc_tvram;
	 	struct hpcfb_vchar *vc = &vscn[row].col[col];
	-	struct hpcfb_vchar *vcb;
	 
	 	if (vscn == 0)
	 		return;
	@@ -978,14 +978,6 @@
	 		dc->dc_max_row = row;
	 
	 #endif /* HPCFB_JUMP */
	-	if (vscn[row].maxcol +1 == col)
	-		vscn[row].maxcol = col;
	-	else if (vscn[row].maxcol < col) {
	-		vcb =  &vscn[row].col[vscn[row].maxcol+1];
	-		memset(vcb, 0,
	-		    sizeof(struct hpcfb_vchar)*(col-vscn[row].maxcol-1));
	-		vscn[row].maxcol = col;
	-	}
	 	vc->c = uc;
	 	vc->attr = attr;
	 	dc->dc_state &= ~HPCFB_DC_TDRAWING;
	@@ -1062,10 +1054,7 @@
	 #endif /* HPCFB_JUMP */
	 
	 	memcpy(dvc, svc, ncols*sizeof(struct hpcfb_vchar));
	-	if (vscn[row].maxcol < srccol+ncols-1)
	-		vscn[row].maxcol = srccol+ncols-1;
	-	if (vscn[row].maxcol < dstcol+ncols-1)
	-		vscn[row].maxcol = dstcol+ncols-1;
	+
	 	dc->dc_state &= ~HPCFB_DC_TDRAWING;
	 #ifdef HPCFB_JUMP
	 	hpcfb_check_update(dc);
	@@ -1124,6 +1113,7 @@
	     int ncols, long attr)
	 {
	 	struct hpcfb_tvrow *vscn = dc->dc_tvram;
	+	struct hpcfb_tvrow *r;
	 
	 	if (vscn == 0)
	 		return;
	@@ -1136,9 +1126,12 @@
	 		dc->dc_max_row = row;
	 #endif /* HPCFB_JUMP */
	 
	-	vscn[row].maxcol = startcol-1;
	-	if (vscn[row].spacecol < startcol+ncols-1)
	-		vscn[row].spacecol = startcol+ncols-1;
	+	r = &vscn[row];
	+	for (;ncols>0;startcol++,ncols--) {
	+		r->col[startcol].c = ' ';
	+		r->col[startcol].attr = 0;
	+	}
	+
	 	dc->dc_state &= ~HPCFB_DC_TDRAWING;
	 #ifdef HPCFB_JUMP
	 	hpcfb_check_update(dc);
	@@ -1223,10 +1216,7 @@
	 	}
	 
	 	for (i = 0; i < num; i++) {
	-		memcpy(&dvc->col[0], &svc->col[0], sizeof(struct hpcfb_vchar)*(svc->maxcol+1));
	-		if (svc->maxcol < dvc->maxcol && dvc->spacecol < dvc->maxcol)
	-			dvc->spacecol = dvc->maxcol;
	-		dvc->maxcol = svc->maxcol;
	+		memcpy(&dvc->col[0], &svc->col[0], sizeof(struct hpcfb_vchar)*dc->dc_cols);
	 		svc+=d;
	 		dvc+=d;
	 	}
	@@ -1244,7 +1234,6 @@
	 {
	 	struct hpcfb_devconfig *dc = (struct hpcfb_devconfig *)cookie;
	 	struct rasops_info *ri = &dc->dc_rinfo;
	-	int cols;
	 	struct hpcfb_tvrow *vscn = dc->dc_tvram;
	 	struct hpcfb_vchar *svc;
	 	int i, j;
	@@ -1272,6 +1261,20 @@
	 	if (ri->ri_bits == NULL)
	 		return;
	 
	+	if (all) {
	+		/* Make sure we clear the whole framebuffer, even if
	+		   it's not all in use by characters.  XXX goes under
	+		   the hood of rasops allocattr in the way it extracts
	+		   the bg colour-- but so does hpcfb_putchar().... */
	+		long int attr;
	+		struct rasops_info *ri;
	+		hpcfb_allocattr(dc,WSCOL_WHITE,WSCOL_BLACK,0,&attr);
	+		ri = &dc->dc_rinfo;
	+		memset( dc->dc_fbaddr,
	+			ri->ri_devcmap[(attr>>16)&15],
	+			ri->ri_stride*ri->ri_height );
	+	}
	+
	 	dc->dc_state |= HPCFB_DC_DRAWING;
	 	dc->dc_state |= HPCFB_DC_TDRAWING;
	 	for (i = 0; i < num; i++) {
	@@ -1279,27 +1282,15 @@
	 			break;
	 		if ((dc->dc_state&HPCFB_DC_CURRENT) == 0)
	 			break;
	-		cols = vscn[row+i].maxcol;
	-		for (j = 0; j <= cols; j++) {
	+		svc = &vscn[row+i].col[0];
	+		for (j = 0; j < dc->dc_cols; j++) {
	 			if (dc->dc_state&HPCFB_DC_ABORT)
	 				continue;
	 			if ((dc->dc_state&HPCFB_DC_CURRENT) == 0)
	 				continue;
	-			svc = &vscn[row+i].col[j];
	 			rasops_emul.putchar(ri, row + i, j, svc->c, svc->attr);
	+			svc ++;
	 		}
	-		if (all)
	-			cols = dc->dc_cols-1;
	-		else
	-			cols = vscn[row+i].spacecol;
	-		for (; j <= cols; j++) {
	-			if (dc->dc_state&HPCFB_DC_ABORT)
	-				continue;
	-			if ((dc->dc_state&HPCFB_DC_CURRENT) == 0)
	-				continue;
	-			rasops_emul.putchar(ri, row + i, j, ' ', 0);
	-		}
	-		vscn[row+i].spacecol = 0;
	 	}
	 	if (dc->dc_state&HPCFB_DC_ABORT)
	 		dc->dc_state &= ~HPCFB_DC_ABORT;
	@@ -1446,8 +1437,9 @@
	 hpcfb_tv_eraserows(struct hpcfb_devconfig *dc, int row, int nrow, long attr)
	 {
	 	struct hpcfb_tvrow *vscn = dc->dc_tvram;
	-	int cols;
	 	int i;
	+	int j;
	+	struct hpcfb_vchar *svc;
	 
	 	if (vscn == 0)
	 		return;
	@@ -1462,10 +1454,11 @@
	 #endif /* HPCFB_JUMP */
	 
	 	for (i = 0; i < nrow; i++) {
	-		cols = vscn[row+i].maxcol;
	-		if (vscn[row+i].spacecol < cols)
	-			vscn[row+i].spacecol = cols;
	-		vscn[row+i].maxcol = -1;
	+		svc = &vscn[row+i].col[0];
	+		for (j = 0; j < dc->dc_cols; j ++) {
	+			svc[j].c = ' ';
	+			svc[j].attr = 0;
	+		}
	 	}
	 #ifdef HPCFB_JUMP
	 	hpcfb_check_update(dc);

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