bootloader: usability improvements

- add "edit" menu option, to edit menu commands before executing them;
- add "menu" boot command, to return to the menu from the prompt;
- provide more line editing features when getting input;
- fix a few potential buffer overflows as a side effect.

etc/boot.cfg.default

@@ -4,4 +4,5 @@ default=2
 menu=Start MINIX 3:load_mods /boot/minix_default/mod*;multiboot /boot/minix_default/kernel rootdevname=$rootdevname
 menu=Start latest MINIX 3:load_mods /boot/minix_latest/mod*;multiboot /boot/minix_latest/kernel rootdevname=$rootdevname
 menu=Start latest MINIX 3 in single user mode:load_mods /boot/minix_latest/mod*;multiboot /boot/minix_latest/kernel rootdevname=$rootdevname bootopts=-s
+menu=Edit menu option:edit
 menu=Drop to boot prompt:prompt

man/man5/boot.cfg.5

@@ -130,6 +130,9 @@ Each command is executed just as though the user had typed it in
 and so can be any valid command that would be accepted at the
 normal boot prompt.
 In addition,
+.Dq Ic edit
+can be used to put the menu in editing mode, allowing the user to modify the
+next selected option before executing it, and
 .Dq Ic prompt
 can be used to drop to the normal boot prompt.
 .It Sy timeout

releasetools/release.functions

@@ -61,6 +61,7 @@ banner=Welcome to the MINIX 3 installation CD
 banner================================================================================
 banner=
 menu=Regular MINIX 3:multiboot /kernel bootcd=1 cdproberoot=1 rootdevname=ram disable=inet
+menu=Edit menu option:edit
 menu=Drop to boot prompt:prompt
 clear=1
 timeout=10
@@ -106,6 +107,7 @@ hdemu_root_changes()
 
 cat >$RELEASEMNTDIR/boot.cfg <<END_BOOT_CFG
 menu=Regular MINIX 3:load_mods /boot/minix_default/mod*;multiboot /boot/minix_default/kernel bootcd=2 disable=inet bios_wini=yes bios_remap_first=1 ramimagedev=c0d7p0s0
+menu=Edit menu option:edit
 menu=Drop to boot prompt:prompt
 clear=1
 timeout=10
@@ -120,6 +122,7 @@ usb_root_changes()
 	echo \
 cat >$RELEASEMNTDIR/boot.cfg <<END_BOOT_CFG
 menu=Regular MINIX 3:load_mods /boot/minix_default/mod*;multiboot /boot/minix_default/kernel bios_wini=yes bios_remap_first=1 rootdevname=c0d7p0s0
+menu=Edit menu option:edit
 menu=Drop to boot prompt:prompt
 clear=1
 timeout=10

sys/arch/i386/stand/lib/bootmenu.c

@@ -297,11 +297,10 @@ getchoicefrominput(char *input, int def)
 	return choice;
 }
 
-void
-doboottypemenu(void)
+static void
+showmenu(void)
 {
 	int choice;
-	char input[80], *ic, *oc;
 
 	printf("\n");
 	/* Display menu */
@@ -317,19 +316,31 @@ doboottypemenu(void)
 			    choice + 1,
 			    bootconf.desc[choice]);
 	}
+}
+
+void
+doboottypemenu(void)
+{
+	int choice, editing;
+	char input[256], *ic, *oc;
+
+	showmenu();
 	choice = -1;
+	editing = 0;
 	for (;;) {
 		input[0] = '\0';
 
 		if (bootconf.timeout < 0) {
 			if (bootconf.menuformat == MENUFORMAT_LETTER)
-				printf("\nOption: [%c]:",
+				printf("\nOption%s: [%c]:",
+				    editing ? " (edit)" : "",
 				    bootconf.def + 'A');
 			else
-				printf("\nOption: [%d]:",
+				printf("\nOption%s: [%d]:",
+				    editing ? " (edit)" : "",
 				    bootconf.def + 1);
 
-			gets(input);
+			editline(input, sizeof(input), NULL);
 			choice = getchoicefrominput(input, bootconf.def);
 		} else if (bootconf.timeout == 0)
 			choice = bootconf.def;
@@ -351,27 +362,45 @@ doboottypemenu(void)
 		}
 		if (choice < 0)
 			continue;
-		if (!strcmp(bootconf.command[choice], "prompt") &&
+		ic = bootconf.command[choice];
+		if (editing) {
+			printf("> ");
+			editline(input, sizeof(input), ic);
+			ic = input;
+		}
+		if (!strcmp(ic, "edit") &&
 		    ((boot_params.bp_flags & X86_BP_FLAGS_PASSWORD) == 0 ||
 		    check_password((char *)boot_params.bp_password))) {
-			printf("type \"?\" or \"help\" for help.\n");
-			bootmenu(); /* does not return */
+			editing = 1;
+			bootconf.timeout = -1;
+		} else if (!strcmp(ic, "prompt") &&
+		    ((boot_params.bp_flags & X86_BP_FLAGS_PASSWORD) == 0 ||
+		    check_password((char *)boot_params.bp_password))) {
+			printf("type \"?\" or \"help\" for help, "
+			    "or \"menu\" to return to the menu.\n");
+			prompt(1);
+			showmenu();
+			editing = 0;
+			bootconf.timeout = -1;
 		} else {
-			ic = bootconf.command[choice];
 			/* Split command string at ; into separate commands */
 			do {
+				/*
+				 * This must support inline editing, since ic
+				 * may also point to input.
+				 */
 				oc = input;
 				/* Look for ; separator */
 				for (; *ic && *ic != COMMAND_SEPARATOR; ic++)
 					*oc++ = *ic;
-				if (*input == '\0')
+				if (*ic == COMMAND_SEPARATOR)
+					ic++;
+				if (oc == input)
 					continue;
 				/* Strip out any trailing spaces */
 				oc--;
 				for (; *oc == ' ' && oc > input; oc--);
 				*++oc = '\0';
-				if (*ic == COMMAND_SEPARATOR)
-					ic++;
 				/* Stop silly command strings like ;;; */
 				if (*input != '\0')
 					docommand(input);

sys/arch/i386/stand/lib/conio.S

@@ -45,9 +45,30 @@ ENTRY(conputc)
 	call	_C_LABEL(prot_to_real)	# enter real mode
 	.code16
 
+	cmp	$0x08, %al	# backspace?
+	jne	print_char
+
+	# Multiline backspace support.
+	push	%ax
+	movb	$0x3, %ah	# get cursor position
+	xorw	%bx, %bx
+	int	$0x10
+	pop	%ax
+	testb	%dl, %dl	# cursor on first column?
+	jnz	print_char
+	testb	%dh, %dh	# cursor not on first row?
+	jz	print_char
+	decb	%dh		# move up one row
+	movb	$0x4f, %dl	# move to last column
+	xorw	%bx, %bx
+	movb	$0x02, %ah	# set cursor position
+	jmp	do_int
+
+print_char:
 	movw	$1,%bx
-	movb	$0x0e,%ah
+	movb	$0x0e,%ah	# print character
 	movb	%al, %cl
+do_int:
 	int	$0x10
 
 	calll	_C_LABEL(real_to_prot) # back to protected mode
@@ -68,12 +89,12 @@ ENTRY(congetc)
 
 	movb	$0x0,%ah
 	int	$0x16
-	movb	%al,%bl
+	movw	%ax,%bx
 
 	calll	_C_LABEL(real_to_prot) # back to protected mode
 	.code32
 
-	movb	%bl, 28(%esp)
+	movw	%bx, 28(%esp)
 
 	popa
 	ret

sys/arch/i386/stand/lib/libi386.h

@@ -91,7 +91,9 @@ struct bootblk_command {
 	void (*c_fn)(char *);
 };
 void bootmenu(void);
+void prompt(int);
 void docommand(char *);
+void editline(char *, size_t, char *);
 
 /* in "user code": */
 void command_help(char *);
@@ -114,6 +116,8 @@ int coniskey(void);
 __compactcall void conputc(int);
 void conclr(void);
 
+int getchar_ex(void);
+
 int getextmem2(int *);
 __compactcall int getextmemps2(void *);
 int getmementry(int *, int *);

sys/arch/i386/stand/lib/menuutils.c

@@ -62,23 +62,136 @@ docommand(char *arg)
 }
 
 void
-bootmenu(void)
+prompt(int allowreturn)
 {
 	char input[80];
 
 	for (;;) {
 		char *c = input;
 
-		input[0] = '\0';
 		printf("> ");
-		gets(input);
+		editline(input, sizeof(input), NULL);
 
 		/*
 		 * Skip leading whitespace.
 		 */
 		while (*c == ' ')
 			c++;
+		if (allowreturn && !strcmp(c, "menu"))
+			break;
 		if (*c)
 			docommand(c);
 	}
 }
+
+void
+bootmenu(void)
+{
+	prompt(0);
+}
+
+/* Derived from libsa gets(). */
+void
+editline(char *buf, size_t size, char *input)
+{
+	int c, i, pos, len = 0;
+
+	/* If an initial input has been given, copy and print this first. */
+	if (input != NULL) {
+		while (*input && len < size - 1)
+			putchar(buf[len++] = *input++);
+	}
+	pos = len;
+
+	for (;;) {
+		c = getchar_ex();
+		switch (c & 0177) {
+		case '\0':
+			switch (c) {
+			case 0x4b00: /* Left arrow: move cursor to left. */
+				if (pos > 0) {
+					putchar('\b');
+					pos--;
+				}
+				break;
+			case 0x4d00: /* Right arrow: move cursor to right. */
+				if (pos < len) putchar(buf[pos++]);
+				break;
+			}
+			break;
+		case 'b' & 037: /* Ctrl+B: move cursor to left. */
+			if (pos > 0) {
+				putchar('\b');
+				pos--;
+			}
+			break;
+		case 'f' & 037: /* Ctrl+F: move cursor to right. */
+			if (pos < len) putchar(buf[pos++]);
+			break;
+		case 'a' & 037: /* Ctrl+A: move cursor to start of line. */
+			for ( ; pos > 0; pos--) putchar('\b');
+			break;
+		case 'e' & 037: /* Ctrl+E: move cursor to end of line. */
+			for ( ; pos < len; pos++) putchar(buf[pos]);
+			break;
+		case '\n': /* Enter: return line. */
+		case '\r':
+			for ( ; pos < len; pos++) putchar(buf[pos]);
+			buf[len] = '\0';
+			putchar('\n');
+			return;
+#if HASH_ERASE
+		case '#':
+#endif
+		case '\b': /* Backspace: erase character before cursor. */
+		case '\177':
+			if (pos > 0) {
+				pos--;
+				len--;
+				putchar('\b');
+				for (i = pos; i < len; i++)
+					putchar(buf[i] = buf[i + 1]);
+				putchar(' ');
+				for (i = pos; i < len; i++) putchar('\b');
+				putchar('\b');
+			}
+			break;
+		case 'r' & 037: /* Ctrl+R: reprint line. */
+			putchar('\n');
+			for (i = 0; i < len; i++) putchar(buf[i]);
+			for (i = len; i > pos; i--) putchar('\b');
+			break;
+#if AT_ERASE
+		case '@':
+#endif
+		case 'u' & 037: /* Ctrl+U: clear entire line. */
+		case 'w' & 037:
+			for ( ; pos > 0; pos--) putchar('\b');
+			for ( ; pos < len; pos++) putchar(' ');
+			for ( ; pos > 0; pos--) putchar('\b');
+			len = 0;
+			break;
+		case '\a': /* Ctrl+G: sound bell but do not store character. */
+			putchar(c);
+			break;
+		case '\t': /* Tab: convert to single space. */
+			c = ' ';
+			/*FALLTHROUGH*/
+		default: /* Insert character at cursor position. */
+			if (len < size - 1) {
+				for (i = len; i > pos; i--)
+					buf[i] = buf[i - 1];
+				buf[pos] = c;
+				pos++;
+				len++;
+				putchar(c);
+				for (i = pos; i < len; i++) putchar(buf[i]);
+				for (i = pos; i < len; i++) putchar('\b');
+			} else {
+				putchar('\a');
+			}
+			break;
+		}
+	}
+	/*NOTREACHED*/
+}

sys/arch/i386/stand/lib/pcio.c

@@ -259,7 +259,7 @@ putchar(int c)
 }
 
 int
-getchar(void)
+getchar_ex(void)
 {
 	int c;
 #ifdef SUPPORT_SERIAL
@@ -272,9 +272,9 @@ getchar(void)
 		c = congetc();
 #ifdef CONSOLE_KEYMAP
 		{
-			char *cp = strchr(CONSOLE_KEYMAP, c);
+			char *cp = strchr(CONSOLE_KEYMAP, c & 0xff);
 			if (cp != 0 && cp[1] != 0)
-				c = cp[1];
+				c = cp[1] | (c & 0xff00);
 		}
 #endif
 		return c;
@@ -302,6 +302,12 @@ getchar(void)
 #endif /* SUPPORT_SERIAL */
 }
 
+int
+getchar(void)
+{
+	return getchar_ex() & 0xff;
+}
+
 int
 iskey(int intr)
 {