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.

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)
 {