[efi] Use EFI_SIMPLE_TEXT_INPUT_EX_PROTOCOL if available

The original EFI_SIMPLE_TEXT_INPUT_PROTOCOL is not technically
required to handle the use of the Ctrl key, and the long-obsolete EFI
1.10 specification lists only backspace, tab, linefeed, and carriage
return as required.  Some particularly brain-dead vendor UEFI firmware
implementations dutifully put in the extra effort of ensuring that all
other control characters (such as Ctrl-C) are impossible to type via
EFI_SIMPLE_TEXT_INPUT_PROTOCOL.

Current versions of the UEFI specification mandate that the console
input handle must support both EFI_SIMPLE_TEXT_INPUT_PROTOCOL and
EFI_SIMPLE_TEXT_INPUT_EX_PROTOCOL, the latter of which at least
provides access to modifier key state.

Unlike EFI_SIMPLE_TEXT_INPUT_PROTOCOL, the pointer to the
EFI_SIMPLE_TEXT_INPUT_EX_PROTOCOL instance does not appear within the
EFI system table and must therefore be opened explicitly.  The UEFI
specification provides no safe way to do so, since we cannot open the
handle BY_DRIVER or BY_CHILD_CONTROLLER and so nothing guarantees that
this pointer will remain valid for the lifetime of iPXE.  We must
simply hope that no UEFI firmware implementation ever discovers a
motivation for reinstalling the EFI_SIMPLE_TEXT_INPUT_EX_PROTOCOL
instance.

Use EFI_SIMPLE_TEXT_INPUT_EX_PROTOCOL if available, falling back to
the existing EFI_SIMPLE_TEXT_PROTOCOL otherwise.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/interface/efi/efi_console.c

@@ -54,6 +54,8 @@ FILE_LICENCE ( GPL2_OR_LATER );
 
 #define ATTR_DEFAULT		ATTR_FCOL_WHITE
 
+#define CTRL_MASK		0x1f
+
 /* Set default console usage if applicable */
 #if ! ( defined ( CONSOLE_EFI ) && CONSOLE_EXPLICIT ( CONSOLE_EFI ) )
 #undef CONSOLE_EFI
@@ -67,6 +69,9 @@ static unsigned int efi_attr = ATTR_DEFAULT;
 static EFI_CONSOLE_CONTROL_PROTOCOL *conctrl;
 EFI_REQUEST_PROTOCOL ( EFI_CONSOLE_CONTROL_PROTOCOL, &conctrl );
 
+/** Extended simple text input protocol, if present */
+static EFI_SIMPLE_TEXT_INPUT_EX_PROTOCOL *efi_conin_ex;
+
 /**
  * Handle ANSI CUP (cursor position)
  *
@@ -278,8 +283,9 @@ static const char * scancode_to_ansi_seq ( unsigned int scancode ) {
  */
 static int efi_getchar ( void ) {
 	EFI_SIMPLE_TEXT_INPUT_PROTOCOL *conin = efi_systab->ConIn;
+	EFI_SIMPLE_TEXT_INPUT_EX_PROTOCOL *conin_ex = efi_conin_ex;
 	const char *ansi_seq;
-	EFI_INPUT_KEY key;
+	EFI_KEY_DATA key;
 	EFI_STATUS efirc;
 	int rc;
 
@@ -288,20 +294,42 @@ static int efi_getchar ( void ) {
 		return *(ansi_input++);
 
 	/* Read key from real EFI console */
-	if ( ( efirc = conin->ReadKeyStroke ( conin, &key ) ) != 0 ) {
-		rc = -EEFI ( efirc );
-		DBG ( "EFI could not read keystroke: %s\n", strerror ( rc ) );
-		return 0;
+	memset ( &key, 0, sizeof ( key ) );
+	if ( conin_ex ) {
+		if ( ( efirc = conin_ex->ReadKeyStrokeEx ( conin_ex,
+							   &key ) ) != 0 ) {
+			rc = -EEFI ( efirc );
+			DBG ( "EFI could not read extended keystroke: %s\n",
+			      strerror ( rc ) );
+			return 0;
+		}
+	} else {
+		if ( ( efirc = conin->ReadKeyStroke ( conin,
+						      &key.Key ) ) != 0 ) {
+			rc = -EEFI ( efirc );
+			DBG ( "EFI could not read keystroke: %s\n",
+			      strerror ( rc ) );
+			return 0;
+		}
+	}
+	DBG2 ( "EFI read key stroke shift %08x toggle %02x unicode %04x "
+	       "scancode %04x\n", key.KeyState.KeyShiftState,
+	       key.KeyState.KeyToggleState, key.Key.UnicodeChar,
+	       key.Key.ScanCode );
+
+	/* Translate Ctrl-<key> */
+	if ( ( key.KeyState.KeyShiftState & EFI_SHIFT_STATE_VALID ) &&
+	     ( key.KeyState.KeyShiftState & ( EFI_LEFT_CONTROL_PRESSED |
+					      EFI_RIGHT_CONTROL_PRESSED ) ) ) {
+		key.Key.UnicodeChar &= CTRL_MASK;
 	}
-	DBG2 ( "EFI read key stroke with unicode %04x scancode %04x\n",
-	       key.UnicodeChar, key.ScanCode );
 
 	/* If key has a Unicode representation, return it */
-	if ( key.UnicodeChar )
-		return key.UnicodeChar;
+	if ( key.Key.UnicodeChar )
+		return key.Key.UnicodeChar;
 
 	/* Otherwise, check for a special key that we know about */
-	if ( ( ansi_seq = scancode_to_ansi_seq ( key.ScanCode ) ) ) {
+	if ( ( ansi_seq = scancode_to_ansi_seq ( key.Key.ScanCode ) ) ) {
 		/* Start of escape sequence: return ESC (0x1b) */
 		ansi_input = ansi_seq;
 		return 0x1b;
@@ -319,6 +347,8 @@ static int efi_getchar ( void ) {
 static int efi_iskey ( void ) {
 	EFI_BOOT_SERVICES *bs = efi_systab->BootServices;
 	EFI_SIMPLE_TEXT_INPUT_PROTOCOL *conin = efi_systab->ConIn;
+	EFI_SIMPLE_TEXT_INPUT_EX_PROTOCOL *conin_ex = efi_conin_ex;
+	EFI_EVENT *event;
 	EFI_STATUS efirc;
 
 	/* If we are mid-sequence, we are always ready */
@@ -326,7 +356,8 @@ static int efi_iskey ( void ) {
 		return 1;
 
 	/* Check to see if the WaitForKey event has fired */
-	if ( ( efirc = bs->CheckEvent ( conin->WaitForKey ) ) == 0 )
+	event = ( conin_ex ? conin_ex->WaitForKeyEx : conin->WaitForKey );
+	if ( ( efirc = bs->CheckEvent ( event ) ) == 0 )
 		return 1;
 
 	return 0;
@@ -345,7 +376,14 @@ struct console_driver efi_console __console_driver = {
  *
  */
 static void efi_console_init ( void ) {
+	EFI_BOOT_SERVICES *bs = efi_systab->BootServices;
 	EFI_CONSOLE_CONTROL_SCREEN_MODE mode;
+	union {
+		void *interface;
+		EFI_SIMPLE_TEXT_INPUT_EX_PROTOCOL *wtf;
+	} u;
+	EFI_STATUS efirc;
+	int rc;
 
 	/* On some older EFI 1.10 implementations, we must use the
 	 * (now obsolete) EFI_CONSOLE_CONTROL_PROTOCOL to switch the
@@ -358,6 +396,23 @@ static void efi_console_init ( void ) {
 					   EfiConsoleControlScreenText );
 		}
 	}
+
+	/* Attempt to open the Simple Text Input Ex protocol on the
+	 * console input handle.  This is provably unsafe, but is
+	 * apparently the expected behaviour for all UEFI
+	 * applications.  Don't ask.
+	 */
+	if ( ( efirc = bs->OpenProtocol ( efi_systab->ConsoleInHandle,
+				&efi_simple_text_input_ex_protocol_guid,
+				&u.interface, efi_image_handle,
+				efi_systab->ConsoleInHandle,
+				EFI_OPEN_PROTOCOL_GET_PROTOCOL ) ) == 0 ) {
+		efi_conin_ex = u.wtf;
+		DBG ( "EFI using SimpleTextInputEx\n" );
+	} else {
+		rc = -EEFI ( efirc );
+		DBG ( "EFI has no SimpleTextInputEx: %s\n", strerror ( rc ) );
+	}
 }
 
 /**