[console] Support AltGr to access ASCII characters via remapping

Several keyboard layouts define ASCII characters as accessible only
via the AltGr modifier.  Add support for this modifier to ensure that
all ASCII characters are accessible.

Experiments suggest that the BIOS console is likely to fail to
generate ASCII characters when the AltGr key is pressed.  Work around
this limitation by accepting LShift+RShift (which will definitely
produce an ASCII character) as a synonym for AltGr.

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

src/arch/x86/include/bios.h

@@ -7,6 +7,8 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 #define BDA_EBDA 0x000e
 #define BDA_EQUIPMENT_WORD 0x0010
 #define BDA_KB0 0x0017
+#define BDA_KB0_RSHIFT 0x01
+#define BDA_KB0_LSHIFT 0x02
 #define BDA_KB0_CTRL 0x04
 #define BDA_KB0_CAPSLOCK 0x040
 #define BDA_FBMS 0x0013
@@ -16,5 +18,7 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 #define BDA_REBOOT_WARM 0x1234
 #define BDA_NUM_DRIVES 0x0075
 #define BDA_CHAR_HEIGHT 0x0085
+#define BDA_KB2 0x0096
+#define BDA_KB2_RALT 0x08
 
 #endif /* BIOS_H */

src/arch/x86/interface/pcbios/bios_console.c

@@ -362,6 +362,7 @@ static const char * bios_ansi_seq ( unsigned int scancode ) {
 static int bios_getchar ( void ) {
 	uint16_t keypress;
 	uint8_t kb0;
+	uint8_t kb2;
 	unsigned int scancode;
 	unsigned int character;
 	const char *ansi_seq;
@@ -387,6 +388,7 @@ static int bios_getchar ( void ) {
 	scancode = ( keypress >> 8 );
 	character = ( keypress & 0xff );
 	get_real ( kb0, BDA_SEG, BDA_KB0 );
+	get_real ( kb2, BDA_SEG, BDA_KB2 );
 
 	/* If it's a normal character, map (if applicable) and return it */
 	if ( character && ( character < 0x80 ) ) {
@@ -405,6 +407,16 @@ static int bios_getchar ( void ) {
 			character |= KEYMAP_CTRL;
 		if ( kb0 & BDA_KB0_CAPSLOCK )
 			character |= KEYMAP_CAPSLOCK_REDO;
+		if ( kb2 & BDA_KB2_RALT )
+			character |= KEYMAP_ALTGR;
+
+		/* Treat LShift+RShift as AltGr since many BIOSes will
+		 * not return ASCII characters when AltGr is pressed.
+		 */
+		if ( ( kb0 & ( BDA_KB0_LSHIFT | BDA_KB0_RSHIFT ) ) ==
+		     ( BDA_KB0_LSHIFT | BDA_KB0_RSHIFT ) ) {
+			character |= KEYMAP_ALTGR;
+		}
 
 		/* Map and return */
 		return key_remap ( character );

src/core/keymap.c

@@ -65,8 +65,11 @@ unsigned int key_remap ( unsigned int character ) {
 	if ( ( character & KEYMAP_CAPSLOCK_UNDO ) && isalpha ( mapped ) )
 		mapped ^= CASE_TOGGLE;
 
+	/* Select remapping table */
+	key = ( ( character & KEYMAP_ALTGR ) ? keymap->altgr : keymap->basic );
+
 	/* Remap via table */
-	for ( key = keymap->basic ; key->from ; key++ ) {
+	for ( ; key->from ; key++ ) {
 		if ( mapped == key->from ) {
 			mapped = key->to;
 			break;

src/drivers/usb/usbkbd.c

@@ -132,6 +132,8 @@ static unsigned int usbkbd_map ( unsigned int keycode, unsigned int modifiers,
 		/* Apply modifiers */
 		if ( modifiers & USBKBD_CTRL )
 			key |= KEYMAP_CTRL;
+		if ( modifiers & USBKBD_ALT_RIGHT )
+			key |= KEYMAP_ALTGR;
 		if ( leds & USBKBD_LED_CAPS_LOCK )
 			key |= KEYMAP_CAPSLOCK;
 

src/hci/keymap/keymap_al.c

@@ -35,8 +35,16 @@ static struct keymap_key al_basic[] = {
 	{ 0, 0 }
 };
 
+/** "al" AltGr remapping */
+static struct keymap_key al_altgr[] = {
+	{ 0x31, 0x7e },	/* '1' => '~' */
+	{ 0x37, 0x60 },	/* '7' => '`' */
+	{ 0, 0 }
+};
+
 /** "al" keyboard map */
 struct keymap al_keymap __keymap = {
 	.name = "al",
 	.basic = al_basic,
+	.altgr = al_altgr,
 };

src/hci/keymap/keymap_az.c

@@ -26,8 +26,15 @@ static struct keymap_key az_basic[] = {
 	{ 0, 0 }
 };
 
+/** "az" AltGr remapping */
+static struct keymap_key az_altgr[] = {
+	{ 0xdc, 0x7c },	/* Pseudo-'\\' => '|' */
+	{ 0, 0 }
+};
+
 /** "az" keyboard map */
 struct keymap az_keymap __keymap = {
 	.name = "az",
 	.basic = az_basic,
+	.altgr = az_altgr,
 };

src/hci/keymap/keymap_by.c

@@ -17,8 +17,14 @@ static struct keymap_key by_basic[] = {
 	{ 0, 0 }
 };
 
+/** "by" AltGr remapping */
+static struct keymap_key by_altgr[] = {
+	{ 0, 0 }
+};
+
 /** "by" keyboard map */
 struct keymap by_keymap __keymap = {
 	.name = "by",
 	.basic = by_basic,
+	.altgr = by_altgr,
 };

src/hci/keymap/keymap_cf.c

@@ -24,8 +24,17 @@ static struct keymap_key cf_basic[] = {
 	{ 0, 0 }
 };
 
+/** "cf" AltGr remapping */
+static struct keymap_key cf_altgr[] = {
+	{ 0x32, 0x40 },	/* '2' => '@' */
+	{ 0x3b, 0x7e },	/* ';' => '~' */
+	{ 0x60, 0x5c },	/* '`' => '\\' */
+	{ 0, 0 }
+};
+
 /** "cf" keyboard map */
 struct keymap cf_keymap __keymap = {
 	.name = "cf",
 	.basic = cf_basic,
+	.altgr = cf_altgr,
 };

src/hci/keymap/keymap_cz.c

@@ -46,8 +46,34 @@ static struct keymap_key cz_basic[] = {
 	{ 0, 0 }
 };
 
+/** "cz" AltGr remapping */
+static struct keymap_key cz_altgr[] = {
+	{ 0x2c, 0x3c },	/* ',' => '<' */
+	{ 0x2e, 0x3e },	/* '.' => '>' */
+	{ 0x2f, 0x2a },	/* '/' => '*' */
+	{ 0x30, 0x7d },	/* '0' => '}' */
+	{ 0x32, 0x40 },	/* '2' => '@' */
+	{ 0x33, 0x23 },	/* '3' => '#' */
+	{ 0x34, 0x24 },	/* '4' => '$' */
+	{ 0x36, 0x5e },	/* '6' => '^' */
+	{ 0x37, 0x26 },	/* '7' => '&' */
+	{ 0x38, 0x2a },	/* '8' => '*' */
+	{ 0x39, 0x7b },	/* '9' => '{' */
+	{ 0x3b, 0x24 },	/* ';' => '$' */
+	{ 0x62, 0x7b },	/* 'b' => '{' */
+	{ 0x63, 0x26 },	/* 'c' => '&' */
+	{ 0x67, 0x5d },	/* 'g' => ']' */
+	{ 0x68, 0x60 },	/* 'h' => '`' */
+	{ 0x6d, 0x5e },	/* 'm' => '^' */
+	{ 0x6e, 0x7d },	/* 'n' => '}' */
+	{ 0x76, 0x40 },	/* 'v' => '@' */
+	{ 0x78, 0x23 },	/* 'x' => '#' */
+	{ 0, 0 }
+};
+
 /** "cz" keyboard map */
 struct keymap cz_keymap __keymap = {
 	.name = "cz",
 	.basic = cz_basic,
+	.altgr = cz_altgr,
 };

src/hci/keymap/keymap_de.c

@@ -41,8 +41,19 @@ static struct keymap_key de_basic[] = {
 	{ 0, 0 }
 };
 
+/** "de" AltGr remapping */
+static struct keymap_key de_altgr[] = {
+	{ 0x2d, 0x5c },	/* '-' => '\\' */
+	{ 0x30, 0x7d },	/* '0' => '}' */
+	{ 0x39, 0x5d },	/* '9' => ']' */
+	{ 0x71, 0x40 },	/* 'q' => '@' */
+	{ 0xdc, 0x7c },	/* Pseudo-'\\' => '|' */
+	{ 0, 0 }
+};
+
 /** "de" keyboard map */
 struct keymap de_keymap __keymap = {
 	.name = "de",
 	.basic = de_basic,
+	.altgr = de_altgr,
 };

src/hci/keymap/keymap_dk.c

@@ -33,8 +33,17 @@ static struct keymap_key dk_basic[] = {
 	{ 0, 0 }
 };
 
+/** "dk" AltGr remapping */
+static struct keymap_key dk_altgr[] = {
+	{ 0x32, 0x40 },	/* '2' => '@' */
+	{ 0x3d, 0x7c },	/* '=' => '|' */
+	{ 0x71, 0x40 },	/* 'q' => '@' */
+	{ 0, 0 }
+};
+
 /** "dk" keyboard map */
 struct keymap dk_keymap __keymap = {
 	.name = "dk",
 	.basic = dk_basic,
+	.altgr = dk_altgr,
 };

src/hci/keymap/keymap_es.c

@@ -33,8 +33,19 @@ static struct keymap_key es_basic[] = {
 	{ 0, 0 }
 };
 
+/** "es" AltGr remapping */
+static struct keymap_key es_altgr[] = {
+	{ 0x30, 0x7d },	/* '0' => '}' */
+	{ 0x32, 0x40 },	/* '2' => '@' */
+	{ 0x39, 0x5d },	/* '9' => ']' */
+	{ 0x5c, 0x7d },	/* '\\' => '}' */
+	{ 0x71, 0x40 },	/* 'q' => '@' */
+	{ 0, 0 }
+};
+
 /** "es" keyboard map */
 struct keymap es_keymap __keymap = {
 	.name = "es",
 	.basic = es_basic,
+	.altgr = es_altgr,
 };

src/hci/keymap/keymap_et.c

@@ -31,8 +31,18 @@ static struct keymap_key et_basic[] = {
 	{ 0, 0 }
 };
 
+/** "et" AltGr remapping */
+static struct keymap_key et_altgr[] = {
+	{ 0x27, 0x5e },	/* '\'' => '^' */
+	{ 0x2d, 0x5c },	/* '-' => '\\' */
+	{ 0x32, 0x40 },	/* '2' => '@' */
+	{ 0xdc, 0x7c },	/* Pseudo-'\\' => '|' */
+	{ 0, 0 }
+};
+
 /** "et" keyboard map */
 struct keymap et_keymap __keymap = {
 	.name = "et",
 	.basic = et_basic,
+	.altgr = et_altgr,
 };

src/hci/keymap/keymap_fi.c

@@ -31,8 +31,17 @@ static struct keymap_key fi_basic[] = {
 	{ 0, 0 }
 };
 
+/** "fi" AltGr remapping */
+static struct keymap_key fi_altgr[] = {
+	{ 0x2d, 0x5c },	/* '-' => '\\' */
+	{ 0x32, 0x40 },	/* '2' => '@' */
+	{ 0xdc, 0x7c },	/* Pseudo-'\\' => '|' */
+	{ 0, 0 }
+};
+
 /** "fi" keyboard map */
 struct keymap fi_keymap __keymap = {
 	.name = "fi",
 	.basic = fi_basic,
+	.altgr = fi_altgr,
 };

src/hci/keymap/keymap_fr.c

@@ -62,8 +62,20 @@ static struct keymap_key fr_basic[] = {
 	{ 0, 0 }
 };
 
+/** "fr" AltGr remapping */
+static struct keymap_key fr_altgr[] = {
+	{ 0x2d, 0x5d },	/* '-' => ']' */
+	{ 0x30, 0x40 },	/* '0' => '@' */
+	{ 0x33, 0x23 },	/* '3' => '#' */
+	{ 0x38, 0x5c },	/* '8' => '\\' */
+	{ 0x39, 0x5e },	/* '9' => '^' */
+	{ 0x61, 0x40 },	/* 'a' => '@' */
+	{ 0, 0 }
+};
+
 /** "fr" keyboard map */
 struct keymap fr_keymap __keymap = {
 	.name = "fr",
 	.basic = fr_basic,
+	.altgr = fr_altgr,
 };

src/hci/keymap/keymap_gr.c

@@ -17,8 +17,14 @@ static struct keymap_key gr_basic[] = {
 	{ 0, 0 }
 };
 
+/** "gr" AltGr remapping */
+static struct keymap_key gr_altgr[] = {
+	{ 0, 0 }
+};
+
 /** "gr" keyboard map */
 struct keymap gr_keymap __keymap = {
 	.name = "gr",
 	.basic = gr_basic,
+	.altgr = gr_altgr,
 };

src/hci/keymap/keymap_hu.c

@@ -35,8 +35,25 @@ static struct keymap_key hu_basic[] = {
 	{ 0, 0 }
 };
 
+/** "hu" AltGr remapping */
+static struct keymap_key hu_altgr[] = {
+	{ 0x2e, 0x3e },	/* '.' => '>' */
+	{ 0x2f, 0x2a },	/* '/' => '*' */
+	{ 0x33, 0x5e },	/* '3' => '^' */
+	{ 0x37, 0x60 },	/* '7' => '`' */
+	{ 0x3b, 0x24 },	/* ';' => '$' */
+	{ 0x63, 0x26 },	/* 'c' => '&' */
+	{ 0x6d, 0x3c },	/* 'm' => '<' */
+	{ 0x76, 0x40 },	/* 'v' => '@' */
+	{ 0x78, 0x23 },	/* 'x' => '#' */
+	{ 0x7a, 0x3e },	/* 'z' => '>' */
+	{ 0xdc, 0x3c },	/* Pseudo-'\\' => '<' */
+	{ 0, 0 }
+};
+
 /** "hu" keyboard map */
 struct keymap hu_keymap __keymap = {
 	.name = "hu",
 	.basic = hu_basic,
+	.altgr = hu_altgr,
 };

src/hci/keymap/keymap_il.c

@@ -29,8 +29,14 @@ static struct keymap_key il_basic[] = {
 	{ 0, 0 }
 };
 
+/** "il" AltGr remapping */
+static struct keymap_key il_altgr[] = {
+	{ 0, 0 }
+};
+
 /** "il" keyboard map */
 struct keymap il_keymap __keymap = {
 	.name = "il",
 	.basic = il_basic,
+	.altgr = il_altgr,
 };

src/hci/keymap/keymap_it.c

@@ -35,8 +35,20 @@ static struct keymap_key it_basic[] = {
 	{ 0, 0 }
 };
 
+/** "it" AltGr remapping */
+static struct keymap_key it_altgr[] = {
+	{ 0x2d, 0x60 },	/* '-' => '`' */
+	{ 0x30, 0x7d },	/* '0' => '}' */
+	{ 0x39, 0x5d },	/* '9' => ']' */
+	{ 0x3b, 0x40 },	/* ';' => '@' */
+	{ 0x3d, 0x7e },	/* '=' => '~' */
+	{ 0x71, 0x40 },	/* 'q' => '@' */
+	{ 0, 0 }
+};
+
 /** "it" keyboard map */
 struct keymap it_keymap __keymap = {
 	.name = "it",
 	.basic = it_basic,
+	.altgr = it_altgr,
 };

src/hci/keymap/keymap_lt.c

@@ -15,8 +15,14 @@ static struct keymap_key lt_basic[] = {
 	{ 0, 0 }
 };
 
+/** "lt" AltGr remapping */
+static struct keymap_key lt_altgr[] = {
+	{ 0, 0 }
+};
+
 /** "lt" keyboard map */
 struct keymap lt_keymap __keymap = {
 	.name = "lt",
 	.basic = lt_basic,
+	.altgr = lt_altgr,
 };

src/hci/keymap/keymap_mk.c

@@ -17,8 +17,14 @@ static struct keymap_key mk_basic[] = {
 	{ 0, 0 }
 };
 
+/** "mk" AltGr remapping */
+static struct keymap_key mk_altgr[] = {
+	{ 0, 0 }
+};
+
 /** "mk" keyboard map */
 struct keymap mk_keymap __keymap = {
 	.name = "mk",
 	.basic = mk_basic,
+	.altgr = mk_altgr,
 };

src/hci/keymap/keymap_mt.c

@@ -20,8 +20,15 @@ static struct keymap_key mt_basic[] = {
 	{ 0, 0 }
 };
 
+/** "mt" AltGr remapping */
+static struct keymap_key mt_altgr[] = {
+	{ 0x2d, 0x5c },	/* '-' => '\\' */
+	{ 0, 0 }
+};
+
 /** "mt" keyboard map */
 struct keymap mt_keymap __keymap = {
 	.name = "mt",
 	.basic = mt_basic,
+	.altgr = mt_altgr,
 };

src/hci/keymap/keymap_nl.c

@@ -38,8 +38,16 @@ static struct keymap_key nl_basic[] = {
 	{ 0, 0 }
 };
 
+/** "nl" AltGr remapping */
+static struct keymap_key nl_altgr[] = {
+	{ 0x2d, 0x5c },	/* '-' => '\\' */
+	{ 0x39, 0x7d },	/* '9' => '}' */
+	{ 0, 0 }
+};
+
 /** "nl" keyboard map */
 struct keymap nl_keymap __keymap = {
 	.name = "nl",
 	.basic = nl_basic,
+	.altgr = nl_altgr,
 };

src/hci/keymap/keymap_no-latin1.c

@@ -37,8 +37,18 @@ static struct keymap_key no_latin1_basic[] = {
 	{ 0, 0 }
 };
 
+/** "no-latin1" AltGr remapping */
+static struct keymap_key no_latin1_altgr[] = {
+	{ 0x30, 0x7d },	/* '0' => '}' */
+	{ 0x32, 0x40 },	/* '2' => '@' */
+	{ 0x39, 0x5d },	/* '9' => ']' */
+	{ 0x5b, 0x7d },	/* '[' => '}' */
+	{ 0, 0 }
+};
+
 /** "no-latin1" keyboard map */
 struct keymap no_latin1_keymap __keymap = {
 	.name = "no-latin1",
 	.basic = no_latin1_basic,
+	.altgr = no_latin1_altgr,
 };

src/hci/keymap/keymap_no.c

@@ -35,8 +35,16 @@ static struct keymap_key no_basic[] = {
 	{ 0, 0 }
 };
 
+/** "no" AltGr remapping */
+static struct keymap_key no_altgr[] = {
+	{ 0x32, 0x40 },	/* '2' => '@' */
+	{ 0x71, 0x40 },	/* 'q' => '@' */
+	{ 0, 0 }
+};
+
 /** "no" keyboard map */
 struct keymap no_keymap __keymap = {
 	.name = "no",
 	.basic = no_basic,
+	.altgr = no_altgr,
 };

src/hci/keymap/keymap_pl.c

@@ -17,8 +17,14 @@ static struct keymap_key pl_basic[] = {
 	{ 0, 0 }
 };
 
+/** "pl" AltGr remapping */
+static struct keymap_key pl_altgr[] = {
+	{ 0, 0 }
+};
+
 /** "pl" keyboard map */
 struct keymap pl_keymap __keymap = {
 	.name = "pl",
 	.basic = pl_basic,
+	.altgr = pl_altgr,
 };

src/hci/keymap/keymap_pt.c

@@ -34,8 +34,18 @@ static struct keymap_key pt_basic[] = {
 	{ 0, 0 }
 };
 
+/** "pt" AltGr remapping */
+static struct keymap_key pt_altgr[] = {
+	{ 0x32, 0x40 },	/* '2' => '@' */
+	{ 0x37, 0x7b },	/* '7' => '{' */
+	{ 0x38, 0x5b },	/* '8' => '[' */
+	{ 0x71, 0x40 },	/* 'q' => '@' */
+	{ 0, 0 }
+};
+
 /** "pt" keyboard map */
 struct keymap pt_keymap __keymap = {
 	.name = "pt",
 	.basic = pt_basic,
+	.altgr = pt_altgr,
 };

src/hci/keymap/keymap_ro.c

@@ -15,8 +15,14 @@ static struct keymap_key ro_basic[] = {
 	{ 0, 0 }
 };
 
+/** "ro" AltGr remapping */
+static struct keymap_key ro_altgr[] = {
+	{ 0, 0 }
+};
+
 /** "ro" keyboard map */
 struct keymap ro_keymap __keymap = {
 	.name = "ro",
 	.basic = ro_basic,
+	.altgr = ro_altgr,
 };

src/hci/keymap/keymap_ru.c

@@ -18,8 +18,14 @@ static struct keymap_key ru_basic[] = {
 	{ 0, 0 }
 };
 
+/** "ru" AltGr remapping */
+static struct keymap_key ru_altgr[] = {
+	{ 0, 0 }
+};
+
 /** "ru" keyboard map */
 struct keymap ru_keymap __keymap = {
 	.name = "ru",
 	.basic = ru_basic,
+	.altgr = ru_altgr,
 };

src/hci/keymap/keymap_sg.c

@@ -43,8 +43,18 @@ static struct keymap_key sg_basic[] = {
 	{ 0, 0 }
 };
 
+/** "sg" AltGr remapping */
+static struct keymap_key sg_altgr[] = {
+	{ 0x32, 0x40 },	/* '2' => '@' */
+	{ 0x33, 0x23 },	/* '3' => '#' */
+	{ 0x37, 0x7c },	/* '7' => '|' */
+	{ 0x5c, 0x7d },	/* '\\' => '}' */
+	{ 0, 0 }
+};
+
 /** "sg" keyboard map */
 struct keymap sg_keymap __keymap = {
 	.name = "sg",
 	.basic = sg_basic,
+	.altgr = sg_altgr,
 };

src/hci/keymap/keymap_sr-latin.c

@@ -17,8 +17,14 @@ static struct keymap_key sr_latin_basic[] = {
 	{ 0, 0 }
 };
 
+/** "sr-latin" AltGr remapping */
+static struct keymap_key sr_latin_altgr[] = {
+	{ 0, 0 }
+};
+
 /** "sr-latin" keyboard map */
 struct keymap sr_latin_keymap __keymap = {
 	.name = "sr-latin",
 	.basic = sr_latin_basic,
+	.altgr = sr_latin_altgr,
 };

src/hci/keymap/keymap_ua.c

@@ -17,8 +17,14 @@ static struct keymap_key ua_basic[] = {
 	{ 0, 0 }
 };
 
+/** "ua" AltGr remapping */
+static struct keymap_key ua_altgr[] = {
+	{ 0, 0 }
+};
+
 /** "ua" keyboard map */
 struct keymap ua_keymap __keymap = {
 	.name = "ua",
 	.basic = ua_basic,
+	.altgr = ua_altgr,
 };

src/hci/keymap/keymap_uk.c

@@ -19,8 +19,14 @@ static struct keymap_key uk_basic[] = {
 	{ 0, 0 }
 };
 
+/** "uk" AltGr remapping */
+static struct keymap_key uk_altgr[] = {
+	{ 0, 0 }
+};
+
 /** "uk" keyboard map */
 struct keymap uk_keymap __keymap = {
 	.name = "uk",
 	.basic = uk_basic,
+	.altgr = uk_altgr,
 };

src/hci/keymap/keymap_us.c

@@ -15,8 +15,14 @@ static struct keymap_key us_basic[] = {
 	{ 0, 0 }
 };
 
+/** "us" AltGr remapping */
+static struct keymap_key us_altgr[] = {
+	{ 0, 0 }
+};
+
 /** "us" keyboard map */
 struct keymap us_keymap __keymap = {
 	.name = "us",
 	.basic = us_basic,
+	.altgr = us_altgr,
 };

src/include/ipxe/keymap.h

@@ -32,6 +32,8 @@ struct keymap {
 	const char *name;
 	/** Basic remapping table (zero-terminated) */
 	struct keymap_key *basic;
+	/** AltGr remapping table (zero-terminated) */
+	struct keymap_key *altgr;
 };
 
 /** Keyboard mapping table */
@@ -64,6 +66,9 @@ struct keymap {
 /** Undo and redo CapsLock key flags */
 #define KEYMAP_CAPSLOCK_REDO ( KEYMAP_CAPSLOCK | KEYMAP_CAPSLOCK_UNDO )
 
+/** AltGr key flag */
+#define KEYMAP_ALTGR 0x0800
+
 extern unsigned int key_remap ( unsigned int character );
 
 #endif /* _IPXE_KEYMAP_H */

src/interface/efi/efi_console.c

@@ -334,6 +334,9 @@ static int efi_getchar ( void ) {
 				       EFI_RIGHT_CONTROL_PRESSED ) ) {
 				character |= KEYMAP_CTRL;
 			}
+			if ( shift & EFI_RIGHT_ALT_PRESSED ) {
+				character |= KEYMAP_ALTGR;
+			}
 		}
 
 		/* Apply toggle state */

src/util/genkeymap.py

@@ -171,6 +171,11 @@ class KeyLayout(UserDict[KeyModifiers, Sequence[Key]]):
         """Basic shifted keyboard layout"""
         return self[KeyModifiers.SHIFT]
 
+    @property
+    def altgr(self):
+        """AltGr keyboard layout"""
+        return self.get(KeyModifiers.ALTGR, self.unshifted)
+
     @classmethod
     def load(cls, name: str) -> KeyLayout:
         """Load keymap using 'loadkeys -b'"""
@@ -278,6 +283,7 @@ class KeymapKeys(UserDict[str, str]):
                 self.ascii_name(source), self.ascii_name(target)
             )
             for source, target in self.items()
+            if ord(source) & ~BiosKeyLayout.KEY_PSEUDO != ord(target)
         ) + '\t{ 0, 0 }\n}'
 
 
@@ -301,13 +307,12 @@ class Keymap:
         raw = {source: self.target[key.modifiers][key.keycode].ascii
                for source, key in self.source.inverse.items()}
         # Eliminate any null mappings, mappings that attempt to remap
-        # the backspace key, or mappings that would become identity
-        # mappings after clearing the high bit
+        # the backspace key, or identity mappings
         table = {source: target for source, target in raw.items()
                  if target
                  and ord(source) != 0x7f
                  and ord(target) != 0x7f
-                 and ord(source) & ~BiosKeyLayout.KEY_PSEUDO != ord(target)}
+                 and source != target}
         # Recursively delete any mappings that would produce
         # unreachable alphanumerics (e.g. the "il" keymap, which maps
         # away the whole lower-case alphabet)
@@ -327,6 +332,28 @@ class Keymap:
                              (unshifted, shifted))
         return KeymapKeys(dict(sorted(table.items())))
 
+    @property
+    def altgr(self) -> KeymapKeys:
+        """AltGr remapping table"""
+        # Construct raw mapping from source ASCII to target ASCII
+        raw = {source: self.target.altgr[key.keycode].ascii
+               for source, key in self.source.inverse.items()
+               if key.modifiers == KeyModifiers.NONE}
+        # Identify printable keys that are unreachable via the basic map
+        basic = self.basic
+        unmapped = set(x for x in basic.keys()
+                       if x.isascii() and x.isprintable())
+        remapped = set(basic.values())
+        unreachable = unmapped - remapped
+        # Eliminate any null mappings, mappings for unprintable
+        # characters, or mappings for characters that are reachable
+        # via the basic map
+        table = {source: target for source, target in raw.items()
+                 if source.isprintable()
+                 and target
+                 and target in unreachable}
+        return KeymapKeys(dict(sorted(table.items())))
+
     def cname(self, suffix: str) -> str:
         """C variable name"""
         return re.sub(r'\W', '_', (self.name + '_' + suffix))
@@ -336,6 +363,7 @@ class Keymap:
         """Generated source code"""
         keymap_name = self.cname("keymap")
         basic_name = self.cname("basic")
+        altgr_name = self.cname("altgr")
         code = textwrap.dedent(f"""
         /** @file
          *
@@ -352,12 +380,16 @@ class Keymap:
         /** "{self.name}" basic remapping */
         static struct keymap_key {basic_name}[] = %s;
 
+        /** "{self.name}" AltGr remapping */
+        static struct keymap_key {altgr_name}[] = %s;
+
         /** "{self.name}" keyboard map */
         struct keymap {keymap_name} __keymap = {{
         \t.name = "{self.name}",
         \t.basic = {basic_name},
+        \t.altgr = {altgr_name},
         }};
-        """).strip() % self.basic.code
+        """).strip() % (self.basic.code, self.altgr.code)
         return code