RFE: Support the ASCII console in the zipl boot menu

[huth]

The zipl boot menu currently only enables the line mode console with sclp_setup(SCLP_INIT) in zipl/boot/menu.c. That's ok for most use-cases, but recently I wanted to boot a KVM guest from a DASD that has been passed-through to the guest via vfio-ccw, and noticed that I can not get the boot menu in that case:

qemu-system-s390x -accel kvm -m 4G -nographic -boot menu=on
-device vfio-ccw,devno=fe.0.2345,sysfsdev=/sys/bus/mdev/devices/UUID,bootindex=1

Would it be feasible to support the ASCII console for these scenarios, too (i.e. to fall back to sclp_setup(SCLP_LINE_ASCII_INIT) in case the line mode init fails)?

[mhartmay]

The last time I wanted to implement this, there were size limitations in the stage[123] loaders. If I remember correctly the tables in ebcdic_conv.c were too large.

[huth]

Currently, the two tables in ebcdic_conv.c are the same, so maybe one could get removed (see #125 )? Or if you care about the right code pages, maybe a patch like this could help to save approx. 90 bytes (not sure whether that's enough, though):

diff --git a/zipl/boot/ebcdic_conv.c b/zipl/boot/ebcdic_conv.c
--- a/zipl/boot/ebcdic_conv.c
+++ b/zipl/boot/ebcdic_conv.c
@@ -84,84 +84,41 @@ static unsigned char ebcdic_037[256] = {
 	0x38, 0x39, 0x07, 0x07, 0x9A, 0x07, 0x07, 0x07
 };
 
-static unsigned char ebcdic_500[256] = {
-/* 0x00  NUL   SOH   STX   ETX  *SEL    HT  *RNL   DEL */
-	0x00, 0x01, 0x02, 0x03, 0x07, 0x09, 0x07, 0x7F,
-/* 0x08  -GE  -SPS  -RPT    VT    FF    CR    SO    SI */
-	0x07, 0x07, 0x07, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F,
-/* 0x10  DLE   DC1   DC2   DC3  -RES   -NL    BS  -POC
-				-ENP  ->LF             */
-	0x10, 0x11, 0x12, 0x13, 0x07, 0x0A, 0x08, 0x07,
-/* 0x18  CAN    EM  -UBS  -CU1  -IFS  -IGS  -IRS  -ITB
-						  -IUS */
-	0x18, 0x19, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07,
-/* 0x20  -DS  -SOS    FS  -WUS  -BYP    LF   ETB   ESC
-				-INP                   */
-	0x07, 0x07, 0x1C, 0x07, 0x07, 0x0A, 0x17, 0x1B,
-/* 0x28  -SA  -SFE   -SM  -CSP  -MFA   ENQ   ACK   BEL
-		     -SW                               */
-	0x07, 0x07, 0x07, 0x07, 0x07, 0x05, 0x06, 0x07,
-/* 0x30 ----  ----   SYN   -IR   -PP  -TRN  -NBS   EOT */
-	0x07, 0x07, 0x16, 0x07, 0x07, 0x07, 0x07, 0x04,
-/* 0x38 -SBS   -IT  -RFF  -CU3   DC4   NAK  ----   SUB */
-	0x07, 0x07, 0x07, 0x07, 0x14, 0x15, 0x07, 0x1A,
-/* 0x40   SP   RSP           ä              ----       */
-	0x20, 0xFF, 0x83, 0x84, 0x85, 0xA0, 0x07, 0x86,
-/* 0x48                      .     <     (     +     | */
-	0x87, 0xA4, 0x9B, 0x2E, 0x3C, 0x28, 0x2B, 0x7C,
+static unsigned char ebcdic_500_4a[22] = {
+/* 0x48                [     .     <     (     +     ! */
+                    0x5B, 0x2E, 0x3C, 0x28, 0x2B, 0x21,
 /* 0x50    &                                      ---- */
-	0x26, 0x82, 0x88, 0x89, 0x8A, 0xA1, 0x8C, 0x07,
-/* 0x58          ß     !     $     *     )     ;       */
-	0x8D, 0xE1, 0x21, 0x24, 0x2A, 0x29, 0x3B, 0xAA,
-/* 0x60    -     /  ----     Ä  ----  ----  ----       */
-	0x2D, 0x2F, 0x07, 0x8E, 0x07, 0x07, 0x07, 0x8F,
-/* 0x68             ----     ,     %     _     >     ? */
-	0x80, 0xA5, 0x07, 0x2C, 0x25, 0x5F, 0x3E, 0x3F,
-/* 0x70  ---        ----  ----  ----  ----  ----  ---- */
-	0x07, 0x90, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07,
-/* 0x78    *     `     :     #     @     '     =     " */
-	0x70, 0x60, 0x3A, 0x23, 0x40, 0x27, 0x3D, 0x22,
-/* 0x80    *     a     b     c     d     e     f     g */
-	0x07, 0x61, 0x62, 0x63, 0x64, 0x65, 0x66, 0x67,
-/* 0x88    h     i              ----  ----  ----       */
-	0x68, 0x69, 0xAE, 0xAF, 0x07, 0x07, 0x07, 0xF1,
-/* 0x90    °     j     k     l     m     n     o     p */
-	0xF8, 0x6A, 0x6B, 0x6C, 0x6D, 0x6E, 0x6F, 0x70,
-/* 0x98    q     r                    ----        ---- */
-	0x71, 0x72, 0xA6, 0xA7, 0x91, 0x07, 0x92, 0x07,
-/* 0xA0          ~     s     t     u     v     w     x */
-	0xE6, 0x7E, 0x73, 0x74, 0x75, 0x76, 0x77, 0x78,
-/* 0xA8    y     z              ----  ----  ----  ---- */
-	0x79, 0x7A, 0xAD, 0xAB, 0x07, 0x07, 0x07, 0x07,
-/* 0xB0    ^                    ----     §  ----       */
-	0x5E, 0x9C, 0x9D, 0xFA, 0x07, 0x07, 0x07, 0xAC,
-/* 0xB8       ----     [     ]  ----  ----  ----  ---- */
-	0xAB, 0x07, 0x5B, 0x5D, 0x07, 0x07, 0x07, 0x07,
-/* 0xC0    {     A     B     C     D     E     F     G */
-	0x7B, 0x41, 0x42, 0x43, 0x44, 0x45, 0x46, 0x47,
-/* 0xC8    H     I  ----           ö              ---- */
-	0x48, 0x49, 0x07, 0x93, 0x94, 0x95, 0xA2, 0x07,
-/* 0xD0    }     J     K     L     M     N     O     P */
-	0x7D, 0x4A, 0x4B, 0x4C, 0x4D, 0x4E, 0x4F, 0x50,
-/* 0xD8    Q     R  ----           ü                   */
-	0x51, 0x52, 0x07, 0x96, 0x81, 0x97, 0xA3, 0x98,
-/* 0xE0    \           S     T     U     V     W     X */
-	0x5C, 0xF6, 0x53, 0x54, 0x55, 0x56, 0x57, 0x58,
-/* 0xE8    Y     Z        ----     Ö  ----  ----  ---- */
-	0x59, 0x5A, 0xFD, 0x07, 0x99, 0x07, 0x07, 0x07,
-/* 0xF0    0     1     2     3     4     5     6     7 */
-	0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37,
-/* 0xF8    8     9  ----  ----     Ü  ----  ----  ---- */
-	0x38, 0x39, 0x07, 0x07, 0x9A, 0x07, 0x07, 0x07
+        0x26, 0x82, 0x88, 0x89, 0x8A, 0xA1, 0x8C, 0x07,
+/* 0x58          ß     ]     $     *     )     ;     ^ */
+        0x8D, 0xE1, 0x5D, 0x24, 0x2A, 0x29, 0x3B, 0x5E,
+};
+
+static unsigned char ebcdic_500_b0[12] = {
+/* 0xB0                         ----     §  ----       */
+        0x9B, 0x9C, 0x9D, 0xFA, 0x07, 0x07, 0x07, 0xAC,
+/* 0xB8       ----           |  ----  ----  ----  ---- */
+        0xAB, 0x07, 0xAA, 0x7C,
 };
 
 void ebcdic_to_ascii(unsigned char *target, const unsigned char *source,
 		     unsigned int l)
 {
-	unsigned char *ebc;
 	unsigned int i;
+	unsigned char dc, sc;
 
-	ebc = is_zvm() ? ebcdic_037 : ebcdic_500;
-	for (i = 0; i < l; i++)
-		target[i] = ebc[source[i]];
+	if (is_zvm()) {
+		for (i = 0; i < l; i++)
+			target[i] = ebcdic_037[source[i]];
+	} else {
+		for (i = 0; i < l; i++) {
+			sc = source[i];
+			if (sc >= 0x4a && sc <= 0x5f)
+				dc = ebcdic_500_4a[sc - 0x4a];
+			else if (sc >= 0xb0 && sc <= 0xbb)
+				dc = ebcdic_500_b0[sc - 0xb0];
+			else
+				dc = ebcdic_037[sc];
+			target[i] = dc;
+		}
+	}
 }