fix linuxboot.bin and multiboot.bin to not hijack int19

Currently linuxboot.bin and multiboot.bin option roms override int19
vector to intercept boot process. No sane option rom should do that.
Provide bev entry instead that will be called by BIOS if option rom
is selected for booting.
Signed-off-by: Gleb Natapov <gleb@redhat.com>
Acked-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>

pc-bios/optionrom/linuxboot.S

@@ -22,6 +22,8 @@
 
 #include "optionrom.h"
 
+#define BOOT_ROM_PRODUCT "Linux loader"
+
 BOOT_ROM_START
 
 run_linuxboot:

pc-bios/optionrom/multiboot.S

@@ -20,6 +20,8 @@
 
 #include "optionrom.h"
 
+#define BOOT_ROM_PRODUCT "multiboot loader"
+
 #define MULTIBOOT_MAGIC		0x2badb002
 
 #define GS_PROT_JUMP		0

pc-bios/optionrom/optionrom.h

@@ -97,22 +97,28 @@
 
 #define BOOT_ROM_START					\
 	OPTION_ROM_START				\
-	push		%eax;				\
-	push		%ds;				\
-							\
-	/* setup ds so we can access the IVT */		\
-	xor		%ax, %ax;			\
-	mov		%ax, %ds;			\
-							\
-	/* install our int 19 handler */		\
-	movw		$int19_handler, (0x19*4);	\
-	mov		%cs, (0x19*4+2);		\
-							\
-	pop		%ds;				\
-	pop		%eax;				\
 	lret;						\
-							\
-    int19_handler:;					\
+	.org 		0x18;				\
+	.short		0;				\
+	.short		_pnph;				\
+    _pnph:						\
+	.ascii		"$PnP";				\
+	.byte		0x01;				\
+	.byte		( _pnph_len / 16 );		\
+	.short		0x0000;				\
+	.byte		0x00;				\
+	.byte		0x00;				\
+	.long		0x00000000;			\
+	.short		_manufacturer;			\
+	.short		_product;			\
+	.long		0x00000000;			\
+	.short		0x0000;				\
+	.short		0x0000;				\
+	.short		_bev;				\
+	.short		0x0000;				\
+	.short		0x0000;				\
+	.equ		_pnph_len, . - _pnph;		\
+    _bev:;						\
 	/* DS = CS */					\
 	movw		%cs, %ax;			\
 	movw		%ax, %ds;
@@ -122,5 +128,9 @@
     _end:
 
 #define BOOT_ROM_END					\
+    _manufacturer:;					\
+	.asciz "QEMU";					\
+    _product:;						\
+	.asciz BOOT_ROM_PRODUCT;			\
 	OPTION_ROM_END