From 8ca43ccbc1984d60e50711ea326ca59ac03985d2 Mon Sep 17 00:00:00 2001 From: Michael Brown Date: Tue, 13 Apr 2021 20:30:20 +0100 Subject: [int13] Do not report INT 13 extension support for emulated floppies The INT 13 extensions provide a mechanism for accessing disks using linear (LBA) rather than C/H/S addressing. SAN protocols such as iSCSI invariably support only linear addresses and so iPXE currently provides LBA access to all SAN disks (with autodetection and emulation of an appropriate geometry for C/H/S accesses). Most BIOSes will not report support for INT 13 extensions for floppy disk drives, and some operating systems may be confused by a floppy drive that claims such support. Minimise surprise by reporting the existence of support for INT 13 extensions only for non-floppy drive numbers. Continue to provide support for all drive numbers, to avoid breaking operating systems that may unconditionally use the INT 13 extensions without first checking for support. Reported-by: Valdo Toost Signed-off-by: Michael Brown --- src/arch/x86/interface/pcbios/int13.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/src/arch/x86/interface/pcbios/int13.c b/src/arch/x86/interface/pcbios/int13.c index 30530e1..d6c4d7e 100644 --- a/src/arch/x86/interface/pcbios/int13.c +++ b/src/arch/x86/interface/pcbios/int13.c @@ -678,10 +678,10 @@ static int int13_get_disk_type ( struct san_device *sandev, * @ret cx Extensions API support bitmap * @ret status Status code / API version */ -static int int13_extension_check ( struct san_device *sandev __unused, +static int int13_extension_check ( struct san_device *sandev, struct i386_all_regs *ix86 ) { - if ( ix86->regs.bx == 0x55aa ) { + if ( ( ix86->regs.bx == 0x55aa ) && ! int13_is_fdd ( sandev ) ) { DBGC2 ( sandev, "INT13 extensions installation check\n" ); ix86->regs.bx = 0xaa55; ix86->regs.cx = ( INT13_EXTENSION_LINEAR | -- cgit v1.1