From 7f22ab7345aac8f5066fd52864d73d262ce8ed07 Mon Sep 17 00:00:00 2001 From: Jan Beulich Date: Thu, 31 May 2012 10:18:13 +0200 Subject: [PATCH] x86/EDD: check MBR for BIOS magic before considering signature valid Signed-off-by: Jan Beulich Acked-by: Keir Fraser --- xen/arch/x86/boot/edd.S | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/xen/arch/x86/boot/edd.S b/xen/arch/x86/boot/edd.S index 59874ce4c6..2c8df8ccc8 100644 --- a/xen/arch/x86/boot/edd.S +++ b/xen/arch/x86/boot/edd.S @@ -53,12 +53,16 @@ edd_mbr_sig_read: jc edd_mbr_sig_done # on failure, we're done. cmpb $0, %ah # some BIOSes do not set CF jne edd_mbr_sig_done # on failure, we're done. + cmpw $0xaa55, bootsym(boot_edd_info)+0x1fe + jne .Ledd_mbr_sig_next movl bootsym(boot_edd_info)+EDD_MBR_SIG_OFFSET,%eax movb %dl, (%bx) # store BIOS drive number movl %eax, 4(%bx) # store signature from MBR incb bootsym(boot_mbr_signature_nr) # note that we stored something - incb %dl # increment to next device addw $8, %bx # increment sig buffer ptr +.Ledd_mbr_sig_next: + incb %dl # increment to next device + jz edd_mbr_sig_done cmpb $EDD_MBR_SIG_MAX,bootsym(boot_mbr_signature_nr) jb edd_mbr_sig_read edd_mbr_sig_done: -- 2.39.5