Jan Beulich
2012-May-30 15:36 UTC
[PATCH] x86/EDD: check MBR for BIOS magic before considering signature valid
Signed-off-by: Jan Beulich <JBeulich@suse.com> --- 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: _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel
Keir Fraser
2012-May-30 16:48 UTC
Re: [PATCH] x86/EDD: check MBR for BIOS magic before considering signature valid
On 30/05/2012 16:36, "Jan Beulich" <JBeulich@suse.com> wrote:> Signed-off-by: Jan Beulich <JBeulich@suse.com>Acked-by: Keir Fraser <keir@xen.org>> --- 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: > > > > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xen.org > http://lists.xen.org/xen-devel