TODO: remove //temp-s We place the trampoline no lower than at 256k, so we have ample space to read the MBRs of BIOS disks into an aligned buffer right below the trampoline (not doing so has been found to be a problem on a buggy BIOS coming with a Skull Canyon NUC). To facilitate that move MBR reading past EDD info retrieval. Also add a wrap check to the EDD info retrieval loop, to match that in the MBR reading one. Reported-by: Paul Durrant --- Using 512-byte sector size as default right now - perhaps worth considering to use 4k instead. I'm also not sure whether we shouldn't sanity check the sector size some more. --- unstable.orig/xen/arch/x86/boot/edd.S 2017-02-09 14:28:18.000000000 +0100 +++ unstable/xen/arch/x86/boot/edd.S 2017-06-12 12:33:36.353082705 +0200 @@ -26,46 +26,6 @@ get_edd: cmpb $2, bootsym(opt_edd) # edd=off ? je edd_done - cmpb $1, bootsym(opt_edd) # edd=skipmbr ? - je edd_start - -# Read the first sector of each BIOS disk device and store the 4-byte signature -edd_mbr_sig_start: - movb $0x80, %dl # from device 80 - movw $bootsym(boot_mbr_signature),%bx # store buffer ptr in bx -edd_mbr_sig_read: - pushw %bx - movb $0x02, %ah # 0x02 Read Sectors - movb $1, %al # read 1 sector - movb $0, %dh # at head 0 - movw $1, %cx # cylinder 0, sector 0 - pushw %es - pushw %ds - popw %es - movw $bootsym(boot_edd_info), %bx # disk's data goes into info - pushw %dx # work around buggy BIOSes - stc # work around buggy BIOSes - int $0x13 - sti # work around buggy BIOSes - popw %dx - popw %es - popw %bx - 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 - 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: # Do the BIOS Enhanced Disk Drive calls # This consists of two calls: @@ -136,10 +96,72 @@ edd_legacy_done: edd_next: incb %dl # increment to next device + jz edd_done cmpb $EDD_INFO_MAX,bootsym(boot_edd_info_nr) jb edd_check_ext edd_done: + cmpb $1, bootsym(opt_edd) # edd=skipmbr ? + je .Ledd_mbr_sig_skip + +# Read the first sector of each BIOS disk device and store the 4-byte signature +.Ledd_mbr_sig_start: + pushw %es + movb $0x80, %dl # from device 80 + movw $bootsym(boot_mbr_signature), %bx # store buffer ptr in bx +.Ledd_mbr_sig_read: + pushw %bx + movw $bootsym(boot_edd_info), %bx + movzbw bootsym(boot_edd_info_nr), %cx + jcxz .Ledd_mbr_sig_default +.Ledd_mbr_sig_find_info: + cmpb %dl, (%bx) + ja .Ledd_mbr_sig_default + je .Ledd_mbr_sig_get_size + add $EDDEXTSIZE+EDDPARMSIZE, %bx + loop .Ledd_mbr_sig_find_info +.Ledd_mbr_sig_default: + movw $(512 >> 4), %bx + jmp .Ledd_mbr_sig_set_buf +.Ledd_mbr_sig_get_size: + movw EDDEXTSIZE+0x18(%bx), %bx # sector size + shr $4, %bx # convert to paragraphs + jz .Ledd_mbr_sig_default +.Ledd_mbr_sig_set_buf: + movw %ds, %ax + subw %bx, %ax # disk's data goes right ahead + movw %ax, %es # of trampoline + xorw %bx, %bx + movw %bx, %es:0x1fe(%bx) # clear BIOS magic just in case + pushw %dx # work around buggy BIOSes + stc # work around buggy BIOSes + movw $0x0201, %ax # read 1 sector + movb $0, %dh # at head 0 + movw $1, %cx # cylinder 0, sector 0 + int $0x13 + sti # work around buggy BIOSes + popw %dx + movw %es:0x1fe(%bx), %si + movl %es:EDD_MBR_SIG_OFFSET(%bx), %ecx + popw %bx + jc .Ledd_mbr_sig_done # on failure, we're done. + testb %ah, %ah # some BIOSes do not set CF + jnz .Ledd_mbr_sig_done # on failure, we're done. + cmpw $0xaa55, %si + jne .Ledd_mbr_sig_next + movb %dl, (%bx) # store BIOS drive number + movw %es,2(%bx)//temp + movl %ecx, 4(%bx) # store signature from MBR + incb bootsym(boot_mbr_signature_nr) # note that we stored something + addw $8, %bx # increment sig buffer ptr +.Ledd_mbr_sig_next: + incb %dl # increment to next device + jz .Ledd_mbr_sig_done + cmpb $EDD_MBR_SIG_MAX, bootsym(boot_mbr_signature_nr) + jb .Ledd_mbr_sig_read +.Ledd_mbr_sig_done: + popw %es +.Ledd_mbr_sig_skip: ret GLOBAL(boot_edd_info_nr) @@ -149,4 +171,4 @@ GLOBAL(boot_mbr_signature_nr) GLOBAL(boot_mbr_signature) .fill EDD_MBR_SIG_MAX*8,1,0 GLOBAL(boot_edd_info) - .fill 512,1,0 # big enough for a disc sector + .fill EDD_INFO_MAX * (EDDEXTSIZE + EDDPARMSIZE), 1, 0 --- unstable.orig/xen/arch/x86/platform_hypercall.c 2015-07-20 14:49:38.000000000 +0200 +++ unstable/xen/arch/x86/platform_hypercall.c 2017-06-12 12:22:01.658928095 +0200 @@ -376,6 +376,7 @@ ret_t do_platform_op(XEN_GUEST_HANDLE_PA break; sig = bootsym(boot_mbr_signature) + op->u.firmware_info.index; +printk("MBR[%02x] @ %02x%02x (%04lx)\n", sig->device, sig->pad[2], sig->pad[1], trampoline_phys);//temp op->u.firmware_info.u.disk_mbr_signature.device = sig->device; op->u.firmware_info.u.disk_mbr_signature.mbr_signature =