diskstart: clean up GPT handling

We only need 56 bytes, not 92, and we should check for 0xED as the
partition type.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>

diff --git a/core/diskstart.inc b/core/diskstart.inc
index f557098..40330dd 100644 (file)
--- a/core/diskstart.inc
+++ b/core/diskstart.inc
@@ -22,7 +22,7 @@
 PartInfo:                              ; Partition table info
 .mbr:          resb 16                 ; MBR partition info
 .gptlen:       resd 1
-.gpt:          resb 92
+.gpt:          resb 56                 ; GPT partition info (minus name)
 FloppyTable    resb 16                 ; Floppy info table (must follow PartInfo)
 
                section .init
@@ -121,10 +121,10 @@ start:
 
 ;
 ; DS:SI may contain a partition table entry and possibly a GPT entry.
-; Preserve it for us.  This saves 92 bytes of the GPT entry, which is
-; currently the maximum we care about.
+; Preserve it for us.  This saves 56 bytes of the GPT entry, which is
+; currently the maximum we care about.  Total is 76 bytes.
 ;
-               mov cl,(16+4+92)/2      ; Save partition info
+               mov cl,(16+4+56)/2      ; Save partition info
                mov di,PartInfo
                rep movsw               ; This puts CX back to zero
 
@@ -158,7 +158,7 @@ floppy:
                mov [bx+2],ax           ; Segment 0
                fs rep movsw            ; Faster to move words
                mov cl,[bsSecPerTrack]  ; Patch the sector count
-               mov [di-112+8],cl
+               mov [di-76+8],cl
                int 13h                 ; Some BIOSes need this
 
                push cx                 ; Partition offset == 0
@@ -174,17 +174,19 @@ floppy:
 ; Note: di points to beyond the end of PartInfo
 ;
 harddisk:
-               test byte [di-112],7Fh  ; Sanity check: "active flag" should
+               test byte [di-76],7Fh   ; Sanity check: "active flag" should
                jnz no_partition        ; be 00 or 80
                cmp eax,'!GPT'          ; !GPT signature?
                jne .not_gpt
-               push dword [di-112+20+36]
-               push dword [di-112+20+32]
+               cmp byte [di-76+4],0EDh ; Synthetic GPT partition entry?
+               jne .not_gpt
+               push dword [di-76+20+36]
+               push dword [di-76+20+32]
                jmp .gotoffs
 .not_gpt:
                push cx                 ; Upper half partition offset == 0
                push cx
-               push dword [di-112+8]   ; Partition offset (dword)
+               push dword [di-76+8]    ; Partition offset (dword)
 .gotoffs:
 no_partition:
 ;