Correct the handling for full 64K regions safe; correct the parsing of

FAT12 FAT entries.

diff --git a/ldlinux.asm b/ldlinux.asm
index 157fae9..8eaa396 100644 (file)
--- a/ldlinux.asm
+++ b/ldlinux.asm
@@ -888,8 +888,8 @@ genfatinfo:
                mov [RootDir],eax               ; For FAT12/16 == root dir location
 
                mov edx,[bxRootDirEnts]
-               add dx,512-32
-               shr dx,9-5
+               add dx,SECTOR_SIZE/32-1
+               shr dx,SECTOR_SHIFT-5
                mov [RootDirSize],edx
                add eax,edx
                mov [DataArea],eax              ; Beginning of data area
@@ -1329,11 +1329,13 @@ getfssec_edx:
                inc bp
                dec cx
                jz .do_read
+               xor eax,eax
                mov ax,es
                shl ax,4
                add ax,bx                       ; Now DI = how far into 64K block we are
-               neg ax                          ; Bytes left in 64K block
-               shr ax,9                        ; Sectors left in 64K block
+               not ax                          ; Bytes left in 64K block
+               inc eax
+               shr eax,SECTOR_SHIFT            ; Sectors left in 64K block
                cmp bp,ax
                jnb .do_read                    ; Unless there is at least 1 more sector room...
                lea eax,[edx+1]                 ; Linearly next sector
@@ -1403,6 +1405,7 @@ nextcluster_fat12:
                push si
                mov edx,edi
                shr edi,1
+               pushf                   ; Save the shifted-out LSB (=CF)
                add edx,edi
                mov eax,edx
                shr eax,9
@@ -1417,8 +1420,8 @@ nextcluster_fat12:
                mov bx,dx
                and bx,1FFh
                mov ch,[gs:si+bx]
-               test di,1
-               jz .even
+               popf
+               jnc .even
                shr cx,4
 .even:         and cx,0FFFh
                movzx edi,cx