X-Git-Url: http://git.dujemihanovic.xyz/posts?a=blobdiff_plain;f=boot%2Fx86%2Ffat32%2Ffat32.s;fp=boot%2Fx86%2Ffat32.s;h=df5dd89260a3fff08e70e6729ee54f170def9559;hb=750b9e3f093f34310a05ffbac7f6b1317ef786e7;hp=75e7904ae5b94a2116529542e0342fb2f1791e0b;hpb=c4408dfedc5d7b3a4e6b584c37c58e064265ef2d;p=nameless-os.git

diff --git a/boot/x86/fat32.s b/boot/x86/fat32/fat32.s
similarity index 91%
rename from boot/x86/fat32.s
rename to boot/x86/fat32/fat32.s
index 75e7904..df5dd89 100644
--- a/boot/x86/fat32.s
+++ b/boot/x86/fat32/fat32.s
@@ -7,6 +7,7 @@
 
 ; eax - start cluster number
 ; es:di - where to load the cluster chain
+; RETURN: CF set = error
 ; NOTE: Cluster chain might be the root directory or a file.
 read_cluster_chain:
 	push eax
@@ -14,8 +15,10 @@ read_cluster_chain:
 	push di
 	.loop:
 		call read_cluster
+		jc .done
 		cmp eax, 0xffffff7
 		jl .loop
+.done:
 	pop di
 	pop es
 	pop eax
@@ -24,6 +27,7 @@ read_cluster_chain:
 ; eax - cluster number
 ; es:di - where to load the cluster (incremented automatically)
 ; RETURN: eax - next cluster number
+;	  CF set = error
 read_cluster:
 	push ebx
 	push ecx
@@ -44,6 +48,8 @@ read_cluster:
 	movzx cx, BPB_SecPerClus
 	call read_sectors
 	pop cx
+	cmp dl, 0
+	je .error
 
 	; increment the load offset (and segment if needed)
 	push eax
@@ -78,16 +84,20 @@ read_cluster:
 	xor ax, ax
 	mov es, ax
 	pop ebx ; pop LBA into EBX
-	mov di, 0x1000
+	mov di, 0x6000
 	mov cx, 1
 	call read_sectors
-	
+	cmp dl, 0
 	; find the cluster we're looking for
 	pop es ; restore STAGE3_SEGMENT
 	pop ebx ; pop FAT offset back into EBX for cmp
 	mov eax, [di+bx]
 	pop di
+	jne .end
 	; cleanup and return
+.error:
+	stc
+.end:
 	pop edx
 	pop ecx
 	pop ebx
@@ -96,8 +106,11 @@ read_cluster:
 ; es:di - where to load the sector(s)
 ; ebx - start LBA address
 ; cx - how many sectors to read
+; RETURN: DL=0 means error
 read_sectors:
-	pusha
+	clc
+	push ax
+	push si
 	mov ah, 0x42
 	push dword 0
 	push dword ebx
@@ -108,15 +121,14 @@ read_sectors:
 	mov si, sp
 	mov dl, [BOOT_DRIVE]
 	int 0x13
-	jc .error
+	mov dl, 1
+	jnc .done
+	mov dl, 0
+.done:
 	add sp, 16
-	popa
+	pop si
+	pop ax
 	ret
-	.error:
-		mov si, read_error
-		call print
-		hlt
-		jmp $-1
 
 ; ds:si - pointer to partition table entry
 ; RETURN: ecx - first data sector