FAT32 bootloader boots the kernel

[nameless-os.git] / boot / x86 / fat32 / fat32.s

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 75e7904ae5b94a2116529542e0342fb2f1791e0b..df5dd89260a3fff08e70e6729ee54f170def9559 100644 (file)
--- 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