Support loading filesystems from MBR partitions.

x86_64/bootsector.asm

@@ -150,6 +150,7 @@ DAPACK:
 .seg:   dw 0 ; in memory page zero
 .addr:  dq 0 ; put the lba to read in this spot
 
-times 510-($-$$) db 0
+times 446-($-$$) db 0
+partitions: times 4 * 16 db 0
 db 0x55
 db 0xaa

x86_64/disk.asm

@@ -22,12 +22,10 @@ startup_end:
 %else
     align BLOCK_SIZE, db 0
     %ifdef FILESYSTEM
-        filesystem:
-            %defstr FILESYSTEM_STR %[FILESYSTEM]
-            incbin FILESYSTEM_STR
-        .end:
-        align BLOCK_SIZE, db 0
-    %else
-        filesystem:
+     filesystem:
+         %defstr FILESYSTEM_STR %[FILESYSTEM]
+         incbin FILESYSTEM_STR
+     align BLOCK_SIZE, db 0
+     .end:
     %endif
 %endif

x86_64/partitions.asm

@@ -0,0 +1,38 @@
+struc mbr_partition_rec
+.sys: resb 1
+.chs_start: resb 3
+.ty: resb 1
+.chs_end: resb 3
+.lba_start: resd 1
+.sector_count: resd 1
+endstruc
+
+; Find a partition to load RedoxFS from.
+; The partition has to be one of the primary MBR partitions.
+; OUT
+;   eax - start_lba
+;   edx - sector count
+; CLOBBER
+;   ebx
+find_redoxfs_partition:
+    xor ebx, ebx
+.loop:
+    mov al, byte [partitions + mbr_partition_rec + mbr_partition_rec.ty]
+    cmp al, 0x83
+    je .found
+    add ebx, 1
+    cmp ebx, 4
+    jb .loop
+    jmp .notfound
+.found:
+    mov eax, [partitions + mbr_partition_rec + mbr_partition_rec.lba_start]
+    mov edx, [partitions + mbr_partition_rec + mbr_partition_rec.sector_count]
+    ret
+.notfound:
+    mov si, .no_partition_found_msg
+    call print
+.halt:
+    cli
+    hlt
+    jmp .halt
+.no_partition_found_msg: db "No MBR partition with type 0x83 found", 0xA, 0xD, 0

x86_64/redoxfs.asm

@@ -37,7 +37,12 @@ struc Header
     .padding: resb (BLOCK_SIZE - 56)
 endstruc
 
+; IN
+; eax - the first sector of the filesystem
+; edx - the amount of sectors in the filesystem
 redoxfs:
+        mov [.first_sector], eax
+        mov [.sector_count], ebx
         call redoxfs.open
         test eax, eax
         jz .good_header
@@ -53,7 +58,7 @@ redoxfs:
     ; node in eax, buffer in bx
     .node:
         shl eax, (BLOCK_SHIFT - 9)
-        add eax, (filesystem - boot)/512
+        add eax, [redoxfs.first_sector]
         mov cx, (BLOCK_SIZE/512)
         mov dx, 0
         call load
@@ -71,6 +76,9 @@ redoxfs:
     .file:
         times BLOCK_SIZE db 0
 
+    .first_sector: dd 0
+    .sector_count: dd 0
+
     .env:
         db "REDOXFS_BLOCK="
     .env.block:
@@ -111,7 +119,15 @@ redoxfs.open:
         mov al, ' '
         call print_char
 
-        mov ebx, (filesystem - boot)/BLOCK_SIZE
+        push eax
+        push edx
+        xor edx, edx
+        mov eax, [redoxfs.first_sector]
+        mov ebx, (BLOCK_SIZE / 512)
+        div ebx ; EDX:EAX = EDX:EAX / EBX
+        mov ebx, eax
+        pop edx
+        pop eax
         mov di, redoxfs.env.block_end - 1
     .block:
         mov al, bl
@@ -314,7 +330,7 @@ redoxfs.kernel:
 
 
         shl eax, (BLOCK_SHIFT - 9)
-        add eax, (filesystem - boot)/512
+        add eax, [redoxfs.first_sector]
         add ecx, BLOCK_SIZE
         dec ecx
         shr ecx, 9

x86_64/startup-common.asm

@@ -25,6 +25,14 @@ startup:
         shr ecx, 9
         call load_extent
     %else
+
+        %ifdef FILESYSTEM
+            mov eax, (filesystem - boot) / 512
+            mov ebx, (filesystem.end - filesystem) / 512
+        %else
+            call find_redoxfs_partition
+        %endif
+
         call redoxfs
         test eax, eax
         jnz error
@@ -50,10 +58,10 @@ startup:
 
     jmp startup_arch
 
-# load a disk extent into high memory
-# eax - sector address
-# ecx - sector count
-# edi - destination
+; load a disk extent into high memory
+; eax - sector address
+; ecx - sector count
+; edi - destination
 load_extent:
     ; loading kernel to 1MiB
     ; move part of kernel to startup_end via bootsector#load and then copy it up
@@ -132,6 +140,9 @@ load_extent:
 %include "initialize.asm"
 %ifndef KERNEL
     %include "redoxfs.asm"
+    %ifndef FILESYSTEM
+        %include "partitions.asm"
+    %endif
 %endif
 
 init_fpu_msg: db "Init FPU",13,10,0