Real mode load_sector to support 1MB ram

Author: scopeInfinity

src/drivers/disk/disk.c

@@ -1,3 +1,4 @@
+// written for protected mode
 #include <lib/utils/logging.h>
 #include <fuzzy/real_mode/client.h>
 

src/drivers/disk/disk.h

@@ -1,6 +1,6 @@
 #pragma once
 
-int load_sectors(unsigned int address,
+int load_sectors(unsigned int full_address,
                  unsigned char drive,
-                 unsigned int sector_index, // 1-based
+                 unsigned int lba, // 0-based
                  unsigned char count);

src/drivers/disk/disk_16.asm

@@ -1,29 +1,28 @@
 [BITS 16]
 
-global _low_disk_read_sectors
+global _low_int_0x13
 
 [SECTION .text]
-    _low_disk_read_sectors:
+    _low_int_0x13:
         push ebp
         mov ebp, esp
         ; callee save register
         push ebx
         push esi
         push edi
+        push es
 
         ; check es
-        mov ah, 0x02                ; (read sectors)
-        mov al, [ebp + 0x8]         ; (sector count)
-        mov cx, [ebp + 0xc]         ; (cylinder 10bit, sector 6bit)
-        mov dx, [ebp + 0x10]        ; (head, drive index)
-        mov bx, [ebp + 0x14]        ; (es:bx as write address)
-        int 0x13
+        mov ax, [ebp + 0x18]        ; (es)
+        mov es, ax
 
-        mov ah, 0x01                 ; (get status of last drive operation)
+        mov ax, [ebp + 0x08]
+        mov bx, [ebp + 0x0C]
+        mov cx, [ebp + 0x10]
+        mov dx, [ebp + 0x14]
         int 0x13
-        mov al, ah                   ; (result status code, 0 means no error)
-        and eax, 0xFF
 
+        pop es
         pop edi
         pop esi
         pop ebx

src/drivers/disk/disk_16.c

@@ -1,18 +1,35 @@
-extern int _low_disk_read_sectors(
-    unsigned char count,
-    unsigned short cylinder_sector,  // 10 bit + 6bit
-    unsigned short head_driveindex, // 8 bit + 8bit
-    unsigned short memory_address);
+// written for real mode
 
-int load_sectors(unsigned int address,
+extern unsigned short _low_int_0x13(unsigned short ax,
+                                    unsigned short bx,
+                                    unsigned short cx,
+                                    unsigned short dx,
+                                    unsigned short es);
+
+int load_sectors(unsigned int full_address,
                  unsigned char drive,
-                 unsigned int sector_index, // 0-based
+                 unsigned int lba, // 0-based
                  unsigned char count) {
-    int cylinder_head = (sector_index/63);
-    sector_index = sector_index%63 + 1;
-    _low_disk_read_sectors(
-        count,
+    int es = (full_address&0xF0000)>>4;
+    int es_address = full_address&0xFFFF;
+    int cylinder_head = (lba/63);
+    int sector_index = lba%63 + 1;
+    // https://en.wikipedia.org/wiki/INT_13H#INT_13h_AH=02h:_Read_Sectors_From_Drive
+    _low_int_0x13(
+        (0x02<<8) | count,
+        es_address,
         ((cylinder_head>>2)&0xFFC0) | (sector_index),
         ((cylinder_head<<8)&0xFF00) | (drive),
-        address);
-}
+        es
+    );
+    // https://en.wikipedia.org/wiki/INT_13H#INT_13h_AH=01h:_Get_Status_of_Last_Drive_Operation
+    unsigned short ax = _low_int_0x13(
+        (0x01<<8),
+        0,
+        0,
+        drive,
+        0
+    );
+    int status = ax >> 8;
+    return status;
+}