bootsect: Do not assume 512-byte sectors

bootsect/bootsect.asm

@@ -54,11 +54,11 @@ start:
     ; make sure that is the case now.
     mov esp, 0x7c00
 
-    push 0x7000
+    push 0x6fe0
     pop es
     mov eax, dword [stage2_sector]
     xor bx, bx
-    mov cx, 63
+    mov ecx, 32768
     call read_sectors
     jc err
 
@@ -112,7 +112,7 @@ vector:
 bits 16
 
 times 0x1b0-($-$$) db 0
-stage2_sector: dd 1
+stage2_sector: dd 0
 
 times 0x1b8-($-$$) db 0
 times 510-($-$$) db 0

bootsect/disk.inc

@@ -7,7 +7,7 @@
 ; DL = Drive number
 ; ES = Buffer segment
 ; BX = Buffer offset
-; CX = Sectors count
+; ECX = Byte count
 
 ; OUT:
 ; Carry if error
@@ -15,40 +15,49 @@
 read_sectors:
     pusha
 
-    push es
-    pop word [.target_segment]
-    mov word [.target_offset], bx
-    mov dword [.lba_address_low], eax
+    mov esi, .da_struct
 
-    mov word [.countdown], cx
+    mov word  [si],    16
+    mov word  [si+2],  1
+    mov word  [si+4],  bx
+    mov word  [si+6],  es
+    mov dword [si+8],  eax
+    mov dword [si+12], 0
+
+    ; Get bytes per sector
+    push dx
+    push si
+    mov ah, 0x48
+    mov si, .drive_params
+    mov word [si], 30       ; buf_size
+    int 0x13
+    jc .done
+    mov bp, word [si+24]    ; bytes_per_sect
+    mov ax, cx
+    shr ecx, 16
+    mov dx, cx
+    xor cx, cx
+    div bp
+    test dx, dx
+    adc cx, ax
+    pop si
+    pop dx
 
   .loop:
-    mov esi, .da_struct
     mov ah, 0x42
 
     clc
     int 0x13
     jc .done
 
-    add word [.target_offset], 512
-    inc dword [.lba_address_low]
+    add word  [si+4], bp
+    inc dword [si+8]
 
-    dec word [.countdown]
-    jnz .loop
+    loop .loop
 
   .done:
     popa
     ret
 
-align 2
-  .countdown: dw 0
-
-align 4
-  .da_struct:
-    .packet_size        db  16
-    .unused             db  0
-    .count              dw  1
-    .target_offset      dw  0
-    .target_segment     dw  0
-    .lba_address_low    dd  0
-    .lba_address_high   dd  0
+  .da_struct:    equ 0x8000
+  .drive_params: equ 0x8010

limine-install.c

@@ -8,10 +8,10 @@ int main(int argc, char *argv[]) {
     FILE    *bootloader_file, *device;
     uint8_t *bootloader_img;
     uint8_t  orig_mbr[70], timestamp[6];
-    uint32_t stage2_sect;
+    uint32_t stage2_sect, sect_size;
 
     if (argc < 3) {
-        printf("Usage: %s <bootloader image> <device> [stage2 start sector]\n", argv[0]);
+        printf("Usage: %s <bootloader image> <device> [<stage2 start sector> <sector size>]\n", argv[0]);
         return 1;
     }
 
@@ -41,9 +41,12 @@ int main(int argc, char *argv[]) {
         return 1;
     }
 
-    stage2_sect = 1;
+    stage2_sect = 0;
+    sect_size   = 512;
     if (argc >= 4)
         sscanf(argv[3], "%" SCNu32, &stage2_sect);
+    if (argc >= 5)
+        sscanf(argv[4], "%" SCNu32, &sect_size);
 
     // Save original timestamp
     fseek(device, 218, SEEK_SET);
@@ -58,8 +61,8 @@ int main(int argc, char *argv[]) {
     fwrite(&bootloader_img[0], 1, 512, device);
 
     // Write the rest of stage 2 to the device
-    fseek(device, stage2_sect * 512, SEEK_SET);
-    fwrite(&bootloader_img[512], 63, 512, device);
+    fseek(device, stage2_sect * sect_size, SEEK_SET);
+    fwrite(&bootloader_img[0], 64, 512, device);
 
     // Hardcode in the bootsector the location of stage 2
     fseek(device, 0x1b0, SEEK_SET);