Improve bootsector linking

boot/Tupfile

@@ -1,6 +1,5 @@
 include_rules
-LDFLAGS += -T boot.ld
+LDFLAGS += -T boot.ld -z max-page-size=1
 
 : foreach *.68k |> !as |>
-: *.o | boot.ld |> !ld |> boot.elf
+: *.o | boot.ld |> !ld |> boot.bin
-: boot.elf |> m68k-elf-objcopy -O binary %f %o |> boot.bin

boot/boot.68k

@@ -1,5 +1,3 @@
-.equ SEC_BUF_START, 0x400
-.equ PHDR_BUF_START, 0x600
 .equ PHDR_BUF_SEC_SIZE, 5
 .equ STORAGE_SEC, 0x0
 .equ STORAGE_CNT, 0x4
@@ -11,14 +9,14 @@ _start:
 move.w #0x4, d0 | Find a storage card
 bsr.w find_first_card
 | load the first PHDR_BUF_SEC_SIZE sectors of the ELF kernel binary off the disk
-move.l #PHDR_BUF_START, a1 | Set the destination address to PHDR_BUF_START
+move.l #phdr_buf, a1 | Set the destination address to PHDR_BUF_START
 move.l #0x2, d0 | Set the starting sector number to 2
 move.l #PHDR_BUF_SEC_SIZE, d1 | Set the sector count
 bsr.w read_sectors
-move.l (PHDR_BUF_START + 0x1C), d0 | Load the offset of the program headers in the file
+move.l (phdr_buf + 0x1C), d0 | Load the offset of the program headers in the file
-move.l #PHDR_BUF_START, a1 | Put the address of the program headers in a1
+move.l #phdr_buf, a1 | Put the address of the program headers in a1
 adda.w d0, a1
-move.w (PHDR_BUF_START + 0x2C), d0 | Put the number of program headers - 1 in d0
+move.w (phdr_buf + 0x2C), d0 | Put the number of program headers - 1 in d0
 subq.w #0x1, d0
 phead_loop:
 move.l (a1), d1 | If the type of the program header isn't 1 (LOAD), skip the header
@@ -45,11 +43,11 @@ move.l d4,d0 | Restore d0 from d4
 next_seg:
 lea (0x20, a1), a1 | Advance a1 to point to the next program header
 dbra d0, phead_loop | If there are more program headers, loop back
-move.l (PHDR_BUF_START + 0x18), a1 | Load the entry point of the program into a1
+move.l (phdr_buf + 0x18), a1 | Load the entry point of the program into a1
-move.l (PHDR_BUF_START + 0x1C), d0 | Load the offset of the program headers in the file
+move.l (phdr_buf + 0x1C), d0 | Load the offset of the program headers in the file
-move.l #PHDR_BUF_START, a0 | Put the address of the program headers in a0
+move.l #phdr_buf, a0 | Put the address of the program headers in a0
 adda.w d0, a0
-move.w (PHDR_BUF_START + 0x2C), d0 | Put the number of program headers in d0
+move.w (phdr_buf + 0x2C), d0 | Put the number of program headers in d0
 jmp (a1) | Jump to the entry point of the program
 
 
@@ -95,7 +93,7 @@ lsr.l #8, d0  | Divide start byte by 512 to compute starting sector
 lsr.l #1, d0
 move.l d0, d5 | Save the starting sector in d5
 move.l #1, d1 | Read the starting sector into the sector buffer
-move.l #SEC_BUF_START, a1
+move.l #sec_buf, a1
 bsr.b read_sectors
 move.l a6, a2 | Load the destination into a2
 move.l d6, d0 | Load the start byte into d0
@@ -127,7 +125,7 @@ lsl.l #1, d1
 adda.l d1, a2 | Add the number of bytes transferred to a2
 add.l d5, d0 | Compute the end sector number by adding the start and count of the middle sectors
 move.l #1, d1 | Set the number of sectors to read to 1
-move.l #SEC_BUF_START, a1 | Set the read address of the sector to the sector buffer
+move.l #sec_buf, a1 | Set the read address of the sector to the sector buffer
 bsr.b read_sectors | Read the end sector
 move.l d6, d1 | Load the number of remaining bytes into d1
 end_sec_loop: | Transfer the required bytes from the start sector to the destination buffer
@@ -136,10 +134,11 @@ dbra d1, end_sec_loop
 read_bytes_done:
 rts
 
-.if . != 512
+.section .bss
-.org 511
+sec_buf: 
-.byte 0
+.ds.b 512
-.endif
+phdr_buf:
+.ds.b (PHDR_BUF_SEC_SIZE * 512) 
 
 /* read_bytes theory: */
 

boot/boot.ld

@@ -1,5 +1,12 @@
+OUTPUT_FORMAT(binary)
+
+MEMORY {
+  bootsector : ORIGIN = 0, LENGTH = 512
+  free_ram : ORIGIN = 512, LENGTH = (4096 - 512)
+}
 SECTIONS {
   . = 0x0;
-  _etext = .;
+  .text : { *(.text) . = 512; } > bootsector
-  .text : { *(.text) }
+  .data : { *(.data) } > bootsector
+  .bss : { *(.bss) } > free_ram
 }