.text .globl _startit _startit: move.l sp,a3 move.l 4,a6 lea (start_super,pc),a5 jmp (-0x1e,a6) | supervisor-call start_super: move.w #0x2700,sr | the BSD kernel wants values into the following registers: | a0: fastmem-start | d0: fastmem-size | d1: chipmem-size | d3: Amiga specific flags | d4: E clock frequency | d5: AttnFlags (cpuid) | d7: boothowto | a4: esym location | a2: Inhibit sync flags | All other registers zeroed for possible future requirements. lea (_startit,pc),sp | make sure we have a good stack *** move.l (4,a3),a1 | loaded kernel move.l (8,a3),d2 | length of loaded kernel | move.l (12,a3),sp | entry point in stack pointer move.l (12,a3),a6 | push entry point *** move.l (16,a3),a0 | fastmem-start move.l (20,a3),d0 | fastmem-size move.l (24,a3),d1 | chipmem-size move.l (28,a3),d7 | boothowto move.l (32,a3),a4 | esym move.l (36,a3),d5 | cpuid move.l (40,a3),d4 | E clock frequency move.l (44,a3),d3 | Amiga flags move.l (48,a3),a2 | Inhibit sync flags move.l (52,a3),d6 | Load to fastmem flag sub.l a5,a5 | target, load to 0 cmp.b #0x7D,(36,a3) | is it DraCo? beq nott | yes, switch off MMU later | no, it is an Amiga: | move.w #0xf00,0xdff180 |red | move.b #0,0x200003c8 | move.b #63,0x200003c9 | move.b #0,0x200003c9 | move.b #0,0x200003c9 move.w #(1<<9),0xdff096 | disable DMA on Amigas. | ------ mmu off start ----- btst #3,d5 | AFB_68040,SysBase->AttnFlags beq not040 | Turn off 68040/060 MMU sub.l a3,a3 .word 0x4e7b,0xb003 | movec a3,tc .word 0x4e7b,0xb806 | movec a3,urp .word 0x4e7b,0xb807 | movec a3,srp .word 0x4e7b,0xb004 | movec a3,itt0 .word 0x4e7b,0xb005 | movec a3,itt1 .word 0x4e7b,0xb006 | movec a3,dtt0 .word 0x4e7b,0xb007 | movec a3,dtt1 bra nott not040: lea (zero,pc),a3 pmove (a3),tc | Turn off MMU lea (nullrp,pc),a3 pmove (a3),crp | Turn off MMU some more pmove (a3),srp | Really, really, turn off MMU | Turn off 68030 TT registers btst #2,d5 | AFB_68030,SysBase->AttnFlags beq nott | Skip TT registers if not 68030 lea (zero,pc),a3 .word 0xf013,0x0800 | pmove a3@,tt0 (gas only knows about 68851 ops..) .word 0xf013,0x0c00 | pmove a3@,tt1 (gas only knows about 68851 ops..) nott: | ---- mmu off end ---- | move.w #0xf60,0xdff180 | orange | move.b #0,0x200003c8 | move.b #63,0x200003c9 | move.b #24,0x200003c9 | move.b #0,0x200003c9 | ---- copy kernel start ---- tst.l d6 | Can we load to fastmem? beq L0 | No, leave destination at 0 move.l a0,a5 | Move to start of fastmem chunk add.l a0,a6 | relocate kernel entry point L0: move.l (a1)+,(a5)+ sub.l #4,d2 bcc L0 lea (ckend,pc),a1 move.l a5,-(sp) move.l #_startit_end-ckend,d2 L2: move.l (a1)+,(a5)+ sub.l #4,d2 bcc L2 btst #3,d5 jeq L1 .word 0xf4f8 L1: moveq.l #0,d2 | switch off cache to ensure we use movec d2,cacr | valid kernel data | move.w #0xFF0,0xdff180 | yellow | move.b #0,0x200003c8 | move.b #63,0x200003c9 | move.b #0,0x200003c9 | move.b #0,0x200003c9 rts | ---- copy kernel end ---- ckend: | move.w #0x0ff,0xdff180 | petrol | move.b #0,0x200003c8 | move.b #0,0x200003c9 | move.b #63,0x200003c9 | move.b #63,0x200003c9 move.l d5,d2 rol.l #8,d2 cmp.b #0x7D,d2 jne noDraCo | DraCo: switch off MMU now: sub.l a3,a3 .word 0x4e7b,0xb003 | movec a3,tc .word 0x4e7b,0xb806 | movec a3,urp .word 0x4e7b,0xb807 | movec a3,srp .word 0x4e7b,0xb004 | movec a3,itt0 .word 0x4e7b,0xb005 | movec a3,itt1 .word 0x4e7b,0xb006 | movec a3,dtt0 .word 0x4e7b,0xb007 | movec a3,dtt1 noDraCo: moveq #0,d2 | zero out unused registers moveq #0,d6 | (might make future compatibility move.l d6,a1 | would have known contents) move.l d6,a3 move.l d6,a5 move.l a6,sp | entry point into stack pointer move.l d6,a6 | move.w #0x0F0,0xdff180 | green | move.b #0,0x200003c8 | move.b #0,0x200003c9 | move.b #63,0x200003c9 | move.b #0,0x200003c9 jmp (sp) | jump to kernel entry point | A do-nothing MMU root pointer (includes the following long as well) nullrp: .long 0x7fff0001 zero: .long 0 _startit_end: .data .globl _startit_sz _startit_sz: .long _startit_end-_startit
