/* ** head.S -- This file contains the initial boot code for the the ** ATARI Linux kernel. ** ** Copyright 1994 by Bj”rn Brauel ** ** This file is subject to the terms and conditions of the GNU General Public ** License. See the file README.legal in the main directory of this archive ** for more details. ** */ #include "assyms.h" /* * Linux startup code. * * At this point, the boot loader has: * Disabled interrupts * Disabled caches * Put us in supervisor state. * * The kernel setup code takes the following steps: * Raise interrupt level * Set up initial kernel memory mapping. * This sets up a mapping of the 4M of memory the kernel * is located in. It also does a mapping of any initial * machine specific areas. * Enable cache memories * Jump to kernel startup * * Register d6 contains the CPU flags from the boot_info information * for most of this file. */ .text .globl _start, _krt, _kpt, _availmem .even _start: /* * raise interrupt level with MASTER bit set, copy isp to msp */ movew #0x3700,sr movec isp,d0 movel d0,sp /* * Initialize serial port */ bsr Lserial_init moveq #13,d7 bsr Lserial_putc moveq #10,d7 bsr Lserial_putc moveq #65,d7 bsr Lserial_putc /* * Record the CPU type. */ movel #_boot_info,a0 /* pcrel */ subl #LKSTART_ADDR,a0 addl #LVSTART_STRAM,a0 movel a0@(LBI_CPU),d6 /* * Get address at end of kernel code/data/bss and * mask off at a page boundary. */ movel #_end,a0 /* pcrel */ subl #LKSTART_ADDR,a0 addl #LVSTART_STRAM,a0 movel a0,d0 addl #0x00000fff,d0 andl #0xfffff000,d0 movel d0,a6 moveq #66,d7 bsr Lserial_putc /* * allocate the kernel root table and initialize it. */ movel a6,a5 addw #LPAGE_SIZE,a6 /* clear the root table */ movel a5,a0 moveq #0,d0 moveq #127,d1 lopei: movel d0,a0@+ dbra d1,lopei /* * Initialize root table descriptor pointing to the kernel pointer * table. The pointer table is situated in memory right after * the root table. */ /* * Coming up specific Code for ATARI */ lea a5@,a0 movel #0x0000001,d0 movel #0x2000000,d1 movel #127,d2 f_rpt: movel d0,a0@+ addl d1,d0 dbra d2,f_rpt lea a5@(1024),a0 addl #2,a0 movel a0,a5@(508) moveq #67,d7 bsr Lserial_putc /* * Initialize the pointer tables referred to above. They either point * to page tables in the case of the 68040 or contain early * termination page descriptors in the case of the 68851 or 68030. * * Each pointer table entry points to a 64 entry page table. 16 of these * page tables are grouped to form a single 1024 entry page table which * fits in a single 4096 byte page. * * Some register usages: * a0 -> pointer table descriptor address * a1 -> pointer table descriptor * d1 -> counter * d2 -> pointer table descriptor increment (varies according to CPU) */ /* clear the kernel pointer table */ lea a5@(512),a0 moveq #0,d0 moveq #127,d1 lopzw: movel d0,a0@+ dbra d1,lopzw lea a5@(512),a0 moveq #127,d1 /* * base value of pointer table descriptor is either * the address of the first page table (68040) * or the base address of physical memory (68030). */ /* 680[23]0 */ movel #0,a1 /* base address */ addql #1,a1 /* descriptor type */ movel #0x40000,d2 /* increment */ lopb: movel a1,a0@+ addl d2,a1 dbra d1,lopb addl #0x40,a5@(0x2f0) addl #0x40,a5@(0x2f4) addl #0x40,a5@(0x2f8) addl #0x40,a5@(0x2fc) lea a5@(1024),a0 movel #0xfe000041,d0 movel #0x40000,d1 movel #63,d2 f_kpt: movel d0,a0@+ addl d1,d0 dbra d2,f_kpt movel #63,d2 movel #0x01,d0 f_kpt2: movel d0,a0@+ addl d1,d0 dbra d2,f_kpt2 lea a5@(1536),a0 movel #0x01,d0 movel #127,d2 movel #0x40000,d1 f_vkpt: movel d0,a0@+ addl d1,d0 dbra d2,f_vkpt addl #0x40,a5@(1532) addl #0x40,a5@(1520) lea a5@(1536),a0 addl #2,a0 movel a0,a5@(0x180) moveq #74,d7 bsr Lserial_putc /* * Setup Supervisor Root Pointer register to point to page directory, * setup translation register contents and enable translation. */ moveq #75,d7 bsr Lserial_putc movel #Lmmu,a0 /* pcrel */ subl #LKSTART_ADDR,a0 addl #LVSTART_STRAM,a0 movel #0x80000002,a0@ /* no limit, 4byte descriptors */ movel a5,a0@(4) pmove a0@,srp /* * enable,super root enable,4096 byte pages,7 bit root index, * 7 bit pointer index, 6 bit page table index. */ movel #0x82c07760,a0@ pmove a0@,tc /* * Fixup the addresses for the kernel pointer table and availmem. * Convert them from physical addresses to virtual addresses. */ moveq #77,d7 bsr Lserial_putc lea a5@(1536),a0 subl #LVSTART_STRAM,a0 addl #LKSTART_ADDR,a0 movel a0,_kpt /* * do the same conversion on the first available memory * address (in a6). */ lea a6@,a0 subl #LVSTART_STRAM,a0 addl #LKSTART_ADDR,a0 movel a0,_availmem /* convert and save the root table address in memory */ lea a5@,a0 subl #LVSTART_STRAM,a0 addl #LKSTART_ADDR,a0 movel a0,_krt /* * Record starting address and jump into the virtual address space. */ movel #_start,a0 /* pcrel */ subl #LKSTART_ADDR,a0 addl #LVSTART_STRAM,a0 jmp Lvirt Lvirt: moveq #78,d7 bsr Lserial_putc /* * Clean up the temporary physical mapping. */ pflusha /* flush address translation cache */ moveq #79,d7 bsr Lserial_putc /* * Enable caches */ movel #0x00000919,d0 movec d0,cacr /* * Setup initial stack pointer */ lea _user_stack+LPAGE_SIZE,sp /* jump to memory management initialization */ moveq #0,d0 movel d0,sp@- /* parameters to main */ movel d0,sp@- movel d0,sp@- bsr _start_kernel /* * Serial port output support. */ /* * Initialize serial port hardware for 9600/8/1 */ Lserial_init: rts /* * Output character in d7 on serial port. * d7 unchanged. */ Lserial_putc: rts /* * Output string pointed to by a0 to serial port. * a0 trashed. */ Lserial_puts: rts /* * Output number in d7 in hex notation on serial port. * d0-d2 trashed. * d7 trashed. */ Lserial_putnum: rts /* Some nops to shift main.o backwards. This is necessary because the first * 2 KByte of RAM are supervisor-only by hardware. */ nop nop nop nop nop nop nop nop nop nop nop nop nop nop nop nop .data Lmmu: .long 0,0 _krt: .long 0 _kpt: .long 0 _availmem: .long 0