| $NetBSD: boot.S,v 1.13 2020/08/16 06:43:43 isaki Exp $ | | (1) IPL (or previous stage loader) loads first 1KB of this primary | bootloader to (*). (*) is 0x2000 (from FD) or 0x2400 (from SASI/SCSI). | | (2) The first 1KB loads full primary bootloader (including first 1KB) from | the boot partition to 0x3000. And jump to there. | | (3) The full primary bootloader loads the secondary bootloader known as | /boot from its filesystem to 0x6000. And jump to there. | | (1) -> (2) -> (3) | +------------+ +------------+ +------------+ 0x000000 | : : : : : : | +------------+ +------------+ +------------+ (*) | | first 1KB | | first 1KB | | first 1KB | | +------------+ +------------+ +------------+ (*)+0x400 | : : : : : : | : : +------------+ +------------+ 0x003000 | : : |full primary| |full primary| | : : |boot loader | |boot loader | | : : |(text+data) | |(text+data) | | : : +------------+ +------------+ 0x005000 | : : |(startregs) | |(startregs) | | : : |(bss) | |(bss) | | : : +------------+ +------------+ 0x006000 | : : : : | /boot | | : : : : +------------+ | : : : : : : | ~ ~ ~ ~ ~ ~ | : : : :<-SP : :<-SP | + - - - - - -+ + - - - - - -+ + - - - - - -+ 0x100000 | : : :(heap) : :(heap) : | : : : : : : | | The program code before first_kbyte | - must not access any text/data labels after first_kbyte | (because it may not be loaded yet). | - must access any labels before first_kbyte by PC relative addressing | (because this loader is assembled as starting from 0x3000 but is loaded | at 0x2000 or 0x2400). | - must use RELOC() macro to access bss section (and first_kbyte as a jump | destination address). | | The program code after first_kbyte can access any labels in all sections | directly. #include <machine/asm.h> #include "iocscall.h" #define RELOC(var) %a5@(((var)-top):W) #define BOOT_ERROR(s) jbsr boot_error; .asciz s; .even #define minN (0) #define minC (1) #define minH (2) #define minR (3) #define maxN (4) #define maxC (5) #define maxH (6) #define maxR (7) .globl _C_LABEL(bootmain) .globl _C_LABEL(startregs) .text ASENTRY_NOPROFILE(start) ASENTRY_NOPROFILE(top) bras entry .ascii "SHARP/" .ascii "X680x0" .word 0x8199,0x94e6,0x82ea,0x82bd .word 0x8e9e,0x82c9,0x82cd,0x8cbb .word 0x8ec0,0x93a6,0x94f0,0x8149 msg_progname: | This will be printed on boot_error. And it also roles | a signature in binary dump. | Max length of PROG(without \0) is 14 ("fdboot_ustarfs"). .ascii "\r\n\n" | 3 .ascii PROG | 14 .asciz ": " | 2+1 .org msg_progname + 20 entry: jbra disklabel_end | Disklabel must be placed at 0x40 and the size is 404 bytes. | (See LABELOFFSET in <machine/disklabel.h>) .org 0x40 disklabel: .space 404 disklabel_end: | At first save all initial registers for observing traces | of the IPL (or the previous bootloader). At this point | we cannot use RELOC() yet so that use absolute addressing. | To prevent startregs from being cleared by subsequent bss | initialization, we place it out of bss area. moveml %d0-%d7/%a0-%a7,startregs:W | Initialize the screen. Some IPL (060turbo ROM or genuine | boot selector) don't initialize the screen. It should be | done as early as possible. moveql #0x10,%d1 IOCS(__CRTMOD) | Set system stack swap %d1 | %d1 = 0x0010_0000 moveal %d1,%sp | Set base pointer. Now we can use RELOC() macro. leal TEXTADDR:W,%a5 | Initialize bss. | This code limits bss less than 64KB but it's no matter. | The bss cannot grow more than 4KB. See xxboot.ldscript. leal RELOC(__bss_start),%a1 movew #_end - 1,%d0 | bss end subw %a1,%d0 | don't change this op!! clrbss: | see chkmpu below clrb %a1@+ dbra %d0,clrbss | If it boots from SCSI, %d4 has SCSI ID. movel %d4,RELOC(SCSI_ID) chkmpu: | Check MPU beforehand since we want to use 68020 instructions. | Here the above "subw %a1,%d0" = 0x9049 and %d0.w = -1 at this | point, so that subsequent moveb loads | 0x49 if MPU <= 010 (clrbss + %d0.w) | 0x90 if MPU >= 020 (clrbss + %d0.w*2). | This is a MOVE op, not a TST op because TST with pc-relative | is not available on 000/010. moveb %pc@(clrbss-chkmpu-2:B,%d0:W:2),%d0 jmi mpuok BOOT_ERROR("MPU 68000?"); mpuok: | | Check where did I boot from. | IOCS(__BOOTINF) movel %d0,RELOC(BOOT_INFO) | save whole result | %d0 = 0xHHWWWWWW | | HH: how did I boot (powersw or alarm etc) | WWWWWW: where did I boot from | 0x80...0x8f SASI | 0x90...0x93 Floppy | 0xed0000...0xed3ffe SRAM | others ROM (maybe SCSI) bfextu %d0{#8:#8},%d1 jne boot_rom_ram | ROM or SRAM | FALLTHROUGH | SASI or Floppy boot_sasi_floppy: | Floppy or SASI cmpiw #0x90,%d0 jlt boot_dev_not_supp | SASI | | Boot from floppy | boot_floppy: | Make PDA+MODE lslw #8,%d0 | %d0=$00009X00 (X is unit#) moveql #0x70,%d1 orw %d0,%d1 | %d1=$00009X70 = (PDA<<8)+MODE movel %d1,RELOC(FDMODE) check_fd_format: | Check fd format. | Obtain min & max sector # of track(cylinder) 0. | On x68k, we can consider only double-sided floppy. moveql #0,%d2 init_loop: | On 1st time, clear %d3-%d5 with zero. | On 2nd time, initialize %d3-%d5 with first %d2. movel %d2,%d3 | %d3: initial NCHR movel %d2,%d4 | %d4: minimum NCHR movel %d2,%d5 | %d5: maximum NCHR loop: | B_READID with MSB of %d2 set obtains detected CHRN to %d2. moveql #1,%d2 | %d2 = 0x00000001 rorl #1,%d2 | %d2 = 0x80000000 IOCS(__B_READID) | %d2 = 0xCCHHRRNN rorl #8,%d2 | %d2 = 0xNNCCHHRR | On 1st time, goto init_loop with %d2 (%d2 is not zero). | On 2nd time, fall through because %d3 is not zero. tstl %d3 jeq init_loop cmpl %d4,%d2 | if (%d2 < %d4) jge 1f | movel %d2,%d4 | min = %d2 1: cmpl %d5,%d2 | if (%d2 > %d5) jle 1f | movel %d2,%d5 | max = %d2 1: cmpl %d3,%d2 | if (%d2 == %d3) break jne loop | Assume 2HD oriw #0x0100,%d5 | FDSEC.maxsec.H = 1 moveml %d4-%d5,RELOC(FDSEC) | Store | end of check_fd_format | read 8KB myself from floppy | %d1: (PDA<<8)+MODE already movel %d4,%d2 | %d2: read pos = first sector moveql #0x20,%d3 | %d3: read bytes = (0x20 << 8) lsll #8,%d3 | = 0x2000 = 8192 leal %a5@,%a1 | %a1: dest buffer IOCS(__B_READ) | Jump to full parimary loader jmp RELOC(first_kbyte) boot_rom_ram: | ROM(SCSI) or SRAM cmpib #0xed,%d1 jeq boot_dev_not_supp | SRAM | | Boot from SCSI | boot_scsi: | get block length of the SCSI disk leal RELOC(SCSI_CAP),%a1 SCSIIOCS(__S_READCAP) tstl %d0 jeq boot_scsi1 BOOT_ERROR("READCAP failed") boot_scsi1: movel RELOC(SCSI_CAP+4),%d0 | %d0 = blocksize in bytes lsrl #2,%d0 | %d0 = blocksize in longword moveql #25,%d5 bfffo %d0{#0:#32},%d1 | 25:256 24:512 23:1024 22:2048 subl %d1,%d5 | 0:256 1:512 2:1024 3:2048 movel %d5,RELOC(SCSI_BLKLEN) | %d5 = sector length index | Find out the start position of the boot partition. | There seems to be no interface or consensus about this and | so that we would have to do it heuristicly. | | ROM firmware: | pass read pos (in block #, aka sector #) in %d2. | Human68k-style partition table does not exist. | %d2 is 4 at the maximum. | SCSI IPLs (genuine and SxSI): | pass read pos (in kilobytes) in %d2. | %d2 is bigger than 0x20. | partition table on the memory is destroyed. | BOOT MENU Ver.2.22: | passes partition table entry address in %a0. | %d2 is cleared to zero | No other IPLs are supported. tstl %d2 jne 1f | If no information in %d2, probably from BOOT MENU. | %a0 points the on-memory partition table entry. movel %a0@(0x0008),%d2 | %d2 = pos in kbyte 1: moveql #0x20,%d3 cmpl %d3,%d2 jcs 1f | jump if %d2 > 0x20 | SCSI IPL or BOOT MENU. | At this point, %d2 is pos in kbyte in all cases. lsll #8,%d2 | %d2 = pos in longword divul %d0,%d2 | %d2 = pos in sector 1: | At this point, %d2 is pos in sector in all cases. | TDSIZE = 8192, TDSIZE / 4 = 0x800 = (0x20 << 6). lsll #6,%d3 | %d3 = TDSIZE in longword divul %d0,%d3 | %d0 = TDSIZE in sector | Read full primary bootloader moveal %a5,%a1 | %a1 = dest buffer jbsr scsiread | Selected start sector should not <= 4. There should be | partition table. If so, repoints to zero(?). moveql #5,%d0 cmpl %d0,%d2 bcc 1f moveql #0,%d2 1: movel %d2,RELOC(SCSI_PARTTOP) | Jump to full parimary loader jmp RELOC(first_kbyte) | | scsiread | Read SCSI disk using __S_READ as possible. If __S_READ cannot be | used (due to read length or offset), use __S_READEXT instead. | input: | %d2.l: pos in sector | %d3.l: len in sector (must be < 65536) | %d4.l: target SCSI ID | %d5.l: sector length index (0:256, 1:512, 2:1024, 3:2048, ...) | %a1.l: buffer address | destroy: | %d0,%d1 scsiread: | if (len >= 256 || pos + len >= 0x200000) | use READEXT | else | use READ moveql #__S_READEXT,%d1 cmpiw #256,%d3 jge scsiread_core | if (d3 >= 256) use READEXT movel %d2,%d0 addl %d3,%d0 | %d0 = pos + len jcs scsiread_core | if overflow, use READEXT bftst %d0{#0:#11} | if (pos + len >= 0x200000) jne scsiread_core | use REAEXT moveql #__S_READ,%d1 | else use READ scsiread_core: IOCS(__SCSIDRV) rts boot_dev_not_supp: BOOT_ERROR("not supported device"); | | void __dead BOOT_ERROR(const char *msg); | Print an error message, wait for key press, and reboot. | Called from C. ENTRY_NOPROFILE(BOOT_ERROR) addql #4,%sp | throw away return address | FALLTHROUGH | | BOOT_ERROR(msg) | Print an error message, wait for key press, and reboot. | Called from asm. boot_error: leal %pc@(msg_progname),%a1 IOCS(__B_PRINT) moveal %sp@+,%a1 IOCS(__B_PRINT) ENTRY_NOPROFILE(exit) ENTRY_NOPROFILE(_rtt) leal %pc@(msg_reboot),%a1 IOCS(__B_PRINT) | wait for a key press (or release of a modifier) IOCS(__B_KEYINP) | issue software reset trap #10 | NOTREACHED msg_reboot: .asciz "\r\n[Hit key to reboot]" .even .globl first_kbyte first_kbyte: |-------------------------------------------------------------------------- | #if defined(SELFTEST) jbsr selftest_ashldi3 jbsr selftest_ashrdi3 jbsr selftest_memcmp jbsr selftest_memmove jbsr selftest_memset #endif jmp _C_LABEL(bootmain) | NOTREACHED | | uint32_t badbadd(void *addr) | returns 1 if reading addr occurs bus error. Otherwise it returns 0. ENTRY_NOPROFILE(badbaddr) leal 0x0008:W,%a1 | bus error vector moveql #1,%d0 leal %pc@(badbaddr1),%a0 movew %sr,%sp@- oriw #0x0700,%sr | keep out interrupts movel %a1@,%sp@- movel %a0,%a1@ | set bus error vector movel %sp,%d1 | save sp moveal %sp@(10),%a0 tstb %a0@ | try read... moveql #0,%d0 | this is skipped on bus error badbaddr1: moveal %d1,%sp | restore sp movel %sp@+,%a1@ movew %sp@+,%sr rts | | int raw_read(uint32_t blkpos, uint32_t bytelen, void *buf) | blkpos: read start position in 512 byte block unit (always?). | bytelen: read length in bytes. | caller already avoids bytelen == 0 so that no checks here. | must be a multiple of sector size on scsi. | buf: destination buffer address | ENTRY_NOPROFILE(raw_read) moveal %sp,%a1 moveml %d2-%d7/%a2-%a6,%sp@- moveml %a1@,%d0/%d2-%d3/%a1 | %d0 (return address) | %d2 blkpos | %d3 bytelen | %a1 buf | At this point boot device is either floppy or SCSI. tstb %pc@(BOOT_INFO+1) jeq raw_read_floppy | FALLTHROUGH raw_read_scsi: | %d2 = pos from device top | in 512 bytes/block lsll #1,%d2 | %d2 = in 256 bytes/block movel %pc@(SCSI_BLKLEN),%d5 | %d5 = sector length index lsrl %d5,%d2 | %d2 = pos from device top | in media sector size divull %pc@(SCSI_CAP+4),%d0:%d3| %d3 = bytelen / sectsize | %d0 = bytelen % sectsize tstl %d0 jeq .Lraw1 BOOT_ERROR("Err1") | ASSERT(bytelen%sectsize==0) .Lraw1: movel %pc@(SCSI_ID),%d4 | %d4 = SCSI ID jbsr scsiread raw_read_exit: moveml %sp@+,%d2-%d7/%a2-%a6 rts raw_read_floppy: | nhead = FDSEC.maxsec.H - FDSEC.minsec.H + 1 | = 2; | nsect = FDSEC.maxsec.R - FDSEC.minsec.R + 1; | | sect = (blkpos % nsect) + FDSEC.minsec.R; | head = ((blkpos / nsect) % nhead) + FDSEC.minsec.H; | cyl = ((blkpos / nsect) / nhead) + FDSEC.minsec.C; | | NCHR = (FDSEC.minsec.N << 24) | | (cyl << 16) | | (head << 8) | | sect; | calc nsect. moveql #1,%d0 | %d0 = 1 addb %pc@(FDSEC+maxR),%d0 | %d0 = 1 + maxsec.R subb %pc@(FDSEC+minR),%d0 | %d0 = 1 + maxsec.R - minsec.R | = nsect | Convert blkpos to N/C/H/R. divuw %d0,%d2 | %d2.hw = blkpos % nsect | %d2.lw = blkpos / nsect | Here, %d2.hw becomes sector number and .lw becomes cyl+head. | %d2.lw = %0000_0000_CCCC_CCCH in binary form. LSB of | (blkpos / nsect) is head number because we support only | double-sided floppy here. | %d2.w = %0000_0000_CCCC_CCCH lslw #7,%d2 | %d2.w = %0CCC_CCCC_H000_0000 lsrb #7,%d2 | %d2.w = %0CCC_CCCC_0000_000H | i.e, | %d2 = $00rrCCHH swap %d2 | %d2 = $CCHH00rr lslw #8,%d2 | %d2 = $CCHHrr00 | two bytes from odd FDSEC+minR is (minR << 8 | maxN) and | minN == maxN always. addw %pc@(FDSEC+minR),%d2 | %d2 = $CCHHRRNN rorl #8,%d2 | %d2 = $NNCCHHRR movel %pc@(FDMODE),%d1 | %d1 = PDA+MODE IOCS(__B_READ) andil #0xf8ffff00,%d0 | Check status (must be zero) jeq raw_read_exit BOOT_ERROR("B_READ failed"); | | BSS | BSS(BOOT_INFO, 4) | whole result of IOCS BOOTINF BSS(FDMODE, 4) BSS(FDSEC, 8) | +0: (minN) sector length | +1: (minC) track number | +2: (minH) head | +3: (minR) sector number | +4: (maxN) sector length | +5: (maxC) track number | +6: (maxH) head | +7: (maxR) sector number BSS(SCSI_ID, 4) | SCSI ID, if booted from SCSI BSS(SCSI_CAP, 8) | result of SCSI READCAP | +0.L: total number of logical blocks | +4.L: block length in bytes BSS(SCSI_PARTTOP, 4) | top sector # of this partition BSS(SCSI_BLKLEN ,4) | sector length index | 0:256, 1:512, 2:1024, 3:2048, ..
