| $NetBSD: boot.S,v 1.13 2020/08/16 06:43:43 isaki Exp $

| $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, ..