diff options
author | jhb <jhb@FreeBSD.org> | 2000-05-05 13:22:10 +0000 |
---|---|---|
committer | jhb <jhb@FreeBSD.org> | 2000-05-05 13:22:10 +0000 |
commit | 86ec308f90cca57fecab8062b5a26e6ae1bca976 (patch) | |
tree | 7d5f66ec7a494eab4782e7bf0d9112ca2c622dd0 /sys/boot/i386 | |
parent | 63dadfa7b33775d11fd78119b27340accfc52b66 (diff) | |
download | FreeBSD-src-86ec308f90cca57fecab8062b5a26e6ae1bca976.zip FreeBSD-src-86ec308f90cca57fecab8062b5a26e6ae1bca976.tar.gz |
Switch to using the .code16 as(1) directive and using 16-bit assembly
code instead of using 32-bit code and having to just "know" that it's
really 16-bit instructions when things run. This also allows the code
to use fewer macros and more actual assembly statements, which eases
maintenance. Unfortunately, due to as(1) brokenness, we still use m4
macros for all 16-bit addresses, and all short jumps (i.e., 8-bit
relative addresses in the jump instruction) must be wrapped in .code32
directives to avoid useless bloat by as(1). This also fixes a few
problems that were preventing boot0 from compiling with the latest
and greatest version of as(1).
Diffstat (limited to 'sys/boot/i386')
-rw-r--r-- | sys/boot/i386/boot0/boot0.m4 | 1 | ||||
-rw-r--r-- | sys/boot/i386/boot0/boot0.s | 200 |
2 files changed, 138 insertions, 63 deletions
diff --git a/sys/boot/i386/boot0/boot0.m4 b/sys/boot/i386/boot0/boot0.m4 index d318d2a..7515d58 100644 --- a/sys/boot/i386/boot0/boot0.m4 +++ b/sys/boot/i386/boot0/boot0.m4 @@ -74,3 +74,4 @@ define(jmpnwi,`.byte 0xe9; .word $1 - . - 0x2')dnl define(tstbi1,`.byte 0xf6; .byte 0x40 | $3; .byte $2; .byte $1')dnl define(incb1,`.byte 0xfe; .byte 0x40 | $2; .byte $1')dnl define(pushw1,`.byte 0xff; .byte 0x70 | $2; .byte $1')dnl +define(retn,`.byte 0xc3')dnl diff --git a/sys/boot/i386/boot0/boot0.s b/sys/boot/i386/boot0/boot0.s index 25f631d..f7a3ec2 100644 --- a/sys/boot/i386/boot0/boot0.s +++ b/sys/boot/i386/boot0/boot0.s @@ -45,6 +45,7 @@ .set _MNUOPT,0xc # Menu options .globl start # Entry point + .code16 # This runs in real mode # # Initialise segments and registers to known values. @@ -52,49 +53,59 @@ # The stack is immediatly below the address we were loaded to. # start: cld # String ops inc - xorl %eax,%eax # Zero - movl %eax,%es # Address - movl %eax,%ds # data - movl %eax,%ss # Set up - movwir(LOAD,_sp) # stack + xorw %ax,%ax # Zero + movw %ax,%es # Address + movw %ax,%ds # data + movw %ax,%ss # Set up + movw $LOAD,%sp # stack + # # Copy this code to the address it was linked for # - movl %esp,%esi # Source - movwir(start,_di) # Destination - movwir(0x100,_cx) # Word count + movw %sp,%si # Source + movw $start,%di # Destination + movw $0x100,%cx # Word count rep # Relocate - movsl # code + movsw # code # # Set address for variable space beyond code, and clear it. # Notice that this is also used to point to the values embedded in in the block, # by using negative offsets. # - movl %edi,%ebp # Address variables + movw %di,%bp # Address variables movb $0x8,%cl # Words to clear rep # Zero - stosl # them + stosw # them # # Relocate to the new copy of the code. # incb1(-0xe,_di_) # Sector number + /* incb $-0xe(%di) */ jmpnwi(main-LOAD+ORIGIN) # To relocated code + /* jmp main-LOAD+ORIGIN */ # # Check what flags were loaded with us, specifically, Use a predefined Drive. # If what the bios gives us is bad, use the '0' in the block instead, as well. # main: tstbi1(0x20,_FLAGS,_bp_) # Set number drive? + /* testb $(0x20+_FLAGS)(%bp) */ + .code32 jnz main.1 # Yes + .code16 testb %dl,%dl # Drive number valid? + .code32 js main.2 # Possibly (0x80 set) + .code16 main.1: movb1r(_SETDRV,_bp_,_dl) # Drive number to use + /* movb $_SETDRV(%bp),%dl */ # # Whatever we decided to use, now store it into the fake # partition entry that lives in the data space above us. # main.2: movbr1(_dl,_FAKE,_bp_) # Save drive number + /* movb %dl,$_FAKE(%bp) */ callwi(putn) # To new line - pushl %edx # Save drive number + pushw %dx # Save drive number # # Start out with a pointer to the 4th byte of the first table entry # so that after 4 iterations it's beyond the end of the sector. @@ -102,59 +113,75 @@ main.2: movbr1(_dl,_FAKE,_bp_) # Save drive number # (remember that the table starts 2 bytes earlier than you would expect # as the bootable flag is after it in the block) # - movwir(partbl+0x4,_bx) # Partition table (+4) - xorl %edx,%edx # Item number + movw $(partbl+0x4),%bx # Partition table (+4) + xorw %dx,%dx # Item number # # Loop around on the partition table, printing values until we # pass a 256 byte boundary. The end of loop test is at main.5. # main.3: movbr1(_ch,-0x4,_bx_) # Zero active flag (ch == 0) + /* movb %ch,$-0x4(%bx) */ btwr1(_dx,_FLAGS,_bp_) # Entry enabled? + /* bt %dx,$_FLAGS(%bp) */ + .code32 jnc main.5 # No + .code16 # # If any of the entries in the table are # the same as the 'type' in the slice table entry, # then this is an empty or non bootable partition. Skip it. # movb0r(_bx_,_al) # Load type - movwir(tables,_di) # Lookup tables + /* movb (%bx),%al */ + movw $tables,%di # Lookup tables movb $TBL0SZ,%cl # Number of entries repne # Exclude scasb # partition? + .code32 je main.5 # Yes + .code16 # # Now scan the table of known types # movb $TBL1SZ,%cl # Number of entries repne # Known scasb # type? + .code32 jne main.4 # No + .code16 # # If it matches get the matching element in the # next array. if it doesn't, we are already # pointing at its first element which points to a "?". # - addwir(TBL1SZ,_di) # Adjust -main.4: movb0r(_di_,_cl) # Partition - addl %ecx,%edi # description + addw $TBL1SZ,%di # Adjust +main.4: movb0r(_di_,_cl) # Partition + /* movb (%di),%cl */ + addw %cx,%di # description callwi(putx) # Display it -main.5: incl %edx # Next item +main.5: incw %dx # Next item addb $0x10,%bl # Next entry + .code32 jnc main.3 # Till done + .code16 # # Passed a 256 byte boundary.. # table is finished. # Add one to the drive number and check it is valid, # - popl %eax # Drive number + popw %ax # Drive number subb $0x80-0x1,%al # Does next - cmpbmr(NHRDRV,_al) # drive exist? (from BIOS?) + cmpb NHRDRV,%al # drive exist? (from BIOS?) + .code32 jb main.6 # Yes + .code16 # If not then if there is only one drive, # Don't display drive as an option. # - decl %eax # Already drive 0? + decw %ax # Already drive 0? + .code32 jz main.7 # Yes + .code16 # If it was illegal or we cycled through them, # then go back to drive 0. # @@ -168,37 +195,47 @@ main.5: incl %edx # Next item # main.6: addb $'0'|0x80,%al # Save next movbr1(_al,_NXTDRV,_bp_) # drive number - movwir(drive,_di) # Display + /* movb %al,$NXTDRV(%bp) */ + movw $drive,%di # Display callwi(putx) # item # # Now that we've printed the drive (if we needed to), display a prompt. # Get ready for the input byt noting the time. # -main.7: movwir(prompt,_si) # Display +main.7: movw $prompt,%si # Display callwi(putstr) # prompt movb1r(_OPT,_bp_,_dl) # Display - decl %esi # default + /* movb $_OPT(%bp),%dl */ + decw %si # default callwi(putkey) # key xorb %ah,%ah # BIOS: Get int $0x1a # system time - movl %edx,%edi # Ticks when + movw %dx,%di # Ticks when addw1r(_TICKS,_bp_,_di) # timeout + /* addw $_TICKS(%bp),%di */ # # Busy loop, looking for keystrokes but # keeping one eye on the time. # main.8: movb $0x1,%ah # BIOS: Check int $0x16 # for keypress + .code32 jnz main.11 # Have one + .code16 xorb %ah,%ah # BIOS: Get int $0x1a # system time - cmpl %edi,%edx # Timeout? + cmpw %di,%dx # Timeout? + .code32 jb main.8 # No + .code16 # # If timed out or defaulting, come here. # main.9: movb1r(_OPT,_bp_,_al) # Load default + /* movb $_OPT(%bp),%al */ + .code32 jmp main.12 # Join common code + .code16 # # User's last try was bad, beep in displeasure. # Since nothing was printed, just continue on as if the user @@ -218,74 +255,99 @@ main.11: xorb %ah,%ah # BIOS: Get # If it's CR act as if timed out. # cmpb $KEY_ENTER,%al # Enter pressed? + .code32 je main.9 # Yes + .code16 # # Otherwise check if legal # If not ask again. # subb $KEY_F1,%al # Less F1 scan code cmpb $0x4,%al # F1..F5? + .code32 ja main.10 # No + .code16 # # We have a selection. # but if it's a bad selection go back to complain. # The bits in MNUOPT were set when the options were printed. # Anything not printed is not an option. # -main.12: cwtl # Option +main.12: cbtw # Option btwr1(_ax,_MNUOPT,_bp_) # enabled? + /* btw %ax,$_MNUOPT(%bp) */ + .code32 jnc main.10 # No + .code16 # # Save the info in the original tables # for rewriting to the disk. # movbr1(_al,_OPT,_bp_) # Save option - movwir(FAKE,_si) # Partition for write + /* movb %al,$OPT(%bp) */ + movw $FAKE,%si # Partition for write movb0r(_si_,_dl) # Drive number - movl %esi,%ebx # Partition for read + /* movb (%si),%dl */ + movw %si,%bx # Partition for read cmpb $0x4,%al # F5 pressed? - pushfl # Save + pushf # Save + .code32 je main.13 # Yes + .code16 shlb $0x4,%al # Point to - addwia(partbl) # selected - xchgl %ebx,%eax # partition + addw $partbl,%ax # selected + xchgw %bx,%ax # partition movbi0(0x80,_bx_) # Flag active + /* movb $0x80,(%bx) */ # # If not asked to do a write-back (flags 0x40) don't do one. # -main.13: pushl %ebx # Save +main.13: pushw %bx # Save tstbi1(0x40,_FLAGS,_bp_) # No updates? + /* testb $0x40,$_FLAGS(%bp) */ + .code32 jnz main.14 # Yes - movwir(start,_bx) # Data to write + .code16 + movw $start,%bx # Data to write movb $0x3,%ah # Write sector callwi(intx13) # to disk -main.14: popl %esi # Restore - popfl # Restore +main.14: popw %si # Restore + popf # Restore # # If going to next drive, replace drive with selected one. # Remember to un-ascii it. Hey 0x80 is already set, cool! # + .code32 jne main.15 # If not F5 + .code16 movb1r(_NXTDRV,_bp_,_dl) # Next drive + /* movb $_NXTDRV(%bp),%dl */ subb $'0',%dl # number # # load selected bootsector to the LOAD location in RAM. # If it fails to read or isn't marked bootable, treat it # as a bad selection. -# XXX what does %esi carry? +# XXX what does %si carry? # -main.15: movwir(LOAD,_bx) # Address for read +main.15: movw $LOAD,%bx # Address for read movb $0x2,%ah # Read sector callwi(intx13) # from disk + .code32 jc main.10 # If error + .code16 cmpwi2(MAGIC,0x1fe,_bx_) # Bootable? + /* cmpw $MAGIC,$0x1fe(%bx) */ + .code32 jne main.10 # No - pushl %esi # Save - movwir(crlf,_si) # Leave some + .code16 + pushw %si # Save + movw $crlf,%si # Leave some callwi(puts) # space - popl %esi # Restore + popw %si # Restore + .code32 jmp *%ebx # Invoke bootstrap - + /* jmp *%bx */ + .code16 # # Display routines # @@ -294,59 +356,71 @@ putkey: movb $'F',%al # Display callwi(putchr) # 'F' movb $'1',%al # Prepare addb %dl,%al # digit + .code32 jmp putstr.1 # Display the rest + .code16 # # Display the option and note that it is a valid option. # That last point is a bit tricky.. # putx: btswr1(_dx,_MNUOPT,_bp_) # Enable menu option - movwir(item,_si) # Display + /* btsw %dx,$_MNUOPT(%bp) */ + movw $item,%si # Display callwi(putkey) # key - movl %edi,%esi # Display the rest + movw %di,%si # Display the rest puts: callwi(putstr) # Display string -putn: movwir(crlf,_si) # To next line +putn: movw $crlf,%si # To next line putstr: lodsb # Get byte testb $0x80,%al # End of string? + .code32 jnz putstr.2 # Yes + .code16 putstr.1: callwi(putchr) # Display char + .code32 jmp putstr # Continue + .code16 putstr.2: andb $~0x80,%al # Clear MSB -putchr: pushl %ebx # Save - movwir(0x7,_bx) # Page:attribute +putchr: pushw %bx # Save + movw $0x7,%bx # Page:attribute movb $0xe,%ah # BIOS: Display int $0x10 # character - popl %ebx # Restore - ret # To caller + popw %bx # Restore + retn # To caller # One-sector disk I/O routine intx13: movb1r(0x1,_si_,_dh) # Load head + /* movb $0x1(%si),%dh */ movw1r(0x2,_si_,_cx) # Load cylinder:sector + /* movw $0x2(%si),%cx */ movb $0x1,%al # Sector count - pushl %esi # Save - movl %esp,%edi # Save + pushw %si # Save + movw %sp,%di # Save tstbi1(0x80,_FLAGS,_bp_) # Use packet interface? + /* testb $0x80,$_FLAGS(%bp) */ + .code32 jz intx13.1 # No - o16 # Set - pushb $0x0 # the + .code16 + pushl $0x0 # Set the o16 # LBA pushw1(0x8,_si_) # address - pushl %es # Set the transfer - pushl %ebx # buffer address - pushb $0x1 # Block count - pushb $0x10 # Packet size - movl %esp,%esi # Packet pointer - decl %eax # Verify off + /* pushl $0x8(%si) */ + pushw %es # Set the transfer + pushw %bx # buffer address + push $0x1 # Block count + push $0x10 # Packet size + movw %sp,%si # Packet pointer + decw %ax # Verify off orb $0x40,%ah # Use disk packet intx13.1: int $0x13 # BIOS: Disk I/O - movl %edi,%esp # Restore - popl %esi # Restore - ret # To caller + movw %di,%sp # Restore + popw %si # Restore + retn # To caller # Menu strings |