Comment the boot manager. So I don't have to work it all out again :-)
Reviewed by: rnordier@freebsd.org
This commit is contained in:
julian
parent
ff51285d10
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082c01dec6
@ -1,5 +1,8 @@
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#
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# Copyright (c) 1998 Robert Nordier
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# Copyright (c) 1998 Robert NordierSince nothing was printed, just continue on as if the user
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# hadn't done anything. This gives the effect of the user getting a beep
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# for all bad keystrokes but no action until either the timeout
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# occurs or the user hits a good key.
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# All rights reserved.
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#
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# Redistribution and use in source and binary forms are freely
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@ -32,6 +35,10 @@
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.set KEY_ENTER,0x1c # Enter key scan code
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.set KEY_F1,0x3b # F1 key scan code
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#
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# Addresses in the sector of embedded data values.
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# Accessed with negative offsets from the end of the relocated sector (%ebp).
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#
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.set _NXTDRV,-0x48 # Next drive
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.set _OPT,-0x47 # Default option
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.set _SETDRV,-0x46 # Drive to force
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@ -42,65 +49,134 @@
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.globl start # Entry point
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#
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# Initialise segments and registers to known values.
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# segments start at 0.
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# The stack is immediatly below the address we were loaded to.
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#
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start: cld # String ops inc
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xorl %eax,%eax # Zero
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movl %eax,%es # Address
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movl %eax,%ds # data
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movl %eax,%ss # Set up
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movwir(LOAD,_sp) # stack
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#
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# Copy this code to the address it was linked for
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#
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movl %esp,%esi # Source
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movwir(start,_di) # Destination
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movwir(0x100,_cx) # Word count
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rep # Relocate
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movsl # code
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#
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# Set address for variable space beyond code, and clear it.
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# Notice that this is also used to point to the values embedded in in the block,
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# by using negative offsets.
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#
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movl %edi,%ebp # Address variables
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movb $0x8,%cl # Words to clear
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rep # Zero
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stosl # them
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#
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# Relocate to the new copy of the code.
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#
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incb1(-0xe,_di_) # Sector number
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jmpnwi(main-LOAD+ORIGIN) # To relocated code
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#
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# Check what flags were loaded with us, specifically, Use a predefined Drive.
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# If what the bios gives us is bad, use the '0' in the block instead, as well.
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#
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main: tstbi1(0x20,_FLAGS,_bp_) # Set number drive?
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jnz main.1 # Yes
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testb %dl,%dl # Drive number valid?
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js main.2 # Possibly
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js main.2 # Possibly (0x80 set)
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main.1: movb1r(_SETDRV,_bp_,_dl) # Drive number to use
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#
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# Whatever we decided to use, now store it into the fake
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# partition entry that lives in the data space above us.
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#
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main.2: movbr1(_dl,_FAKE,_bp_) # Save drive number
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callwi(putn) # To new line
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pushl %edx # Save drive number
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movwir(partbl+0x4,_bx) # Partition table
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#
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# Start out with a pointer to the 4th byte of the first table entry
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# so that after 4 iterations it's beyond the end of the sector.
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# and beyond a 256 byte boundary and thos overflowed 8 bits (see next comment).
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# (remember that the table starts 2 bytes earlier than you would expect
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# as the bootable flag is after it in the block)
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#
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movwir(partbl+0x4,_bx) # Partition table (+4)
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xorl %edx,%edx # Item number
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main.3: movbr1(_ch,-0x4,_bx_) # Zero active flag
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#
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# Loop around on the partition table, printing values until we
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# pass a 256 byte boundary. The end of loop test is at main.5.
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#
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main.3: movbr1(_ch,-0x4,_bx_) # Zero active flag (ch == 0)
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btwr1(_dx,_FLAGS,_bp_) # Entry enabled?
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jnc main.5 # No
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#
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# If any of the entries in the table are
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# the same as the 'type' in the slice table entry,
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# then this is an empty or non bootable partition. Skip it.
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#
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movb0r(_bx_,_al) # Load type
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movwir(tables,_di) # Lookup tables
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movb $TBL0SZ,%cl # Number of entries
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repne # Exclude
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scasb # partition?
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je main.5 # Yes
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#
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# Now scan the table of known types
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#
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movb $TBL1SZ,%cl # Number of entries
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repne # Known
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scasb # type?
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jne main.4 # No
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#
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# If it matches get the matching element in the
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# next array. if it doesn't, we are already
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# pointing at its first element which points to a "?".
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#
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addwir(TBL1SZ,_di) # Adjust
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main.4: movb0r(_di_,_cl) # Partition
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main.4: movb0r(_di_,_cl) # Partition
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addl %ecx,%edi # description
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callwi(putx) # Display it
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main.5: incl %edx # Next item
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main.5: incl %edx # Next item
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addb $0x10,%bl # Next entry
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jnc main.3 # Till done
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#
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# Passed a 256 byte boundary..
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# table is finished.
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# Add one to the drive number and check it is valid,
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#
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popl %eax # Drive number
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subb $0x80-0x1,%al # Does next
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cmpbmr(NHRDRV,_al) # drive exist?
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cmpbmr(NHRDRV,_al) # drive exist? (from BIOS?)
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jb main.6 # Yes
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# If not then if there is only one drive,
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# Don't display drive as an option.
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#
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decl %eax # Already drive 0?
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jz main.7 # Yes
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# If it was illegal or we cycled through them,
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# then go back to drive 0.
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#
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xorb %al,%al # Drive 0
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#
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# Whatever drive we selected, make it an ascii digit and save it back
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# to the "next drive" location in the loaded block in case we
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# want to save it for next time.
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# This also is part of the printed drive string so add 0x80 to indicate
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# end of string.
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#
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main.6: addb $'0'|0x80,%al # Save next
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movbr1(_al,_NXTDRV,_bp_) # drive number
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movwir(drive,_di) # Display
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callwi(putx) # item
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#
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# Now that we've printed the drive (if we needed to), display a prompt.
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# Get ready for the input byt noting the time.
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#
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main.7: movwir(prompt,_si) # Display
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callwi(putstr) # prompt
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movb1r(_OPT,_bp_,_dl) # Display
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@ -110,6 +186,10 @@ main.7: movwir(prompt,_si) # Display
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int $0x1a # system time
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movl %edx,%edi # Ticks when
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addw1r(_TICKS,_bp_,_di) # timeout
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#
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# Busy loop, looking for keystrokes but
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# keeping one eye on the time.
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#
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main.8: movb $0x1,%ah # BIOS: Check
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int $0x16 # for keypress
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jnz main.11 # Have one
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@ -117,21 +197,51 @@ main.8: movb $0x1,%ah # BIOS: Check
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int $0x1a # system time
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cmpl %edi,%edx # Timeout?
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jb main.8 # No
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#
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# If timed out or defaulting, come here.
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#
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main.9: movb1r(_OPT,_bp_,_al) # Load default
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jmp main.12 # Join common code
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#
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# User's last try was bad, beep in displeasure.
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# Since nothing was printed, just continue on as if the user
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# hadn't done anything. This gives the effect of the user getting a beep
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# for all bad keystrokes but no action until either the timeout
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# occurs or the user hits a good key.
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#
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main.10: movb $0x7,%al # Signal
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callwi(putchr) # error
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#
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# Get the keystroke.
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#
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main.11: xorb %ah,%ah # BIOS: Get
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int $0x16 # keypress
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movb %ah,%al # Scan code
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#
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# If it's CR act as if timed out.
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#
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cmpb $KEY_ENTER,%al # Enter pressed?
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je main.9 # Yes
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#
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# Otherwise check if legal
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# If not ask again.
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#
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subb $KEY_F1,%al # Less F1 scan code
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cmpb $0x4,%al # F1..F5?
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ja main.10 # No
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#
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# We have a selection.
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# but if it's a bad selection go back to complain.
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# The bits in MNUOPT were set when the options were printed.
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# Anything not printed is not an option.
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#
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main.12: cwtl # Option
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btwr1(_ax,_MNUOPT,_bp_) # enabled?
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jnc main.10 # No
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#
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# Save the info in the original tables
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# for rewriting to the disk.
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#
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movbr1(_al,_OPT,_bp_) # Save option
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movwir(FAKE,_si) # Partition for write
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movb0r(_si_,_dl) # Drive number
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@ -143,6 +253,9 @@ main.12: cwtl # Option
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addwia(partbl) # selected
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xchgl %ebx,%eax # partition
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movbi0(0x80,_bx_) # Flag active
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#
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# If not asked to do a write-back (flags 0x40) don't do one.
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#
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main.13: pushl %ebx # Save
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tstbi1(0x40,_FLAGS,_bp_) # No updates?
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jnz main.14 # Yes
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@ -151,9 +264,19 @@ main.13: pushl %ebx # Save
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callwi(intx13) # to disk
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main.14: popl %esi # Restore
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popfl # Restore
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#
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# If going to next drive, replace drive with selected one.
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# Remember to un-ascii it. Hey 0x80 is already set, cool!
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#
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jne main.15 # If not F5
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movb1r(_NXTDRV,_bp_,_dl) # Next drive
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subb $'0',%dl # number
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#
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# load selected bootsector to the LOAD location in RAM.
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# If it fails to read or isn't marked bootable, treat it
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# as a bad selection.
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# XXX what does %esi carry?
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#
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main.15: movwir(LOAD,_bx) # Address for read
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movb $0x2,%ah # Read sector
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callwi(intx13) # from disk
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@ -166,7 +289,9 @@ main.15: movwir(LOAD,_bx) # Address for read
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popl %esi # Restore
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jmp *%ebx # Invoke bootstrap
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#
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# Display routines
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#
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putkey: movb $'F',%al # Display
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callwi(putchr) # 'F'
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@ -174,6 +299,10 @@ putkey: movb $'F',%al # Display
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addb %dl,%al # digit
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jmp putstr.1 # Display the rest
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#
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# Display the option and note that it is a valid option.
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# That last point is a bit tricky..
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#
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putx: btswr1(_dx,_MNUOPT,_bp_) # Enable menu option
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movwir(item,_si) # Display
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callwi(putkey) # key
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@ -231,11 +360,19 @@ crlf: .ascii "\r"; .byte '\n'|0x80
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# Partition type tables
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tables:
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#
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# These entries identify invalid or NON BOOT types and partitions.
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#
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.byte 0x0, 0x5, 0xf
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#
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# These valuse indicate botable types we know the names of
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#
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.byte 0x1, 0x4, 0x6, 0xb, 0xc, 0xe, 0x63, 0x83
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.byte 0xa5, 0xa6, 0xa9
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#
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# These are offsets that match the known names above and point to the strings
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# that will be printed.
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#
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.byte os_misc-. # Unknown
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.byte os_dos-. # DOS
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.byte os_dos-. # DOS
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@ -248,7 +385,10 @@ tables:
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.byte os_freebsd-. # FreeBSD
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.byte os_bsd-. # OpenBSD
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.byte os_bsd-. # NetBSD
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#
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# And here are the strings themselves. 0x80 or'd into a byte indicates
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# the end of the string. (not so great for Russians but...)
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#
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os_misc: .ascii "?"; .byte '?'|0x80
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os_dos: .ascii "DO"; .byte 'S'|0x80
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os_unix: .ascii "UNI"; .byte 'X'|0x80
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@ -257,7 +397,11 @@ os_freebsd: .ascii "Free"
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os_bsd: .ascii "BS"; .byte 'D'|0x80
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.org PRT_OFF-0xc,0x90
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#
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# These values are sometimes changed before writing back to the drive
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# Be especially careful that nxtdrv: must come after drive:, as it
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# is part of the same string.
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#
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drive: .ascii "Drive "
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nxtdrv: .byte 0x0 # Next drive number
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opt: .byte 0x0 # Option
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@ -265,5 +409,8 @@ setdrv: .byte 0x80 # Drive to force
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flags: .byte FLAGS # Flags
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ticks: .word TICKS # Delay
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#
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# here is the 64 byte partition table that fdisk would fiddle with.
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#
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partbl: .fill 0x40,0x1,0x0 # Partition table
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.word MAGIC # Magic number
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