BIOS Guard Script tool

The tool allows you to assemble and disassemble BIOS Guard script.

Assembly

To assemble a script, you need to use big-script-tool.py -a <script_file>. Assembled script will be saved to file <script_file>_assembled.bin.

Also you can use class BigScript directly:

script = BigScript(code_string=src)
script.to_bytes()

or

script = BigScript()
script.assemble(src)
script.to_bytes()

Operands

The operands are:

• buffers
• flash pointers
• registers
• immediate values
• labels

Buffers: buffer<number_of_the_buffer> (or b<number_of_the_buffer>). Storages of the data. buffer0 points to the actual BGUP. Other buffers are temporal.

set b0 0xAA00
add b0 0x1

Flash pointers: flash<number_of_the_flash_ptr> (or f<number_of_the_flash_ptr>). Stores some linear address of the flash.

set f0 0xA00000
sub f0 0x10

Registers: r<number_of_the_register> - a little storage of the temporal data.

set r1 0x10
set r2 0x20
add r1 r2
and r1 0x30

Imm values: <number> or 0x<number> if you prefer to use hex. Please note, that hex numbers are start only with 0x prefix. If you write something like 10000h it will be interpreted as a decimal number.

Labels: _<name_of_the_label> - an arbitrary script line name. Can be used only in control flow instructions. Please note, that labels start with _ and must not end with symbols like :. If you use that symbol, you will need to refer to the label like jmp _label:.

_loop
  sub r1 r2
  cmp r1 0x0
  jne _loop

Opcodes

Opcode name	Operands	Info
start	-	marks the start of the script
store	flash ptr, buffer, register	write data from a buffer to the flash
store	flash ptr, buffer, immediate value	write data from a buffer to the flash
load	buffer, flash ptr, register	read data from the flash to the buffer
load	buffer, flash ptr, immediate value	read data from the flash to the buffer
eraseblk	flash ptr	Erase flash blk
eraseblk64kb	flash ptr	Erase 64kb flash block
add	register, register
add	register, immediate value
add	buffer, register
add	buffer, immediate value
add	flash ptr, register
add	flash ptr, immediate value
sub	register, register
sub	register, immediate value
sub	buffer, register
sub	buffer, immediate value
sub	flash ptr, register
sub	flash ptr, immediate value
and	register, register
and	register, immediate value
or	register, register
or	register, immediate value
shr	register, immediate value
shl	register, immediate value
ror	register, immediate value
rol	register, immediate value
set	register, register
set	register, immediate value
set	buffer, register	Set an offset from the beggining of the buffer
set	buffer, immediate value	Set an offset from the beggining of the buffer
set	flash ptr, register	Set a linear address of the flash
set	flash ptr, immediate value	Set a linear address of the flash
loadbyte	register, buffer
loadword	register, buffer
loaddword	register, buffer
storebyte	buffer, register
storeword	buffer, register
storedword	buffer, register
cmp	register, register
cmp	register, immediate value
cmp	buffer, register
cmp	buffer, immediate value
cmp	flash ptr, register
cmp	flash ptr, immediate value
cmp	buffer, buffer, register	Compare buffers with specified length
cmp	buffer, buffer, immediate value	Compare buffers with specified length
copy	buffer, buffer, register	Copy data with the specified length
copy	buffer, buffer, immediate value	Copy data with the specified length
jmp	label (or imm)	Uncoditional jump to the label. Also you can use a line number directly.
je	label (or imm)	Coditional jump to the label. Also you can use a line number directly.
jne	label(or imm)	Coditional jump to the label. Also you can use a line number directly.
jg	label (or imm)	Coditional jump to the label. Also you can use a line number directly.
jge	label (or imm)	Coditional jump to the label. Also you can use a line number directly.
jl	label (or imm)	Coditional jump to the label. Also you can use a line number directly.
jle	label (or imm)	Coditional jump to the label. Also you can use a line number directly.
jmp	register	Uncoditional jump to the line number stored in register.
log	immediate value, register	Write data from second operand to the BiG Log. The BiG log needs to be setup properly.
log	immediate value, immediate value	Write data from second operand to the BiG Log. The BiG log needs to be setup properly.
rdsts	register	Read status of previous operation into register.
rand	register
sleep	immediate value
end	-

Disassembly

To disassemble a script, you need to use big-script-tool.py -d <script_file>. Disassembled script will be saved to file <script_file>_disassembled.txt.

Also you can use class BigScript directly:

script = BigScript(code_bytes=bin_script)
script.to_string()

or

script = BigScript()
script.disassemble(bin_script)
script.to_string()