165 lines
2 KiB
ArmAsm
165 lines
2 KiB
ArmAsm
#
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! $Source$
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! $State$
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! Declare segments (the order is important).
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.sect .text
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.sect .rom
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.sect .data
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.sect .bss
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.sect .bss
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.define __sys_params_in
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.comm __sys_params_in, 6
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.define __sys_params_out
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.comm __sys_params_out, 2
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.comm opcode, 2
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.comm returnto, 2
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.sect .text
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! Called on system call. This does *not* use the C calling convention:
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! ax: syscall number
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! stack: ( param3 param2 param1 - result )
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.define .mon
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.mon:
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mov (opcode), ax
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pop (returnto)
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cmp ax, 1
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je exit
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cmp ax, 3
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je read
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cmp ax, 4
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je write
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cmp ax, 5
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je open
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cmp ax, 6
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je nop_1 ! close
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cmp ax, 20
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je nop_0 ! getpid
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cmp ax, 35
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je nop_1 ! time
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cmp ax, 48
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je sigtrp
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cmp ax, 54
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je ioctl
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! Syscall not supported --- write out an error message and halt.
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unsupported:
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mov si, msg
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1:
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lodsb
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andb al, al
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jz 2f
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movb ah, 0xE ! service
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mov bx, 0x0007 ! page 0, white
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int 0x10
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jmp 1b
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2:
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! Write out the syscall number.
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mov dx, (opcode)
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mov cx, 4 ! 4 hex digits
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1:
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rol dx, 1 ! rotate so that highest 4 bits are at the bottom
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rol dx, 1
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rol dx, 1
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rol dx, 1
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mov ax, 0xE0F ! ah = request, al = mask for nybble
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andb al, dl
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addb al, 0x90 ! convert al to ascii hex (four instructions)
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daa
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adcb al, 0x40
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daa
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int 0x10
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loop 1b
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! Exit.
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jmp EXIT
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.sect .rom
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msg:
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.asciz 'NOSYS'
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.sect .text
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exit:
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jmp EXIT
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read:
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mov ax, __sys_read
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jmp in_3_out_1
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write:
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mov ax, __sys_write
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jmp in_3_out_1
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open:
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add sp, 2*2
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jmp unimplemented
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ioctl:
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mov ax, __sys_ioctl
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jmp in_3_out_0
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sigtrp:
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add sp, 4
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jmp unimplemented
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in_3_out_0:
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pop (__sys_params_in+0)
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pop (__sys_params_in+2)
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pop (__sys_params_in+4)
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call ax
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jmp out_0
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in_3_out_1:
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pop (__sys_params_in+0)
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pop (__sys_params_in+2)
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pop (__sys_params_in+4)
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call ax
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jmp out_1
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out_0:
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or ax, ax
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jnz failed
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push ax
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jmp return
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out_1:
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or ax, ax
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jnz failed
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push (__sys_params_out)
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push ax
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jmp return
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unimplemented:
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mov ax, EBADMON
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failed:
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push ax
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push ax
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jmp return
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nop_1:
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add sp, 1*2
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jmp nop_0
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nop_3:
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add sp, 3*2
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nop_0:
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mov ax, 0
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push ax
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jmp return
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return:
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jmp (returnto)
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