IDApython - Turning a modified operand into a string reference

Question

I am working on an IDAPython script that is supposed to fix the disassembly of a firmware, by resolving it's symbol table.

The core of the script is working fine, but I have some issue when it comes to editing the way IDA is displaying stuff in the disassembly panel.

The idea is the following:

I have an original instruction like:

LDR          R1,=0xAAAAAAAA

After the execution of my script, the offset 0xAAAAAAAA is resolved into it's current value, let's say 0xBBBBBBBB, and it adds a comment next to the original instruction:

LDR          R1,=0xAAAAAAAA ; symbol_address=0xBBBBBBBB, symbol_value='DummyString'

But since I'm only adding a comment, I'm loosing the xRefs to and from the strings.

What i want to achieve is to edit the instruction itself, so IDA can create the xRefs to the Strings. Something like:

LDR          R1,=aDummyString 

I used this snippet to edit the operand address, which is working:

create_strlit(resolved_addr, 0, STRTYPE_C) # Defined the resolved string's addr as a proper string
new_inst = original_ins.replace(hex(original_addr), hex(resolved_addr))  # Simplified for clarity
set_manual_insn(addr, new_inst)            # Edit the instruction with the new resolved addr

But my disassembly view does not make the link between the address and the string itself.

LDR          R1,=0xBBBBBBBB

When i hover my cursor on 0xBBBBBBBB, i can see the correct string; When I click on this address, IDA takes me to the string's location. But it has not created any proper xRefs, and the display does not inform me that this is a string location.

I tried theses functions to turn the operand into a string reference, but without success:

op_plain_offset(addr, 1, 0)
op_offset(addr, 1, REF_OFF32)    # I also tried REF_OFF8 and REF_OFF16, just in case

But it does not update the disassembly view as I want.

And when i try to do it by hand by doing "right click" -> "Enter the current operand manually", it works fine :/

Any suggestion how to do that ?

Thanks

Answer 1

Well, I managed to do it with the add_dref() function:

add_dref(frm, to, type)
 
Create a data cross-reference.

Parameters:

    to - linear address of referenced data (C++: ea_t)
    type - cross-reference type (C++: dref_t)

Returns: bool
    success (may fail if user-defined xref exists from->to) 

So I can just call this for every resolved symbols:

add_dref(instruction_addr, resolved_symbol_address, 1)