Bit Fields tutorial
In this tutorial, you will learn how to enhance disassembly output by using bitfields.
Suppose the source code looked like this:
We have a disassembly that looks like this:
Let’s improve it by using bitfields.
We first define a bitfield type by going to the Local types window (menu Open subviews -> Local types). We press Ins to add a new enum and make it a bitfield. The name given to the bitfield does not matter much.
Note that Bitmask has been checked. Click OK.
Then we edit the enum and update it using the C syntax tab as shown in the screenshot below.
Click OK.
The first bitfield mask is 3 (or 2 bits). The name of the mask is not used by IDA, it is intended as a memory helper. The enum definition becomes:
We finally switch to the disassembly window. Through the Edit -> Operand types -> Enum member menu (or by pressing M on the second operand at addresses 0x130003E39 and 0x130003E40) we select the enum type we just defined and get this result…
That’s all folks!
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