Meaning of REX.w prefix before AMD64 jmp (FF25)
<p>While solving a bug I came across a difference between import jump tables of two Win64 DLLs. 64bit version of <code>kernel32.dll</code> uses plain <code>FF25</code> <em>jmp</em> instruction in its import jump tables. On the other hand 64bit version of <code>advapi32.dll</code> uses <code>48FF25</code> which indicates <code>REX.w=1</code> prefix before the <em>jmp</em> opcode. However, both seem to have 32bit operand specifying a RIP+offset address.</p>

<p>Is there any meaning for REX.w prefix on this specific opcode?</p>

<p>I'm not working with machine code often, so please excuse any factual mistakes.</p>