What does 'Segment type: Externs' mean in IDA?
<p>I'm trying to analyse an dynamically linked 64-bit ELF file using IDA pro, and I find a segment with an <code>extern</code> tpye, which is right after the <code>.bss</code>, as follows</p>

<pre><code>extern:00000000006021C0 ; Segment type: Externs
extern:00000000006021C0 ; extern
extern:00000000006021C0 ; void free(void *ptr)
extern:00000000006021C0        extrn free:near      ; DATA XREF: .got.plt:off_602018o
</code></pre>

<p>However, when I debug it at the runtime using gdb, I find that this 'extern' segment contains ONLY ZERO! There isn't any valid data other than zero in this segment. Also, there is no descriptions about the permissions of this segment, it looks as if this segment doesn't even exist.</p>

<p>Since there is DATA XREF in GOT, maybe it has something to do with import functions? But I couldn't find relevant documents, I wonder how IDA recognizes it, and what it is exactly?</p>

<p>Thanks!</p>