[llvm] [BOLT] Ignore AArch64 markers outside their sections. (PR #74106)

[Jacob Bramley via llvm-commits]

jacobbramley wrote:

> Out of interest, I was also looking for an explanation of why a $d symbol could appear in .eh_frame pointing to a text section. Would you happen to have an explanation for that?

Well, I can't find any specification (or other document) that explains why that might happen, but (to my surprise) I also couldn't find a statement that symbols had to remain within their sections, perhaps it is actually valid input. I'm not ruling out that it has a special meaning, but my working theory about why it happens in the first place is that it's simply a bug. I'm still working on tracking that down.

These symbols turn up reliably in Rust binaries, including the default "hello world" project, so BOLT will probably see it in the wild even if it is a bug that we later fix. Most users won't notice; the binary loads and runs fine, and `objdump` implementations hide the out-of-section symbols.

https://github.com/llvm/llvm-project/pull/74106