[llvm-branch-commits] [ELF][AArch64][PAC][MTE] Handle Memtag globals for R_AARCH64_AUTH_ABS64 (PR #173291)

[Peter Smith via llvm-branch-commits]

smithp35 wrote:

> > LDG(Delta(S) + A + *P) - *P
> 
> The `*P`s here should have some function like SIGN to extract the low 32 bits normally used for a REL(R) addend.
> 

Thanks for the suggestion. I expect it would be something like:

* `ADDEND(*P)` represents the dynamic linker reading the addend field from the contents of the place P

The R_AARCH64_AUTH_RELATIVE entry would then be:
`SIGN((LDG(Delta(S) + A + ADDEND(*P)) - ADDEND(*P), SCHEMA(*P))`

> PAuthABI also has the following for AUTH_RELATIVE talking about "reserved for addend":
> 
> > It must be set to 0 if not used for an addend.
> 
> Probably should have a sentence here to explicitly override that?

Yes, I could mention that the addend field can be used by the memtagabi extension.



https://github.com/llvm/llvm-project/pull/173291