[Lldb-commits] [lld] [lldb] [llvm] [lld] Add -z mark-plt support for X86_64 (PR #206002)

[Phoebe Wang via lldb-commits]

phoebewang wrote:

> > > Is this feature actually used in the wild?
> > 
> > 
> > This can be used on targets have APX feature enabled. But I didn't observe performance different on spec.
> 
> If there is no performance difference, what's the point of supporting this option, which is incompatible with security practices? Note, unsupported `-z mark-plt` just leads to a linker warning, not breaking the build.

Microarchitectural level speaking, direct jmp is always better than indirect jmp. Hence we introduced JMPABS in APX. But nowadays, PIC makes absolute jmp useless in normal applications. However, there are scenarios that have very large footprint can benefit from JMPABS. So it is a choice between performance and security. The linker option just does the same. We provide such a choice for applicable users.

https://github.com/llvm/llvm-project/pull/206002