122b66defd
This is a follow-on to the previous patch to support the ELFv2 ABI in the dynamic loader, split off into its own patch since it is just an optional optimization. In the ELFv2 ABI, most functions define both a global and a local entry point; the local entry requires r2 to be already set up by the caller to point to the callee's TOC; while the global entry does not require the caller to know about the callee's TOC, but it needs to set up r12 to the callee's entry point address. Now, when setting up a PLT slot, the dynamic linker will usually need to enter the target function's global entry point. However, if the linker can prove that the target function is in the same DSO as the PLT slot itself, and the whole DSO only uses a single TOC (which the linker will let ld.so know via a DT_PPC64_OPT entry), then it is possible to actually enter the local entry point address into the PLT slot, for a slight improvement in performance. Note that this uncovered a problem on the first call via _dl_runtime_resolve, because that routine neglected to restore the caller's TOC before calling the target function for the first time, since it assumed that function would always reload its own TOC anyway ...
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