runtime/cgo: avoid taking the address of crosscall2 in code
Currently, set_crosscall2 takes the address of crosscall2 without
using the GOT, which, on some architectures, results in a
PC-relative relocation (e.g. R_AARCH64_ADR_PREL_PG_HI21 on ARM64)
to the crosscall2 symbol. But crosscall2 is dynamically exported,
so the C linker thinks it may bind to a symbol from a different
DSO. Some C linker may not like a PC-relative relocation to such a
symbol. Using a local trampoline to avoid taking the address of a
dynamically exported symbol.
It may be possible to not dynamically export crosscall2. But this
CL is safer for backport. Later we may remove the trampolines
after unexport crosscall2, if they are not needed.
Fixes #62556.
Change-Id: Id28457f65ef121d3f87d8189803abc65ed453283
Reviewed-on: https://go-review.googlesource.com/c/go/+/533535
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: Ian Lance Taylor <iant@google.com>