runtime: save frame pointer to the stack in signal handlers for arm64
When taking over the goroutine stack in the panic or preemption signal
handlers on arm64, the frame pointer should be saved on the stack (like
the link register) so that frame-pointer unwinding from a panic stack
works properly. Otherwise, tests like TestStackWrapperStackPanic will
fail with the frame pointer check in adjustframe (enabled with
debugCheckBP) when checking the sigpanic frame.
Updates #39524, #58432
Change-Id: I8b89e6fc4877af29b1b81e55e591e6398159855c
Reviewed-on: https://go-review.googlesource.com/c/go/+/481635 Reviewed-by: Felix Geisendörfer <felix.geisendoerfer@datadoghq.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Nick Ripley <nick.ripley@datadoghq.com> Reviewed-by: Cherry Mui <cherryyz@google.com> Reviewed-by: Michael Knyszek <mknyszek@google.com>