commit a76c4d0a0096537dc565908b53073460d96c8539
author Cherry Mui <cherryyz@google.com> Thu May 06 21:57:46 2021 -0400
committer Cherry Mui <cherryyz@google.com> Fri May 07 16:14:34 2021 +0000
tree 524b0f7008ebdc78ee619fce1d49d00319e6cd0e
parent 30e306a8bba52953c0341a6d28e5ba4635eb0ac2

unix: take address in assembly for Darwin syscall wrappers

In Go 1.17 we will introduce a register-based ABI on some
platforms, as well as ABI wrappers to bridge the ABIs. For Darwin
syscall wrappers, it needs to be called directly, instead of
through wrappers. Currently, it is written as that the syscall
functions are defined in assembly and their addresses are taken
from Go using funcPC. In Go 1.17 this will result in the address
of the ABI wrapper, which is undesired.

In the syscall package in the standard library we changed to use
a compiler intrinsic internal/abi.FuncPCABI0 to take the address
of the syscall function. But that is not available to this repo
and not available in older versions of Go. Here we take a
different approach: taking the address directly from assembly.
This also ensures we get the address of the defined syscall
function, not the ABI wrapper.

Updates golang/go#45702.

Change-Id: Ia7480d0fb0ca4fb9bf2f36d2deb1e3e5e4eb8284
Reviewed-on: https://go-review.googlesource.com/c/sys/+/317894
Trust: Cherry Mui <cherryyz@google.com>
Run-TryBot: Cherry Mui <cherryyz@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Than McIntosh <thanm@google.com>