runtime: mark all Go symbols called from assembly in other packages

This marks all Go symbols called from assembly in other packages with
"go:linkname" directives to ensure they get ABI wrappers.

Now that we have this go:linkname convention, this also removes the
abi0Syms definition in the runtime, which was used to give morestackc
an ABI0 wrapper. Instead, we now just mark morestackc with a
go:linkname directive.

This was tested with buildall.bash in the default configuration, with
-race, and with -gcflags=all=-d=ssa/intrinsics/off. Since I couldn't
test cgo on non-Linux configurations, I manually grepped for runtime
symbols in runtime/cgo.

Updates #31230.

Change-Id: I6c8aa56be2ca6802dfa2bf159e49c411b9071bf1
Reviewed-on: https://go-review.googlesource.com/c/go/+/179862
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Michael Knyszek <mknyszek@google.com>

5 files changed, 41 insertions, 0 deletions

diff --git a/src/runtime/internal/atomic/atomic_386.go b/src/runtime/internal/atomic/atomic_386.go
index 143cd45e61..d7f82cc752 100644
--- a/src/runtime/internal/atomic/atomic_386.go
+++ b/src/runtime/internal/atomic/atomic_386.go
@@ -8,6 +8,10 @@ package atomic
 
 import "unsafe"
 
+// Export some functions via linkname to assembly in sync/atomic.
+//go:linkname Load
+//go:linkname Loadp
+
 //go:nosplit
 //go:noinline
 func Load(ptr *uint32) uint32 {
diff --git a/src/runtime/internal/atomic/atomic_amd64x.go b/src/runtime/internal/atomic/atomic_amd64x.go
index b7e01a3ad5..31c1636b2e 100644
--- a/src/runtime/internal/atomic/atomic_amd64x.go
+++ b/src/runtime/internal/atomic/atomic_amd64x.go
@@ -8,6 +8,11 @@ package atomic
 
 import "unsafe"
 
+// Export some functions via linkname to assembly in sync/atomic.
+//go:linkname Load
+//go:linkname Loadp
+//go:linkname Load64
+
 //go:nosplit
 //go:noinline
 func Load(ptr *uint32) uint32 {
diff --git a/src/runtime/internal/atomic/atomic_mipsx.go b/src/runtime/internal/atomic/atomic_mipsx.go
index 210fc27d9b..6e39262c15 100644
--- a/src/runtime/internal/atomic/atomic_mipsx.go
+++ b/src/runtime/internal/atomic/atomic_mipsx.go
@@ -4,6 +4,13 @@
 
 // +build mips mipsle
 
+// Export some functions via linkname to assembly in sync/atomic.
+//go:linkname Xadd64
+//go:linkname Xchg64
+//go:linkname Cas64
+//go:linkname Load64
+//go:linkname Store64
+
 package atomic
 
 import (
diff --git a/src/runtime/internal/atomic/atomic_s390x.go b/src/runtime/internal/atomic/atomic_s390x.go
index 5a1f411ca1..f6758082a9 100644
--- a/src/runtime/internal/atomic/atomic_s390x.go
+++ b/src/runtime/internal/atomic/atomic_s390x.go
@@ -6,6 +6,13 @@ package atomic
 
 import "unsafe"
 
+// Export some functions via linkname to assembly in sync/atomic.
+//go:linkname Load
+//go:linkname Loadp
+//go:linkname Load64
+//go:linkname Store
+//go:linkname Store64
+
 //go:nosplit
 //go:noinline
 func Load(ptr *uint32) uint32 {
diff --git a/src/runtime/internal/atomic/atomic_wasm.go b/src/runtime/internal/atomic/atomic_wasm.go
index 9ce4892cb6..0731763ac1 100644
--- a/src/runtime/internal/atomic/atomic_wasm.go
+++ b/src/runtime/internal/atomic/atomic_wasm.go
@@ -5,6 +5,24 @@
 // TODO(neelance): implement with actual atomic operations as soon as threads are available
 // See https://github.com/WebAssembly/design/issues/1073
 
+// Export some functions via linkname to assembly in sync/atomic.
+//go:linkname Load
+//go:linkname Loadp
+//go:linkname Load64
+//go:linkname Loaduintptr
+//go:linkname Xadd
+//go:linkname Xadd64
+//go:linkname Xadduintptr
+//go:linkname Xchg
+//go:linkname Xchg64
+//go:linkname Xchguintptr
+//go:linkname Cas
+//go:linkname Cas64
+//go:linkname Casuintptr
+//go:linkname Store
+//go:linkname Store64
+//go:linkname Storeuintptr
+
 package atomic
 
 import "unsafe"