cmd/link: handle dynamic import variables on Darwin in plugin mode

CL 501855 added support for cgo_dynamic_import variables on Darwin.
But it didn't support the plugin build mode on amd64, where the
assembler turns a direct load (R_PCREL) to a load via GOT
(R_GOTPCREL). This CL adds the support. We just need to handle
external linking mode, as this can only occur in plugin or shared
build mode, which requires external linking.

Fixes #67976.
Updates #50891.

Change-Id: I0f56265d50bfcb36047fa5538ad7a5ec77e7ef96
Reviewed-on: https://go-review.googlesource.com/c/go/+/592499
Reviewed-by: David Chase <drchase@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

diff --git a/src/cmd/cgo/internal/testplugin/plugin_test.go b/src/cmd/cgo/internal/testplugin/plugin_test.go
index 4900ada18201567de89e86615f08ce2c2c816618..85dfd31123b5dedd27aa83544caf692bc3805395 100644 (file)
--- a/src/cmd/cgo/internal/testplugin/plugin_test.go
+++ b/src/cmd/cgo/internal/testplugin/plugin_test.go
@@ -414,3 +414,11 @@ func TestTextSectionSplit(t *testing.T) {
                t.Errorf("runtime.text.1 not found, text section not split?")
        }
 }
+
+func TestIssue67976(t *testing.T) {
+       // Issue 67976: build failure with loading a dynimport variable (the runtime/pprof
+       // package does this on darwin) in a plugin on darwin/amd64.
+       // The test program uses runtime/pprof in a plugin.
+       globalSkip(t)
+       goCmd(t, "build", "-buildmode=plugin", "-o", "issue67976.so", "./issue67976/plugin.go")
+}

diff --git a/src/cmd/cgo/internal/testplugin/testdata/issue67976/plugin.go b/src/cmd/cgo/internal/testplugin/testdata/issue67976/plugin.go
new file mode 100644 (file)
index 0000000..502ecc5
--- /dev/null
+++ b/src/cmd/cgo/internal/testplugin/testdata/issue67976/plugin.go
@@ -0,0 +1,16 @@
+// Copyright 2024 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import (
+       "io"
+       "runtime/pprof"
+)
+
+func main() {}
+
+func Start() {
+       pprof.StartCPUProfile(io.Discard)
+}

diff --git a/src/cmd/link/internal/amd64/asm.go b/src/cmd/link/internal/amd64/asm.go
index f86d22493227acbf529bfb6eefb6709a0be3ae7f..9da0541f5263c26d12740cb279074fa859740f83 100644 (file)
--- a/src/cmd/link/internal/amd64/asm.go
+++ b/src/cmd/link/internal/amd64/asm.go
@@ -398,6 +398,13 @@ func adddynrel(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s loade
                        // (e.g. go version).
                        return true
                }
+       case objabi.R_GOTPCREL:
+               if target.IsExternal() {
+                       // External linker will do this relocation.
+                       return true
+               }
+               // We only need to handle external linking mode, as R_GOTPCREL can
+               // only occur in plugin or shared build modes.
        }
 
        return false