runtime: create library startup for aix/ppc64

As .init_array section aren't available on AIX, the Go runtime
initialization is made with gcc constructor attribute.
However, as cgo tool is building a binary in order to get imported
C symbols, Go symbols imported for this initilization must be ignored.
-Wl,-berok is mandatory otherwize ld will fail to create this binary,
_rt0_aix_ppc64_lib and runtime_rt0_go aren't defined in runtime/cgo.
These two symbols must also be ignored when creating _cgo_import.go.

Change-Id: Icf2e0282f5b50de5fa82007439a428e6147efef1
Reviewed-on: https://go-review.googlesource.com/c/go/+/169118
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

3 files changed, 18 insertions, 0 deletions

diff --git a/src/runtime/cgo/callbacks_aix.go b/src/runtime/cgo/callbacks_aix.go
index 7dafb6b310..f4b6fe25fa 100644
--- a/src/runtime/cgo/callbacks_aix.go
+++ b/src/runtime/cgo/callbacks_aix.go
@@ -8,3 +8,4 @@ package cgo
 // longcall on cgo programs (cf gcc_aix_ppc64.c).
 //go:cgo_export_static __cgo_topofstack
 //go:cgo_export_static runtime.rt0_go
+//go:cgo_export_static _rt0_ppc64_aix_lib
diff --git a/src/runtime/cgo/cgo.go b/src/runtime/cgo/cgo.go
index 241a821e4f..eb11c0e100 100644
--- a/src/runtime/cgo/cgo.go
+++ b/src/runtime/cgo/cgo.go
@@ -20,6 +20,7 @@ package cgo
 #cgo !android,linux LDFLAGS: -lpthread
 #cgo netbsd LDFLAGS: -lpthread
 #cgo openbsd LDFLAGS: -lpthread
+#cgo aix LDFLAGS: -Wl,-berok
 
 #cgo CFLAGS: -Wall -Werror
 
diff --git a/src/runtime/cgo/gcc_aix_ppc64.c b/src/runtime/cgo/gcc_aix_ppc64.c
index d54c0ff32d..f4f50b89ce 100644
--- a/src/runtime/cgo/gcc_aix_ppc64.c
+++ b/src/runtime/cgo/gcc_aix_ppc64.c
@@ -12,6 +12,7 @@
  */
 extern int __attribute__((longcall)) __cgo_topofstack(void);
 extern int __attribute__((longcall)) runtime_rt0_go(int argc, char **argv);
+extern void __attribute__((longcall)) _rt0_ppc64_aix_lib(void);
 
 int _cgo_topofstack(void) {
 	return __cgo_topofstack();
@@ -20,3 +21,18 @@ int _cgo_topofstack(void) {
 int main(int argc, char **argv) {
 	return runtime_rt0_go(argc, argv);
 }
+
+static void libinit(void) __attribute__ ((constructor));
+
+/*
+ * libinit aims to replace .init_array section which isn't available on aix.
+ * Using __attribute__ ((constructor)) let gcc handles this instead of
+ * adding special code in cmd/link.
+ * However, it will be called for every Go programs which has cgo.
+ * Inside _rt0_ppc64_aix_lib(), runtime.isarchive is checked in order
+ * to know if this program is a c-archive or a simple cgo program.
+ * If it's not set, _rt0_ppc64_ax_lib() returns directly.
+ */
+static void libinit() {
+	_rt0_ppc64_aix_lib();
+}