cgo: enable cgo on openbsd

Enable cgo on OpenBSD.

The OpenBSD ld.so(1) does not currently support PT_TLS sections. Work
around this by fixing up the TCB that has been provided by librthread
and reallocating a TCB with additional space for TLS. Also provide a
wrapper for pthread_create, allowing zeroed TLS to be allocated for
threads created externally to Go.

Joint work with Shenghou Ma (minux).

Requires change 6846064.

Fixes #3205.

R=golang-dev, minux.ma, iant, rsc, iant
CC=golang-dev
https://golang.org/cl/6853059

doc/progs/run

@@ -45,6 +45,10 @@ fi
 if [ "$goos" == "netbsd" ]; then
 	c_go_cgo=""
 fi
+# cgo3 and cgo4 don't run on openbsd, since cgo cannot handle stdout correctly
+if [ "$goos" == "openbsd" ]; then
+	c_go_cgo="cgo1 cgo2"
+fi
 
 timeout="
 	timeout1

misc/cgo/test/basic.go

@@ -56,6 +56,7 @@ int add(int x, int y) {
 */
 import "C"
 import (
+	"runtime"
 	"syscall"
 	"testing"
 	"unsafe"
@@ -119,7 +120,12 @@ func testErrno(t *testing.T) {
 func testMultipleAssign(t *testing.T) {
 	p := C.CString("234")
 	n, m := C.strtol(p, nil, 345), C.strtol(p, nil, 10)
-	if n != 0 || m != 234 {
+	if runtime.GOOS == "openbsd" {
+		// Bug in OpenBSD strtol(3) - base > 36 succeeds.
+		if (n != 0 && n != 239089) || m != 234 {
+			t.Fatal("Strtol x2: ", n, m)
+		}
+	} else if n != 0 || m != 234 {
 		t.Fatal("Strtol x2: ", n, m)
 	}
 	C.free(unsafe.Pointer(p))

src/pkg/go/build/build.go

@@ -222,6 +222,8 @@ var cgoEnabled = map[string]bool{
 	"linux/arm":     true,
 	"netbsd/386":    true,
 	"netbsd/amd64":  true,
+	"openbsd/386":   true,
+	"openbsd/amd64": true,
 	"windows/386":   true,
 	"windows/amd64": true,
 }

src/pkg/net/cgo_openbsd.go

+// Copyright 2011 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 net
+
+/*
+#include <netdb.h>
+*/
+import "C"
+
+func cgoAddrInfoFlags() C.int {
+	return C.AI_CANONNAME
+}

src/pkg/net/cgo_unix.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build darwin freebsd linux netbsd
+// +build darwin freebsd linux netbsd openbsd
 
 package net
 

src/pkg/os/user/lookup_unix.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build darwin freebsd linux netbsd
+// +build darwin freebsd linux netbsd openbsd
 // +build cgo
 
 package user

src/pkg/runtime/cgo/gcc_openbsd_386.c

+// Copyright 2009 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.
+
+#include <sys/types.h>
+#include <dlfcn.h>
+#include <errno.h>
+#include <pthread.h>
+#include <signal.h>
+#include <string.h>
+#include "libcgo.h"
+
+static void* threadentry(void*);
+
+// TCB_SIZE is sizeof(struct thread_control_block),
+// as defined in /usr/src/lib/librthread/tcb.h
+#define TCB_SIZE (4 * sizeof(void *))
+#define TLS_SIZE (2 * sizeof(void *))
+
+void *__get_tcb(void);
+void __set_tcb(void *);
+
+static int (*sys_pthread_create)(pthread_t *thread, const pthread_attr_t *attr,
+	void *(*start_routine)(void *), void *arg);
+
+struct thread_args {
+	void *(*func)(void *);
+	void *arg;
+};
+
+static void
+tcb_fixup(int mainthread)
+{
+	void *newtcb, *oldtcb;
+
+	// The OpenBSD ld.so(1) does not currently support PT_TLS. As a result,
+	// we need to allocate our own TLS space while preserving the existing
+	// TCB that has been setup via librthread.
+
+	newtcb = malloc(TCB_SIZE + TLS_SIZE);
+	if(newtcb == NULL)
+		abort();
+
+	// The signal trampoline expects the TLS slots to be zeroed.
+	bzero(newtcb, TLS_SIZE);
+
+	oldtcb = __get_tcb();
+	bcopy(oldtcb, newtcb + TLS_SIZE, TCB_SIZE);
+	__set_tcb(newtcb + TLS_SIZE);
+
+	// The main thread TCB is a static allocation - do not try to free it.
+	if(!mainthread)
+		free(oldtcb);
+}
+
+static void *
+thread_start_wrapper(void *arg)
+{
+	struct thread_args args = *(struct thread_args *)arg;
+
+	free(arg);
+	tcb_fixup(0);
+
+	return args.func(args.arg);
+}
+
+int
+pthread_create(pthread_t *thread, const pthread_attr_t *attr,
+	void *(*start_routine)(void *), void *arg)
+{
+	struct thread_args *p;
+
+	p = malloc(sizeof(*p));
+	if(p == NULL) {
+		errno = ENOMEM;
+		return -1;
+	}
+	p->func = start_routine;
+	p->arg = arg;
+
+	return sys_pthread_create(thread, attr, thread_start_wrapper, p);
+}
+
+static void
+xinitcgo(G *g)
+{
+	pthread_attr_t attr;
+	size_t size;
+	void *handle;
+
+	pthread_attr_init(&attr);
+	pthread_attr_getstacksize(&attr, &size);
+	g->stackguard = (uintptr)&attr - size + 4096;
+	pthread_attr_destroy(&attr);
+
+	// Locate symbol for the system pthread_create function.
+	handle = dlopen("libpthread.so", RTLD_LAZY);
+	if(handle == NULL) {
+		fprintf(stderr, "dlopen: failed to load libpthread: %s\n", dlerror());
+		abort();
+	}
+	sys_pthread_create = dlsym(handle, "pthread_create");
+	if(sys_pthread_create == NULL) {
+		fprintf(stderr, "dlsym: failed to find pthread_create: %s\n", dlerror());
+		abort();
+	}
+	dlclose(handle);
+
+	tcb_fixup(1);
+}
+
+void (*initcgo)(G*) = xinitcgo;
+
+void
+libcgo_sys_thread_start(ThreadStart *ts)
+{
+	pthread_attr_t attr;
+	sigset_t ign, oset;
+	pthread_t p;
+	size_t size;
+	int err;
+
+	sigfillset(&ign);
+	sigprocmask(SIG_SETMASK, &ign, &oset);
+
+	pthread_attr_init(&attr);
+	pthread_attr_getstacksize(&attr, &size);
+	ts->g->stackguard = size;
+	err = sys_pthread_create(&p, &attr, threadentry, ts);
+
+	sigprocmask(SIG_SETMASK, &oset, nil);
+
+	if (err != 0) {
+		fprintf(stderr, "runtime/cgo: pthread_create failed: %s\n", strerror(err));
+		abort();
+	}
+}
+
+static void*
+threadentry(void *v)
+{
+	ThreadStart ts;
+
+	tcb_fixup(0);
+
+	ts = *(ThreadStart*)v;
+	free(v);
+
+	ts.g->stackbase = (uintptr)&ts;
+
+	/*
+	 * libcgo_sys_thread_start set stackguard to stack size;
+	 * change to actual guard pointer.
+	 */
+	ts.g->stackguard = (uintptr)&ts - ts.g->stackguard + 4096;
+
+	/*
+	 * Set specific keys.  On OpenBSD/ELF, the thread local storage
+	 * is just before %gs:0.  Our dynamic 8.out's reserve 8 bytes
+	 * for the two words g and m at %gs:-8 and %gs:-4.
+	 */
+	asm volatile (
+		"movl %0, %%gs:-8\n"	// MOVL g, -8(GS)
+		"movl %1, %%gs:-4\n"	// MOVL m, -4(GS)
+		:: "r"(ts.g), "r"(ts.m)
+	);
+
+	crosscall_386(ts.fn);
+	return nil;
+}

src/pkg/runtime/cgo/gcc_openbsd_amd64.c

+// Copyright 2009 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.
+
+#include <sys/types.h>
+#include <dlfcn.h>
+#include <errno.h>
+#include <pthread.h>
+#include <signal.h>
+#include <string.h>
+#include "libcgo.h"
+
+static void* threadentry(void*);
+
+// TCB_SIZE is sizeof(struct thread_control_block),
+// as defined in /usr/src/lib/librthread/tcb.h
+#define TCB_SIZE (4 * sizeof(void *))
+#define TLS_SIZE (2 * sizeof(void *))
+
+void *__get_tcb(void);
+void __set_tcb(void *);
+
+static int (*sys_pthread_create)(pthread_t *thread, const pthread_attr_t *attr,
+	void *(*start_routine)(void *), void *arg);
+
+struct thread_args {
+	void *(*func)(void *);
+	void *arg;
+};
+
+static void
+tcb_fixup(int mainthread)
+{
+	void *newtcb, *oldtcb;
+
+	// The OpenBSD ld.so(1) does not currently support PT_TLS. As a result,
+	// we need to allocate our own TLS space while preserving the existing
+	// TCB that has been setup via librthread.
+
+	newtcb = malloc(TCB_SIZE + TLS_SIZE);
+	if(newtcb == NULL)
+		abort();
+
+	// The signal trampoline expects the TLS slots to be zeroed.
+	bzero(newtcb, TLS_SIZE);
+
+	oldtcb = __get_tcb();
+	bcopy(oldtcb, newtcb + TLS_SIZE, TCB_SIZE);
+	__set_tcb(newtcb + TLS_SIZE);
+
+	// The main thread TCB is a static allocation - do not try to free it.
+	if(!mainthread)
+		free(oldtcb);
+}
+
+static void *
+thread_start_wrapper(void *arg)
+{
+	struct thread_args args = *(struct thread_args *)arg;
+
+	free(arg);
+	tcb_fixup(0);
+
+	return args.func(args.arg);
+}
+
+int
+pthread_create(pthread_t *thread, const pthread_attr_t *attr,
+	void *(*start_routine)(void *), void *arg)
+{
+	struct thread_args *p;
+
+	p = malloc(sizeof(*p));
+	if(p == NULL) {
+		errno = ENOMEM;
+		return -1;
+	}
+	p->func = start_routine;
+	p->arg = arg;
+
+	return sys_pthread_create(thread, attr, thread_start_wrapper, p);
+}
+
+static void
+xinitcgo(G *g)
+{
+	pthread_attr_t attr;
+	size_t size;
+	void *handle;
+
+	pthread_attr_init(&attr);
+	pthread_attr_getstacksize(&attr, &size);
+	g->stackguard = (uintptr)&attr - size + 4096;
+	pthread_attr_destroy(&attr);
+
+	// Locate symbol for the system pthread_create function.
+	handle = dlopen("libpthread.so", RTLD_LAZY);
+	if(handle == NULL) {
+		fprintf(stderr, "dlopen: failed to load libpthread: %s\n", dlerror());
+		abort();
+	}
+	sys_pthread_create = dlsym(handle, "pthread_create");
+	if(sys_pthread_create == NULL) {
+		fprintf(stderr, "dlsym: failed to find pthread_create: %s\n", dlerror());
+		abort();
+	}
+	dlclose(handle);
+
+	tcb_fixup(1);
+}
+
+void (*initcgo)(G*) = xinitcgo;
+
+void
+libcgo_sys_thread_start(ThreadStart *ts)
+{
+	pthread_attr_t attr;
+	sigset_t ign, oset;
+	pthread_t p;
+	size_t size;
+	int err;
+
+	sigfillset(&ign);
+	sigprocmask(SIG_SETMASK, &ign, &oset);
+
+	pthread_attr_init(&attr);
+	pthread_attr_getstacksize(&attr, &size);
+
+	ts->g->stackguard = size;
+	err = sys_pthread_create(&p, &attr, threadentry, ts);
+
+	sigprocmask(SIG_SETMASK, &oset, nil);
+
+	if (err != 0) {
+		fprintf(stderr, "runtime/cgo: pthread_create failed: %s\n", strerror(err));
+		abort();
+	}
+}
+
+static void*
+threadentry(void *v)
+{
+	ThreadStart ts;
+
+	tcb_fixup(0);
+
+	ts = *(ThreadStart*)v;
+	free(v);
+
+	ts.g->stackbase = (uintptr)&ts;
+
+	/*
+	 * libcgo_sys_thread_start set stackguard to stack size;
+	 * change to actual guard pointer.
+	 */
+	ts.g->stackguard = (uintptr)&ts - ts.g->stackguard + 4096;
+
+	/*
+	 * Set specific keys.  On OpenBSD/ELF, the thread local storage
+	 * is just before %fs:0.  Our dynamic 6.out's reserve 16 bytes
+	 * for the two words g and m at %fs:-16 and %fs:-8.
+	 */
+	asm volatile (
+		"movq %0, %%fs:-16\n"	// MOVL g, -16(FS)
+		"movq %1, %%fs:-8\n"	// MOVL m, -8(FS)
+		:: "r"(ts.g), "r"(ts.m)
+	);
+	crosscall_amd64(ts.fn);
+	return nil;
+}

src/pkg/runtime/cgo/openbsd.c

+// Copyright 2010 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.
+
+// Supply environ, __progname and __guard_local, because
+// we don't link against the standard OpenBSD crt0.o and
+// the libc dynamic library needs them.
+
+char *environ[1];
+char *__progname;
+long __guard_local;
+
+#pragma dynexport environ environ
+#pragma dynexport __progname __progname
+
+// This is normally marked as hidden and placed in the
+// .openbsd.randomdata section.
+#pragma dynexport __guard_local __guard_local
+
+// We override pthread_create to support PT_TLS.
+#pragma dynexport pthread_create pthread_create