From 092b7cfb08f6bc843050c71f1aae9ffbf4b512a5 Mon Sep 17 00:00:00 2001
From: Shenghou Ma <minux.ma@gmail.com>
Date: Sat, 23 Mar 2013 03:21:30 +0800
Subject: [PATCH] runtime/cgo, go/build: re-enable cgo for FreeBSD/ARM.

R=dave, rsc
CC=golang-dev
https://golang.org/cl/7970043
---
 src/pkg/go/build/build.go             |  1 +
 src/pkg/runtime/cgo/gcc_freebsd_arm.c | 14 +++++++++++++-
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/src/pkg/go/build/build.go b/src/pkg/go/build/build.go
index f4a84b8a7f..dc3669c1df 100644
--- a/src/pkg/go/build/build.go
+++ b/src/pkg/go/build/build.go
@@ -262,6 +262,7 @@ var cgoEnabled = map[string]bool{
 	"darwin/amd64":  true,
 	"freebsd/386":   true,
 	"freebsd/amd64": true,
+	"freebsd/arm":   true,
 	"linux/386":     true,
 	"linux/amd64":   true,
 	"linux/arm":     true,
diff --git a/src/pkg/runtime/cgo/gcc_freebsd_arm.c b/src/pkg/runtime/cgo/gcc_freebsd_arm.c
index 3bcb0b2701..73c990c28f 100644
--- a/src/pkg/runtime/cgo/gcc_freebsd_arm.c
+++ b/src/pkg/runtime/cgo/gcc_freebsd_arm.c
@@ -2,6 +2,8 @@
 // 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 <machine/sysarch.h>
 #include <pthread.h>
 #include <string.h>
 #include "libcgo.h"
@@ -22,10 +24,20 @@ void x_cgo_load_gm(void) __attribute__((naked));
 void
 __aeabi_read_tp(void)
 {
-	// read @ 0xffff1000
 	__asm__ __volatile__ (
+#ifdef ARM_TP_ADDRESS
+		// ARM_TP_ADDRESS is (ARM_VECTORS_HIGH + 0x1000) or 0xffff1000
+		// GCC inline asm doesn't provide a way to provide a constant
+		// to "ldr r0, =??" pseudo instruction, so we hardcode the value
+		// and check it with cpp.
+#if ARM_TP_ADDRESS != 0xffff1000
+#error Wrong ARM_TP_ADDRESS!
+#endif
 		"ldr r0, =0xffff1000\n\t"
 		"ldr r0, [r0]\n\t"
+#else
+		"mrc p15, 0, r0, c13, c0, 3\n\t"
+#endif
 		"mov pc, lr\n\t"
 	);
 }