1 files changed, 101 insertions, 7 deletions

diff --git a/src/pkg/runtime/cgo/gcc_linux_arm.c b/src/pkg/runtime/cgo/gcc_linux_arm.c
index 8397c75bb..46a1126ad 100644
--- a/src/pkg/runtime/cgo/gcc_linux_arm.c
+++ b/src/pkg/runtime/cgo/gcc_linux_arm.c
@@ -2,19 +2,113 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+#include <pthread.h>
+#include <string.h>
 #include "libcgo.h"
 
-static void
-xinitcgo(G *g)
+static void *threadentry(void*);
+
+// We have to resort to TLS variable to save g(R10) and
+// m(R9). One reason is that external code might trigger
+// SIGSEGV, and our runtime.sigtramp don't even know we
+// are in external code, and will continue to use R10/R9,
+// this might as well result in another SIGSEGV.
+// Note: all three functions will clobber R0, and the last
+// two can be called from 5c ABI code.
+void __aeabi_read_tp(void) __attribute__((naked));
+void x_cgo_save_gm(void) __attribute__((naked));
+void x_cgo_load_gm(void) __attribute__((naked));
+
+void
+__aeabi_read_tp(void)
+{
+	// b __kuser_get_tls @ 0xffff0fe0
+	__asm__ __volatile__ (
+		"mvn r0, #0xf000\n\t"
+		"sub pc, r0, #31\n\t"
+		"nop\n\tnop\n\t"
+	);
+}
+
+// g (R10) at 8(TP), m (R9) at 12(TP)
+void
+x_cgo_load_gm(void)
+{
+	__asm__ __volatile__ (
+		"push {lr}\n\t"
+		"bl __aeabi_read_tp\n\t"
+		"ldr r10, [r0, #8]\n\t"
+		"ldr r9, [r0, #12]\n\t"
+		"pop {pc}\n\t"
+	);
+}
+
+void
+x_cgo_save_gm(void)
+{
+	__asm__ __volatile__ (
+		"push {lr}\n\t"
+		"bl __aeabi_read_tp\n\t"
+		"str r10, [r0, #8]\n\t"
+		"str r9, [r0, #12]\n\t"
+		"pop {pc}\n\t"
+	);
+}
+
+void
+x_cgo_init(G *g)
 {
-	// unimplemented
+	pthread_attr_t attr;
+	size_t size;
+	x_cgo_save_gm(); // save g and m for the initial thread
+
+	pthread_attr_init(&attr);
+	pthread_attr_getstacksize(&attr, &size);
+	g->stackguard = (uintptr)&attr - size + 4096;
+	pthread_attr_destroy(&attr);
 }
 
-void (*initcgo)(G*) = xinitcgo;
 
 void
-libcgo_sys_thread_start(ThreadStart *ts)
+_cgo_sys_thread_start(ThreadStart *ts)
+{
+	pthread_attr_t attr;
+	pthread_t p;
+	size_t size;
+	int err;
+
+	// Not sure why the memset is necessary here,
+	// but without it, we get a bogus stack size
+	// out of pthread_attr_getstacksize.  C'est la Linux.
+	memset(&attr, 0, sizeof attr);
+	pthread_attr_init(&attr);
+	size = 0;
+	pthread_attr_getstacksize(&attr, &size);
+	ts->g->stackguard = size;
+	err = pthread_create(&p, &attr, threadentry, ts);
+	if (err != 0) {
+		fprintf(stderr, "runtime/cgo: pthread_create failed: %s\n", strerror(err));
+		abort();
+	}
+}
+
+extern void crosscall_arm2(void (*fn)(void), void *g, void *m);
+static void*
+threadentry(void *v)
 {
-	// unimplemented
-	*(int*)0 = 0;
+	ThreadStart ts;
+
+	ts = *(ThreadStart*)v;
+	free(v);
+
+	ts.g->stackbase = (uintptr)&ts;
+
+	/*
+	 * _cgo_sys_thread_start set stackguard to stack size;
+	 * change to actual guard pointer.
+	 */
+	ts.g->stackguard = (uintptr)&ts - ts.g->stackguard + 4096 * 2;
+
+	crosscall_arm2(ts.fn, (void *)ts.g, (void *)ts.m);
+	return nil;
 }