runtime/cgo: get getstackbound for set_stacklo

Change-Id: Ia63a4604449b5e460e6f54c962fb7d6db2bc6a43
Reviewed-on: https://go-review.googlesource.com/c/go/+/519457
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>

src/runtime/cgo/gcc_freebsd_amd64.c

@@ -17,17 +17,17 @@ static void (*setg_gcc)(void*);
 void
 x_cgo_init(G *g, void (*setg)(void*))
 {
-	pthread_attr_t *attr;
+	uintptr *pbounds;
 
 	// Deal with memory sanitizer/clang interaction.
 	// See gcc_linux_amd64.c for details.
 	setg_gcc = setg;
-	attr = (pthread_attr_t*)malloc(sizeof *attr);
-	if (attr == NULL) {
+	pbounds = (uintptr*)malloc(2 * sizeof(uintptr));
+	if (pbounds == NULL) {
 		fatalf("malloc failed: %s", strerror(errno));
 	}
-	_cgo_set_stacklo(g, attr);
-	free(attr);
+	_cgo_set_stacklo(g, pbounds);
+	free(pbounds);
 }
 
 void

src/runtime/cgo/gcc_libinit.c

@@ -85,29 +85,25 @@ _cgo_wait_runtime_init_done(void) {
 // _cgo_set_stacklo sets g->stacklo based on the stack size.
 // This is common code called from x_cgo_init, which is itself
 // called by rt0_go in the runtime package.
-void _cgo_set_stacklo(G *g, pthread_attr_t *pattr)
+void _cgo_set_stacklo(G *g, uintptr *pbounds)
 {
-	pthread_attr_t attr;
-	size_t size;
+	uintptr bounds[2];
 
-	// pattr can be passed in by the caller; see gcc_linux_amd64.c.
-	if (pattr == NULL) {
-		pattr = &attr;
+	// pbounds can be passed in by the caller; see gcc_linux_amd64.c.
+	if (pbounds == NULL) {
+		pbounds = &bounds[0];
 	}
 
-	pthread_attr_init(pattr);
-	pthread_attr_getstacksize(pattr, &size);
+	x_cgo_getstackbound(pbounds);
 
-	g->stacklo = (uintptr)(__builtin_frame_address(0)) - size + 4096;
+	g->stacklo = *pbounds;
 
 	// Sanity check the results now, rather than getting a
 	// morestack on g0 crash.
 	if (g->stacklo >= g->stackhi) {
 		fprintf(stderr, "runtime/cgo: bad stack bounds: lo=%p hi=%p\n", (void*)(g->stacklo), (void*)(g->stackhi));
 		abort();
 	}
-
-	pthread_attr_destroy(pattr);
 }
 
 // Store the g into a thread-specific value associated with the pthread key pthread_g.

src/runtime/cgo/gcc_linux_amd64.c

@@ -19,7 +19,7 @@ void (*x_cgo_inittls)(void **tlsg, void **tlsbase) __attribute__((common));
 void
 x_cgo_init(G *g, void (*setg)(void*), void **tlsg, void **tlsbase)
 {
-	pthread_attr_t *attr;
+	uintptr *pbounds;
 
 	/* The memory sanitizer distributed with versions of clang
 	   before 3.8 has a bug: if you call mmap before malloc, mmap
@@ -37,12 +37,12 @@ x_cgo_init(G *g, void (*setg)(void*), void **tlsg, void **tlsbase)
 	   malloc, so we actually use the memory we allocate.  */
 
 	setg_gcc = setg;
-	attr = (pthread_attr_t*)malloc(sizeof *attr);
-	if (attr == NULL) {
+	pbounds = (uintptr*)malloc(2 * sizeof(uintptr));
+	if (pbounds == NULL) {
 		fatalf("malloc failed: %s", strerror(errno));
 	}
-	_cgo_set_stacklo(g, attr);
-	free(attr);
+	_cgo_set_stacklo(g, pbounds);
+	free(pbounds);
 
 	if (x_cgo_inittls) {
 		x_cgo_inittls(tlsg, tlsbase);

src/runtime/cgo/gcc_linux_arm64.c

@@ -56,7 +56,7 @@ threadentry(void *v)
 void
 x_cgo_init(G *g, void (*setg)(void*), void **tlsg, void **tlsbase)
 {
-	pthread_attr_t *attr;
+	uintptr *pbounds;
 
 	/* The memory sanitizer distributed with versions of clang
 	   before 3.8 has a bug: if you call mmap before malloc, mmap
@@ -74,12 +74,12 @@ x_cgo_init(G *g, void (*setg)(void*), void **tlsg, void **tlsbase)
 	   malloc, so we actually use the memory we allocate.  */
 
 	setg_gcc = setg;
-	attr = (pthread_attr_t*)malloc(sizeof *attr);
-	if (attr == NULL) {
+	pbounds = (uintptr*)malloc(2 * sizeof(uintptr));
+	if (pbounds == NULL) {
 		fatalf("malloc failed: %s", strerror(errno));
 	}
-	_cgo_set_stacklo(g, attr);
-	free(attr);
+	_cgo_set_stacklo(g, pbounds);
+	free(pbounds);
 
 	if (x_cgo_inittls) {
 		x_cgo_inittls(tlsg, tlsbase);

src/runtime/cgo/libcgo.h

@@ -68,6 +68,11 @@ void _cgo_sys_thread_start(ThreadStart *ts);
  */
 uintptr_t _cgo_wait_runtime_init_done(void);
 
+/*
+ * Get the low and high boundaries of the stack.
+ */
+void x_cgo_getstackbound(uintptr bounds[2]);
+
 /*
  * Prints error then calls abort. For linux and android.
  */

src/runtime/cgo/libcgo_unix.h

@@ -5,7 +5,7 @@
 /*
  * Initialize g->stacklo.
  */
-extern void _cgo_set_stacklo(G *, pthread_attr_t*);
+extern void _cgo_set_stacklo(G *, uintptr *);
 
 /*
  * Call pthread_create, retrying on EAGAIN.