1 files changed, 90 insertions, 0 deletions
diff --git a/src/runtime/cgo/gcc_android.c b/src/runtime/cgo/gcc_android.c
new file mode 100644
index 0000000..7ea2135
--- /dev/null
+++ b/src/runtime/cgo/gcc_android.c
@@ -0,0 +1,90 @@
+// Copyright 2014 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 <stdarg.h>
+#include <android/log.h>
+#include <pthread.h>
+#include <dlfcn.h>
+#include "libcgo.h"
+
+void
+fatalf(const char* format, ...)
+{
+	va_list ap;
+
+	// Write to both stderr and logcat.
+	//
+	// When running from an .apk, /dev/stderr and /dev/stdout
+	// redirect to /dev/null. And when running a test binary
+	// via adb shell, it's easy to miss logcat.
+
+	fprintf(stderr, "runtime/cgo: ");
+	va_start(ap, format);
+	vfprintf(stderr, format, ap);
+	va_end(ap);
+	fprintf(stderr, "\n");
+
+	va_start(ap, format);
+	__android_log_vprint(ANDROID_LOG_FATAL, "runtime/cgo", format, ap);
+	va_end(ap);
+
+	abort();
+}
+
+// Truncated to a different magic value on 32-bit; that's ok.
+#define magic1 (0x23581321345589ULL)
+
+// From https://android.googlesource.com/platform/bionic/+/refs/heads/android10-tests-release/libc/private/bionic_asm_tls.h#69.
+#define TLS_SLOT_APP 2
+
+// inittls allocates a thread-local storage slot for g.
+//
+// It finds the first available slot using pthread_key_create and uses
+// it as the offset value for runtime.tls_g.
+static void
+inittls(void **tlsg, void **tlsbase)
+{
+	pthread_key_t k;
+	int i, err;
+	void *handle, *get_ver, *off;
+
+	// Check for Android Q where we can use the free TLS_SLOT_APP slot.
+	handle = dlopen("libc.so", RTLD_LAZY);
+	if (handle == NULL) {
+		fatalf("inittls: failed to dlopen main program");
+		return;
+	}
+	// android_get_device_api_level is introduced in Android Q, so its mere presence
+	// is enough.
+	get_ver = dlsym(handle, "android_get_device_api_level");
+	dlclose(handle);
+	if (get_ver != NULL) {
+		off = (void *)(TLS_SLOT_APP*sizeof(void *));
+		// tlsg is initialized to Q's free TLS slot. Verify it while we're here.
+		if (*tlsg != off) {
+			fatalf("tlsg offset wrong, got %ld want %ld\n", *tlsg, off);
+		}
+		return;
+	}
+
+	err = pthread_key_create(&k, nil);
+	if(err != 0) {
+		fatalf("pthread_key_create failed: %d", err);
+	}
+	pthread_setspecific(k, (void*)magic1);
+	// If thread local slots are laid out as we expect, our magic word will
+	// be located at some low offset from tlsbase. However, just in case something went
+	// wrong, the search is limited to sensible offsets. PTHREAD_KEYS_MAX was the
+	// original limit, but issue 19472 made a higher limit necessary.
+	for (i=0; i<384; i++) {
+		if (*(tlsbase+i) == (void*)magic1) {
+			*tlsg = (void*)(i*sizeof(void *));
+			pthread_setspecific(k, 0);
+			return;
+		}
+	}
+	fatalf("inittls: could not find pthread key");
+}
+
+void (*x_cgo_inittls)(void **tlsg, void **tlsbase) = inittls;