[tests] Regression test for EGL-glibc TLS conflict

bionic and glibc have different layouts for TLS space.
Since libEGL used a bionic slot directly (in inlined code),
libhybris's hooks didn't translate it properly and libEGL ended
up overwriting some unrelated thread-local values in glibc.

The problem only showed up when linking with libGLESv2 (which
pulls in libEGL), not when linking with libEGL directly. That's
why the test was added to test_glesv2.c

libhybris/hybris/tests/test_glesv2.c

@@ -22,6 +22,23 @@
 #include <math.h>
 #include <stddef.h>
 
+/* Regression test: make sure that there's no conflict between
+ * the TLS (thread-local storage) slots used via libEGL/bionic
+ * and the TLS space allocated by the host toolchain. The array
+ * declared here should remain unchanged regardless of GL activity.
+ * Since this array is the first __thread storage declared in the main
+ * program, glibc will allocate it before any others.
+ */
+#define SLOT_FILLER (void *) 0x11122111  /* arbitrary non-zero value */
+#define S SLOT_FILLER
+__thread void *tls_space[64] = {
+    S, S, S, S, S, S, S, S,  S, S, S, S, S, S, S, S,
+    S, S, S, S, S, S, S, S,  S, S, S, S, S, S, S, S,
+    S, S, S, S, S, S, S, S,  S, S, S, S, S, S, S, S,
+    S, S, S, S, S, S, S, S,  S, S, S, S, S, S, S, S,
+};
+#undef S
+
 const char vertex_src [] =
 "                                        \
    attribute vec4        position;       \
@@ -175,6 +192,18 @@ int main(int argc, char **argv)
     printf("terminated\n");
     android_dlclose(baz);
 #endif
+
+	int bad_tls = 0;
+	for (i=0; i<64; ++i) {
+		if (tls_space[i] != SLOT_FILLER) {
+			printf("TLS array slot %d polluted: %p\n", i, tls_space[i]);
+			bad_tls++;
+		}
+	}
+	if (bad_tls)
+		return 1;
+
+	return 0;
 }
 
 // vim:ts=4:sw=4:noexpandtab