opengl: Ensure we only load the GLES emulation library when the emulator supports it.

This patch modifies the libEGL.so loader to only load the emulator-specific
EGL/GLES libraries if it detects at runtime that the emulator supports it.

This prevents the system crashing when booting the platform image under an old
emulator version, or one without GPU emulation enabled.

Change-Id: I711b3f0a4ee1f3b080263780726ce7ec28ff11d6

Author: digit-android

opengl/libs/EGL/Loader.cpp

@@ -23,6 +23,7 @@
 #include <limits.h>
 
 #include <cutils/log.h>
+#include <cutils/properties.h>
 
 #include <EGL/egl.h>
 
@@ -45,6 +46,39 @@ namespace android {
 
 ANDROID_SINGLETON_STATIC_INSTANCE( Loader )
 
+/* This function is called to check whether we run inside the emulator,
+ * and if this is the case whether GLES GPU emulation is supported.
+ *
+ * Returned values are:
+ *  -1   -> not running inside the emulator
+ *   0   -> running inside the emulator, but GPU emulation not supported
+ *   1   -> running inside the emulator, GPU emulation is supported
+ *          through the "emulation" config.
+ */
+static int
+checkGlesEmulationStatus(void)
+{
+    /* We're going to check for the following kernel parameters:
+     *
+     *    qemu=1                      -> tells us that we run inside the emulator
+     *    android.qemu.gles=<number>  -> tells us the GLES GPU emulation status
+     *
+     * Note that we will return <number> if we find it. This let us support
+     * more additionnal emulation modes in the future.
+     */
+    char  prop[PROPERTY_VALUE_MAX];
+    int   result = -1;
+
+    /* First, check for qemu=1 */
+    property_get("ro.kernel.qemu",prop,"0");
+    if (atoi(prop) != 1)
+        return -1;
+
+    /* We are in the emulator, get GPU status value */
+    property_get("ro.kernel.qemu.gles",prop,"0");
+    return atoi(prop);
+}
+
 // ----------------------------------------------------------------------------
 
 Loader::driver_t::driver_t(void* gles) 
@@ -94,6 +128,15 @@ Loader::Loader()
 {
     char line[256];
     char tag[256];
+
+    /* Special case for GLES emulation */
+    if (checkGlesEmulationStatus() == 0) {
+        LOGD("Emulator without GPU support detected. Fallback to software renderer.");
+        gConfig.add( entry_t(0, 0, "android") );
+        return;
+    }
+
+    /* Otherwise, use egl.cfg */
     FILE* cfg = fopen("/system/lib/egl/egl.cfg", "r");
     if (cfg == NULL) {
         // default config