Fix[ffmpeg_plugin]: replace LD_LIBRARY_PATH/PATH for ffmpeg, switch default exec mode

app_pojavlauncher/src/main/java/net/kdt/pojavlaunch/utils/JREUtils.java

@@ -368,7 +368,8 @@ public class JREUtils {
 
                 "-Dnet.minecraft.clientmodname=" + Tools.APP_NAME,
                 "-Dfml.earlyprogresswindow=false", //Forge 1.14+ workaround
-                "-Dloader.disable_forked_guis=true"
+                "-Dloader.disable_forked_guis=true",
+                "-Djdk.lang.Process.launchMechanism=FORK" // Default is POSIX_SPAWN which requires starting jspawnhelper, which doesn't work on Android
         ));
         if(LauncherPreferences.PREF_ARC_CAPES) {
             overridableArguments.add("-javaagent:"+new File(Tools.DIR_DATA,"arc_dns_injector/arc_dns_injector.jar").getAbsolutePath()+"=23.95.137.176");

app_pojavlauncher/src/main/jni/Android.mk

@@ -45,6 +45,7 @@ LOCAL_SRC_FILES := \
     jre_launcher.c \
     utils.c \
     stdio_is.c \
+    java_exec_hooks.c \
     driver_helper/nsbypass.c
 
 ifeq ($(TARGET_ARCH_ABI),arm64-v8a)

app_pojavlauncher/src/main/jni/input_bridge_v3.c

@@ -30,8 +30,6 @@
 #define EVENT_TYPE_MOUSE_BUTTON 1006
 #define EVENT_TYPE_SCROLL 1007
 
-jint (*orig_ProcessImpl_forkAndExec)(JNIEnv *env, jobject process, jint mode, jbyteArray helperpath, jbyteArray prog, jbyteArray argBlock, jint argc, jbyteArray envBlock, jint envc, jbyteArray dir, jintArray std_fds, jboolean redirectErrorStream);
-
 static void registerFunctions(JNIEnv *env);
 
 jint JNI_OnLoad(JavaVM* vm, __attribute__((unused)) void* reserved) {
@@ -230,56 +228,6 @@ void sendData(int type, int i1, int i2, int i3, int i4) {
     atomic_fetch_add_explicit(&pojav_environ->eventCounter, 1, memory_order_acquire);
 }
 
-static jbyteArray stringToBytes(JNIEnv *env, const char* string) {
-    const jsize string_data_len = (jsize)(strlen(string) + 1);
-    jbyteArray result = (*env)->NewByteArray(env, (jsize)string_data_len);
-    (*env)->SetByteArrayRegion(env, result, 0, (jsize)string_data_len, (const jbyte*) string);
-    return result;
-}
-
-/**
- * Hooked version of java.lang.UNIXProcess.forkAndExec()
- * which is used to handle the "open" command and "ffmpeg" invocations
- */
-jint
-hooked_ProcessImpl_forkAndExec(JNIEnv *env, jobject process, jint mode, jbyteArray helperpath, jbyteArray prog, jbyteArray argBlock, jint argc, jbyteArray envBlock, jint envc, jbyteArray dir, jintArray std_fds, jboolean redirectErrorStream) {
-    const char *pProg = (char *)((*env)->GetByteArrayElements(env, prog, NULL));
-    const char* pProgBaseName = basename(pProg);
-    const size_t basename_len = strlen(pProgBaseName);
-    char prog_basename[basename_len];
-    memcpy(&prog_basename, pProgBaseName, basename_len + 1);
-    (*env)->ReleaseByteArrayElements(env, prog, (jbyte *)pProg, 0);
-
-    if(strcmp(prog_basename, "xdg-open") == 0) {
-        // When invoking xdg-open, send that open command into the android half instead
-        Java_org_lwjgl_glfw_CallbackBridge_nativeClipboard(env, NULL, /* CLIPBOARD_OPEN */ 2002, argBlock);
-        return 0;
-    }else if(strcmp(prog_basename, "ffmpeg") == 0) {
-        // When invoking ffmpeg, always replace the program path with the path to ffmpeg from the plugin.
-        const char* ffmpeg_path = getenv("POJAV_FFMPEG_PATH");
-        if(ffmpeg_path != NULL) {
-            prog = stringToBytes(env, ffmpeg_path);
-        }
-    }
-    return orig_ProcessImpl_forkAndExec(env, process, mode, helperpath, prog, argBlock, argc, envBlock, envc, dir, std_fds, redirectErrorStream);
-}
-
-void hookExec() {
-    jclass cls;
-    orig_ProcessImpl_forkAndExec = dlsym(RTLD_DEFAULT, "Java_java_lang_UNIXProcess_forkAndExec");
-    if (!orig_ProcessImpl_forkAndExec) {
-        orig_ProcessImpl_forkAndExec = dlsym(RTLD_DEFAULT, "Java_java_lang_ProcessImpl_forkAndExec");
-        cls = (*pojav_environ->runtimeJNIEnvPtr_JRE)->FindClass(pojav_environ->runtimeJNIEnvPtr_JRE, "java/lang/ProcessImpl");
-    } else {
-        cls = (*pojav_environ->runtimeJNIEnvPtr_JRE)->FindClass(pojav_environ->runtimeJNIEnvPtr_JRE, "java/lang/UNIXProcess");
-    }
-    JNINativeMethod methods[] = {
-        {"forkAndExec", "(I[B[B[BI[BI[B[IZ)I", (void *)&hooked_ProcessImpl_forkAndExec}
-    };
-    (*pojav_environ->runtimeJNIEnvPtr_JRE)->RegisterNatives(pojav_environ->runtimeJNIEnvPtr_JRE, cls, methods, 1);
-    printf("Registered forkAndExec\n");
-}
-
 /**
  * Basically a verbatim implementation of ndlopen(), found at
  * https://github.com/PojavLauncherTeam/lwjgl3/blob/3.3.1/modules/lwjgl/core/src/generated/c/linux/org_lwjgl_system_linux_DynamicLinkLoader.c#L11

app_pojavlauncher/src/main/jni/java_exec_hooks.c

@@ -0,0 +1,90 @@
+//
+// Created by maks on 05.01.2025.
+//
+
+#include <jni.h>
+#include <libgen.h>
+#include <string.h>
+#include <stdlib.h>
+#include <dlfcn.h>
+
+#include <environ/environ.h>
+#include <android/log.h>
+#include <utils.h>
+
+static jint (*orig_ProcessImpl_forkAndExec)(JNIEnv *env, jobject process, jint mode, jbyteArray helperpath, jbyteArray prog, jbyteArray argBlock, jint argc, jbyteArray envBlock, jint envc, jbyteArray dir, jintArray std_fds, jboolean redirectErrorStream);
+
+// Turn a C-style string into a Java byte array
+static jbyteArray stringToBytes(JNIEnv *env, const char* string) {
+    const jsize string_data_len = (jsize)(strlen(string) + 1);
+    jbyteArray result = (*env)->NewByteArray(env, (jsize)string_data_len);
+    (*env)->SetByteArrayRegion(env, result, 0, (jsize)string_data_len, (const jbyte*) string);
+    return result;
+}
+
+// Replace the env block with the one that has the desired LD_LIBRARY_PATH/PATH.
+// (Due to my laziness this ignores the current contents of the block)
+static void replaceLibPathInEnvBlock(JNIEnv *env, jbyteArray* envBlock, jint* envc, const char* directory) {
+    static bool env_block_replacement_warning = false;
+    if(*envBlock != NULL && !env_block_replacement_warning) {
+        printf("exec_hooks WARN: replaceLibPathInEnvBlock does not preserve original env. Please notify PojavLauncherTeam if you need that feature\n");
+        env_block_replacement_warning = true;
+    }
+    char envStr[1024];
+    jsize new_envl = snprintf(envStr, sizeof(envStr) / sizeof(char), "LD_LIBRARY_PATH=%s%cPATH=%s", directory, 0 ,directory) + 1;
+    jbyteArray newBlock = (*env)->NewByteArray(env, new_envl);
+    (*env)->SetByteArrayRegion(env, newBlock, 0, new_envl, (jbyte*) envStr);
+    *envBlock = newBlock;
+    *envc = 2;
+}
+
+/**
+ * Hooked version of java.lang.UNIXProcess.forkAndExec()
+ * which is used to handle the "open" command and "ffmpeg" invocations
+ */
+static jint hooked_ProcessImpl_forkAndExec(JNIEnv *env, jobject process, jint mode, jbyteArray helperpath, jbyteArray prog, jbyteArray argBlock, jint argc, jbyteArray envBlock, jint envc, jbyteArray dir, jintArray std_fds, jboolean redirectErrorStream) {
+    const char *pProg = (char *)((*env)->GetByteArrayElements(env, prog, NULL));
+    const char* pProgBaseName = basename(pProg);
+    const size_t basename_len = strlen(pProgBaseName);
+    char prog_basename[basename_len];
+    memcpy(&prog_basename, pProgBaseName, basename_len + 1);
+    (*env)->ReleaseByteArrayElements(env, prog, (jbyte *)pProg, 0);
+
+    if(strcmp(prog_basename, "xdg-open") == 0) {
+        // When invoking xdg-open, send the open URL into Android
+        Java_org_lwjgl_glfw_CallbackBridge_nativeClipboard(env, NULL, /* CLIPBOARD_OPEN */ 2002, argBlock);
+        return 0;
+    }else if(strcmp(prog_basename, "ffmpeg") == 0) {
+        // When invoking ffmpeg, always replace the program path with the path to ffmpeg from the plugin.
+        // This allows us to replace the executable name, which is needed because android doesn't allow
+        // us to put files that don't start with "lib" and end with ".so" into folders that we can execute
+        // from
+
+        // Also add LD_LIBRARY_PATH and PATH for the lib in order to override the ones from the launcher, since
+        // they may interfere with ffmpeg dependencies.
+        const char* ffmpeg_path = getenv("POJAV_FFMPEG_PATH");
+        prog = NULL;
+        if(ffmpeg_path != NULL) {
+            replaceLibPathInEnvBlock(env, &envBlock, &envc, dirname(ffmpeg_path));
+            prog = stringToBytes(env, ffmpeg_path);
+        }
+    }
+    return orig_ProcessImpl_forkAndExec(env, process, mode, helperpath, prog, argBlock, argc, envBlock, envc, dir, std_fds, redirectErrorStream);
+}
+
+// Hook the forkAndExec method in the Java runtime for custom executable overriding.
+void hookExec() {
+    jclass cls;
+    orig_ProcessImpl_forkAndExec = dlsym(RTLD_DEFAULT, "Java_java_lang_UNIXProcess_forkAndExec");
+    if (!orig_ProcessImpl_forkAndExec) {
+        orig_ProcessImpl_forkAndExec = dlsym(RTLD_DEFAULT, "Java_java_lang_ProcessImpl_forkAndExec");
+        cls = (*pojav_environ->runtimeJNIEnvPtr_JRE)->FindClass(pojav_environ->runtimeJNIEnvPtr_JRE, "java/lang/ProcessImpl");
+    } else {
+        cls = (*pojav_environ->runtimeJNIEnvPtr_JRE)->FindClass(pojav_environ->runtimeJNIEnvPtr_JRE, "java/lang/UNIXProcess");
+    }
+    JNINativeMethod methods[] = {
+            {"forkAndExec", "(I[B[B[BI[BI[B[IZ)I", (void *)&hooked_ProcessImpl_forkAndExec}
+    };
+    (*pojav_environ->runtimeJNIEnvPtr_JRE)->RegisterNatives(pojav_environ->runtimeJNIEnvPtr_JRE, cls, methods, 1);
+    printf("Registered forkAndExec\n");
+}