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authorJari Vetoniemi <mailroxas@gmail.com>2018-02-28 22:47:59 +0200
committerJari Vetoniemi <mailroxas@gmail.com>2018-02-28 23:30:16 +0200
commitc81db335051806c06e3bda5ef6ffdb55cf51baf7 (patch)
tree7a6bd6f76ff1924f04a8e300c36b6454e63b2f1d
parentc4f74c166671e1d00ae7bc342c4570e765c79afe (diff)
android: Add libwrap.c for inspecting on android
This lets us see what native calls android apps make.
-rw-r--r--android/libwrap.c95
1 files changed, 95 insertions, 0 deletions
diff --git a/android/libwrap.c b/android/libwrap.c
new file mode 100644
index 0000000..2a029d6
--- /dev/null
+++ b/android/libwrap.c
@@ -0,0 +1,95 @@
+// Need android-ndk, compile with:
+// i686-linux-android-gcc --sysroot=$ANDROID_NDK/platforms/android-9/arch-x86 -std=c99 -shared -I../src -DANDROID_X86_LINKER -DVERBOSE_FUNCTIONS libwrap.c ../src/wrapper/wrapper.c ../src/jvm/jvm.c -llog -o libwrap.so
+// Rename libwrap.so to the library's name you want to middle-man, and the original library to liborig.so
+//
+// We use logging thread to avoid putting android specific code to verbose/wrapper.h
+// Logging thread will catch stdout && stderr.
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <dlfcn.h>
+#include <pthread.h>
+#include <assert.h>
+#include <android/log.h>
+#include "jvm/jvm.h"
+#include "wrapper/wrapper.h"
+
+static int pfd[2];
+
+static void*
+log_thread(void *arg)
+{
+ char buf[255];
+ ssize_t r;
+ while ((r = read(pfd[0], buf, sizeof(buf) - 1)) > 0) {
+ r = (r > 0 && buf[r - 1] == '\n' ? r - 1 : r);
+ buf[r] = 0;
+ __android_log_write(ANDROID_LOG_INFO, "native", buf);
+ }
+ return NULL;
+}
+
+static void
+stdlog_workaround(void)
+{
+ setvbuf(stdout, 0, _IOLBF, 0);
+ setvbuf(stderr, 0, _IONBF, 0);
+ pipe(pfd);
+ dup2(pfd[1], 1);
+ dup2(pfd[1], 2);
+ pthread_t thread;
+ pthread_create(&thread, 0, log_thread, NULL);
+ pthread_detach(thread);
+}
+
+JNIEXPORT jint JNICALL
+JNI_OnLoad(JavaVM *vm, void *reserved)
+{
+ stdlog_workaround();
+
+ __android_log_print(ANDROID_LOG_INFO, "native", "Loading liborig.so");
+ void *handle = dlopen("liborig.so", RTLD_NOW);
+ assert(handle);
+
+ jint (*JNI_OnLoad)(JavaVM*, void*) = dlsym(handle, "JNI_OnLoad");
+ assert(JNI_OnLoad);
+
+ struct jvm jvm;
+ jvm_init(&jvm);
+
+ __android_log_print(ANDROID_LOG_INFO, "native", "Call liborig's JNI_OnLoad with fakevm");
+ JNI_OnLoad(&jvm.vm, NULL);
+
+ // Sort of hack, may fail on some libraries maybe.
+ // Some libs store the vm ^ in above call, we want it to use the real vm though.
+ // We only pass fake vm in above call to know what natives it registered.
+ JNI_OnLoad(vm, NULL);
+
+ JNIEnv *env;
+ if ((*vm)->GetEnv(vm, (void**)&env, JNI_VERSION_1_6) != JNI_OK)
+ return -1;
+
+ __android_log_print(ANDROID_LOG_INFO, "native", "Wrapping natives methods");
+
+ jclass old_klass = jvm.methods[0].method.klass;
+ JNINativeMethod methods[255];
+ for (size_t i = 0, c = 0; c < 255 && i < 255; ++i, ++c) {
+ if (jvm.methods[i].method.klass != old_klass) {
+ assert(old_klass > 0);
+ jclass klass = (*env)->FindClass(env, jvm.objects[(intptr_t)old_klass - 1].klass.name.data);
+ (*env)->RegisterNatives(env, klass, methods, c);
+ old_klass = jvm.methods[i].method.klass;
+ c = 0;
+ }
+
+ if (!jvm.methods[i].function)
+ break;
+
+ methods[c].name = jvm.methods[i].method.name.data;
+ methods[c].signature = jvm.methods[i].method.signature.data;
+ methods[c].fnPtr = wrapper_create(methods[c].name, jvm.methods[i].function);
+ }
+
+ return JNI_VERSION_1_6;
+}