Tell bionic when we overwrite argv[0].

Otherwise bionic might still have a pointer into the old content.

Bug: https://issuetracker.google.com/152893281
Test: treehugger
Change-Id: I25e31c5da33e529c750ef6f2e3f36ca62cf4d231

core/jni/AndroidRuntime.cpp

@@ -342,6 +342,8 @@ AndroidRuntime::~AndroidRuntime()
 }
 
 void AndroidRuntime::setArgv0(const char* argv0, bool setProcName) {
+    // Set the kernel's task name, for as much of the name as we can fit.
+    // The kernel's TASK_COMM_LEN minus one for the terminating NUL == 15.
     if (setProcName) {
         int len = strlen(argv0);
         if (len < 15) {
@@ -350,8 +352,14 @@ void AndroidRuntime::setArgv0(const char* argv0, bool setProcName) {
             pthread_setname_np(pthread_self(), argv0 + len - 15);
         }
     }
+
+    // Directly change the memory pointed to by argv[0].
     memset(mArgBlockStart, 0, mArgBlockLength);
     strlcpy(mArgBlockStart, argv0, mArgBlockLength);
+
+    // Let bionic know that we just did that, because __progname points
+    // into argv[0] (https://issuetracker.google.com/152893281).
+    setprogname(mArgBlockStart);
 }
 
 status_t AndroidRuntime::callMain(const String8& className, jclass clazz,