RFR (M): 7198429: need checked categorization of caller-sensitive methods in the JDK

Christian Thalinger christian.thalinger at oracle.com
Wed Mar 20 01:02:53 UTC 2013

On Mar 19, 2013, at 5:21 PM, John Rose <john.r.rose at oracle.com> wrote:

> On Mar 14, 2013, at 8:31 PM, Christian Thalinger <christian.thalinger at oracle.com> wrote:
>> [This is the HotSpot part of JEP 176]
>> http://cr.openjdk.java.net/~twisti/7198429
>> 7198429: need checked categorization of caller-sensitive methods in the JDK
>> Reviewed-by:
> Over all, great work on a tricky problem.  I'd add a few asserts and tweak a couple of lines; see below.  Reviewed as is or with suggested changes. — John
> --- Method::is_ignored_by_security_stack_walk
> I would like to see reflect_invoke_cache go away some day.  Would it be possible to strengthen the asserts to prove that it is an expensive alias for an intrinsic_id check?  (I realize this is a question mainly for folks working on JVMTI.)

That's what I tried to do:  if the intrinsic_id == _invoke it also must be the same method in reflect_invoke_cache.  More than that would mean to enhance ActiveMethodOopsCache because you can't ask for methods in the cache.

> --- JVM_GetCallerClass
> Suggest an assert for vfst.method() == NULL.  Should not happen, and previous code would apparently have crashed already, but...
> (The corner case I'm thinking of is a compiled frame with nmethod::method returning null after nmethod::make_unloaded.  Should not happen.)

Sure, I can add that assert but there is other code in jvm.cpp that relies on the fact that vfst.method() is non-null.  We should add asserts in all that places but that's for another RFE.

> --- JVM_GetClassContext
> What do these lines do:
> +   // Collect method holders
> +   GrowableArray<KlassHandle>* klass_array = new GrowableArray<KlassHandle>();
> It looks like a paste-o from another source base.

Left over.  I filed an RFE for that improvement:

JDK-8010124: JVM_GetClassContext: use GrowableArray instead of KlassLink

> --- LibraryCallKit::inline_native_Reflection_getCallerClass
> I believe this assertion, but I would prefer to see it checked more forcibly:
> +   // NOTE: Start the loop at depth 1 because the current JVM state does
> +   // not include the Reflection.getCallerClass() frame.
> Not sure there is a good way to do this.  But, perhaps put the comment here:
>   case 0:
>     // ...comment...
>     ShouldNotReachHere();

How about:

    case 0:
      fatal("current JVM state does not include the Reflection.getCallerClass() frame");

> Also, if something goes wrong with caller sensitivity, we just get a "return false".  Perhaps do a "caller_jvm=NULL;break" to branch to the pretty failure message?  That makes it slightly easier to see what happened.

It seems easier to add printing code to the case statement:

    case 1:
      // Frame 0 and 1 must be caller sensitive (see JVM_GetCallerClass).
      if (!m->caller_sensitive()) {
#ifndef PRODUCT
        if ((PrintIntrinsics || PrintInlining || PrintOptoInlining) && Verbose) {
          tty->print_cr("  Bailing out: CallerSensitive annotation expected at frame %d", n);
        return false;  // bail-out; let JVM_GetCallerClass do the work

> The LogCompilation switch should leave a "paper trail".  Actually, I see that LogCompilation doesn't mention failed intrinsic inlines.  Rats.  At least PrintInlining or PrintIntrinsics (diagnostic flags) will give us some leverage if we need to debug.
> --- JVM_RegisterUnsafeMethods
> That's an improvement.  Thanks.
> (A nagging worry:  How big are those static tables getting?)

We could remove some very old ones like 1.4.0 and 1.4.1.  This time, next time?

> --- vframeStreamCommon::security_get_caller_frame
> This now does something odd if depth < 0.  Suggest an assert.

The behavior with depth < 0 in the current code is even worse.  An assert is a good idea.  As discussed I want to remove that method in the future because its uses are dubious.

-- Chris

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