[DTrace-devel] [PATCH v3] trace: print alloca pointers as actual pointer values

[Kris Van Hees]

On Mon, Sep 15, 2025 at 09:44:14PM -0400, Kris Van Hees wrote:
> On Mon, Sep 15, 2025 at 04:41:43PM -0400, Eugene Loh wrote:
> > Largely similar comments to previous versions of this patch:
> > 
> > On 9/15/25 13:36, Kris Van Hees via DTrace-devel wrote:
> > > Because alloca pointers are stored internally as ofssets into the
> > 
> > The same as for v1 and v2:  s/ofssets/offsets/.
> 
> Ok, yes, sorry - been spending time on functionality over typos.
> 
> > > scratchmem area, they were printed as small integers.  They are
> > > now printed as actual pointer values into kernel space.
> > 
> > And, again, the patch performs poorly against testing.
> > 
> > The new test gives me:
> >     -OK 1 OK 333 OK 55555
> >     +OK 1059965305 OK 1059965637 OK 1060020859
> > which is to say that the dereferenced values are wrong.  (They are all the
> > correct values plus some offset.)
> > 
> > And with this patch, these pre-existing tests fail:
> >     test/unittest/builtinvar/tst.tid_pid.sh: FAIL: erroneous exitcode (1).
> >     test/unittest/funcs/alloca/tst.alloca-bcopy-top.d: FAIL: expected
> > results differ.
> >     test/unittest/funcs/bcopy/tst.bcopy_arg_order.d: FAIL: expected results
> > differ.
> >     test/unittest/funcs/copyinto/tst.copyinto_arg_order.d: FAIL: expected
> > results differ.
> 
> Hm, this is getting frustrating.  Tracking down why I was not seeing those
> failures on my end.

Where are you seeing these failures?  Do you have the pointer subtraction patch
applied before this one?

> > btw...
> > 
> > > diff --git a/test/unittest/actions/trace/tst.alloca.r.p b/test/unittest/actions/trace/tst.alloca.r.p
> > > new file mode 100755
> > > @@ -0,0 +1,11 @@
> > > +#!/usr/bin/gawk -f
> > > +
> > > +{
> > > +	$1 = $1 > 0x7fffffff ? "OK" : "BAD";
> > > +	$3 = $3 > 0x7fffffff ? "OK" : "BAD";
> > > +	$5 = $5 > 0x7fffffff ? "OK" : "BAD";
> > > +}
> > > +
> > > +{
> > > +	print;
> > > +}
> > 
> > Why are these split over two awk clauses?  Can't they co-exist in the same
> > clause?
> 
> Yes they can.  But they don't have to.