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

[Kris Van Hees]

Eugene: Can you test with my kvh/2.0-branch-dev branch from ca-tools4?  I
cannot reproduce the failures you are seeing with this patch, so I wonder
if it is a combination of patches that resolves these issues, and testing
with just this one just doesn't give you the right picture.

On Mon, Sep 15, 2025 at 11:20:28PM -0400, Kris Van Hees wrote:
> 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.