[DTrace-devel] [PATCH 2/2] test: add a test for libctf bug 30264

[Kris Van Hees]

On Thu, Mar 23, 2023 at 09:22:53PM -0400, Eugene Loh via DTrace-devel wrote:
> Reviewed-by: Eugene Loh <eugene.loh at oracle.com>
> though I confess there is stuff here I do not understand.  E.g.,
> 
>     $ grep rds /proc/modules
>     $ sudo build/run-dtrace -n 'BEGIN { trace(offsetof(struct rds_message,
> atomic)); exit(0) }'
>     dtrace: description 'BEGIN ' matched 1 probe
>     CPU     ID                    FUNCTION:NAME
>       2      1                           :BEGIN         296
> 
> I do not need to have rds loaded?
> 
> (Also, the offset is nonzero, but I confess I don't know what CTF I'm
> using.)

The difference is that you are using struct rds_message whereas Nick is using
the more specific struct rds`rds_message type specification.

> On 3/23/23 08:13, Nick Alcock via DTrace-devel wrote:
> > If present, this bug breaks offsetof (and anything else requiring
> > reliable offset info, like, oh, say, *any access*) to fields of
> > unnamed structs/unions at nonzero offsets within their containing
> > struct/union.
> > 
> > (We just check offsetof, because it's simpler than doing full access
> > checks.  We check only the in-kernel CTF, because the D language does
> > not support unnamed struct/union fields at all.)
> > 
> > Signed-off-by: Nick Alcock <nick.alcock at oracle.com>
> > ---
> >   .../types/tst.nested-unnamed-structs.d        | 32 +++++++++++++++++++
> >   .../types/tst.nested-unnamed-structs.x        |  7 ++++
> >   2 files changed, 39 insertions(+)
> >   create mode 100644 test/unittest/types/tst.nested-unnamed-structs.d
> >   create mode 100755 test/unittest/types/tst.nested-unnamed-structs.x
> > 
> > diff --git a/test/unittest/types/tst.nested-unnamed-structs.d b/test/unittest/types/tst.nested-unnamed-structs.d
> > new file mode 100644
> > index 0000000000000..a2b174434574d
> > --- /dev/null
> > +++ b/test/unittest/types/tst.nested-unnamed-structs.d
> > @@ -0,0 +1,32 @@
> > +/*
> > + * Oracle Linux DTrace.
> > + * Copyright (c) 2023, Oracle and/or its affiliates. All rights reserved.
> > + * Licensed under the Universal Permissive License v 1.0 as shown at
> > + * http://oss.oracle.com/licenses/upl.
> > + */
> > +
> > +/*
> > + * ASSERTION:
> > + *	Check for the absence of a libctf bug breaking offsets of
> > + *	members of nested unnamed structs in the kernel.
> > + *	See https://sourceware.org/bugzilla/show_bug.cgi?id=30264
> > + *
> > + */
> > +
> > +#pragma D option quiet
> > +
> > +BEGIN {
> > +	printf("offset is %i\n", offsetof(struct rds`rds_message, atomic));
> > +}
> > +
> > +BEGIN
> > +/ offsetof(struct rds`rds_message, atomic) == 0 /
> > +{
> > +	exit(1);
> > +}
> > +
> > +BEGIN
> > +/ offsetof(struct rds`rds_message, atomic) != 0 /
> > +{
> > +	exit(0);
> > +}
> > diff --git a/test/unittest/types/tst.nested-unnamed-structs.x b/test/unittest/types/tst.nested-unnamed-structs.x
> > new file mode 100755
> > index 0000000000000..47e579ed00f60
> > --- /dev/null
> > +++ b/test/unittest/types/tst.nested-unnamed-structs.x
> > @@ -0,0 +1,7 @@
> > +#!/bin/sh
> > +
> > +if ! $(grep -q '^rds ' /proc/modules); then
> > +    exit 1
> > +fi
> > +
> > +exit 0
> 
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