[DTrace-devel] [PATCH] test: fix the bitfield-offset fix

[Kris Van Hees]

On Wed, Mar 06, 2024 at 03:52:07PM +0000, Nick Alcock via DTrace-devel wrote:
> Many systems on which CTF is too old for tst.bitfield-offset.d to pass will
> also be too old for objdump --ctf=.ctf to work: in that case, we have no way
> to tell how new the CTF is (and thus whether this bug is expected to be
> fixed), so we have to skip it.
> 
> Even figuring out if this is the case is hard.  We don't want to try to
> objdump the entire kernel CTFA again in case it works (it's huge and takes
> ages to dump: we're not exiting early on a version check here, after all).
> But objdump returns with an exitcode of 1 both if an unrecognized option is
> found *and* if the target contains no CTF at all -- so we must literally
> grep for 'Unrecognized option' (under LANG=C) to be sure of spotting an
> instance we must skip.  (We also check for a zero exit code, because if our
> random test executable *does* contain CTF and dumping it works there's no
> need to grep the stderr for anything at all.)
> 
> Signed-off-by: Nick Alcock <nick.alcock at oracle.com>

Reviewed-by: Kris Van Hees <kris.van.hees at oracle.com>

> ---
>  test/unittest/bitfields/tst.bitfield-offset.x | 12 +++++++++++-
>  1 file changed, 11 insertions(+), 1 deletion(-)
> 
> diff --git a/test/unittest/bitfields/tst.bitfield-offset.x b/test/unittest/bitfields/tst.bitfield-offset.x
> index 316c54a0d08f9..e49713af37830 100755
> --- a/test/unittest/bitfields/tst.bitfield-offset.x
> +++ b/test/unittest/bitfields/tst.bitfield-offset.x
> @@ -7,11 +7,21 @@
>  # objdump, because the CTF version number differs.
>  #
>  # Alas objdump cannot read vmlinux.ctfa of this vintage on its
> -# own: we must embed it into an ELF file ourselves.
> +# own: we must embed it into an ELF file ourselves.  Worse yet,
> +# objdump might be too old to read CTF at all: in this case, just
> +# skip the test, since we can't possibly tell what it was
> +# generated by.
> +
> +if ! objdump --ctf=.ctf --ctf-parent=shared_ctf /bin/true > /dev/null 2>&1 && \
> +    LANG=C objdump --ctf=.ctf --ctf-parent=shared_ctf /bin/true 2>&1 | \
> +    grep 'unrecognized option' > /dev/null 2>&1; then
> +    exit 2
> +fi
>  
>  ctfa=$tmpdir/vmlinux.ctfa
>  trap "rm -f $ctfa" EXIT ERR
>  
>  objcopy --add-section=.ctf=/lib/modules/$(uname -r)/kernel/vmlinux.ctfa /bin/true $ctfa
> +
>  objdump --ctf=.ctf --ctf-parent=shared_ctf $ctfa |\
>      awk '/Version: 3/ { exit 1; } /Version: / { exit 0; }'
> -- 
> 2.43.0.272.gce700b77fd
> 
> 
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