[DTrace-devel] [PATCH] test: Account for pid:::entry ucaller being correct

[Kris Van Hees]

On Wed, Mar 19, 2025 at 02:32:26AM -0400, eugene.loh at oracle.com wrote:
> From: Eugene Loh <eugene.loh at oracle.com>
> 
> In commit f38bdf9ea ("test: Account for pid:::entry ustack() being correct")
> we accounted for x86-specific heuristics introduced in Linux 6.11 that
> dealt with pid:::entry uprobes firing so early in the function preamble
> that the frame pointer is not yet set and the caller is not (yet)
> correctly identified.
> 
> Update a related test to account for the same effect with ucaller.
> 
> Signed-off-by: Eugene Loh <eugene.loh at oracle.com>

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

> ---
>  test/unittest/vars/tst.ucaller.r.p | 28 ++++++++++++++++++++++++++++
>  1 file changed, 28 insertions(+)
>  create mode 100755 test/unittest/vars/tst.ucaller.r.p
> 
> diff --git a/test/unittest/vars/tst.ucaller.r.p b/test/unittest/vars/tst.ucaller.r.p
> new file mode 100755
> index 000000000..8e03f110d
> --- /dev/null
> +++ b/test/unittest/vars/tst.ucaller.r.p
> @@ -0,0 +1,28 @@
> +#!/bin/sh
> +
> +# A pid entry probe places a uprobe on the first instruction of a function.
> +# Unfortunately, this is so early in the function preamble that the function
> +# frame pointer has not yet been established and the actual caller of the
> +# traced function is missed.
> +#
> +# In Linux 6.11, x86-specific heuristics are introduced to fix this problem.
> +# See commit cfa7f3d
> +# ("perf,x86: avoid missing caller address in stack traces captured in uprobe")
> +# for both a description of the problem and an explanation of the heuristics.
> +#
> +# Add post processing to these test results to allow for both cases:
> +# caller frame is missing or not missing.
> +
> +if [ $(uname -m) == "x86_64" ]; then
> +        read MAJOR MINOR <<< `uname -r | grep -Eo '^[0-9]+\.[0-9]+' | tr '.' ' '`
> +
> +        if [ $MAJOR -ge 6 ]; then
> +                if [ $MAJOR -gt 6 -o $MINOR -ge 11 ]; then
> +                        awk '{ sub("myfunc_w", "myfunc_v"); print; }'
> +                        exit 0
> +                fi
> +        fi
> +fi
> +
> +# Otherwise, just pass the output through.
> +cat
> -- 
> 2.43.5
>