[DTrace-devel] [PATCH 2/2] test: Account for pid:::entry ustack() being correct

[Kris Van Hees]

On Sat, Feb 08, 2025 at 06:21:06PM -0500, eugene.loh at oracle.com wrote:
> From: Eugene Loh <eugene.loh at oracle.com>
> 
> The pid:::entry uprobe fires so early in the function preamble
> that the frame pointer is not yet set and the caller is not (yet)
> correctly identified.  In Linux 6.11, x86-specific heuristics
> address this problem.
> 
> Post process results from this test to accommodate both cases --
> missing caller and not missing caller.
> 
> Orabug: 37459289
> Signed-off-by: Eugene Loh <eugene.loh at oracle.com>

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

> ---
>  test/unittest/ustack/tst.ustack25_pid.r   |  1 +
>  test/unittest/ustack/tst.ustack25_pid.r.p | 37 +++++++++++++++++++++++
>  2 files changed, 38 insertions(+)
>  create mode 100755 test/unittest/ustack/tst.ustack25_pid.r.p
> 
> diff --git a/test/unittest/ustack/tst.ustack25_pid.r b/test/unittest/ustack/tst.ustack25_pid.r
> index 89b35c028..e7732fb81 100644
> --- a/test/unittest/ustack/tst.ustack25_pid.r
> +++ b/test/unittest/ustack/tst.ustack25_pid.r
> @@ -1,5 +1,6 @@
>  
>                ustack-tst-basic`myfunc_z
> +              ustack-tst-basic`myfunc_y+{ptr}
>                ustack-tst-basic`myfunc_x+{ptr}
>                ustack-tst-basic`myfunc_w+{ptr}
>                ustack-tst-basic`myfunc_v+{ptr}
> diff --git a/test/unittest/ustack/tst.ustack25_pid.r.p b/test/unittest/ustack/tst.ustack25_pid.r.p
> new file mode 100755
> index 000000000..6486f7ec6
> --- /dev/null
> +++ b/test/unittest/ustack/tst.ustack25_pid.r.p
> @@ -0,0 +1,37 @@
> +#!/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.
> +
> +missing_caller=1
> +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
> +                        missing_caller=0
> +                fi
> +        fi
> +fi
> +
> +if [ $missing_caller -eq 1 ]; then
> +        # Add the missing caller function after the current function.
> +        awk '{ print }
> +             /myfunc_z/ { print "              ustack-tst-basic`myfunc_y+{ptr}" }'
> +else
> +        # The .r results file has an extra frame at the end in case
> +        # the caller frame is missing and the 25-frame limit goes
> +        # "too far."  If the caller is not missing, fake that extra frame.
> +        awk '{ print }
> +             /myfunc_b/ { print "              ustack-tst-basic`myfunc_a+{ptr}" }'
> +fi
> -- 
> 2.43.5
>