Re: [PATCH v3 bpf 0/3] Fix ftrace for livepatch + BPF fexit programs

[Jiri Olsa <olsajiri@gmail.com>]

On Sun, Oct 26, 2025 at 01:54:42PM -0700, Song Liu wrote:
> livepatch and BPF trampoline are two special users of ftrace. livepatch
> uses ftrace with IPMODIFY flag and BPF trampoline uses ftrace direct
> functions. When livepatch and BPF trampoline with fexit programs attach to
> the same kernel function, BPF trampoline needs to call into the patched
> version of the kernel function.
> 
> 1/3 and 2/3 of this patchset fix two issues with livepatch + fexit cases,
> one in the register_ftrace_direct path, the other in the
> modify_ftrace_direct path.
> 
> 3/3 adds selftests for both cases.
> 
> ---
> 
> Changes v2 => v3:
> 1. Incorporate feedback by AI, which also fixes build error reported by
>    Steven and kernel test robot.

Reviewed-by: Jiri Olsa <jolsa@kernel.org>

thanks,
jirka


> 
> v2: https://lore.kernel.org/bpf/20251024182901.3247573-1-song@kernel.org/
> 
> Changes v1 => v2:
> 1. Target bpf tree. (Alexei)
> 2. Bring back the FTRACE_WARN_ON in __ftrace_hash_update_ipmodify
>    for valid code paths. (Steven)
> 3. Update selftests with cleaner way to find livepatch-sample.ko.
>    (offlline discussion with Ihor)
> 
> v1: https://lore.kernel.org/bpf/20251024071257.3956031-1-song@kernel.org/
> 
> Song Liu (3):
>   ftrace: Fix BPF fexit with livepatch
>   ftrace: bpf: Fix IPMODIFY + DIRECT in modify_ftrace_direct()
>   selftests/bpf: Add tests for livepatch + bpf trampoline
> 
>  kernel/bpf/trampoline.c                       |   5 -
>  kernel/trace/ftrace.c                         |  46 ++++++--
>  tools/testing/selftests/bpf/config            |   3 +
>  .../bpf/prog_tests/livepatch_trampoline.c     | 107 ++++++++++++++++++
>  .../bpf/progs/livepatch_trampoline.c          |  30 +++++
>  5 files changed, 177 insertions(+), 14 deletions(-)
>  create mode 100644 tools/testing/selftests/bpf/prog_tests/livepatch_trampoline.c
>  create mode 100644 tools/testing/selftests/bpf/progs/livepatch_trampoline.c
> 
> --
> 2.47.3