On Thu, Sep 22, 2022 at 2:04 PM Jiri Olsa <jolsa@xxxxxxxxxx> wrote:
>
> Martynas reported bpf_get_func_ip returning +4 address when
> CONFIG_X86_KERNEL_IBT option is enabled.
>
> When CONFIG_X86_KERNEL_IBT is enabled we'll have endbr instruction
> at the function entry, which screws return value of bpf_get_func_ip()
> helper that should return the function address.
>
> There's short term workaround for kprobe_multi bpf program made by
> Alexei [1], but we need this fixup also for bpf_get_attach_cookie,
> that returns cookie based on the entry_ip value.
>
> Moving the fixup in the fprobe handler, so both bpf_get_func_ip
> and bpf_get_attach_cookie get expected function address when
> CONFIG_X86_KERNEL_IBT option is enabled.
>
> Also renaming kprobe_multi_link_handler entry_ip argument to fentry_ip
> so it's clearer this is an ftrace __fentry__ ip.
>
> [1] commit 7f0059b58f02 ("selftests/bpf: Fix kprobe_multi test.")
>
> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Reported-by: Martynas Pumputis <m@xxxxxxxxx>
> Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
> ---
lgtm
Acked-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
> kernel/trace/bpf_trace.c | 20 +++++++++++++++++--
> .../selftests/bpf/progs/kprobe_multi.c | 4 +---
> 2 files changed, 19 insertions(+), 5 deletions(-)
>
[...]
