On Mon, Sep 9, 2024 at 1:17 PM Mathieu Desnoyers
<mathieu.desnoyers@efficios.com> wrote:
>
> In preparation for allowing system call enter/exit instrumentation to
> handle page faults, make sure that bpf can handle this change by
> explicitly disabling preemption within the bpf system call tracepoint
> probes to respect the current expectations within bpf tracing code.
>
> This change does not yet allow bpf to take page faults per se within its
> probe, but allows its existing probes to adapt to the upcoming change.
>
> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
> Cc: Michael Jeanson <mjeanson@efficios.com>
> Cc: Steven Rostedt <rostedt@goodmis.org>
> Cc: Masami Hiramatsu <mhiramat@kernel.org>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Alexei Starovoitov <ast@kernel.org>
> Cc: Yonghong Song <yhs@fb.com>
> Cc: Paul E. McKenney <paulmck@kernel.org>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
> Cc: Namhyung Kim <namhyung@kernel.org>
> Cc: Andrii Nakryiko <andrii.nakryiko@gmail.com>
> Cc: bpf@vger.kernel.org
> Cc: Joel Fernandes <joel@joelfernandes.org>
> ---
> include/trace/bpf_probe.h | 11 ++++++++++-
> 1 file changed, 10 insertions(+), 1 deletion(-)
>
LGTM.
Acked-by: Andrii Nakryiko <andrii@kernel.org>
> diff --git a/include/trace/bpf_probe.h b/include/trace/bpf_probe.h
> index c85bbce5aaa5..211b98d45fc6 100644
> --- a/include/trace/bpf_probe.h
> +++ b/include/trace/bpf_probe.h
> @@ -53,8 +53,17 @@ __bpf_trace_##call(void *__data, proto) \
> #define DECLARE_EVENT_CLASS(call, proto, args, tstruct, assign, print) \
> __BPF_DECLARE_TRACE(call, PARAMS(proto), PARAMS(args))
>
> +#define __BPF_DECLARE_TRACE_SYSCALL(call, proto, args) \
> +static notrace void \
> +__bpf_trace_##call(void *__data, proto) \
> +{ \
> + guard(preempt_notrace)(); \
> + CONCATENATE(bpf_trace_run, COUNT_ARGS(args))(__data, CAST_TO_U64(args)); \
> +}
> +
> #undef DECLARE_EVENT_SYSCALL_CLASS
> -#define DECLARE_EVENT_SYSCALL_CLASS DECLARE_EVENT_CLASS
> +#define DECLARE_EVENT_SYSCALL_CLASS(call, proto, args, tstruct, assign, print) \
> + __BPF_DECLARE_TRACE_SYSCALL(call, PARAMS(proto), PARAMS(args))
>
> /*
> * This part is compiled out, it is only here as a build time check
> --
> 2.39.2
>