On Thu, Mar 21, 2024 at 5:01 PM Andrii Nakryiko <andrii@xxxxxxxxxx> wrote:
>
> Add a simple bpf_test_tp() kfunc, available to all program types, that
> is useful for various testing and benchmarking scenarios, as it allows
> to trigger most tracing BPF program types from BPF side, allowing to do
> complex testing and benchmarking scenarios.
>
> Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
> ---
> kernel/bpf/bpf_test.h | 34 ++++++++++++++++++++++++++++++++++
> kernel/bpf/helpers.c | 13 +++++++++++++
> 2 files changed, 47 insertions(+)
> create mode 100644 kernel/bpf/bpf_test.h
>
> diff --git a/kernel/bpf/bpf_test.h b/kernel/bpf/bpf_test.h
> new file mode 100644
> index 000000000000..c779927d3574
> --- /dev/null
> +++ b/kernel/bpf/bpf_test.h
> @@ -0,0 +1,34 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#undef TRACE_SYSTEM
> +#define TRACE_SYSTEM bpf_test
> +
> +#if !defined(_TRACE_BPF_TEST_H) || defined(TRACE_HEADER_MULTI_READ)
> +
> +#define _TRACE_BPF_TEST_H
> +
> +#include <linux/tracepoint.h>
> +
> +TRACE_EVENT(bpf_test,
> +
> + TP_PROTO(int nonce),
> +
> + TP_ARGS(nonce),
> +
> + TP_STRUCT__entry(
> + __field(int, nonce)
> + ),
> +
> + TP_fast_assign(
> + __entry->nonce = nonce;
> + ),
> +
> + TP_printk("nonce %d", __entry->nonce)
> +);
> +
> +#endif /* _TRACE_BPF_TEST_H */
> +
> +#undef TRACE_INCLUDE_PATH
> +#define TRACE_INCLUDE_PATH .
> +#define TRACE_INCLUDE_FILE bpf_test
> +
> +#include <trace/define_trace.h>
> diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
> index 9234174ccb21..67bf9659c447 100644
> --- a/kernel/bpf/helpers.c
> +++ b/kernel/bpf/helpers.c
> @@ -26,6 +26,10 @@
>
> #include "../../lib/kstrtox.h"
>
> +#define CREATE_TRACE_POINTS
> +#include "bpf_test.h"
> +
> +
> /* If kernel subsystem is allowing eBPF programs to call this function,
> * inside its own verifier_ops->get_func_proto() callback it should return
> * bpf_map_lookup_elem_proto, so that verifier can properly check the arguments
> @@ -2549,6 +2553,14 @@ __bpf_kfunc void bpf_throw(u64 cookie)
> WARN(1, "A call to BPF exception callback should never return\n");
> }
>
> +__bpf_kfunc int bpf_test_tp(int nonce)
> +{
> + trace_bpf_test(nonce);
> +
> + return nonce;
> +}
> +ALLOW_ERROR_INJECTION(bpf_test_tp, ERRNO);
There is a better way with register_btf_fmodret_id_set().
Error injection can be disabled in config.
Also we have two such test funcs already:
bpf_modify_return_test*
and they can be exercised by bpf_prog_test_run_tracing.
Let's make it recognize 'repeat' argument and call
bpf_modify_return_test or 3rd such func multiple times ?
Exercise of test tracepoint can be there as well.
Asking bpf prog to call a kfunc to call a tracepoint
looks like extra hop.
Existing test_run facility should be able to accommodate.
I still don't get it how modifying the kernel is better than
adding all that to a kernel module.
When you want to run bench tool on a different server
you either need to build/copy bpf_testmod or
build/copy the whole kernel.
But fine.
All the test things in net/bpf/test_run.c will stay.
