Re: [PATCH RFC bpf-next 2/3] selftests/bpf: Add uretprobe syscall test

[Andrii Nakryiko <andrii.nakryiko@xxxxxxxxx>]

On Mon, Mar 18, 2024 at 2:32 AM Jiri Olsa <jolsa@xxxxxxxxxx> wrote:
>
> Add uretprobe syscall test and compare register values before
> and after the uretprobe is hit. Also compare the register values
> seen from attached bpf program.
>
> Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
> ---
>  tools/testing/selftests/bpf/Makefile          | 13 ++-
>  .../bpf/prog_tests/arch/x86/uprobe_syscall.S  | 89 +++++++++++++++++++
>  .../selftests/bpf/prog_tests/uprobe_syscall.c | 84 +++++++++++++++++
>  .../selftests/bpf/progs/uprobe_syscall.c      | 15 ++++
>  4 files changed, 200 insertions(+), 1 deletion(-)
>  create mode 100644 tools/testing/selftests/bpf/prog_tests/arch/x86/uprobe_syscall.S
>  create mode 100644 tools/testing/selftests/bpf/prog_tests/uprobe_syscall.c
>  create mode 100644 tools/testing/selftests/bpf/progs/uprobe_syscall.c
>

Can all the above be achieved with inline assembly inside .c files? It
would probably simplify logistics overall. We can guard with
arch-specific #ifdefs, of course.

[...]

> diff --git a/tools/testing/selftests/bpf/progs/uprobe_syscall.c b/tools/testing/selftests/bpf/progs/uprobe_syscall.c
> new file mode 100644
> index 000000000000..0cc7e8761410
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/uprobe_syscall.c
> @@ -0,0 +1,15 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#include "vmlinux.h"
> +#include <bpf/bpf_helpers.h>
> +#include <string.h>
> +
> +struct pt_regs regs;
> +
> +char _license[] SEC("license") = "GPL";
> +
> +SEC("uretprobe//proc/self/exe:uprobe_syscall_arch_test")
> +int uretprobe(struct pt_regs *ctx)
> +{
> +       memcpy(&regs, ctx, sizeof(regs));

nit: please use __builtin_memcpy(), given this is BPF code. And we
don't need string.h include.

> +       return 0;
> +}
> --
> 2.44.0
>