Re: [PATCH v4 3/3] libbpf: Add a test to confirm PT_REGS_PARM4_SYSCALL

[Andrii Nakryiko <andrii.nakryiko@gmail.com>]

On Wed, Jan 19, 2022 at 5:14 AM Kenta Tada <Kenta.Tada@sony.com> wrote:
>
> Add a selftest to verify the behavior of PT_REGS_xxx.
>
> Signed-off-by: Kenta Tada <Kenta.Tada@sony.com>
> ---
>  .../bpf/prog_tests/test_bpf_syscall_macro.c   | 49 ++++++++++++++++++
>  .../selftests/bpf/progs/bpf_syscall_macro.c   | 51 +++++++++++++++++++
>  2 files changed, 100 insertions(+)
>  create mode 100644 tools/testing/selftests/bpf/prog_tests/test_bpf_syscall_macro.c
>  create mode 100644 tools/testing/selftests/bpf/progs/bpf_syscall_macro.c
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/test_bpf_syscall_macro.c b/tools/testing/selftests/bpf/prog_tests/test_bpf_syscall_macro.c
> new file mode 100644
> index 000000000000..2f725393195b
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/prog_tests/test_bpf_syscall_macro.c
> @@ -0,0 +1,49 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/* Copyright 2022 Sony Group Corporation */
> +#include <sys/prctl.h>
> +#include <test_progs.h>
> +#include "bpf_syscall_macro.skel.h"
> +
> +//void serial_bpf_syscall_macro(void)

leftover

> +void test_bpf_syscall_macro(void)
> +{
> +       struct bpf_syscall_macro *skel = NULL;
> +       int err;
> +       int exp_arg1 = 1001;
> +       unsigned long exp_arg2 = 12;
> +       unsigned long exp_arg3 = 13;
> +       unsigned long exp_arg4 = 14;
> +       unsigned long exp_arg5 = 15;
> +
> +       /* check whether it can open program */
> +       skel = bpf_syscall_macro__open();
> +       if (!ASSERT_OK_PTR(skel, "bpf_syscall_macro__open"))
> +               return;
> +
> +       skel->rodata->filter_pid = getpid();
> +
> +       /* check whether it can load program */
> +       err = bpf_syscall_macro__load(skel);
> +       if (!ASSERT_OK(err, "bpf_syscall_macro__load"))
> +               goto cleanup;
> +
> +       /* check whether it can attach kprobe */
> +       err = bpf_syscall_macro__attach(skel);
> +       if (!ASSERT_OK(err, "bpf_syscall_macro__attach"))
> +               goto cleanup;
> +
> +       /* check whether args of syscall are copied correctly */
> +       prctl(exp_arg1, exp_arg2, exp_arg3, exp_arg4, exp_arg5);
> +       ASSERT_EQ(skel->bss->arg1, exp_arg1, "syscall_arg1");
> +       ASSERT_EQ(skel->bss->arg2, exp_arg2, "syscall_arg2");
> +       ASSERT_EQ(skel->bss->arg3, exp_arg3, "syscall_arg3");
> +       /* it cannot copy arg4 when uses PT_REGS_PARM4 on x86_64 */
> +#ifdef __x86_64__
> +       ASSERT_NEQ(skel->bss->arg4_cx, exp_arg4, "syscall_arg4_from_cx");
> +#endif

else ASSERT_EQ(arg4_cx and exp_arg4) ?

> +       ASSERT_EQ(skel->bss->arg4, exp_arg4, "syscall_arg4");
> +       ASSERT_EQ(skel->bss->arg5, exp_arg5, "syscall_arg5");
> +
> +cleanup:
> +       bpf_syscall_macro__destroy(skel);
> +}
> diff --git a/tools/testing/selftests/bpf/progs/bpf_syscall_macro.c b/tools/testing/selftests/bpf/progs/bpf_syscall_macro.c
> new file mode 100644
> index 000000000000..5a7063de27c3
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/bpf_syscall_macro.c
> @@ -0,0 +1,51 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/* Copyright 2022 Sony Group Corporation */
> +#include <linux/bpf.h>
> +#include <linux/ptrace.h>
> +#include <sys/types.h>
> +#include <unistd.h>

Use #include <vmlinux.h> instead, please

> +
> +#include <bpf/bpf_helpers.h>
> +#include <bpf/bpf_tracing.h>
> +#include "bpf_misc.h"
> +
> +int arg1 = 0;
> +unsigned long arg2 = 0;
> +unsigned long arg3 = 0;
> +unsigned long arg4_cx = 0;
> +unsigned long arg4 = 0;
> +unsigned long arg5 = 0;
> +
> +const volatile pid_t filter_pid = 0;
> +
> +SEC("kprobe/" SYS_PREFIX "sys_prctl")
> +int BPF_KPROBE(handle_sys_prctl)
> +{
> +       struct pt_regs *real_regs;
> +       int orig_arg1;
> +       unsigned long orig_arg2, orig_arg3, orig_arg4_cx, orig_arg4, orig_arg5;
> +       pid_t pid = bpf_get_current_pid_tgid() >> 32;
> +
> +       if (pid != filter_pid)
> +               return 0;
> +
> +       real_regs = (struct pt_regs *)PT_REGS_PARM1(ctx);
> +       bpf_probe_read_kernel(&orig_arg1, sizeof(orig_arg1), &PT_REGS_PARM1_SYSCALL(real_regs));

orig_arg1 = PT_REGS_PARM1_CORE_SYSCALL(real_regs);

and same for others (the whole point of _CORE_SYSCALL macros!)


> +       bpf_probe_read_kernel(&orig_arg2, sizeof(orig_arg2), &PT_REGS_PARM2_SYSCALL(real_regs));
> +       bpf_probe_read_kernel(&orig_arg3, sizeof(orig_arg3), &PT_REGS_PARM3_SYSCALL(real_regs));
> +       bpf_probe_read_kernel(&orig_arg4_cx, sizeof(orig_arg4_cx), &PT_REGS_PARM4(real_regs));
> +       bpf_probe_read_kernel(&orig_arg4, sizeof(orig_arg4), &PT_REGS_PARM4_SYSCALL(real_regs));
> +       bpf_probe_read_kernel(&orig_arg5, sizeof(orig_arg5), &PT_REGS_PARM5_SYSCALL(real_regs));
> +
> +       /* copy all actual args and the wrong arg4 on x86_64 */
> +       arg1 = orig_arg1;
> +       arg2 = orig_arg2;
> +       arg3 = orig_arg3;
> +       arg4_cx = orig_arg4_cx;
> +       arg4 = orig_arg4;
> +       arg5 = orig_arg5;
> +
> +       return 0;
> +}
> +
> +char _license[] SEC("license") = "GPL";
> --
> 2.32.0
>