Re: [PATCH bpf-next v5 12/17] selftests/bpf: add tests for bpf_hid_hw_request

[Kumar Kartikeya Dwivedi <memxor@gmail.com>]

On Thu, May 19, 2022 at 05:42:40PM IST, Benjamin Tissoires wrote:
> On Thu, May 19, 2022 at 12:20 AM Kumar Kartikeya Dwivedi
> <memxor@gmail.com> wrote:
> >
> > On Thu, May 19, 2022 at 02:29:19AM IST, Benjamin Tissoires wrote:
> > > Add tests for the newly implemented function.
> > > We test here only the GET_REPORT part because the other calls are pure
> > > HID protocol and won't infer the result of the test of the bpf hook.
> > >
> > > Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
> > >
> > > ---
> > >
> > > changes in v5:
> > > - use the new hid_bpf_allocate_context() API
> > > - remove the need for ctx_in for syscall TEST_RUN
> > >
> > > changes in v3:
> > > - use the new hid_get_data API
> > > - directly use HID_FEATURE_REPORT and HID_REQ_GET_REPORT from uapi
> > >
> > > changes in v2:
> > > - split the series by bpf/libbpf/hid/selftests and samples
> > > ---
> > >  tools/testing/selftests/bpf/prog_tests/hid.c | 114 ++++++++++++++++---
> > >  tools/testing/selftests/bpf/progs/hid.c      |  59 ++++++++++
> > >  2 files changed, 155 insertions(+), 18 deletions(-)
> > >
> > > diff --git a/tools/testing/selftests/bpf/prog_tests/hid.c b/tools/testing/selftests/bpf/prog_tests/hid.c
> > > index 47bc0a30c275..54c0a0fcd54d 100644
> > > --- a/tools/testing/selftests/bpf/prog_tests/hid.c
> > > +++ b/tools/testing/selftests/bpf/prog_tests/hid.c
> > > @@ -77,12 +77,23 @@ static unsigned char rdesc[] = {
> > >       0xc0,                   /* END_COLLECTION */
> > >  };
> > >
> > > +static u8 feature_data[] = { 1, 2 };
> > > +
> > >  struct attach_prog_args {
> > >       int prog_fd;
> > >       unsigned int hid;
> > >       int retval;
> > >  };
> > >
> > > +struct hid_hw_request_syscall_args {
> > > +     __u8 data[10];
> > > +     unsigned int hid;
> > > +     int retval;
> > > +     size_t size;
> > > +     enum hid_report_type type;
> > > +     __u8 request_type;
> > > +};
> > > +
> > >  static pthread_mutex_t uhid_started_mtx = PTHREAD_MUTEX_INITIALIZER;
> > >  static pthread_cond_t uhid_started = PTHREAD_COND_INITIALIZER;
> > >
> > > @@ -142,7 +153,7 @@ static void destroy(int fd)
> > >
> > >  static int uhid_event(int fd)
> > >  {
> > > -     struct uhid_event ev;
> > > +     struct uhid_event ev, answer;
> > >       ssize_t ret;
> > >
> > >       memset(&ev, 0, sizeof(ev));
> > > @@ -183,6 +194,15 @@ static int uhid_event(int fd)
> > >               break;
> > >       case UHID_GET_REPORT:
> > >               fprintf(stderr, "UHID_GET_REPORT from uhid-dev\n");
> > > +
> > > +             answer.type = UHID_GET_REPORT_REPLY;
> > > +             answer.u.get_report_reply.id = ev.u.get_report.id;
> > > +             answer.u.get_report_reply.err = ev.u.get_report.rnum == 1 ? 0 : -EIO;
> > > +             answer.u.get_report_reply.size = sizeof(feature_data);
> > > +             memcpy(answer.u.get_report_reply.data, feature_data, sizeof(feature_data));
> > > +
> > > +             uhid_write(fd, &answer);
> > > +
> > >               break;
> > >       case UHID_SET_REPORT:
> > >               fprintf(stderr, "UHID_SET_REPORT from uhid-dev\n");
> > > @@ -391,6 +411,7 @@ static int open_hidraw(int dev_id)
> > >  struct test_params {
> > >       struct hid *skel;
> > >       int hidraw_fd;
> > > +     int hid_id;
> > >  };
> > >
> > >  static int prep_test(int dev_id, const char *prog_name, struct test_params *test_data)
> > > @@ -419,27 +440,33 @@ static int prep_test(int dev_id, const char *prog_name, struct test_params *test
> > >       if (!ASSERT_OK_PTR(hid_skel, "hid_skel_open"))
> > >               goto cleanup;
> > >
> > > -     prog = bpf_object__find_program_by_name(*hid_skel->skeleton->obj, prog_name);
> > > -     if (!ASSERT_OK_PTR(prog, "find_prog_by_name"))
> > > -             goto cleanup;
> > > +     if (prog_name) {
> > > +             prog = bpf_object__find_program_by_name(*hid_skel->skeleton->obj, prog_name);
> > > +             if (!ASSERT_OK_PTR(prog, "find_prog_by_name"))
> > > +                     goto cleanup;
> > >
> > > -     bpf_program__set_autoload(prog, true);
> > > +             bpf_program__set_autoload(prog, true);
> > >
> > > -     err = hid__load(hid_skel);
> > > -     if (!ASSERT_OK(err, "hid_skel_load"))
> > > -             goto cleanup;
> > > +             err = hid__load(hid_skel);
> > > +             if (!ASSERT_OK(err, "hid_skel_load"))
> > > +                     goto cleanup;
> > >
> > > -     attach_fd = bpf_program__fd(hid_skel->progs.attach_prog);
> > > -     if (!ASSERT_GE(attach_fd, 0, "locate attach_prog")) {
> > > -             err = attach_fd;
> > > -             goto cleanup;
> > > -     }
> > > +             attach_fd = bpf_program__fd(hid_skel->progs.attach_prog);
> > > +             if (!ASSERT_GE(attach_fd, 0, "locate attach_prog")) {
> > > +                     err = attach_fd;
> > > +                     goto cleanup;
> > > +             }
> > >
> > > -     args.prog_fd = bpf_program__fd(prog);
> > > -     err = bpf_prog_test_run_opts(attach_fd, &tattr);
> > > -     snprintf(buf, sizeof(buf), "attach_hid(%s)", prog_name);
> > > -     if (!ASSERT_EQ(args.retval, 0, buf))
> > > -             goto cleanup;
> > > +             args.prog_fd = bpf_program__fd(prog);
> > > +             err = bpf_prog_test_run_opts(attach_fd, &tattr);
> > > +             snprintf(buf, sizeof(buf), "attach_hid(%s)", prog_name);
> > > +             if (!ASSERT_EQ(args.retval, 0, buf))
> > > +                     goto cleanup;
> > > +     } else {
> > > +             err = hid__load(hid_skel);
> > > +             if (!ASSERT_OK(err, "hid_skel_load"))
> > > +                     goto cleanup;
> > > +     }
> > >
> > >       hidraw_fd = open_hidraw(dev_id);
> > >       if (!ASSERT_GE(hidraw_fd, 0, "open_hidraw"))
> > > @@ -447,6 +474,7 @@ static int prep_test(int dev_id, const char *prog_name, struct test_params *test
> > >
> > >       test_data->skel = hid_skel;
> > >       test_data->hidraw_fd = hidraw_fd;
> > > +     test_data->hid_id = hid_id;
> > >
> > >       return 0;
> > >
> > > @@ -693,6 +721,54 @@ static int test_hid_change_report(int uhid_fd, int dev_id)
> > >       return ret;
> > >  }
> > >
> > > +/*
> > > + * Attach hid_user_raw_request to the given uhid device,
> > > + * call the bpf program from userspace
> > > + * check that the program is called and does the expected.
> > > + */
> > > +static int test_hid_user_raw_request_call(int uhid_fd, int dev_id)
> > > +{
> > > +     struct test_params params;
> > > +     int err, prog_fd;
> > > +     int ret = -1;
> > > +     struct hid_hw_request_syscall_args args = {
> > > +             .retval = -1,
> > > +             .type = HID_FEATURE_REPORT,
> > > +             .request_type = HID_REQ_GET_REPORT,
> > > +             .size = 10,
> > > +     };
> > > +     DECLARE_LIBBPF_OPTS(bpf_test_run_opts, tattrs,
> > > +                         .ctx_in = &args,
> > > +                         .ctx_size_in = sizeof(args),
> > > +     );
> > > +
> > > +     err = prep_test(dev_id, NULL, &params);
> > > +     if (!ASSERT_EQ(err, 0, "prep_test()"))
> > > +             goto cleanup;
> > > +
> > > +     args.hid = params.hid_id;
> > > +     args.data[0] = 1; /* report ID */
> > > +
> > > +     prog_fd = bpf_program__fd(params.skel->progs.hid_user_raw_request);
> > > +
> > > +     err = bpf_prog_test_run_opts(prog_fd, &tattrs);
> > > +     if (!ASSERT_EQ(err, 0, "bpf_prog_test_run_opts"))
> > > +             goto cleanup;
> > > +
> > > +     if (!ASSERT_EQ(args.retval, 2, "bpf_prog_test_run_opts_retval"))
> > > +             goto cleanup;
> > > +
> > > +     if (!ASSERT_EQ(args.data[1], 2, "hid_user_raw_request_check_in"))
> > > +             goto cleanup;
> > > +
> > > +     ret = 0;
> > > +
> > > +cleanup:
> > > +     cleanup_test(&params);
> > > +
> > > +     return ret;
> > > +}
> > > +
> > >  void serial_test_hid_bpf(void)
> > >  {
> > >       int err, uhid_fd;
> > > @@ -720,6 +796,8 @@ void serial_test_hid_bpf(void)
> > >       ASSERT_OK(err, "hid_attach_detach");
> > >       err = test_hid_change_report(uhid_fd, dev_id);
> > >       ASSERT_OK(err, "hid_change_report");
> > > +     err = test_hid_user_raw_request_call(uhid_fd, dev_id);
> > > +     ASSERT_OK(err, "hid_change_report");
> > >
> > >       destroy(uhid_fd);
> > >
> > > diff --git a/tools/testing/selftests/bpf/progs/hid.c b/tools/testing/selftests/bpf/progs/hid.c
> > > index ee7529c47ad8..e3444d444303 100644
> > > --- a/tools/testing/selftests/bpf/progs/hid.c
> > > +++ b/tools/testing/selftests/bpf/progs/hid.c
> > > @@ -10,6 +10,13 @@ extern __u8 *hid_bpf_get_data(struct hid_bpf_ctx *ctx,
> > >                             unsigned int offset,
> > >                             const size_t __sz) __ksym;
> > >  extern int hid_bpf_attach_prog(unsigned int hid_id, int prog_fd, u32 flags) __ksym;
> > > +extern struct hid_bpf_ctx *hid_bpf_allocate_context(unsigned int hid_id) __ksym;
> > > +extern void hid_bpf_release_context(struct hid_bpf_ctx *ctx) __ksym;
> > > +extern int hid_bpf_hw_request(struct hid_bpf_ctx *ctx,
> > > +                           __u8 *data,
> > > +                           size_t len,
> > > +                           enum hid_report_type type,
> > > +                           int reqtype) __ksym;
> > >
> > >  struct attach_prog_args {
> > >       int prog_fd;
> > > @@ -56,3 +63,55 @@ int attach_prog(struct attach_prog_args *ctx)
> > >                                         0);
> > >       return 0;
> > >  }
> > > +
> > > +struct hid_hw_request_syscall_args {
> > > +     /* data needs to come at offset 0 so we can do a memcpy into it */
> > > +     __u8 data[10];
> > > +     unsigned int hid;
> > > +     int retval;
> > > +     size_t size;
> > > +     enum hid_report_type type;
> > > +     __u8 request_type;
> > > +};
> > > +
> > > +SEC("syscall")
> > > +int hid_user_raw_request(struct hid_hw_request_syscall_args *args)
> > > +{
> > > +     struct hid_bpf_ctx *ctx;
> > > +     int i, ret = 0;
> > > +     __u8 *data;
> > > +
> > > +     ctx = hid_bpf_allocate_context(args->hid);
> > > +     if (!ctx)
> > > +             return 0; /* EPERM check */
> > > +
> > > +     /* We can not use the context data memory directly in the hid_bpf call,
> > > +      * so we rely on the PTR_TO_MEM allocated in the hid_bpf_context
> > > +      */
> > > +     data = hid_bpf_get_data(ctx, 0 /* offset */, 10 /* size */);
> > > +     if (!data)
> > > +             goto out; /* EPERM check */
> > > +
> >
> > If I'm reading this right, you need more than just returning PTR_TO_MEM. Since
> > this points into allocated ctx, nothing prevents user from accessing data after
> > we do hid_bpf_release_context.
>
> oops. I missed that point.
>
> TBH, ideally I wanted to directly pass args->data into
> hid_bpf_hw_request(). But because args is seen as the context of the
> program, I can not pass it to the kfunc arguments.
> I would happily prevent getting a data pointer for a manually
> allocated context if I could solve that issue. This would save me from
> calling twice  __builtin_memcpy.

Oh, is that why you need to do this? So if you were able to pass args->data, you
wouldn't need this hid_bpf_get_data? kfunc does support taking PTR_TO_CTX (i.e.
args in your case), I am not sure why you're not passing it in directly then.
Did you encounter any errors when trying to do so? The only requirement is that
args offset must be 0 (i.e. passed as is without increment).

>
> That doesn't change the fact that you are correct and the PTR_TO_MEM
> in kfunc code should be fixed.
> But right now, I am not sure what you mean below and I'll need a
> little bit more time to process it.
>
> Cheers,
> Benjamin
>
> >
> > The ref_obj_id of ctx needs to be transferred to R0.ref_obj_id, and R0.id needs
> > to be assigned another id distinct from the ref_obj_id.
> >
> > My idea would be to give this type of function a new set, and handle this case
> > of transferring ref_obj_id into R0. See is_ptr_cast_function in verifier.c.
> > Shouldn't be too much code. You could even use the bpf_kfunc_arg_meta to store
> > the ref_obj_id (and ensure only one referenced register exists among the 5
> > arguments).
> >
> > > +     __builtin_memcpy(data, args->data, sizeof(args->data));
> > > +
> > > +     if (args->size <= sizeof(args->data)) {
> > > +             ret = hid_bpf_hw_request(ctx,
> > > +                                      data,
> > > +                                      args->size,
> > > +                                      args->type,
> > > +                                      args->request_type);
> > > +             args->retval = ret;
> > > +             if (ret < 0)
> > > +                     goto out;
> > > +     } else {
> > > +             ret = -7; /* -E2BIG */
> > > +             goto out;
> > > +     }
> > > +
> > > +     __builtin_memcpy(args->data, data, sizeof(args->data));
> > > +
> > > + out:
> > > +     hid_bpf_release_context(ctx);
> > > +
> > > +     return ret;
> > > +}
> > > --
> > > 2.36.1
> > >
> >
> > --
> > Kartikeya
> >
>

--
Kartikeya