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

Benjamin Tissoires
2022-05-19T13:14:09Z

On 5/19/22 14:51, Kumar Kartikeya Dwivedi wrote:
> 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).

With the following patch applied, the tests are failing:
---
diff --git a/tools/testing/selftests/bpf/progs/hid.c b/tools/testing/selftests/bpf/progs/hid.c
index 43724fd26fb9..976fc8b83934 100644
--- a/tools/testing/selftests/bpf/progs/hid.c
+++ b/tools/testing/selftests/bpf/progs/hid.c
@@ -80,24 +80,14 @@ 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 */
-
- __builtin_memcpy(data, args->data, sizeof(args->data));
-
if (args->size <= sizeof(args->data)) {
ret = hid_bpf_hw_request(ctx,
- data,
+ args->data,
args->size,
args->type,
args->request_type);
@@ -109,8 +99,6 @@ int hid_user_raw_request(struct hid_hw_request_syscall_args *args)
goto out;
}

- __builtin_memcpy(args->data, data, sizeof(args->data));
-
out:
hid_bpf_release_context(ctx);

---

Output of the verifier:

libbpf: prog 'hid_user_raw_request': BPF program load failed: Invalid argument
libbpf: prog 'hid_user_raw_request': -- BEGIN PROG LOAD LOG --
R1 type=ctx expected=fp
0: R1=ctx(off=0,imm=0) R10=fp0
; int hid_user_raw_request(struct hid_hw_request_syscall_args *args)
0: (bf) r7 = r1 ; R1=ctx(off=0,imm=0) R7_w=ctx(off=0,imm=0)
; ctx = hid_bpf_allocate_context(args->hid);
1: (61) r1 = *(u32 *)(r7 +12) ; R1_w=scalar(umax=4294967295,var_off=(0x0; 0xffffffff)) R7_w=ctx(off=0,imm=0)
; ctx = hid_bpf_allocate_context(args->hid);
2: (85) call hid_bpf_allocate_context#66484
3: (bf) r6 = r0 ; R0_w=ptr_or_null_hid_bpf_ctx(id=2,ref_obj_id=2,off=0,imm=0) R6_w=ptr_or_null_hid_bpf_ctx(id=2,ref_obj_id=2,off=0,imm=0) refs=2
4: (b4) w8 = 0 ; R8_w=0 refs=2
; if (!ctx)
5: (15) if r6 == 0x0 goto pc+12 ; R6_w=ptr_hid_bpf_ctx(ref_obj_id=2,off=0,imm=0) refs=2
6: (b4) w8 = -7 ; R8_w=4294967289 refs=2
; if (args->size <= sizeof(args->data)) {
7: (79) r3 = *(u64 *)(r7 +24) ; R3=scalar() R7=ctx(off=0,imm=0) refs=2
; if (args->size <= sizeof(args->data)) {
8: (25) if r3 > 0xa goto pc+7 ; R3=scalar(umax=10,var_off=(0x0; 0xf)) refs=2
; args->request_type);
9: (71) r5 = *(u8 *)(r7 +36) ; R5_w=scalar(umax=255,var_off=(0x0; 0xff)) R7=ctx(off=0,imm=0) refs=2
; args->type,
10: (61) r4 = *(u32 *)(r7 +32) ; R4_w=scalar(umax=4294967295,var_off=(0x0; 0xffffffff)) R7=ctx(off=0,imm=0) refs=2
; ret = hid_bpf_hw_request(ctx,
11: (bf) r1 = r6 ; R1_w=ptr_hid_bpf_ctx(ref_obj_id=2,off=0,imm=0) R6=ptr_hid_bpf_ctx(ref_obj_id=2,off=0,imm=0) refs=2
12: (bf) r2 = r7 ; R2_w=ctx(off=0,imm=0) R7=ctx(off=0,imm=0) refs=2
13: (85) call hid_bpf_hw_request#66480
R2 type=ctx expected=fp
processed 14 insns (limit 1000000) max_states_per_insn 0 total_states 1 peak_states 1 mark_read 1
-- END PROG LOAD LOG --

Maybe I am wrongly declaring hid_bpf_hw_request()?

Cheers,
Benjamin

>
>>
>> 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
>