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

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