Re: [PATCH bpf-next v2 4/6] selftests/bpf: skip verifier tests for unsupported map types

[Stanislav Fomichev <sdf@fomichev.me>]

On 12/19, Daniel Borkmann wrote:
> On 12/17/2018 07:25 PM, Stanislav Fomichev wrote:
> > Use recently introduced bpf_map_type_supported() to skip tests in the
> > test_verifier if map creation (create_map) fails. It's handled
> > explicitly for each fixup, i.e. if bpf_create_map returns negative fd,
> > we probe the kernel for the appropriate map support and skip the
> > test is map type is not supported.
> > 
> > Signed-off-by: Stanislav Fomichev <sdf@google.com>
> > ---
> >  tools/testing/selftests/bpf/test_verifier.c | 34 +++++++++++++++++++--
> >  1 file changed, 31 insertions(+), 3 deletions(-)
> > 
> > diff --git a/tools/testing/selftests/bpf/test_verifier.c b/tools/testing/selftests/bpf/test_verifier.c
> > index 124d21306c27..d267f5248b5d 100644
> > --- a/tools/testing/selftests/bpf/test_verifier.c
> > +++ b/tools/testing/selftests/bpf/test_verifier.c
> > @@ -14221,10 +14221,20 @@ static int create_cgroup_storage(bool percpu)
> >  	return fd;
> >  }
> >  
> > +static bool skip_unsupported_map(int ret, enum bpf_map_type map_type)
> > +{
> > +	if (ret < 0 && !bpf_map_type_supported(map_type)) {
> > +		printf("SKIP (unsupported map type %d)\n", map_type);
> > +		skips++;
> > +		return true;
> > +	}
> > +	return false;
> > +}
> > +
> >  static char bpf_vlog[UINT_MAX >> 8];
> >  
> > -static void do_test_fixup(struct bpf_test *test, enum bpf_map_type prog_type,
> > -			  struct bpf_insn *prog, int *map_fds)
> > +static int do_test_fixup(struct bpf_test *test, enum bpf_map_type prog_type,
> > +			 struct bpf_insn *prog, int *map_fds)
> >  {
> >  	int *fixup_map_hash_8b = test->fixup_map_hash_8b;
> >  	int *fixup_map_hash_48b = test->fixup_map_hash_48b;
> > @@ -14309,6 +14319,9 @@ static void do_test_fixup(struct bpf_test *test, enum bpf_map_type prog_type,
> >  
> >  	if (*fixup_cgroup_storage) {
> >  		map_fds[7] = create_cgroup_storage(false);
> > +		if (skip_unsupported_map(map_fds[7],
> > +					 BPF_MAP_TYPE_CGROUP_STORAGE))
> > +			return -1;
> >  		do {
> >  			prog[*fixup_cgroup_storage].imm = map_fds[7];
> >  			fixup_cgroup_storage++;
> > @@ -14317,6 +14330,9 @@ static void do_test_fixup(struct bpf_test *test, enum bpf_map_type prog_type,
> >  
> >  	if (*fixup_percpu_cgroup_storage) {
> >  		map_fds[8] = create_cgroup_storage(true);
> > +		if (skip_unsupported_map(map_fds[8],
> > +					 BPF_MAP_TYPE_PERCPU_CGROUP_STORAGE))
> > +			return -1;
> >  		do {
> >  			prog[*fixup_percpu_cgroup_storage].imm = map_fds[8];
> >  			fixup_percpu_cgroup_storage++;
> > @@ -14325,6 +14341,8 @@ static void do_test_fixup(struct bpf_test *test, enum bpf_map_type prog_type,
> >  	if (*fixup_map_sockmap) {
> >  		map_fds[9] = create_map(BPF_MAP_TYPE_SOCKMAP, sizeof(int),
> >  					sizeof(int), 1);
> > +		if (skip_unsupported_map(map_fds[9], BPF_MAP_TYPE_SOCKMAP))
> > +			return -1;
> >  		do {
> >  			prog[*fixup_map_sockmap].imm = map_fds[9];
> >  			fixup_map_sockmap++;
> > @@ -14333,6 +14351,8 @@ static void do_test_fixup(struct bpf_test *test, enum bpf_map_type prog_type,
> >  	if (*fixup_map_sockhash) {
> >  		map_fds[10] = create_map(BPF_MAP_TYPE_SOCKHASH, sizeof(int),
> >  					sizeof(int), 1);
> > +		if (skip_unsupported_map(map_fds[10], BPF_MAP_TYPE_SOCKHASH))
> > +			return -1;
> >  		do {
> >  			prog[*fixup_map_sockhash].imm = map_fds[10];
> >  			fixup_map_sockhash++;
> > @@ -14341,6 +14361,8 @@ static void do_test_fixup(struct bpf_test *test, enum bpf_map_type prog_type,
> >  	if (*fixup_map_xskmap) {
> >  		map_fds[11] = create_map(BPF_MAP_TYPE_XSKMAP, sizeof(int),
> >  					sizeof(int), 1);
> > +		if (skip_unsupported_map(map_fds[11], BPF_MAP_TYPE_XSKMAP))
> > +			return -1;
> >  		do {
> >  			prog[*fixup_map_xskmap].imm = map_fds[11];
> >  			fixup_map_xskmap++;
> > @@ -14349,11 +14371,16 @@ static void do_test_fixup(struct bpf_test *test, enum bpf_map_type prog_type,
> >  	if (*fixup_map_stacktrace) {
> >  		map_fds[12] = create_map(BPF_MAP_TYPE_STACK_TRACE, sizeof(u32),
> >  					 sizeof(u64), 1);
> > +		if (skip_unsupported_map(map_fds[12],
> > +					 BPF_MAP_TYPE_STACK_TRACE))
> > +			return -1;
> 
> Nit: Could probably be slightly simplified by moving this into and by reworking
> create_{map,cgroup_storage}() a bit.
Yeah, I stated that option in the cover letter. I did that initially,
but it required some additional argument (skip/supported) to the
create_{map,cgroup_storage} and I scrapped this approach due to too
much plumbing.

But I think since we are not doing any parallel tests in the verifier,
we can do something like the following patch below. WDYT?

---

diff --git a/tools/testing/selftests/bpf/test_verifier.c b/tools/testing/selftests/bpf/test_verifier.c
index 124d21306c27..43f71783f7b5 100644
--- a/tools/testing/selftests/bpf/test_verifier.c
+++ b/tools/testing/selftests/bpf/test_verifier.c
@@ -14113,6 +14113,16 @@ static int probe_filter_length(const struct bpf_insn *fp)
 	return len + 1;
 }
 
+static bool skip_unsupported_map(enum bpf_map_type map_type)
+{
+	if (!bpf_map_type_supported(map_type)) {
+		printf("SKIP (unsupported map type %d)\n", map_type);
+		skips++;
+		return true;
+	}
+	return false;
+}
+
 static int create_map(uint32_t type, uint32_t size_key,
 		      uint32_t size_value, uint32_t max_elem)
 {
@@ -14120,8 +14130,11 @@ static int create_map(uint32_t type, uint32_t size_key,
 
 	fd = bpf_create_map(type, size_key, size_value, max_elem,
 			    type == BPF_MAP_TYPE_HASH ? BPF_F_NO_PREALLOC : 0);
-	if (fd < 0)
+	if (fd < 0) {
+		if (skip_unsupported_map(type))
+			return -1;
 		printf("Failed to create hash map '%s'!\n", strerror(errno));
+	}
 
 	return fd;
 }
@@ -14161,6 +14174,8 @@ static int create_prog_array(enum bpf_map_type prog_type, uint32_t max_elem,
 	mfd = bpf_create_map(BPF_MAP_TYPE_PROG_ARRAY, sizeof(int),
 			     sizeof(int), max_elem, 0);
 	if (mfd < 0) {
+		if (skip_unsupported_map(BPF_MAP_TYPE_PROG_ARRAY))
+			return -1;
 		printf("Failed to create prog array '%s'!\n", strerror(errno));
 		return -1;
 	}
@@ -14191,15 +14206,20 @@ static int create_map_in_map(void)
 	inner_map_fd = bpf_create_map(BPF_MAP_TYPE_ARRAY, sizeof(int),
 				      sizeof(int), 1, 0);
 	if (inner_map_fd < 0) {
+		if (skip_unsupported_map(BPF_MAP_TYPE_ARRAY))
+			return -1;
 		printf("Failed to create array '%s'!\n", strerror(errno));
 		return inner_map_fd;
 	}
 
 	outer_map_fd = bpf_create_map_in_map(BPF_MAP_TYPE_ARRAY_OF_MAPS, NULL,
 					     sizeof(int), inner_map_fd, 1, 0);
-	if (outer_map_fd < 0)
+	if (outer_map_fd < 0) {
+		if (skip_unsupported_map(BPF_MAP_TYPE_ARRAY_OF_MAPS))
+			return -1;
 		printf("Failed to create array of maps '%s'!\n",
 		       strerror(errno));
+	}
 
 	close(inner_map_fd);
 
@@ -14214,9 +14234,12 @@ static int create_cgroup_storage(bool percpu)
 
 	fd = bpf_create_map(type, sizeof(struct bpf_cgroup_storage_key),
 			    TEST_DATA_LEN, 0, 0);
-	if (fd < 0)
+	if (fd < 0) {
+		if (skip_unsupported_map(type))
+			return -1;
 		printf("Failed to create cgroup storage '%s'!\n",
 		       strerror(errno));
+	}
 
 	return fd;
 }
@@ -14392,6 +14415,7 @@ static void do_test_single(struct bpf_test *test, bool unpriv,
 	int map_fds[MAX_NR_MAPS];
 	const char *expected_err;
 	uint32_t expected_val;
+	int fixup_skips;
 	uint32_t retval;
 	__u32 pflags;
 	int i, err;
@@ -14401,7 +14425,13 @@ static void do_test_single(struct bpf_test *test, bool unpriv,
 
 	if (!prog_type)
 		prog_type = BPF_PROG_TYPE_SOCKET_FILTER;
+	fixup_skips = skips;
 	do_test_fixup(test, prog_type, prog, map_fds);
+	/* If there were some map skips during fixup due to missing bpf
+	 * features, skip this test.
+	 */
+	if (fixup_skips != skips)
+		return;
 	prog_len = probe_filter_length(prog);
 
 	pflags = 0;

> 
> >  		do {
> >  			prog[*fixup_map_stacktrace].imm = map_fds[12];
> >  			fixup_map_stacktrace++;
> >  		} while (fixup_map_stacktrace);
> >  	}
> > +
> > +	return 0;
> >  }
> >  
> >  static int set_admin(bool admin)
> > @@ -14401,7 +14428,8 @@ static void do_test_single(struct bpf_test *test, bool unpriv,
> >  
> >  	if (!prog_type)
> >  		prog_type = BPF_PROG_TYPE_SOCKET_FILTER;
> > -	do_test_fixup(test, prog_type, prog, map_fds);
> > +	if (do_test_fixup(test, prog_type, prog, map_fds) < 0)
> > +		return;
> >  	prog_len = probe_filter_length(prog);
> >  
> >  	pflags = 0;
> > 
>