[PATCH stable 5.15 0/1] Fix bpf selftest build failure - error: 'struct bpf_test' has no member named 'fixup_kfunc_btf_id'

[PATCH stable 5.15 0/1] Fix bpf selftest build failure - error: 'struct bpf_test' has no member named 'fixup_kfunc_btf_id'

[Po-Hsu Lin]

The bpf selftest build will fail on the stable 5.15 tree with:

  CC       test_stub.o
  BINARY   test_verifier
In file included from /home/ubuntu/linux/tools/testing/selftests/bpf/verifier/tests.h:21,
                 from test_verifier.c:432:
/home/ubuntu/linux/tools/testing/selftests/bpf/verifier/calls.c:124:10: error: 'struct bpf_test' has no member named 'fixup_kfunc_btf_id'
  124 |         .fixup_kfunc_btf_id = {
      |          ^~~~~~~~~~~~~~~~~~
/home/ubuntu/linux/tools/testing/selftests/bpf/verifier/calls.c:124:9: warning: braces around scalar initializer
  124 |         .fixup_kfunc_btf_id = {
      |         ^

This is because of the fixup_kfunc_btf_id member in struct bpf_test
added in commit 13c6a37d40 ("selftests/bpf: Add test for reg2btf_ids
out of bounds access") from upstream.

We will need commit 0201b80772 ("selftests/bpf: Add test_verifier
support to fixup kfunc call insns") from upstream to solve this build
issue. Some backport work is needed for the 5.15 tree to skip
fixup_map_timer related changes, which came from commit e60e6962c5
("selftests/bpf: Add tests for restricted helpers").

Kumar Kartikeya Dwivedi (1):
  selftests/bpf: Add test_verifier support to fixup kfunc call insns

 tools/testing/selftests/bpf/test_verifier.c | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

-- 
2.7.4

[PATCH stable 5.15 1/1] selftests/bpf: Add test_verifier support to fixup kfunc call insns

[Po-Hsu Lin]

From: Kumar Kartikeya Dwivedi <memxor@gmail.com>

commit 0201b80772ac2b712bbbfe783cdb731fdfb4247e upstream.

This allows us to add tests (esp. negative tests) where we only want to
ensure the program doesn't pass through the verifier, and also verify
the error. The next commit will add the tests making use of this.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20220114163953.1455836-9-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
[PHLin: backport due to lack of fixup_map_timer]
Signed-off-by: Po-Hsu Lin <po-hsu.lin@canonical.com>
---
 tools/testing/selftests/bpf/test_verifier.c | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/tools/testing/selftests/bpf/test_verifier.c b/tools/testing/selftests/bpf/test_verifier.c
index 3a9e332..68a9a89 100644
--- a/tools/testing/selftests/bpf/test_verifier.c
+++ b/tools/testing/selftests/bpf/test_verifier.c
@@ -31,6 +31,7 @@
 #include <linux/if_ether.h>
 #include <linux/btf.h>
 
+#include <bpf/btf.h>
 #include <bpf/bpf.h>
 #include <bpf/libbpf.h>
 
@@ -63,6 +64,11 @@ static bool unpriv_disabled = false;
 static int skips;
 static bool verbose = false;
 
+struct kfunc_btf_id_pair {
+	const char *kfunc;
+	int insn_idx;
+};
+
 struct bpf_test {
 	const char *descr;
 	struct bpf_insn	insns[MAX_INSNS];
@@ -88,6 +94,7 @@ struct bpf_test {
 	int fixup_map_event_output[MAX_FIXUPS];
 	int fixup_map_reuseport_array[MAX_FIXUPS];
 	int fixup_map_ringbuf[MAX_FIXUPS];
+	struct kfunc_btf_id_pair fixup_kfunc_btf_id[MAX_FIXUPS];
 	/* Expected verifier log output for result REJECT or VERBOSE_ACCEPT.
 	 * Can be a tab-separated sequence of expected strings. An empty string
 	 * means no log verification.
@@ -718,6 +725,7 @@ static void do_test_fixup(struct bpf_test *test, enum bpf_prog_type prog_type,
 	int *fixup_map_event_output = test->fixup_map_event_output;
 	int *fixup_map_reuseport_array = test->fixup_map_reuseport_array;
 	int *fixup_map_ringbuf = test->fixup_map_ringbuf;
+	struct kfunc_btf_id_pair *fixup_kfunc_btf_id = test->fixup_kfunc_btf_id;
 
 	if (test->fill_helper) {
 		test->fill_insns = calloc(MAX_TEST_INSNS, sizeof(struct bpf_insn));
@@ -903,6 +911,26 @@ static void do_test_fixup(struct bpf_test *test, enum bpf_prog_type prog_type,
 			fixup_map_ringbuf++;
 		} while (*fixup_map_ringbuf);
 	}
+
+	/* Patch in kfunc BTF IDs */
+	if (fixup_kfunc_btf_id->kfunc) {
+		struct btf *btf;
+		int btf_id;
+
+		do {
+			btf_id = 0;
+			btf = btf__load_vmlinux_btf();
+			if (btf) {
+				btf_id = btf__find_by_name_kind(btf,
+								fixup_kfunc_btf_id->kfunc,
+								BTF_KIND_FUNC);
+				btf_id = btf_id < 0 ? 0 : btf_id;
+			}
+			btf__free(btf);
+			prog[fixup_kfunc_btf_id->insn_idx].imm = btf_id;
+			fixup_kfunc_btf_id++;
+		} while (fixup_kfunc_btf_id->kfunc);
+	}
 }
 
 struct libcap {
-- 
2.7.4

Re: [PATCH stable 5.15 1/1] selftests/bpf: Add test_verifier support to fixup kfunc call insns

[Greg KH]

On Fri, Jul 01, 2022 at 09:08:58PM +0800, Po-Hsu Lin wrote:
> From: Kumar Kartikeya Dwivedi <memxor@gmail.com>
> 
> commit 0201b80772ac2b712bbbfe783cdb731fdfb4247e upstream.
> 
> This allows us to add tests (esp. negative tests) where we only want to
> ensure the program doesn't pass through the verifier, and also verify
> the error. The next commit will add the tests making use of this.
> 
> Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
> Link: https://lore.kernel.org/r/20220114163953.1455836-9-memxor@gmail.com
> Signed-off-by: Alexei Starovoitov <ast@kernel.org>
> [PHLin: backport due to lack of fixup_map_timer]
> Signed-off-by: Po-Hsu Lin <po-hsu.lin@canonical.com>
> ---
>  tools/testing/selftests/bpf/test_verifier.c | 28 ++++++++++++++++++++++++++++
>  1 file changed, 28 insertions(+)

Now queued up, thanks.

greg k-h