[PATCH bpf-next v4 0/2] selftests: add test for kfunc call

Hi,

The patchset add a test for kfunc call to ensure s32 is sufficient for
kfunc offset. Patch #1 unexports the subtests in ksyms_module.c to fix
the confusion in test output and patch #2 adds a test in ksyms_module.c
to ensure s32 is sufficient for kfunc offset.

Change Log:
v4:
 * remove merged patch "bpf, arm64: enable kfunc call"
 * rebased on bpf-next

v3: https://lore.kernel.org/bpf/20220130092917.14544-1-hotforest@gmail.com
  * patch #2: newly-addded to unexport unnecessary subtests
  * patch #3: use kallsyms_find() instead of reimplementing it.
  * patch #3: ensure kfunc call is supported before checking
              whether s32 will be overflowed or not.

v2: https://lore.kernel.org/bpf/20220127071532.384888-1-houtao1@huawei.com
  * add a test to check whether imm will be overflowed for kfunc call

v1: https://lore.kernel.org/bpf/20220119144942.305568-1-houtao1@huawei.com

Hou Tao (2):
  selftests/bpf: do not export subtest as standalone test
  selftests/bpf: check whether s32 is sufficient for kfunc offset

 .../selftests/bpf/prog_tests/ksyms_module.c   | 46 ++++++++++++++++++-
 .../bpf/prog_tests/xdp_adjust_frags.c         |  6 ---
 .../bpf/prog_tests/xdp_adjust_tail.c          |  4 +-
 .../bpf/prog_tests/xdp_cpumap_attach.c        |  4 +-
 .../bpf/prog_tests/xdp_devmap_attach.c        |  2 +-
 5 files changed, 49 insertions(+), 13 deletions(-)

-- 
2.35.1

Two subtests in ksyms_module.c are not qualified as static, so these
subtests are exported as standalone tests in tests.h and lead to
confusion for the output of "./test_progs -t ksyms_module".

By using the following command:

  grep "^void \(serial_\)\?test_[a-zA-Z0-9_]\+(\(void\)\?)" \
      tools/testing/selftests/bpf/prog_tests/*.c | \
	awk -F : '{print $1}' | sort | uniq -c | awk '$1 != 1'

Find out that other tests also have the similar problem, so fix
these tests by marking subtests in these tests as static. For
xdp_adjust_frags.c, there is just one subtest, so just export
the subtest directly.

Signed-off-by: Hou Tao <redacted>
---
 tools/testing/selftests/bpf/prog_tests/ksyms_module.c      | 4 ++--
 tools/testing/selftests/bpf/prog_tests/xdp_adjust_frags.c  | 6 ------
 tools/testing/selftests/bpf/prog_tests/xdp_adjust_tail.c   | 4 ++--
 tools/testing/selftests/bpf/prog_tests/xdp_cpumap_attach.c | 4 ++--
 tools/testing/selftests/bpf/prog_tests/xdp_devmap_attach.c | 2 +-
 5 files changed, 7 insertions(+), 13 deletions(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/ksyms_module.c b/tools/testing/selftests/bpf/prog_tests/ksyms_module.c
index ecc58c9e7631..a1ebac70ec29 100644
--- a/tools/testing/selftests/bpf/prog_tests/ksyms_module.c
+++ b/tools/testing/selftests/bpf/prog_tests/ksyms_module.c

@@ -6,7 +6,7 @@
 #include "test_ksyms_module.lskel.h"
 #include "test_ksyms_module.skel.h"
 
-void test_ksyms_module_lskel(void)
+static void test_ksyms_module_lskel(void)
 {
 	struct test_ksyms_module_lskel *skel;
 	int err;

@@ -33,7 +33,7 @@ void test_ksyms_module_lskel(void)
 	test_ksyms_module_lskel__destroy(skel);
 }
 
-void test_ksyms_module_libbpf(void)
+static void test_ksyms_module_libbpf(void)
 {
 	struct test_ksyms_module *skel;
 	int err;

diff --git a/tools/testing/selftests/bpf/prog_tests/xdp_adjust_frags.c b/tools/testing/selftests/bpf/prog_tests/xdp_adjust_frags.c
index 134d0ac32f59..fc2d8fa8dac5 100644
--- a/tools/testing/selftests/bpf/prog_tests/xdp_adjust_frags.c
+++ b/tools/testing/selftests/bpf/prog_tests/xdp_adjust_frags.c

@@ -102,9 +102,3 @@ void test_xdp_update_frags(void)
 out:
 	bpf_object__close(obj);
 }
-
-void test_xdp_adjust_frags(void)
-{
-	if (test__start_subtest("xdp_adjust_frags"))
-		test_xdp_update_frags();
-}

diff --git a/tools/testing/selftests/bpf/prog_tests/xdp_adjust_tail.c b/tools/testing/selftests/bpf/prog_tests/xdp_adjust_tail.c
index 528a8c387720..21ceac24e174 100644
--- a/tools/testing/selftests/bpf/prog_tests/xdp_adjust_tail.c
+++ b/tools/testing/selftests/bpf/prog_tests/xdp_adjust_tail.c

@@ -133,7 +133,7 @@ static void test_xdp_adjust_tail_grow2(void)
 	bpf_object__close(obj);
 }
 
-void test_xdp_adjust_frags_tail_shrink(void)
+static void test_xdp_adjust_frags_tail_shrink(void)
 {
 	const char *file = "./test_xdp_adjust_tail_shrink.o";
 	__u32 exp_size;

@@ -200,7 +200,7 @@ void test_xdp_adjust_frags_tail_shrink(void)
 	bpf_object__close(obj);
 }
 
-void test_xdp_adjust_frags_tail_grow(void)
+static void test_xdp_adjust_frags_tail_grow(void)
 {
 	const char *file = "./test_xdp_adjust_tail_grow.o";
 	__u32 exp_size;

diff --git a/tools/testing/selftests/bpf/prog_tests/xdp_cpumap_attach.c b/tools/testing/selftests/bpf/prog_tests/xdp_cpumap_attach.c
index b353e1f3acb5..f775a1613833 100644
--- a/tools/testing/selftests/bpf/prog_tests/xdp_cpumap_attach.c
+++ b/tools/testing/selftests/bpf/prog_tests/xdp_cpumap_attach.c

@@ -8,7 +8,7 @@
 
 #define IFINDEX_LO	1
 
-void test_xdp_with_cpumap_helpers(void)
+static void test_xdp_with_cpumap_helpers(void)
 {
 	struct test_xdp_with_cpumap_helpers *skel;
 	struct bpf_prog_info info = {};

@@ -68,7 +68,7 @@ void test_xdp_with_cpumap_helpers(void)
 	test_xdp_with_cpumap_helpers__destroy(skel);
 }
 
-void test_xdp_with_cpumap_frags_helpers(void)
+static void test_xdp_with_cpumap_frags_helpers(void)
 {
 	struct test_xdp_with_cpumap_frags_helpers *skel;
 	struct bpf_prog_info info = {};

diff --git a/tools/testing/selftests/bpf/prog_tests/xdp_devmap_attach.c b/tools/testing/selftests/bpf/prog_tests/xdp_devmap_attach.c
index 463a72fc3e70..ead40016c324 100644
--- a/tools/testing/selftests/bpf/prog_tests/xdp_devmap_attach.c
+++ b/tools/testing/selftests/bpf/prog_tests/xdp_devmap_attach.c

@@ -81,7 +81,7 @@ static void test_neg_xdp_devmap_helpers(void)
 	}
 }
 
-void test_xdp_with_devmap_frags_helpers(void)
+static void test_xdp_with_devmap_frags_helpers(void)
 {
 	struct test_xdp_with_devmap_frags_helpers *skel;
 	struct bpf_prog_info info = {};

-- 
2.35.1

In add_kfunc_call(), bpf_kfunc_desc->imm with type s32 is used to
represent the offset of called kfunc from __bpf_call_base, so
add a test to ensure that the offset will not be overflowed.

Signed-off-by: Hou Tao <redacted>
---
 .../selftests/bpf/prog_tests/ksyms_module.c   | 42 +++++++++++++++++++
 1 file changed, 42 insertions(+)

diff --git a/tools/testing/selftests/bpf/prog_tests/ksyms_module.c b/tools/testing/selftests/bpf/prog_tests/ksyms_module.c
index a1ebac70ec29..8055fbbf720b 100644
--- a/tools/testing/selftests/bpf/prog_tests/ksyms_module.c
+++ b/tools/testing/selftests/bpf/prog_tests/ksyms_module.c

@@ -3,9 +3,49 @@
 
 #include <test_progs.h>
 #include <network_helpers.h>
+#include <trace_helpers.h>
 #include "test_ksyms_module.lskel.h"
 #include "test_ksyms_module.skel.h"
 
+/*
+ * Check whether or not s32 in bpf_kfunc_desc is sufficient
+ * to represent the offset between bpf_testmod_test_mod_kfunc
+ * and __bpf_call_base.
+ */
+static void test_ksyms_module_valid_offset(void)
+{
+	struct test_ksyms_module *skel;
+	unsigned long long kfunc_addr;
+	unsigned long long base_addr;
+	long long actual_offset;
+	int used_offset;
+	int err;
+
+	if (!env.has_testmod) {
+		test__skip();
+		return;
+	}
+
+	/* Ensure kfunc call is supported */
+	skel = test_ksyms_module__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "test_ksyms_module__open"))
+		return;
+
+	err = kallsyms_find("bpf_testmod_test_mod_kfunc", &kfunc_addr);
+	if (!ASSERT_OK(err, "find kfunc addr"))
+		goto cleanup;
+
+	err = kallsyms_find("__bpf_call_base", &base_addr);
+	if (!ASSERT_OK(err, "find base addr"))
+		goto cleanup;
+
+	used_offset = kfunc_addr - base_addr;
+	actual_offset = kfunc_addr - base_addr;
+	ASSERT_EQ((long long)used_offset, actual_offset, "kfunc offset overflowed");
+cleanup:
+	test_ksyms_module__destroy(skel);
+}
+
 static void test_ksyms_module_lskel(void)
 {
 	struct test_ksyms_module_lskel *skel;

@@ -62,6 +102,8 @@ static void test_ksyms_module_libbpf(void)
 
 void test_ksyms_module(void)
 {
+	if (test__start_subtest("valid_offset"))
+		test_ksyms_module_valid_offset();
 	if (test__start_subtest("lskel"))
 		test_ksyms_module_lskel();
 	if (test__start_subtest("libbpf"))

-- 
2.35.1

On 2/5/22 8:31 PM, Hou Tao wrote:

I suggest keep test_xdp_adjust_frags and mark
test_xdp_update_frags as static function, and
this is also good for future extension.
It is confusing that test_xdp_update_frags
test in file xdp_adjust_frags.c. Typical
prog_tests/ test has {test,serial_test}_<TEST> test
with file name <TEST>.c file.

[...]

On 2/5/22 8:31 PM, Hou Tao wrote:

I am a little bit confused about motivation here. Maybe I missed 
something. If we indeed have kfunc offset overflow,
should kernel verifier just reject the program? Specially,
we should make the above test_ksyms_module__open_and_load()
fail?

Hi,

On 2/8/2022 2:17 AM, Yonghong Song wrote:

On 2/5/22 8:31 PM, Hou Tao wrote:

quoted

Two subtests in ksyms_module.c are not qualified as static, so these
subtests are exported as standalone tests in tests.h and lead to
confusion for the output of "./test_progs -t ksyms_module".

By using the following command:

   grep "^void \(serial_\)\?test_[a-zA-Z0-9_]\+(\(void\)\?)" \
       tools/testing/selftests/bpf/prog_tests/*.c | \
    awk -F : '{print $1}' | sort | uniq -c | awk '$1 != 1'

Find out that other tests also have the similar problem, so fix
these tests by marking subtests in these tests as static. For
xdp_adjust_frags.c, there is just one subtest, so just export
the subtest directly.

[...]

quoted

diff --git a/tools/testing/selftests/bpf/prog_tests/xdp_adjust_frags.c

b/tools/testing/selftests/bpf/prog_tests/xdp_adjust_frags.c
index 134d0ac32f59..fc2d8fa8dac5 100644

--- a/tools/testing/selftests/bpf/prog_tests/xdp_adjust_frags.c
+++ b/tools/testing/selftests/bpf/prog_tests/xdp_adjust_frags.c

@@ -102,9 +102,3 @@ void test_xdp_update_frags(void)

  out:
      bpf_object__close(obj);
  }
-
-void test_xdp_adjust_frags(void)
-{
-    if (test__start_subtest("xdp_adjust_frags"))
-        test_xdp_update_frags();
-}

I suggest keep test_xdp_adjust_frags and mark
test_xdp_update_frags as static function, and
this is also good for future extension.
It is confusing that test_xdp_update_frags
test in file xdp_adjust_frags.c. Typical
prog_tests/ test has {test,serial_test}_<TEST> test
with file name <TEST>.c file.

Will do and thanks for your suggestion.

Regards,
Tao

[...]
.

Hi,

On 2/8/2022 2:33 AM, Yonghong Song wrote:

On 2/5/22 8:31 PM, Hou Tao wrote:

quoted

In add_kfunc_call(), bpf_kfunc_desc->imm with type s32 is used to
represent the offset of called kfunc from __bpf_call_base, so
add a test to ensure that the offset will not be overflowed.

Signed-off-by: Hou Tao <redacted>
---
  .../selftests/bpf/prog_tests/ksyms_module.c   | 42 +++++++++++++++++++
  1 file changed, 42 insertions(+)

[...]

quoted

+    /* Ensure kfunc call is supported */
+    skel = test_ksyms_module__open_and_load();
+    if (!ASSERT_OK_PTR(skel, "test_ksyms_module__open"))
+        return;
+
+    err = kallsyms_find("bpf_testmod_test_mod_kfunc", &kfunc_addr);
+    if (!ASSERT_OK(err, "find kfunc addr"))
+        goto cleanup;
+
+    err = kallsyms_find("__bpf_call_base", &base_addr);
+    if (!ASSERT_OK(err, "find base addr"))
+        goto cleanup;
+
+    used_offset = kfunc_addr - base_addr;
+    actual_offset = kfunc_addr - base_addr;
+    ASSERT_EQ((long long)used_offset, actual_offset, "kfunc offset
overflowed");

I am a little bit confused about motivation here. Maybe I missed something. If
we indeed have kfunc offset overflow,
should kernel verifier just reject the program? Specially,
we should make the above test_ksyms_module__open_and_load()
fail?

In add_kfunc_call(), the calculation of imm doesn't consider the overflow
of s32. So test_ksyms_module__open_and_load() will succeed. I think the
better solution is to put the overflow check in add_kfunc_call(), so will
drop this patch and add the overflow check in add_kfunc_call() instead.

Regards,
Tao

[...]