[PATCH v6 2/4] selftests: bpf: add bpf_cpumask_populate selftests

Emil Tsalapatis
2025-03-07T15:38:54Z

Add selftests for the bpf_cpumask_populate helper that sets a
bpf_cpumask to a bit pattern provided by a BPF program.

Signed-off-by: Emil Tsalapatis (Meta) <emil@etsalapatis.com>
---
.../selftests/bpf/prog_tests/cpumask.c | 3 +
.../selftests/bpf/progs/cpumask_common.h | 1 +
.../selftests/bpf/progs/cpumask_failure.c | 38 ++++++
.../selftests/bpf/progs/cpumask_success.c | 110 ++++++++++++++++++
4 files changed, 152 insertions(+)

diff --git a/tools/testing/selftests/bpf/prog_tests/cpumask.c b/tools/testing/selftests/bpf/prog_tests/cpumask.c
index e58a04654238..9b09beba988b 100644
--- a/tools/testing/selftests/bpf/prog_tests/cpumask.c
+++ b/tools/testing/selftests/bpf/prog_tests/cpumask.c
@@ -25,6 +25,9 @@ static const char * const cpumask_success_testcases[] = {
"test_global_mask_nested_deep_rcu",
"test_global_mask_nested_deep_array_rcu",
"test_cpumask_weight",
+ "test_populate_reject_small_mask",
+ "test_populate_reject_unaligned",
+ "test_populate",
};

static void verify_success(const char *prog_name)
diff --git a/tools/testing/selftests/bpf/progs/cpumask_common.h b/tools/testing/selftests/bpf/progs/cpumask_common.h
index 4ece7873ba60..86085b79f5ca 100644
--- a/tools/testing/selftests/bpf/progs/cpumask_common.h
+++ b/tools/testing/selftests/bpf/progs/cpumask_common.h
@@ -61,6 +61,7 @@ u32 bpf_cpumask_any_distribute(const struct cpumask *src) __ksym __weak;
u32 bpf_cpumask_any_and_distribute(const struct cpumask *src1,
const struct cpumask *src2) __ksym __weak;
u32 bpf_cpumask_weight(const struct cpumask *cpumask) __ksym __weak;
+int bpf_cpumask_populate(struct cpumask *cpumask, void *src, size_t src__sz) __ksym __weak;

void bpf_rcu_read_lock(void) __ksym __weak;
void bpf_rcu_read_unlock(void) __ksym __weak;
diff --git a/tools/testing/selftests/bpf/progs/cpumask_failure.c b/tools/testing/selftests/bpf/progs/cpumask_failure.c
index b40b52548ffb..8a2fd596c8a3 100644
--- a/tools/testing/selftests/bpf/progs/cpumask_failure.c
+++ b/tools/testing/selftests/bpf/progs/cpumask_failure.c
@@ -222,3 +222,41 @@ int BPF_PROG(test_invalid_nested_array, struct task_struct *task, u64 clone_flag

return 0;
}
+
+SEC("tp_btf/task_newtask")
+__failure __msg("type=scalar expected=fp")
+int BPF_PROG(test_populate_invalid_destination, struct task_struct *task, u64 clone_flags)
+{
+ struct bpf_cpumask *invalid = (struct bpf_cpumask *)0x123456;
+ u64 bits;
+ int ret;
+
+ ret = bpf_cpumask_populate((struct cpumask *)invalid, &bits, sizeof(bits));
+ if (!ret)
+ err = 2;
+
+ return 0;
+}
+
+SEC("tp_btf/task_newtask")
+__failure __msg("leads to invalid memory access")
+int BPF_PROG(test_populate_invalid_source, struct task_struct *task, u64 clone_flags)
+{
+ void *garbage = (void *)0x123456;
+ struct bpf_cpumask *local;
+ int ret;
+
+ local = create_cpumask();
+ if (!local) {
+ err = 1;
+ return 0;
+ }
+
+ ret = bpf_cpumask_populate((struct cpumask *)local, garbage, 8);
+ if (!ret)
+ err = 2;
+
+ bpf_cpumask_release(local);
+
+ return 0;
+}
diff --git a/tools/testing/selftests/bpf/progs/cpumask_success.c b/tools/testing/selftests/bpf/progs/cpumask_success.c
index 80ee469b0b60..23ef2737af50 100644
--- a/tools/testing/selftests/bpf/progs/cpumask_success.c
+++ b/tools/testing/selftests/bpf/progs/cpumask_success.c
@@ -770,3 +770,113 @@ int BPF_PROG(test_refcount_null_tracking, struct task_struct *task, u64 clone_fl
bpf_cpumask_release(mask2);
return 0;
}
+
+SEC("tp_btf/task_newtask")
+int BPF_PROG(test_populate_reject_small_mask, struct task_struct *task, u64 clone_flags)
+{
+ struct bpf_cpumask *local;
+ u8 toofewbits;
+ int ret;
+
+ local = create_cpumask();
+ if (!local)
+ return 0;
+
+ /* The kfunc should prevent this operation */
+ ret = bpf_cpumask_populate((struct cpumask *)local, &toofewbits, sizeof(toofewbits));
+ if (ret != -EACCES)
+ err = 2;
+
+ bpf_cpumask_release(local);
+
+ return 0;
+}
+
+/* Mask is guaranteed to be large enough for bpf_cpumask_t. */
+#define CPUMASK_TEST_MASKLEN (sizeof(cpumask_t))
+
+/* Add an extra word for the test_populate_reject_unaligned test. */
+u64 bits[CPUMASK_TEST_MASKLEN / 8 + 1];
+extern bool CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS __kconfig __weak;
+
+SEC("tp_btf/task_newtask")
+int BPF_PROG(test_populate_reject_unaligned, struct task_struct *task, u64 clone_flags)
+{
+ struct bpf_cpumask *mask;
+ char *src;
+ int ret;
+
+ /* Skip if unaligned accesses are fine for this arch. */
+ if (CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
+ return 0;
+
+ mask = bpf_cpumask_create();
+ if (!mask) {
+ err = 1;
+ return 0;
+ }
+
+ /* Misalign the source array by a byte. */
+ src = &((char *)bits)[1];
+
+ ret = bpf_cpumask_populate((struct cpumask *)mask, src, CPUMASK_TEST_MASKLEN);
+ if (ret != -EINVAL)
+ err = 2;
+
+ bpf_cpumask_release(mask);
+
+ return 0;
+}
+
+
+SEC("tp_btf/task_newtask")
+int BPF_PROG(test_populate, struct task_struct *task, u64 clone_flags)
+{
+ struct bpf_cpumask *mask;
+ bool bit;
+ int ret;
+ int i;
+
+ /* Set only odd bits. */
+ __builtin_memset(bits, 0xaa, CPUMASK_TEST_MASKLEN);
+
+ mask = bpf_cpumask_create();
+ if (!mask) {
+ err = 1;
+ return 0;
+ }
+
+ /* Pass the entire bits array, the kfunc will only copy the valid bits. */
+ ret = bpf_cpumask_populate((struct cpumask *)mask, bits, CPUMASK_TEST_MASKLEN);
+ if (ret) {
+ err = 2;
+ goto out;
+ }
+
+ /*
+ * Test is there to appease the verifier. We cannot directly
+ * access NR_CPUS, the upper bound for nr_cpus, so we infer
+ * it from the size of cpumask_t.
+ */
+ if (nr_cpus < 0 || nr_cpus >= CPUMASK_TEST_MASKLEN * 8) {
+ err = 3;
+ goto out;
+ }
+
+ bpf_for(i, 0, nr_cpus) {
+ /* Odd-numbered bits should be set, even ones unset. */
+ bit = bpf_cpumask_test_cpu(i, (const struct cpumask *)mask);
+ if (bit == (i % 2 != 0))
+ continue;
+
+ err = 4;
+ break;
+ }
+
+out:
+ bpf_cpumask_release(mask);
+
+ return 0;
+}
+
+#undef CPUMASK_TEST_MASKLEN
--
2.47.1