[PATCH ipsec-next v3 5/9] libbpf: selftests: Add verifier tests for CO-RE bitfield writes

Daniel Xu
2023-12-01T20:24:14Z

Add some tests that exercise BPF_CORE_WRITE_BITFIELD() macro. Since some
non-trivial bit fiddling is going on, make sure various edge cases (such
as adjacent bitfields and bitfields at the edge of structs) are
exercised.

Signed-off-by: Daniel Xu <dxu@dxuuu.xyz>
---
.../selftests/bpf/prog_tests/verifier.c | 2 +
.../bpf/progs/verifier_bitfield_write.c | 100 ++++++++++++++++++
2 files changed, 102 insertions(+)
create mode 100644 tools/testing/selftests/bpf/progs/verifier_bitfield_write.c

diff --git a/tools/testing/selftests/bpf/prog_tests/verifier.c b/tools/testing/selftests/bpf/prog_tests/verifier.c
index 5cfa7a6316b6..67b4948865a3 100644
--- a/tools/testing/selftests/bpf/prog_tests/verifier.c
+++ b/tools/testing/selftests/bpf/prog_tests/verifier.c
@@ -6,6 +6,7 @@
#include "verifier_and.skel.h"
#include "verifier_array_access.skel.h"
#include "verifier_basic_stack.skel.h"
+#include "verifier_bitfield_write.skel.h"
#include "verifier_bounds.skel.h"
#include "verifier_bounds_deduction.skel.h"
#include "verifier_bounds_deduction_non_const.skel.h"
@@ -115,6 +116,7 @@ static void run_tests_aux(const char *skel_name,

void test_verifier_and(void) { RUN(verifier_and); }
void test_verifier_basic_stack(void) { RUN(verifier_basic_stack); }
+void test_verifier_bitfield_write(void) { RUN(verifier_bitfield_write); }
void test_verifier_bounds(void) { RUN(verifier_bounds); }
void test_verifier_bounds_deduction(void) { RUN(verifier_bounds_deduction); }
void test_verifier_bounds_deduction_non_const(void) { RUN(verifier_bounds_deduction_non_const); }
diff --git a/tools/testing/selftests/bpf/progs/verifier_bitfield_write.c b/tools/testing/selftests/bpf/progs/verifier_bitfield_write.c
new file mode 100644
index 000000000000..8fe355a19ba6
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/verifier_bitfield_write.c
@@ -0,0 +1,100 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/bpf.h>
+#include <stdint.h>
+
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_core_read.h>
+
+#include "bpf_misc.h"
+
+struct core_reloc_bitfields {
+ /* unsigned bitfields */
+ uint8_t ub1: 1;
+ uint8_t ub2: 2;
+ uint32_t ub7: 7;
+ /* signed bitfields */
+ int8_t sb4: 4;
+ int32_t sb20: 20;
+ /* non-bitfields */
+ uint32_t u32;
+ int32_t s32;
+} __attribute__((preserve_access_index));
+
+SEC("tc")
+__description("single CO-RE bitfield roundtrip")
+__btf_path("btf__core_reloc_bitfields.bpf.o")
+__success __failure_unpriv
+__retval(3)
+int single_field_roundtrip(struct __sk_buff *ctx)
+{
+ struct core_reloc_bitfields bitfields;
+
+ __builtin_memset(&bitfields, 0, sizeof(bitfields));
+ BPF_CORE_WRITE_BITFIELD(&bitfields, ub2, 3);
+ return BPF_CORE_READ_BITFIELD(&bitfields, ub2);
+}
+
+SEC("tc")
+__description("multiple CO-RE bitfield roundtrip")
+__btf_path("btf__core_reloc_bitfields.bpf.o")
+__success __failure_unpriv
+__retval(0x3FD)
+int multiple_field_roundtrip(struct __sk_buff *ctx)
+{
+ struct core_reloc_bitfields bitfields;
+ uint8_t ub2;
+ int8_t sb4;
+
+ __builtin_memset(&bitfields, 0, sizeof(bitfields));
+ BPF_CORE_WRITE_BITFIELD(&bitfields, ub2, 1);
+ BPF_CORE_WRITE_BITFIELD(&bitfields, sb4, -1);
+
+ ub2 = BPF_CORE_READ_BITFIELD(&bitfields, ub2);
+ sb4 = BPF_CORE_READ_BITFIELD(&bitfields, sb4);
+
+ return (((uint8_t)sb4) << 2) | ub2;
+}
+
+SEC("tc")
+__description("adjacent CO-RE bitfield roundtrip")
+__btf_path("btf__core_reloc_bitfields.bpf.o")
+__success __failure_unpriv
+__retval(7)
+int adjacent_field_roundtrip(struct __sk_buff *ctx)
+{
+ struct core_reloc_bitfields bitfields;
+ uint8_t ub1, ub2;
+
+ __builtin_memset(&bitfields, 0, sizeof(bitfields));
+ BPF_CORE_WRITE_BITFIELD(&bitfields, ub1, 1);
+ BPF_CORE_WRITE_BITFIELD(&bitfields, ub2, 3);
+
+ ub1 = BPF_CORE_READ_BITFIELD(&bitfields, ub1);
+ ub2 = BPF_CORE_READ_BITFIELD(&bitfields, ub2);
+
+ return (ub2 << 1) | ub1;
+}
+
+SEC("tc")
+__description("multibyte CO-RE bitfield roundtrip")
+__btf_path("btf__core_reloc_bitfields.bpf.o")
+__success __failure_unpriv
+__retval(0x21)
+int multibyte_field_roundtrip(struct __sk_buff *ctx)
+{
+ struct core_reloc_bitfields bitfields;
+ uint32_t ub7;
+ uint8_t ub1;
+
+ __builtin_memset(&bitfields, 0, sizeof(bitfields));
+ BPF_CORE_WRITE_BITFIELD(&bitfields, ub1, 1);
+ BPF_CORE_WRITE_BITFIELD(&bitfields, ub7, 16);
+
+ ub1 = BPF_CORE_READ_BITFIELD(&bitfields, ub1);
+ ub7 = BPF_CORE_READ_BITFIELD(&bitfields, ub7);
+
+ return (ub7 << 1) | ub1;
+}
+
+char _license[] SEC("license") = "GPL";
--
2.42.1