[ipsec-next,v3,5/9] libbpf: selftests: Add verifier tests for CO-RE bitfield writes
Commit Message
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
Comments
On Fri, Dec 1, 2023 at 12:24 PM Daniel Xu <dxu@dxuuu.xyz> wrote:
>
> 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
>
LGTM, but I'm not sure why we need all those __failure_unpriv, see
below. Regardless:
Acked-by: Andrii Nakryiko <andrii@kernel.org>
> 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
do we want __failure_unpriv at all? Is this failure related to
*bitfield* logic at all?
> +__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);
> +}
> +
[...]
Hi Andrii,
On Fri, Dec 01, 2023 at 03:52:25PM -0800, Andrii Nakryiko wrote:
> On Fri, Dec 1, 2023 at 12:24 PM Daniel Xu <dxu@dxuuu.xyz> wrote:
> >
> > 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
> >
>
> LGTM, but I'm not sure why we need all those __failure_unpriv, see
> below. Regardless:
>
> Acked-by: Andrii Nakryiko <andrii@kernel.org>
>
> > 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
>
> do we want __failure_unpriv at all? Is this failure related to
> *bitfield* logic at all?
Oh, I pre-emptively added it. From the docs, I thought __failure_unpriv
meant "don't try to load this as an unprivileged used cuz it'll fail".
And since I used the tc hook, I figured it'd fail.
Removing the annotation doesn't seem to do anything bad so I'll drop it
for v4.
[...]
Thanks,
Daniel
On Fri, 2023-12-01 at 17:10 -0700, Daniel Xu wrote:
[...]
> > > +SEC("tc")
> > > +__description("single CO-RE bitfield roundtrip")
> > > +__btf_path("btf__core_reloc_bitfields.bpf.o")
> > > +__success __failure_unpriv
> >
> > do we want __failure_unpriv at all? Is this failure related to
> > *bitfield* logic at all?
>
> Oh, I pre-emptively added it. From the docs, I thought __failure_unpriv
> meant "don't try to load this as an unprivileged used cuz it'll fail".
> And since I used the tc hook, I figured it'd fail.
Actually it means:
"try to load as unprivileged user and expect failure,
report error on successful load".
In general, the meaning of "___xxx" and "___xxx_unpriv" annotations
is identical, except first instructs to run the test in privileged mode,
while second instructs to run test in unprivileged mode:
- if only annotations w/o "*_unpriv" suffix are present the test would
be executed as privileged;
- if only annotations with "*_unpriv" suffix are present the test would
be executed as unprivileged;
- if both kinds of annotations are present the test would be executed
in both modes.
[...]
@@ -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); }
new file mode 100644
@@ -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";