This is a follow-up for threads [1] and [2]:
- The size of the bpf_verifier_state->idmap_scratch array is reduced but
remains sufficient for any valid BPF program.
- selftests/bpf test_loader is updated to allow specifying that program
requires BPF_F_TEST_STATE_FREQ flag.
- Test case for the verifier.c:check_ids() update uses test_loader and is
meant as an example of using it for test_verifier-kind tests.
The combination of test_loader and naked functions (see [3]) with inline
assembly allows to write verifier tests easier than it is done currently
with BPF_RAW_INSN-series macros.
One can follow the steps below to add new tests of such kind:
- add a topic file under bpf/progs/ directory;
- define test programs using naked functions and inline assembly:
#include <linux/bpf.h>
#include "bpf_misc.h"
SEC(...)
__naked int foo_test(void)
{
asm volatile(
"r0 = 0;"
"exit;"
::: __clobber_all);
}
- add skeleton and runner functions in prog_tests/verifier.c:
#include "topic.skel.h"
TEST_SET(topic)
After these steps the test_progs binary would include the topic tests.
Topic tests could be selectively executed using the following command:
$ ./test_progs -vvv -a topic
These changes are suggested by Andrii Nakryiko.
[1] https://lore.kernel.org/bpf/CAEf4BzYN1JmY9t03pnCHc4actob80wkBz2vk90ihJCBzi8CT9w@xxxxxxxxxxxxxx/
[2] https://lore.kernel.org/bpf/CAEf4BzYPsDWdRgx+ND1wiKAB62P=WwoLhr2uWkbVpQfbHqi1oA@xxxxxxxxxxxxxx/
[3] https://gcc.gnu.org/onlinedocs/gcc/Basic-Asm.html#Basic-Asm
Eduard Zingerman (4):
selftests/bpf: support for BPF_F_TEST_STATE_FREQ in test_loader
selftests/bpf: convenience macro for use with 'asm volatile' blocks
bpf: reduce BPF_ID_MAP_SIZE to fit only valid programs
selftests/bpf: check if verifier.c:check_ids() handles 64+5 ids
include/linux/bpf_verifier.h | 4 +-
kernel/bpf/verifier.c | 6 +-
.../selftests/bpf/prog_tests/verifier.c | 12 +++
tools/testing/selftests/bpf/progs/bpf_misc.h | 7 ++
.../selftests/bpf/progs/check_ids_limits.c | 77 +++++++++++++++++++
tools/testing/selftests/bpf/test_loader.c | 10 +++
6 files changed, 112 insertions(+), 4 deletions(-)
create mode 100644 tools/testing/selftests/bpf/prog_tests/verifier.c
create mode 100644 tools/testing/selftests/bpf/progs/check_ids_limits.c
--
2.38.2
