selftests/bpf: Skip callback tests if jit is disabled in test_verifier

If CONFIG_BPF_JIT_ALWAYS_ON is not set and bpf_jit_enable is 0, there
exist 6 failed tests.

[root@linux bpf]# echo 0 > /proc/sys/net/core/bpf_jit_enable
[root@linux bpf]# echo 0 > /proc/sys/kernel/unprivileged_bpf_disabled
[root@linux bpf]# ./test_verifier | grep FAIL
#106/p inline simple bpf_loop call FAIL
#107/p don't inline bpf_loop call, flags non-zero FAIL
#108/p don't inline bpf_loop call, callback non-constant FAIL
#109/p bpf_loop_inline and a dead func FAIL
#110/p bpf_loop_inline stack locations for loop vars FAIL
#111/p inline bpf_loop call in a big program FAIL
Summary: 768 PASSED, 15 SKIPPED, 6 FAILED

The test log shows that callbacks are not allowed in non-JITed programs,
interpreter doesn't support them yet, thus these tests should be skipped
if jit is disabled.

Add an explicit flag F_NEEDS_JIT_ENABLED to those tests to mark that they
require JIT enabled in bpf_loop_inline.c, check the flag and jit_disabled
at the beginning of do_test_single() to handle this case.

With this patch:

[root@linux bpf]# echo 0 > /proc/sys/net/core/bpf_jit_enable
[root@linux bpf]# echo 0 > /proc/sys/kernel/unprivileged_bpf_disabled
[root@linux bpf]# ./test_verifier | grep FAIL
Summary: 768 PASSED, 21 SKIPPED, 0 FAILED

Suggested-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20240123090351.2207-3-yangtiezhu@loongson.cn

selftests/bpf: Fix test_verifier failed test in unprivileged mode

Loading the BTF won't be permitted without privileges, hence only test
for privileged mode by setting the prog type. This makes the
test_verifier show 0 failures when unprivileged BPF is enabled.

Fixes: 41188e9e9def ("selftest/bpf: Test for use-after-free bug fix in inline_bpf_loop")
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20220721134245.2450-14-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

selftest/bpf: Test for use-after-free bug fix in inline_bpf_loop

This test verifies that bpf_loop() inlining works as expected when
address of `env->prog` is updated. This address is updated upon BPF
program reallocation.

Reallocation is handled by bpf_prog_realloc(), which reuses old memory
if page boundary is not crossed. The value of `len` in the test is
chosen to cross this boundary on bpf_loop() patching.

Verify that the use-after-free bug in inline_bpf_loop() reported by
Dan Carpenter is fixed.

Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20220624020613.548108-3-eddyz87@gmail.com

selftests/bpf: BPF test_verifier selftests for bpf_loop inlining

A number of test cases for BPF selftests test_verifier to check how
bpf_loop inline transformation rewrites the BPF program. The following
cases are covered:
- happy path
- no-rewrite when flags is non-zero
- no-rewrite when callback is non-constant
- subprogno in insn_aux is updated correctly when dead sub-programs
are removed
- check that correct stack offsets are assigned for spilling of R6-R8
registers

Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/r/20220620235344.569325-5-eddyz87@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>