selftests/bpf: do not pass NULL for non-nullable params in dummy_st_ops

dummy_st_ops.test_2 and dummy_st_ops.test_sleepable do not have their
'state' parameter marked as nullable. Update dummy_st_ops.c to avoid
passing NULL for such parameters, as the next patch would allow kernel
to enforce this restriction.

Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20240424012821.595216-4-eddyz87@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

selftests/bpf: adjust dummy_st_ops_success to detect additional error

As reported by Jose E. Marchesi in off-list discussion, GCC and LLVM
generate slightly different code for dummy_st_ops_success/test_1():

SEC("struct_ops/test_1")
int BPF_PROG(test_1, struct bpf_dummy_ops_state *state)
{
int ret;

if (!state)
return 0xf2f3f4f5;

ret = state->val;
state->val = 0x5a;
return ret;
}

GCC-generated LLVM-generated
---------------------------- ---------------------------
0: r1 = *(u64 *)(r1 + 0x0) 0: w0 = -0xd0c0b0b
1: if r1 == 0x0 goto 5f 1: r1 = *(u64 *)(r1 + 0x0)
2: r0 = *(s32 *)(r1 + 0x0) 2: if r1 == 0x0 goto 6f
3: *(u32 *)(r1 + 0x0) = 0x5a 3: r0 = *(u32 *)(r1 + 0x0)
4: exit 4: w2 = 0x5a
5: r0 = -0xd0c0b0b 5: *(u32 *)(r1 + 0x0) = r2
6: exit 6: exit

If the 'state' argument is not marked as nullable in
net/bpf/bpf_dummy_struct_ops.c, the verifier would assume that
'r1 == 0x0' is never true:
- for the GCC version, this means that instructions #5-6 would be
marked as dead and removed;
- for the LLVM version, all instructions would be marked as live.

The test dummy_st_ops/dummy_init_ret_value actually sets the 'state'
parameter to NULL.

Therefore, when the 'state' argument is not marked as nullable,
the GCC-generated version of the code would trigger a NULL pointer
dereference at instruction #3.

This patch updates the test_1() test case to always follow a shape
similar to the GCC-generated version above, in order to verify whether
the 'state' nullability is marked correctly.

Reported-by: Jose E. Marchesi <jemarch@gnu.org>
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20240424012821.595216-3-eddyz87@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

bpf/selftests: Verify struct_ops prog sleepable behavior

In a set of prior changes, we added the ability for struct_ops programs
to be sleepable. This patch enhances the dummy_st_ops selftest suite to
validate this behavior by adding a new sleepable struct_ops entry to
dummy_st_ops.

Signed-off-by: David Vernet <void@manifault.com>
Link: https://lore.kernel.org/r/20230125164735.785732-5-void@manifault.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>