selftests/bpf: Declare subprog_noise as static in tailcall_bpf2bpf4

Due to bpf_map_lookup_elem being declared static we need to also
declare subprog_noise as static.

Fixes the following error:
progs/tailcall_bpf2bpf4.c:26:9: error: 'bpf_map_lookup_elem' is static but used in inline function 'subprog_noise' which is not static [-Werror]
26 | bpf_map_lookup_elem(&nop_table, &key);
| ^~~~~~~~~~~~~~~~~~~

Signed-off-by: James Hilliard <james.hilliard1@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Song Liu <song@kernel.org>
Link: https://lore.kernel.org/bpf/20220826035141.737919-1-james.hilliard1@gmail.com

selftests/bpf: Switch SEC("classifier*") usage to a strict SEC("tc")

Convert all SEC("classifier*") uses to a new and strict SEC("tc")
section name. In reference_tracking selftests switch from ambiguous
searching by program title (section name) to non-ambiguous searching by
name in some selftests, getting closer to completely removing
bpf_object__find_program_by_title().

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210928161946.2512801-4-andrii@kernel.org

bpf: Selftest to verify mixing bpf2bpf calls and tailcalls with insn patch

This adds some extra noise to the tailcall_bpf2bpf4 tests that will cause
verify to patch insns. This then moves around subprog start/end insn
index and poke descriptor insn index to ensure that verify and JIT will
continue to track these correctly.

If done correctly verifier should pass this program same as before and
JIT should emit tail call logic.

Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20210707223848.14580-3-john.fastabend@gmail.com

selftests/bpf: Stop using static variables for passing data to/from user-space

In preparation of skipping emitting static variables in BPF skeletons, switch
all current selftests uses of static variables to pass data between BPF and
user-space to use global variables.

All non-read-only `static volatile` variables become just plain global
variables by dropping `static volatile` part.

Read-only `static volatile const` variables, though, still require `volatile`
modifier, otherwise compiler will ignore whatever values are set from
user-space.

Few static linker tests are using name-conflicting static variables to
validate that static linker still properly handles static variables and
doesn't trip up on name conflicts.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210507054119.270888-4-andrii@kernel.org

bpf, selftests: Use bpf_tail_call_static where appropriate

For those locations where we use an immediate tail call map index use the
newly added bpf_tail_call_static() helper.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/3cfb2b799a62d22c6e7ae5897c23940bdcc24cbc.1601477936.git.daniel@iogearbox.net

selftests/bpf: Add tailcall_bpf2bpf tests

Add four tests to tailcalls selftest explicitly named
"tailcall_bpf2bpf_X" as their purpose is to validate that combination
of tailcalls with bpf2bpf calls are working properly.
These tests also validate LD_ABS from subprograms.

Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>