selftests/bpf: Add kprobe_multi kmod attach api tests

Adding kprobe_multi kmod attach api tests that attach bpf_testmod
functions via bpf_program__attach_kprobe_multi_opts.

Running it as serial test, because we don't want other tests to
reload bpf_testmod while it's running.

Acked-by: Song Liu <song@kernel.org>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/r/20221025134148.3300700-9-jolsa@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

bpf: Adjust kprobe_multi entry_ip for CONFIG_X86_KERNEL_IBT

Martynas reported bpf_get_func_ip returning +4 address when
CONFIG_X86_KERNEL_IBT option is enabled.

When CONFIG_X86_KERNEL_IBT is enabled we'll have endbr instruction
at the function entry, which screws return value of bpf_get_func_ip()
helper that should return the function address.

There's short term workaround for kprobe_multi bpf program made by
Alexei [1], but we need this fixup also for bpf_get_attach_cookie,
that returns cookie based on the entry_ip value.

Moving the fixup in the fprobe handler, so both bpf_get_func_ip
and bpf_get_attach_cookie get expected function address when
CONFIG_X86_KERNEL_IBT option is enabled.

Also renaming kprobe_multi_link_handler entry_ip argument to fentry_ip
so it's clearer this is an ftrace __fentry__ ip.

[1] commit 7f0059b58f02 ("selftests/bpf: Fix kprobe_multi test.")

Cc: Peter Zijlstra <peterz@infradead.org>
Reported-by: Martynas Pumputis <m@lambda.lt>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/r/20220926153340.1621984-5-jolsa@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

selftests/bpf: Shuffle cookies symbols in kprobe multi test

There's a kernel bug that causes cookies to be misplaced and
the reason we did not catch this with this test is that we
provide bpf_fentry_test* functions already sorted by name.

Shuffling function bpf_fentry_test2 deeper in the list and
keeping the current cookie values as before will trigger
the bug.

The kernel fix is coming in following changes.

Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/r/20220615112118.497303-2-jolsa@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

selftests/bpf: Use target-less SEC() definitions in various tests

Add new or modify existing SEC() definitions to be target-less and
validate that libbpf handles such program definitions correctly.

For kprobe/kretprobe we also add explicit test that generic
bpf_program__attach() works in cases when kprobe definition contains
proper target. It wasn't previously tested as selftests code always
explicitly specified the target regardless.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20220428185349.3799599-4-andrii@kernel.org

selftests/bpf: Fix kprobe_multi test.

When compiler emits endbr insn the function address could
be different than what bpf_get_func_ip() reports.
This is a short term workaround.
bpf_get_func_ip() will be fixed later.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>

selftests/bpf: Add kprobe_multi bpf_cookie test

Adding bpf_cookie test for programs attached by kprobe_multi links.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20220316122419.933957-12-jolsa@kernel.org

selftests/bpf: Add kprobe_multi attach test

Adding kprobe_multi attach test that uses new fprobe interface to
attach kprobe program to multiple functions.

The test is attaching programs to bpf_fentry_test* functions and
uses single trampoline program bpf_prog_test_run to trigger
bpf_fentry_test* functions.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20220316122419.933957-11-jolsa@kernel.org