selftests/bpf: Use __NR_prlimit64 instead of __NR_getrlimit in user_ringbuf test

After commit 80d7da1cac62 ("asm-generic: Drop getrlimit and setrlimit
syscalls from default list"), new architectures won't need to include
getrlimit and setrlimit, they are superseded with prlimit64.

In order to maintain compatibility for the new architectures, such as
LoongArch which does not define __NR_getrlimit, it is better to use
__NR_prlimit64 instead of __NR_getrlimit in user_ringbuf test to fix
the following build error:

TEST-OBJ [test_progs] user_ringbuf.test.o
tools/testing/selftests/bpf/prog_tests/user_ringbuf.c: In function 'kick_kernel_cb':
tools/testing/selftests/bpf/prog_tests/user_ringbuf.c:593:17: error: '__NR_getrlimit' undeclared (first use in this function)
593 | syscall(__NR_getrlimit);
| ^~~~~~~~~~~~~~
tools/testing/selftests/bpf/prog_tests/user_ringbuf.c:593:17: note: each undeclared identifier is reported only once for each function it appears in
make: *** [Makefile:573: tools/testing/selftests/bpf/user_ringbuf.test.o] Error 1
make: Leaving directory 'tools/testing/selftests/bpf'

Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/1677235015-21717-4-git-send-email-yangtiezhu@loongson.cn

selftests/bpf: Clean up user_ringbuf, cgrp_kfunc, kfunc_dynptr_param tests

Clean up user_ringbuf, cgrp_kfunc, and kfunc_dynptr_param tests to use
the generic verification tester for checking verifier rejections.
The generic verification tester uses btf_decl_tag-based annotations
for verifying that the tests fail with the expected log messages.

Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
Acked-by: David Vernet <void@manifault.com>
Reviewed-by: Roberto Sassu <roberto.sassu@huawei.com>
Link: https://lore.kernel.org/r/20230214051332.4007131-1-joannelkoong@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

selftests/bpf: Add test for dynptr reinit in user_ringbuf callback

The original support for bpf_user_ringbuf_drain callbacks simply
short-circuited checks for the dynptr state, allowing users to pass
PTR_TO_DYNPTR (now CONST_PTR_TO_DYNPTR) to helpers that initialize a
dynptr. This bug would have also surfaced with other dynptr helpers in
the future that changed dynptr view or modified it in some way.

Include test cases for all cases, i.e. both bpf_dynptr_from_mem and
bpf_ringbuf_reserve_dynptr, and ensure verifier rejects both of them.
Without the fix, both of these programs load and pass verification.

While at it, remove sys_nanosleep target from failure cases' SEC
definition, as there is no such tracepoint.

Acked-by: David Vernet <void@manifault.com>
Acked-by: Joanne Koong <joannelkoong@gmail.com>
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20221207204141.308952-8-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

bpf: Rework process_dynptr_func

Recently, user ringbuf support introduced a PTR_TO_DYNPTR register type
for use in callback state, because in case of user ringbuf helpers,
there is no dynptr on the stack that is passed into the callback. To
reflect such a state, a special register type was created.

However, some checks have been bypassed incorrectly during the addition
of this feature. First, for arg_type with MEM_UNINIT flag which
initialize a dynptr, they must be rejected for such register type.
Secondly, in the future, there are plans to add dynptr helpers that
operate on the dynptr itself and may change its offset and other
properties.

In all of these cases, PTR_TO_DYNPTR shouldn't be allowed to be passed
to such helpers, however the current code simply returns 0.

The rejection for helpers that release the dynptr is already handled.

For fixing this, we take a step back and rework existing code in a way
that will allow fitting in all classes of helpers and have a coherent
model for dealing with the variety of use cases in which dynptr is used.

First, for ARG_PTR_TO_DYNPTR, it can either be set alone or together
with a DYNPTR_TYPE_* constant that denotes the only type it accepts.

Next, helpers which initialize a dynptr use MEM_UNINIT to indicate this
fact. To make the distinction clear, use MEM_RDONLY flag to indicate
that the helper only operates on the memory pointed to by the dynptr,
not the dynptr itself. In C parlance, it would be equivalent to taking
the dynptr as a point to const argument.

When either of these flags are not present, the helper is allowed to
mutate both the dynptr itself and also the memory it points to.
Currently, the read only status of the memory is not tracked in the
dynptr, but it would be trivial to add this support inside dynptr state
of the register.

With these changes and renaming PTR_TO_DYNPTR to CONST_PTR_TO_DYNPTR to
better reflect its usage, it can no longer be passed to helpers that
initialize a dynptr, i.e. bpf_dynptr_from_mem, bpf_ringbuf_reserve_dynptr.

A note to reviewers is that in code that does mark_stack_slots_dynptr,
and unmark_stack_slots_dynptr, we implicitly rely on the fact that
PTR_TO_STACK reg is the only case that can reach that code path, as one
cannot pass CONST_PTR_TO_DYNPTR to helpers that don't set MEM_RDONLY. In
both cases such helpers won't be setting that flag.

The next patch will add a couple of selftest cases to make sure this
doesn't break.

Fixes: 205715673844 ("bpf: Add bpf_user_ringbuf_drain() helper")
Acked-by: Joanne Koong <joannelkoong@gmail.com>
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20221207204141.308952-4-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

selftests/bpf: Add selftests validating the user ringbuf

This change includes selftests that validate the expected behavior and
APIs of the new BPF_MAP_TYPE_USER_RINGBUF map type.

Signed-off-by: David Vernet <void@manifault.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20220920000100.477320-5-void@manifault.com