The second argument of the bpf_kptr_xchg() helper function is
ARG_PTR_TO_BTF_ID_OR_NULL. A recent patch fixed a bug whereby the
verifier would fail with an internal error message if a program invoked
the helper with a PTR_TO_BTF_ID | PTR_MAYBE_NULL register. This testcase
adds some testcases to ensure that it fails gracefully moving forward.
Before the fix, these testcases would have failed an error resembling
the following:
; p = bpf_kfunc_call_test_acquire(&(unsigned long){0});
99: (7b) *(u64 *)(r10 -16) = r7 ; frame1: ...
100: (bf) r1 = r10 ; frame1: ...
101: (07) r1 += -16 ; frame1: ...
; p = bpf_kfunc_call_test_acquire(&(unsigned long){0});
102: (85) call bpf_kfunc_call_test_acquire#13908
; frame1: R0_w=ptr_or_null_prog_test_ref_kfunc...
; p = bpf_kptr_xchg(&v->ref_ptr, p);
103: (bf) r1 = r6 ; frame1: ...
104: (bf) r2 = r0
; frame1: R0_w=ptr_or_null_prog_test_ref_kfunc...
105: (85) call bpf_kptr_xchg#194
verifier internal error: invalid PTR_TO_BTF_ID register for type match
Signed-off-by: David Vernet <void@manifault.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20230330145203.80506-2-void@manifault.com
Now that struct bpf_cpumask is RCU safe, there's no need for this kfunc.
Rather than doing the following:
private(MASK) static struct bpf_cpumask __kptr *global;
int BPF_PROG(prog, s32 cpu, ...)
{
struct bpf_cpumask *cpumask;
bpf_rcu_read_lock();
cpumask = bpf_cpumask_kptr_get(&global);
if (!cpumask) {
bpf_rcu_read_unlock();
return -1;
}
bpf_cpumask_setall(cpumask);
...
bpf_cpumask_release(cpumask);
bpf_rcu_read_unlock();
}
Programs can instead simply do (assume same global cpumask):
int BPF_PROG(prog, ...)
{
struct bpf_cpumask *cpumask;
bpf_rcu_read_lock();
cpumask = global;
if (!cpumask) {
bpf_rcu_read_unlock();
return -1;
}
bpf_cpumask_setall(cpumask);
...
bpf_rcu_read_unlock();
}
In other words, no extra atomic acquire / release, and less boilerplate
code.
This patch removes both the kfunc, as well as its selftests and
documentation.
Signed-off-by: David Vernet <void@manifault.com>
Link: https://lore.kernel.org/r/20230316054028.88924-5-void@manifault.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Now that struct bpf_cpumask * is considered an RCU-safe type according
to the verifier, we should add tests that validate its common usages.
This patch adds those tests to the cpumask test suite. A subsequent
changes will remove bpf_cpumask_kptr_get(), and will adjust the selftest
and BPF documentation accordingly.
Signed-off-by: David Vernet <void@manifault.com>
Link: https://lore.kernel.org/r/20230316054028.88924-4-void@manifault.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Once we enable -Wall for BPF sources, compiler will complain about lots
of unused variables, variables that are set but never read, etc.
Fix all these issues first before enabling -Wall in Makefile.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20230309054015.4068562-4-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
bpf_rcu_read_lock/unlock() are only available in clang compiled kernels. Lack
of such key mechanism makes it impossible for sleepable bpf programs to use RCU
pointers.
Allow bpf_rcu_read_lock/unlock() in GCC compiled kernels (though GCC doesn't
support btf_type_tag yet) and allowlist certain field dereferences in important
data structures like tast_struct, cgroup, socket that are used by sleepable
programs either as RCU pointer or full trusted pointer (which is valid outside
of RCU CS). Use BTF_TYPE_SAFE_RCU and BTF_TYPE_SAFE_TRUSTED macros for such
tagging. They will be removed once GCC supports btf_type_tag.
With that refactor check_ptr_to_btf_access(). Make it strict in enforcing
PTR_TRUSTED and PTR_UNTRUSTED while deprecating old PTR_TO_BTF_ID without
modifier flags. There is a chance that this strict enforcement might break
existing programs (especially on GCC compiled kernels), but this cleanup has to
start sooner than later. Note PTR_TO_CTX access still yields old deprecated
PTR_TO_BTF_ID. Once it's converted to strict PTR_TRUSTED or PTR_UNTRUSTED the
kfuncs and helpers will be able to default to KF_TRUSTED_ARGS. KF_RCU will
remain as a weaker version of KF_TRUSTED_ARGS where obj refcnt could be 0.
Adjust rcu_read_lock selftest to run on gcc and clang compiled kernels.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: David Vernet <void@manifault.com>
Link: https://lore.kernel.org/bpf/20230303041446.3630-7-alexei.starovoitov@gmail.com
A recent patch added a new set of kfuncs for allocating, freeing,
manipulating, and querying cpumasks. This patch adds a new 'cpumask'
selftest suite which verifies their behavior.
Signed-off-by: David Vernet <void@manifault.com>
Link: https://lore.kernel.org/r/20230125143816.721952-5-void@manifault.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
