bpf: provide a generic macro for percpu values for selftests
To overcome bugs as described and fixed in 89087c456fb5 ("bpf: Fix
values type used in test_maps"), provide a generic BPF_DECLARE_PERCPU()
and bpf_percpu() accessor macro for all percpu map values used in
tests.
Declaring variables works as follows (also works for structs):
BPF_DECLARE_PERCPU(uint32_t, my_value);
They can then be accessed normally as uint32_t type through:
bpf_percpu(my_value, <cpu_nr>)
For example:
bpf_percpu(my_value, 0)++;
Implicitly, we make sure that the passed type is allocated and aligned
by gcc at least on a 8-byte boundary, so that it works together with
the map lookup/update syscall for percpu maps. We use it as a usage
example in test_maps, so that others are free to adapt this into their
code when necessary.
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/tools/testing/selftests/bpf/bpf_util.h b/tools/testing/selftests/bpf/bpf_util.h
index 7de2796..369e7d7 100644
--- a/tools/testing/selftests/bpf/bpf_util.h
+++ b/tools/testing/selftests/bpf/bpf_util.h
@@ -54,4 +54,11 @@ static inline unsigned int bpf_num_possible_cpus(void)
return possible_cpus;
}
+#define __bpf_percpu_val_align __attribute__((__aligned__(8)))
+
+#define BPF_DECLARE_PERCPU(type, name) \
+ struct { type v; /* padding */ } __bpf_percpu_val_align \
+ name[bpf_num_possible_cpus()]
+#define bpf_percpu(name, cpu) name[(cpu)].v
+
#endif /* __BPF_UTIL__ */