Partially revert 94dfc73e7c ("treewide: uapi: Replace zero-length arrays
with flexible-array members") given it breaks BPF UAPI.
For example, BPF CI run reveals build breakage under LLVM:
[...]
CLNG-BPF [test_maps] map_ptr_kern.o
CLNG-BPF [test_maps] btf__core_reloc_arrays___diff_arr_val_sz.o
CLNG-BPF [test_maps] test_bpf_cookie.o
progs/map_ptr_kern.c:314:26: error: field 'trie_key' with variable sized type 'struct bpf_lpm_trie_key' not at the end of a struct or class is a GNU extension [-Werror,-Wgnu-variable-sized-type-not-at-end]
struct bpf_lpm_trie_key trie_key;
^
CLNG-BPF [test_maps] btf__core_reloc_type_based___diff.o
1 error generated.
make: *** [Makefile:521: /tmp/runner/work/bpf/bpf/tools/testing/selftests/bpf/map_ptr_kern.o] Error 1
make: *** Waiting for unfinished jobs....
[...]
Typical usage of the bpf_lpm_trie_key is that the struct gets embedded into
a user defined key for the LPM BPF map, from the selftest example:
struct bpf_lpm_trie_key { <-- UAPI exported struct
__u32 prefixlen;
__u8 data[];
};
struct lpm_key { <-- BPF program defined struct
struct bpf_lpm_trie_key trie_key;
__u32 data;
};
Undo this for BPF until a different solution can be found. It's the only flexible-
array member case in the UAPI header.
This was discovered in BPF CI after Dave reported that the include/uapi/linux/bpf.h
header was out of sync with tools/include/uapi/linux/bpf.h after 94dfc73e7c. And
the subsequent sync attempt failed CI.
Fixes: 94dfc73e7c ("treewide: uapi: Replace zero-length arrays with flexible-array members")
Reported-by: Dave Marchevsky <davemarchevsky@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Cc: Gustavo A. R. Silva <gustavoars@kernel.org>
Link: https://lore.kernel.org/bpf/22aebc88-da67-f086-e620-dd4a16e2bc69@iogearbox.net
3024d95a4c