On 1/12/24 4:10 AM, Andrey Grafin wrote:
This patch allows to create BPF_MAP_TYPE_ARRAY_OF_MAPS and
BPF_MAP_TYPE_HASH_OF_MAPS with values of BPF_MAP_TYPE_PERF_EVENT_ARRAY.
Previous behaviour created a zero filled btf_map_def for inner maps and
tried to use it for a map creation but the linux kernel forbids to create
a BPF_MAP_TYPE_PERF_EVENT_ARRAY map with max_entries=0.
A simple bpf snippet to reproduce:
struct inner_map {
__uint(type, BPF_MAP_TYPE_PERF_EVENT_ARRAY);
__uint(key_size, sizeof(int));
__uint(value_size, sizeof(u32));
} inner_map0 SEC(".maps"), inner_map1 SEC(".maps");
struct {
__uint(type, BPF_MAP_TYPE_ARRAY_OF_MAPS);
__uint(max_entries, 2);
__type(key, u32);
__array(values, struct inner_map);
} outer_map SEC(".maps") = {
.values = {&inner_map0, &inner_map1}};
...
Previous behaviour:
# sudo bpftool prog load ./bpf_sample.elf /sys/fs/bpf/test
libbpf: map 'outer_map': failed to create inner map: -22
libbpf: map 'outer_map': failed to create: Invalid argument(-22)
libbpf: failed to load object './bpf_sample.elf'
Error: failed to load object file
# sudo strace -e bpf bpftool prog load ./bpf_sample.elf /sys/fs/bpf/test
...
bpf(BPF_MAP_CREATE, {map_type=BPF_MAP_TYPE_PERF_EVENT_ARRAY, key_size=4,
value_size=4, max_entries=16, map_flags=0, inner_map_fd=0,
map_name="inner_map0", map_ifindex=0, btf_fd=0, btf_key_type_id=0,
btf_value_type_id=0, btf_vmlinux_value_type_id=0, map_extra=0}, 72) = 4
bpf(BPF_MAP_CREATE, {map_type=BPF_MAP_TYPE_PERF_EVENT_ARRAY, key_size=4,
value_size=4, max_entries=16, map_flags=0, inner_map_fd=0,
map_name="inner_map1", map_ifindex=0, btf_fd=0, btf_key_type_id=0,
btf_value_type_id=0, btf_vmlinux_value_type_id=0, map_extra=0}, 72) = 5
bpf(BPF_MAP_CREATE, {map_type=BPF_MAP_TYPE_PERF_EVENT_ARRAY, key_size=4,
value_size=4, max_entries=0, map_flags=0, inner_map_fd=0,
map_name="outer_map.inner", map_ifindex=0, btf_fd=0,
btf_key_type_id=0, btf_value_type_id=0, btf_vmlinux_value_type_id=0,
map_extra=0}, 72) = -1 EINVAL (Invalid argument)
The change makes sense. Please help to add a real selftest to catch future
regression. I believe it is what Yonghong has already asked in v1. Some of the
existing "progs/*map_in_map*.c" may be a good candidate to add this test case.
pw-bot: cr
