On 2/7/23 19:31, Alexei Starovoitov wrote:
On Tue, Feb 7, 2023 at 3:09 AM Justin Iurman <justin.iurman@xxxxxxxxx> wrote:Hello, CC'ing netdev as well, since I initially suspected an issue in iproute2. However, after having recompiled iproute2 with libbpf, I'm still stuck facing the same problem. Environment: - OS: Ubuntu 20.04.5 LTS - kernel: 5.4.0-137-generic x86_64 (CONFIG_DEBUG_INFO_BTF=y) - clang version 10.0.0-4ubuntu1 - iproute2-6.1.0, libbpf 1.2.0 (iproute2-ss200127 installed by default without libbpf) Note: same result with kernel 6.2.0-rc6+ (net-next), as a test to be aligned with latest iproute2 version (just in case). Long story short: I can't for the life of me make the ebpf program load correctly with tc. What's the cause? Well, a map, and the verifier doesn't like it. I must definitely be doing something wrong, but can't find what. Here is a reproducible and minimal example: #include "vmlinux.h" #include <bpf/bpf_helpers.h> #define TC_ACT_OK 0 #define MAX_BYTES 2048 char _license[] SEC("license") = "GPL"; struct mystruct_t { __u8 bytes[MAX_BYTES]; }; struct { __uint(type, BPF_MAP_TYPE_PERCPU_ARRAY); __uint(key_size, sizeof(__u8)); __uint(value_size, sizeof(struct mystruct_t)); __uint(max_entries, 1); } percpu_map SEC(".maps"); SEC("egress") int xxx(struct __sk_buff *skb) { __u8 idx = 0; struct mystruct_t *x = bpf_map_lookup_elem(&percpu_map, &idx); return TC_ACT_OK; } Here is how I compile the whole thing: git clone --recursive --depth 1 https://github.com/libbpf/libbpf ./deps/libbpf make -j -C deps/libbpf/src/ BUILD_STATIC_ONLY=y DESTDIR="build" INCLUDEDIR= LIBDIR= UAPIDIR= install git clone --recursive --depth 1 https://github.com/libbpf/bpftool ./deps/bpftool make -j -C deps/bpftool/src/ deps/bpftool/src/bpftool btf dump file /sys/kernel/btf/vmlinux format c > build/vmlinux.h clang -g -O2 -Wall -Wextra -target bpf -D__TARGET_ARCH_x86_64 -I build/ -c program.c -o build/program.o I noticed that "clang-bpf-co-re" is OFF when compiling bpftool, don't know if it's part of the problem or not. Here is what the "build" directory looks like after that: $ ls -al build [...] drwxr-xr-x 2 justin justin 4096 fév 6 18:20 bpf -rw-rw-r-- 1 justin justin 3936504 fév 6 18:20 libbpf.a drwxr-xr-x 2 justin justin 4096 fév 6 18:20 pkgconfig -rw-rw-r-- 1 justin justin 10592 fév 7 10:42 program.o -rw-rw-r-- 1 justin justin 2467774 fév 7 10:42 vmlinux.h And here is the verifier error I got when loading it with tc (qdisc clsact already attached): $ sudo ../deps/iproute2/tc/tc filter add dev eno2 egress bpf da obj program.o sec egress libbpf: map 'percpu_map': failed to create: Invalid argument(-22) libbpf: failed to load object 'program.o' Unable to load programIt's likely due to __uint(key_size, sizeof(__u8)); https://docs.kernel.org/bpf/map_array.html "The key type is an unsigned 32-bit integer (4 bytes) and the map is of constant size."
Sigh... don't know if I should laugh or cry. Thanks!
