libbpf report error: kernel doesn't support global data

[li-xilin]

my kernel release:

~ # uname -a
Linux (none) 4.18.0 #10 SMP Fri Jul 26 10:32:39 CST 2024 x86_64 GNU/Linux

libbpf version is 0.3, to adapt to the version of 4.18 kernel.

...

struct {
	__uint(type, BPF_MAP_TYPE_PERF_EVENT_ARRAY);
	__uint(max_entries, 128);
	__type(key, __u32);
	__type(value, __u32);
} events SEC(".maps");

struct event {
	uint32_t pid;
	uint32_t crc;
	char name[32];
};

SEC("tracepoint/syscalls/sys_exit_init_module")
int func3(struct finit_module_args *ctx)
{
	struct event ev = { .name = "__finished"};
	ev.crc = 0;
	ev.pid = bpf_get_current_pid_tgid();
	// bpf_perf_event_output(ctx, &events, BPF_F_CURRENT_CPU, &ev, sizeof(ev));
	return 0;
}

the code above works fine, but when I enable the commented line bpf_perf_event_output(ctx, &events, BPF_F_CURRENT_CPU, &ev, sizeof(ev));

error occured.

libbpf: loading object '538580-4440' from buffer
libbpf: elf: section(3) kprobe/find_symbol, size 440, link 0, flags 6, type=1
libbpf: sec 'kprobe/find_symbol': found program 'func1' at insn offset 0 (0 bytes), code size 55 insns (440 bytes)
libbpf: elf: section(4) .relkprobe/find_symbol, size 16, link 31, flags 0, type=9
libbpf: elf: section(5) kretprobe/find_symbol, size 144, link 0, flags 6, type=1
libbpf: sec 'kretprobe/find_symbol': found program 'func2' at insn offset 0 (0 bytes), code size 18 insns (144 bytes)
libbpf: elf: section(6) .relkretprobe/find_symbol, size 16, link 31, flags 0, type=9
libbpf: elf: section(7) tracepoint/syscalls/sys_exit_init_module, size 216, link 0, flags 6, type=1
libbpf: sec 'tracepoint/syscalls/sys_exit_init_module': found program 'func3' at insn offset 0 (0 bytes), code size 27 insns (21)
libbpf: elf: section(8) .reltracepoint/syscalls/sys_exit_init_module, size 16, link 31, flags 0, type=9
libbpf: elf: section(9) .maps.events, size 8, link 0, flags 3, type=1
libbpf: elf: skipping unrecognized data section(9) .maps.events
libbpf: elf: section(10) .maps.param_array, size 280, link 0, flags 3, type=1
libbpf: elf: skipping unrecognized data section(10) .maps.param_array
libbpf: elf: section(11) .rodata, size 40, link 0, flags 2, type=1
libbpf: elf: section(12) .maps, size 64, link 0, flags 3, type=1
libbpf: elf: section(13) license, size 4, link 0, flags 3, type=1
libbpf: license of 538580-4440 is GPL
libbpf: elf: section(22) .BTF, size 2850, link 0, flags 0, type=1
libbpf: elf: section(24) .BTF.ext, size 576, link 0, flags 0, type=1
libbpf: elf: section(31) .symtab, size 2640, link 1, flags 0, type=2
libbpf: looking for externs among 110 symbols...
libbpf: collected 0 externs total
libbpf: map 'events': at sec_idx 12, offset 0.
libbpf: map 'events': found type = 4.
libbpf: map 'events': found max_entries = 128.
libbpf: map 'events': found key [1], sz = 4.
libbpf: map 'events': found value [1], sz = 4.
libbpf: map 'param_array': at sec_idx 12, offset 32.
libbpf: map 'param_array': found type = 2.
libbpf: map 'param_array': found max_entries = 1.
libbpf: map 'param_array': found key [1], sz = 4.
libbpf: map 'param_array': found value [7], sz = 272.
libbpf: map '538580_4.rodata' (global data): at sec_idx 11, offset 0, flags 480.
libbpf: map 2 is "538580_4.rodata"
libbpf: sec '.relkprobe/find_symbol': collecting relocation for section(3) 'kprobe/find_symbol'
libbpf: sec '.relkprobe/find_symbol': relo #0: insn #48 against 'param_array'
libbpf: prog 'func1': found map 1 (param_array, sec 12, off 32) for insn #48
libbpf: sec '.relkretprobe/find_symbol': collecting relocation for section(5) 'kretprobe/find_symbol'
libbpf: sec '.relkretprobe/find_symbol': relo #0: insn #6 against 'param_array'
libbpf: prog 'func2': found map 1 (param_array, sec 12, off 32) for insn #6
libbpf: sec '.reltracepoint/syscalls/sys_exit_init_module': collecting relocation for section(7) 'tracepoint/syscalls/sys_exit_i'
libbpf: sec '.reltracepoint/syscalls/sys_exit_init_module': relo #0: insn #19 against 'events'
libbpf: prog 'func3': found map 0 (events, sec 12, off 0) for insn #19
libbpf: kernel doesn't support global data
libbpf: failed to load object '538580-4440'

Thanks.

[yonghong-song]

See 'libbpf: kernel doesn't support global data'. You need newer kernel.