elf: support bpf object linking (bpftool gen object) #466
Description
libbpf has added support for weak symbols, which end up in ELF with an STB_WEAK binding.
libbpf commits that might be relevant due to mentioning STB_WEAK:
- torvalds/linux@166750b (adds LINUX_KERNEL_VERSION)
- torvalds/linux@386b1d2
linked_maps.c fails due to:
struct {
__uint(type, BPF_MAP_TYPE_ARRAY);
__type(key, int);
__type(value, int);
__uint(max_entries, 16);
} map_weak __weak SEC(".maps");linked_funcs.c:
/* this weak instance should win because it's the first one */
__weak int set_output_weak(int x)
{
output_weak1 = x;
return x;
}There is also the following, not sure if that needs additional code:
/* here we'll force set_output_ctx2() to be __hidden in the final obj file */
__attribute__((visibility("hidden"))) extern void set_output_ctx2(__u64 *ctx);