Alan Maguire <alan.maguire@xxxxxxxxxx> writes: > Recently issues were observed with module BTF deduplication failures > [1]. Add a dedup selftest that ensures that core kernel types are > referenced from split BTF as base BTF types. To do this use bpf_testmod > functions which utilize core kernel types, specifically > > ssize_t > bpf_testmod_test_write(struct file *file, struct kobject *kobj, > struct bin_attribute *bin_attr, > char *buf, loff_t off, size_t len); > > __bpf_kfunc struct sock *bpf_kfunc_call_test3(struct sock *sk); > > __bpf_kfunc void bpf_kfunc_call_test_pass_ctx(struct __sk_buff *skb); > > For each of these ensure that the types they reference - > struct file, struct kobject, struct bin_attr etc - are in base BTF. > Note that because bpf_testmod.ko is built with distilled base BTF > the associated reference types - i.e. the PTR that points at a > "struct file" - will be in split BTF. As a result the test resolves > typedef and pointer references and verifies the pointed-at or > typedef'ed type is in base BTF. Because we use BTF from > /sys/kernel/btf/bpf_testmod relocation has occurred for the > referenced types and they will be base - not distilled base - types. > > For large-scale dedup issues, we see such types appear in split BTF and > as a result this test fails. Hence it is proposed as a test which will > fail when large-scale dedup issues have occurred. > > [1] https://lore.kernel.org/dwarves/CAADnVQL+-LiJGXwxD3jEUrOonO-fX0SZC8496dVzUXvfkB7gYQ@xxxxxxxxxxxxxx/ > > Signed-off-by: Alan Maguire <alan.maguire@xxxxxxxxxx> > --- The test passes for LLVM and fails for gcc 14, when using pahole w/o fixes discussed in [1]. Acked-by: Eduard Zingerman <eddyz87@xxxxxxxxx>
