On Fri, Jun 20, 2025 at 04:41:48PM +0100, Alan Maguire wrote: > On 20/06/2025 14:51, Jiri Olsa wrote: > > On Fri, Jun 20, 2025 at 03:34:14PM +0200, Jiri Olsa wrote: > >> On Wed, Apr 30, 2025 at 02:42:49PM +0100, Alan Maguire wrote: > >>> 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> > >> > >> hi Alan, > >> this one started to fail in my tests.. it's likely some screw up in > >> my environment, but I haven't found the cause yet, I'm using the > >> pahole 1.30 .. just cheking if it's known issue already ;-) > > > > hum, it might be my gcc-14 .. will upgrade > > > > hi Jiri, is it possible you were using the pre-dedup-fix pahole, i.e. > the official 1.30, or a version without > > commit 6362d1f1657e3381e3e622d70364145f72804504 > Author: Alan Maguire <alan.maguire@xxxxxxxxxx> > Date: Tue Apr 29 20:49:05 2025 +0100 > > pahole: Sync with libbpf mainline > > To pull in dedup fix in > > commit 8e64c387c942 ("libbpf: Add identical pointer detection to > btf_dedup_is_equiv()") > > sync with latest libbpf. > > ? That would mean you would hit the module dedup failure and the test > would fail as a result. If that's the case, if you could try syncing to > the "next" branch of pahole and see if it recurs, that would be great! > Thanks! yep, that helped, thank you jirka
