Public bug reported: We've seen kernel module size getting larger since 6.15, and this is due to a deduplication failure in libbpf. This means that the installed size of modules has gone up from ~160MB to ~270MB.
The fix is: https://github.com/libbpf/libbpf/commit/c8a28812fbe1af6ff0cbd92edb88c6fcc2291737 libbpf: Add identical pointer detection to btf_dedup_is_equiv() Recently as a side-effect of commit ac053946f5c4 ("compiler.h: introduce TYPEOF_UNQUAL() macro") issues were observed in deduplication between modules and kernel BTF such that a large number of kernel types were not deduplicated so were found in module BTF (task_struct, bpf_prog etc). The root cause appeared to be a failure to dedup struct types, specifically those with members that were pointers with __percpu annotations. The issue in dedup is at the point that we are deduplicating structures, we have not yet deduplicated reference types like pointers. If multiple copies of a pointer point at the same (deduplicated) integer as in this case, we do not see them as identical. Special handling already exists to deal with structures and arrays, so add pointer handling here too. Reported-by: Alexei Starovoitov <[email protected]> Signed-off-by: Alan Maguire <[email protected]> Signed-off-by: Andrii Nakryiko <[email protected]> Link: https://lore.kernel.org/bpf/[email protected] We need to update libbpf to >= 1.6.x, by syncing an updated package from Debian. ** Affects: libbpf (Ubuntu) Importance: Undecided Status: In Progress ** Package changed: linux (Ubuntu) => libbpf (Ubuntu) ** Changed in: libbpf (Ubuntu) Status: New => In Progress -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/2122094 Title: module size bump since 6.15 Status in libbpf package in Ubuntu: In Progress Bug description: We've seen kernel module size getting larger since 6.15, and this is due to a deduplication failure in libbpf. This means that the installed size of modules has gone up from ~160MB to ~270MB. The fix is: https://github.com/libbpf/libbpf/commit/c8a28812fbe1af6ff0cbd92edb88c6fcc2291737 libbpf: Add identical pointer detection to btf_dedup_is_equiv() Recently as a side-effect of commit ac053946f5c4 ("compiler.h: introduce TYPEOF_UNQUAL() macro") issues were observed in deduplication between modules and kernel BTF such that a large number of kernel types were not deduplicated so were found in module BTF (task_struct, bpf_prog etc). The root cause appeared to be a failure to dedup struct types, specifically those with members that were pointers with __percpu annotations. The issue in dedup is at the point that we are deduplicating structures, we have not yet deduplicated reference types like pointers. If multiple copies of a pointer point at the same (deduplicated) integer as in this case, we do not see them as identical. Special handling already exists to deal with structures and arrays, so add pointer handling here too. Reported-by: Alexei Starovoitov <[email protected]> Signed-off-by: Alan Maguire <[email protected]> Signed-off-by: Andrii Nakryiko <[email protected]> Link: https://lore.kernel.org/bpf/[email protected] We need to update libbpf to >= 1.6.x, by syncing an updated package from Debian. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/libbpf/+bug/2122094/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : [email protected] Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
