Re: [PATCH bpf-next v1] selftests/bpf: Guard addr_space_cast code with __BPF_FEATURE_ADDR_SPACE_CAST

["Jiayuan Chen" <jiayuan.chen@linux.dev>]

October 22, 2025 at 23:33, "Yonghong Song" <yonghong.song@linux.dev mailto:yonghong.song@linux.dev?to=%22Yonghong%20Song%22%20%3Cyonghong.song%40linux.dev%3E > wrote:


> 
> On 10/22/25 12:18 AM, Jiayuan Chen wrote:
> 
> > 
> > When compiling the BPF selftests with Clang versions that do not support

> If you are really using llvm18, then I found there are some other
> build failures as well, e.g.,
> 

Yes i'm using llvm18

> /home/yhs/work/bpf-next/tools/testing/selftests/bpf/bpf_arena_common.h:47:15: error: conflicting types for 'bpf_arena_alloc_pages'
>  47 | void __arena* bpf_arena_alloc_pages(void *map, void __arena *addr, __u32 page_cnt,
>  | ^
> /home/yhs/work/bpf-next/tools/testing/selftests/bpf/tools/include/vmlinux.h:160636:48: note: previous declaration is here
>  160636 | extern void __attribute__((address_space(1))) *bpf_arena_alloc_pages(void *p__map, void __attribute__((address_space(1))) *addr__ign, u32 page_cnt, int node_id, u64 flags) __weak __ksym;
>  | ^


I hadn't encountered this error before, but it started appearing after I upgraded LLVM to version 20.


$ make V=1

/home/chenjiayuan/code/upstream/bpf-next/tools/testing/selftests/bpf/tools/sbin/bpftool btf dump file /home/chenjiayuan/code/upstream/bpf-next/vmlinux format c > /home/chenjiayuan/code/upstream/bpf-next/tools/testing/selftests/bpf/tools/include/.vmlinux.h.tmp
cmp -s /home/chenjiayuan/code/upstream/bpf-next/tools/testing/selftests/bpf/tools/include/.vmlinux.h.tmp /home/chenjiayuan/code/upstream/bpf-next/tools/testing/selftests/bpf/tools/include/vmlinux.h || mv /home/chenjiayuan/code/upstream/bpf-next/tools/testing/selftests/bpf/tools/include/.vmlinux.h.tmp /home/chenjiayuan/code/upstream/bpf-next/tools/testing/selftests/bpf/tools/include/vmlinux.h
clang  -g -Wall -Werror -D__TARGET_ARCH_x86 -mlittle-endian -I/home/chenjiayuan/code/upstream/bpf-next/tools/testing/selftests/bpf/tools/include -I/home/chenjiayuan/code/upstream/bpf-next/tools/testing/selftests/bpf -I/home/chenjiayuan/code/upstream/bpf-next/tools/include/uapi -I/home/chenjiayuan/code/upstream/bpf-next/tools/testing/selftests/usr/include -std=gnu11 -fno-strict-aliasing -Wno-compare-distinct-pointer-types -idirafter /usr/lib/llvm-20/lib/clang/20/include -idirafter /usr/local/include -idirafter /usr/include/x86_64-linux-gnu -idirafter /usr/include    -DENABLE_ATOMICS_TESTS   -O2 --target=bpfel -c progs/stream.c -mcpu=v3 -o /home/chenjiayuan/code/upstream/bpf-next/tools/testing/selftests/bpf/stream.bpf.o
In file included from progs/stream.c:8:
/home/chenjiayuan/code/upstream/bpf-next/tools/testing/selftests/bpf/bpf_arena_common.h:47:15: error: conflicting types for 'bpf_arena_alloc_pages'
   47 | void __arena* bpf_arena_alloc_pages(void *map, void __arena *addr, __u32 page_cnt,
      |               ^
/home/chenjiayuan/code/upstream/bpf-next/tools/testing/selftests/bpf/tools/include/vmlinux.h:152158:14: note: previous declaration is here
 152158 | extern void *bpf_arena_alloc_pages(void *p__map, void *addr__ign, u32 page_cnt, int node_id, u64 flags) __weak __ksym;
        |              ^
In file included from progs/stream.c:8:
/home/chenjiayuan/code/upstream/bpf-next/tools/testing/selftests/bpf/bpf_arena_common.h:49:5: error: conflicting types for 'bpf_arena_reserve_pages'
   49 | int bpf_arena_reserve_pages(void *map, void __arena *addr, __u32 page_cnt) __ksym __weak;
      |     ^
/home/chenjiayuan/code/upstream/bpf-next/tools/testing/selftests/bpf/tools/include/vmlinux.h:152160:12: note: previous declaration is here
 152160 | extern int bpf_arena_reserve_pages(void *p__map, void *ptr__ign, u32 page_cnt) __weak __ksym;
        |            ^
In file included from progs/stream.c:8:
/home/chenjiayuan/code/upstream/bpf-next/tools/testing/selftests/bpf/bpf_arena_common.h:50:6: error: conflicting types for 'bpf_arena_free_pages'
   50 | void bpf_arena_free_pages(void *map, void __arena *ptr, __u32 page_cnt) __ksym __weak;
      |      ^
/home/chenjiayuan/code/upstream/bpf-next/tools/testing/selftests/bpf/tools/include/vmlinux.h:152159:13: note: previous declaration is here
 152159 | extern void bpf_arena_free_pages(void *p__map, void *ptr__ign, u32 page_cnt) __weak __ksym;
        |             ^
3 errors generated.
make: *** [Makefile:761: /home/chenjiayuan/code/upstream/bpf-next/tools/testing/selftests/bpf/stream.bpf.o] Error 1

$ clang --version
Ubuntu clang version 20.1.8 (++20250804090239+87f0227cb601-1~exp1~20250804210352.139)
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/lib/llvm-20/bin

$ pahole --version
v1.29


I updated LLVM via https://apt.llvm.org/. Could this be caused by some binaries or libraries still using LLVM 18?