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 23, 2025 at 11:42, "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 8:33 PM, Jiayuan Chen wrote:
> 
> > 
> > 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
> > 
> Please try pahole version 1.30.
> 
> > 
> > I updated LLVM via https://apt.llvm.org/. Could this be caused by some binaries or libraries still using LLVM 18?
> >
>


thanks, but version 1.30 didn't work in my tests - even pahole's master branch fails, only the next branch works...


It seems that the 'old' pahole parses some kfuncs incorrectly, for example bpf_dynptr_slice().


./tools/sbin/bpftool btf dump file ../../../../vmlinux | grep bpf_dynptr_slice -A 2
	'KF_bpf_dynptr_slice' val=23
	'KF_bpf_dynptr_slice_rdwr' val=24
	'KF_bpf_dynptr_clone' val=25
	'KF_bpf_percpu_obj_new_impl' val=26
--
[68242] FUNC 'bpf_dynptr_slice' type_id=68241 linkage=static              <- missing corresponding DECL_TAG ?
[68243] FUNC 'bpf_dynptr_slice_rdwr' type_id=68241 linkage=static
[68244] DECL_TAG 'bpf_kfunc' type_id=68243 component_idx=-1
[68245] FUNC_PROTO '(anon)' ret_type_id=38 vlen=5