Message-ID: <84906f32-955d-4fda-b87d-56c052ddfd87@linux.dev>
Date: Wed, 22 Oct 2025 20:42:54 -0700
From: Yonghong Song <yonghong.song@...ux.dev>
To: Jiayuan Chen <jiayuan.chen@...ux.dev>, bpf@...r.kernel.org
Cc: Andrii Nakryiko <andrii@...nel.org>, Eduard Zingerman
 <eddyz87@...il.com>, Alexei Starovoitov <ast@...nel.org>,
 Daniel Borkmann <daniel@...earbox.net>,
 Martin KaFai Lau <martin.lau@...ux.dev>, Song Liu <song@...nel.org>,
 John Fastabend <john.fastabend@...il.com>, KP Singh <kpsingh@...nel.org>,
 Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>,
 Jiri Olsa <jolsa@...nel.org>, Shuah Khan <shuah@...nel.org>,
 Nathan Chancellor <nathan@...nel.org>,
 Nick Desaulniers <nick.desaulniers+lkml@...il.com>,
 Bill Wendling <morbo@...gle.com>, Justin Stitt <justinstitt@...gle.com>,
 Puranjay Mohan <puranjay@...nel.org>, linux-kselftest@...r.kernel.org,
 linux-kernel@...r.kernel.org, llvm@...ts.linux.dev
Subject: Re: [PATCH bpf-next v1] selftests/bpf: Guard addr_space_cast code
 with __BPF_FEATURE_ADDR_SPACE_CAST



On 10/22/25 8:33 PM, Jiayuan Chen wrote:
> October 22, 2025 at 23:33, "Yonghong Song" <yonghong.song@...ux.dev mailto:yonghong.song@...ux.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?

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