| Message ID | dfd3823f11ffd2d4c838e961d61ec9ae8a646773.1707080349.git.dxu@dxuuu.xyz (mailing list archive) |
|---|---|
| State | Accepted |
| Delegated to: | BPF |
| Headers | show |
| Series | bpf, bpftool: Support dumping kfunc prototypes from BTF | expand |
On 2/4/24 1:06 PM, Daniel Xu wrote: > Since 20d59ee55172 ("libbpf: add bpf_core_cast() macro"), libbpf is now > exporting a const arg version of bpf_rdonly_cast(). This causes the > following conflicting type error when generating kfunc prototypes from > BTF: > > In file included from skeleton/pid_iter.bpf.c:5: > /home/dxu/dev/linux/tools/bpf/bpftool/bootstrap/libbpf/include/bpf/bpf_core_read.h:297:14: error: conflicting types for 'bpf_rdonly_cast' > extern void *bpf_rdonly_cast(const void *obj__ign, __u32 btf_id__k) __ksym __weak; > ^ > ./vmlinux.h:135625:14: note: previous declaration is here > extern void *bpf_rdonly_cast(void *obj__ign, u32 btf_id__k) __weak __ksym; > > This is b/c the kernel defines bpf_rdonly_cast() with non-const arg. > Since const arg is more permissive and thus backwards compatible, we > change the kernel definition as well to avoid conflicting type errors. > > Signed-off-by: Daniel Xu <dxu@dxuuu.xyz> Acked-by: Yonghong Song <yonghong.song@linux.dev>
On Sun, Feb 04, 2024 at 02:06:34PM -0700, Daniel Xu wrote: > Since 20d59ee55172 ("libbpf: add bpf_core_cast() macro"), libbpf is now > exporting a const arg version of bpf_rdonly_cast(). This causes the > following conflicting type error when generating kfunc prototypes from > BTF: > > In file included from skeleton/pid_iter.bpf.c:5: > /home/dxu/dev/linux/tools/bpf/bpftool/bootstrap/libbpf/include/bpf/bpf_core_read.h:297:14: error: conflicting types for 'bpf_rdonly_cast' > extern void *bpf_rdonly_cast(const void *obj__ign, __u32 btf_id__k) __ksym __weak; > ^ > ./vmlinux.h:135625:14: note: previous declaration is here > extern void *bpf_rdonly_cast(void *obj__ign, u32 btf_id__k) __weak __ksym; hi, I'm hiting more of these when compiling bpf selftests (attached), it looks like some kfuncs declarations in bpf_kfuncs.h might be in conflict jirka --- CLNG-BPF [test_maps] connect_unix_prog.bpf.o In file included from progs/connect_unix_prog.c:9: /home/jolsa/kernel/linux-qemu/tools/testing/selftests/bpf/bpf_kfuncs.h:11:12: error: conflicting types for 'bpf_dynptr_from_skb' extern int bpf_dynptr_from_skb(struct __sk_buff *skb, __u64 flags, ^ /home/jolsa/kernel/linux-qemu/tools/testing/selftests/bpf/tools/include/vmlinux.h:164853:12: note: previous declaration is here extern int bpf_dynptr_from_skb(struct sk_buff *skb, u64 flags, struct bpf_dynptr_kern *ptr__uninit) __weak __ksym; ^ In file included from progs/connect_unix_prog.c:9: /home/jolsa/kernel/linux-qemu/tools/testing/selftests/bpf/bpf_kfuncs.h:19:12: error: conflicting types for 'bpf_dynptr_from_xdp' extern int bpf_dynptr_from_xdp(struct xdp_md *xdp, __u64 flags, ^ /home/jolsa/kernel/linux-qemu/tools/testing/selftests/bpf/tools/include/vmlinux.h:164855:12: note: previous declaration is here extern int bpf_dynptr_from_xdp(struct xdp_buff *xdp, u64 flags, struct bpf_dynptr_kern *ptr__uninit) __weak __ksym; ^ In file included from progs/connect_unix_prog.c:9: /home/jolsa/kernel/linux-qemu/tools/testing/selftests/bpf/bpf_kfuncs.h:28:14: error: conflicting types for 'bpf_dynptr_slice' extern void *bpf_dynptr_slice(const struct bpf_dynptr *ptr, __u32 offset, ^ /home/jolsa/kernel/linux-qemu/tools/testing/selftests/bpf/tools/include/vmlinux.h:164747:14: note: previous declaration is here extern void *bpf_dynptr_slice(const struct bpf_dynptr_kern *ptr, u32 offset, void *buffer__opt, u32 buffer__szk) __weak __ksym; ^ In file included from progs/connect_unix_prog.c:9: /home/jolsa/kernel/linux-qemu/tools/testing/selftests/bpf/bpf_kfuncs.h:37:14: error: conflicting types for 'bpf_dynptr_slice_rdwr' extern void *bpf_dynptr_slice_rdwr(const struct bpf_dynptr *ptr, __u32 offset, ^ /home/jolsa/kernel/linux-qemu/tools/testing/selftests/bpf/tools/include/vmlinux.h:164749:14: note: previous declaration is here extern void *bpf_dynptr_slice_rdwr(const struct bpf_dynptr_kern *ptr, u32 offset, void *buffer__opt, u32 buffer__szk) __weak __ksym; ^ In file included from progs/connect_unix_prog.c:9: /home/jolsa/kernel/linux-qemu/tools/testing/selftests/bpf/bpf_kfuncs.h:40:12: error: conflicting types for 'bpf_dynptr_adjust' extern int bpf_dynptr_adjust(const struct bpf_dynptr *ptr, __u32 start, __u32 end) __ksym __weak; ^ /home/jolsa/kernel/linux-qemu/tools/testing/selftests/bpf/tools/include/vmlinux.h:164781:12: note: previous declaration is here extern int bpf_dynptr_adjust(struct bpf_dynptr_kern *ptr, u32 start, u32 end) __weak __ksym; ^ In file included from progs/connect_unix_prog.c:9: /home/jolsa/kernel/linux-qemu/tools/testing/selftests/bpf/bpf_kfuncs.h:41:13: error: conflicting types for 'bpf_dynptr_is_null' extern bool bpf_dynptr_is_null(const struct bpf_dynptr *ptr) __ksym __weak; ^ /home/jolsa/kernel/linux-qemu/tools/testing/selftests/bpf/tools/include/vmlinux.h:164783:13: note: previous declaration is here extern bool bpf_dynptr_is_null(struct bpf_dynptr_kern *ptr) __weak __ksym; ^ In file included from progs/connect_unix_prog.c:9: /home/jolsa/kernel/linux-qemu/tools/testing/selftests/bpf/bpf_kfuncs.h:42:13: error: conflicting types for 'bpf_dynptr_is_rdonly' extern bool bpf_dynptr_is_rdonly(const struct bpf_dynptr *ptr) __ksym __weak; ^ /home/jolsa/kernel/linux-qemu/tools/testing/selftests/bpf/tools/include/vmlinux.h:164785:13: note: previous declaration is here extern bool bpf_dynptr_is_rdonly(struct bpf_dynptr_kern *ptr) __weak __ksym; ^ In file included from progs/connect_unix_prog.c:9: /home/jolsa/kernel/linux-qemu/tools/testing/selftests/bpf/bpf_kfuncs.h:43:14: error: conflicting types for 'bpf_dynptr_size' extern __u32 bpf_dynptr_size(const struct bpf_dynptr *ptr) __ksym __weak; ^ /home/jolsa/kernel/linux-qemu/tools/testing/selftests/bpf/tools/include/vmlinux.h:164787:14: note: previous declaration is here extern __u32 bpf_dynptr_size(const struct bpf_dynptr_kern *ptr) __weak __ksym; ^ In file included from progs/connect_unix_prog.c:9: /home/jolsa/kernel/linux-qemu/tools/testing/selftests/bpf/bpf_kfuncs.h:44:12: error: conflicting types for 'bpf_dynptr_clone' extern int bpf_dynptr_clone(const struct bpf_dynptr *ptr, struct bpf_dynptr *clone__init) __ksym __weak; ^ /home/jolsa/kernel/linux-qemu/tools/testing/selftests/bpf/tools/include/vmlinux.h:164789:12: note: previous declaration is here extern int bpf_dynptr_clone(struct bpf_dynptr_kern *ptr, struct bpf_dynptr_kern *clone__uninit) __weak __ksym; ^ In file included from progs/connect_unix_prog.c:9: /home/jolsa/kernel/linux-qemu/tools/testing/selftests/bpf/bpf_kfuncs.h:61:12: error: conflicting types for 'bpf_sk_assign_tcp_reqsk' extern int bpf_sk_assign_tcp_reqsk(struct __sk_buff *skb, struct sock *sk, ^ /home/jolsa/kernel/linux-qemu/tools/testing/selftests/bpf/tools/include/vmlinux.h:164859:12: note: previous declaration is here extern int bpf_sk_assign_tcp_reqsk(struct sk_buff *skb, struct sock *sk, struct bpf_tcp_req_attrs *attrs, int attrs__sz) __weak __ksym; ^ In file included from progs/connect_unix_prog.c:9: /home/jolsa/kernel/linux-qemu/tools/testing/selftests/bpf/bpf_kfuncs.h:68:12: error: conflicting types for 'bpf_get_file_xattr' extern int bpf_get_file_xattr(struct file *file, const char *name, ^ /home/jolsa/kernel/linux-qemu/tools/testing/selftests/bpf/tools/include/vmlinux.h:164691:12: note: previous declaration is here extern int bpf_get_file_xattr(struct file *file, const char *name__str, struct bpf_dynptr_kern *value_ptr) __weak __ksym; ^ In file included from progs/connect_unix_prog.c:9: /home/jolsa/kernel/linux-qemu/tools/testing/selftests/bpf/bpf_kfuncs.h:75:12: error: conflicting types for 'bpf_verify_pkcs7_signature' extern int bpf_verify_pkcs7_signature(struct bpf_dynptr *data_ptr, ^ /home/jolsa/kernel/linux-qemu/tools/testing/selftests/bpf/tools/include/vmlinux.h:164689:12: note: previous declaration is here extern int bpf_verify_pkcs7_signature(struct bpf_dynptr_kern *data_ptr, struct bpf_dynptr_kern *sig_ptr, struct bpf_key *trusted_keyring) __weak __ksym; ^ 12 errors generated. make: *** [Makefile:642: /home/jolsa/kernel/linux-qemu/tools/testing/selftests/bpf/connect_unix_prog.bpf.o] Error 1
Hi Jiri, On Tue, Feb 06, 2024 at 02:42:22PM +0100, Jiri Olsa wrote: > On Sun, Feb 04, 2024 at 02:06:34PM -0700, Daniel Xu wrote: > > Since 20d59ee55172 ("libbpf: add bpf_core_cast() macro"), libbpf is now > > exporting a const arg version of bpf_rdonly_cast(). This causes the > > following conflicting type error when generating kfunc prototypes from > > BTF: > > > > In file included from skeleton/pid_iter.bpf.c:5: > > /home/dxu/dev/linux/tools/bpf/bpftool/bootstrap/libbpf/include/bpf/bpf_core_read.h:297:14: error: conflicting types for 'bpf_rdonly_cast' > > extern void *bpf_rdonly_cast(const void *obj__ign, __u32 btf_id__k) __ksym __weak; > > ^ > > ./vmlinux.h:135625:14: note: previous declaration is here > > extern void *bpf_rdonly_cast(void *obj__ign, u32 btf_id__k) __weak __ksym; > > hi, > I'm hiting more of these when compiling bpf selftests (attached), > it looks like some kfuncs declarations in bpf_kfuncs.h might be in conflict Yep, I was actually going to put that as an office hours topic on how we want to handle that for selftests. Marking kfuncs in bpf_kfuncs.h and bpf_experimental.h as __weak is an option. ifdef is another option. Final option I can think of is bumping required pahole version up and simply deleting all the kfunc definitions. But given that pahole changes come with the feature flag, I don't see this as a pressing issue. So I was planning on getting to that after current outstanding patchsets (just so there's less stuff for me to juggle). [...] Thanks, Daniel
On Tue, Feb 06, 2024 at 08:44:18AM -0700, Daniel Xu wrote: > Hi Jiri, > > On Tue, Feb 06, 2024 at 02:42:22PM +0100, Jiri Olsa wrote: > > On Sun, Feb 04, 2024 at 02:06:34PM -0700, Daniel Xu wrote: > > > Since 20d59ee55172 ("libbpf: add bpf_core_cast() macro"), libbpf is now > > > exporting a const arg version of bpf_rdonly_cast(). This causes the > > > following conflicting type error when generating kfunc prototypes from > > > BTF: > > > > > > In file included from skeleton/pid_iter.bpf.c:5: > > > /home/dxu/dev/linux/tools/bpf/bpftool/bootstrap/libbpf/include/bpf/bpf_core_read.h:297:14: error: conflicting types for 'bpf_rdonly_cast' > > > extern void *bpf_rdonly_cast(const void *obj__ign, __u32 btf_id__k) __ksym __weak; > > > ^ > > > ./vmlinux.h:135625:14: note: previous declaration is here > > > extern void *bpf_rdonly_cast(void *obj__ign, u32 btf_id__k) __weak __ksym; > > > > hi, > > I'm hiting more of these when compiling bpf selftests (attached), > > it looks like some kfuncs declarations in bpf_kfuncs.h might be in conflict > > Yep, I was actually going to put that as an office hours topic on how we > want to handle that for selftests. Marking kfuncs in bpf_kfuncs.h and > bpf_experimental.h as __weak is an option. ifdef is another option. > Final option I can think of is bumping required pahole version up and > simply deleting all the kfunc definitions. > > But given that pahole changes come with the feature flag, I don't see > this as a pressing issue. So I was planning on getting to that after > current outstanding patchsets (just so there's less stuff for me to > juggle). ok, I guess if the fix goes in together with the scripts/Makefile.btf change then we're fine jirka
On Tue, Feb 6, 2024 at 7:44 AM Daniel Xu <dxu@dxuuu.xyz> wrote: > > Hi Jiri, > > On Tue, Feb 06, 2024 at 02:42:22PM +0100, Jiri Olsa wrote: > > On Sun, Feb 04, 2024 at 02:06:34PM -0700, Daniel Xu wrote: > > > Since 20d59ee55172 ("libbpf: add bpf_core_cast() macro"), libbpf is now > > > exporting a const arg version of bpf_rdonly_cast(). This causes the > > > following conflicting type error when generating kfunc prototypes from > > > BTF: > > > > > > In file included from skeleton/pid_iter.bpf.c:5: > > > /home/dxu/dev/linux/tools/bpf/bpftool/bootstrap/libbpf/include/bpf/bpf_core_read.h:297:14: error: conflicting types for 'bpf_rdonly_cast' > > > extern void *bpf_rdonly_cast(const void *obj__ign, __u32 btf_id__k) __ksym __weak; > > > ^ > > > ./vmlinux.h:135625:14: note: previous declaration is here > > > extern void *bpf_rdonly_cast(void *obj__ign, u32 btf_id__k) __weak __ksym; > > > > hi, > > I'm hiting more of these when compiling bpf selftests (attached), > > it looks like some kfuncs declarations in bpf_kfuncs.h might be in conflict > > Yep, I was actually going to put that as an office hours topic on how we > want to handle that for selftests. Marking kfuncs in bpf_kfuncs.h and > bpf_experimental.h as __weak is an option. ifdef is another option. > Final option I can think of is bumping required pahole version up and > simply deleting all the kfunc definitions. I think we should mark all kfuncs in selftests as __weak. And then audit all of them and add consts where it makes sense and make sure that all definitions are compatible between vmlinux.h and manual declarations. I'd rather avoid #ifdef'ing anything, it should work as is. > > But given that pahole changes come with the feature flag, I don't see > this as a pressing issue. So I was planning on getting to that after > current outstanding patchsets (just so there's less stuff for me to > juggle). > > [...] > > Thanks, > Daniel
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c index 4db1c658254c..3503949b4c1b 100644 --- a/kernel/bpf/helpers.c +++ b/kernel/bpf/helpers.c @@ -2484,9 +2484,9 @@ __bpf_kfunc void *bpf_cast_to_kern_ctx(void *obj) return obj; } -__bpf_kfunc void *bpf_rdonly_cast(void *obj__ign, u32 btf_id__k) +__bpf_kfunc void *bpf_rdonly_cast(const void *obj__ign, u32 btf_id__k) { - return obj__ign; + return (void *)obj__ign; } __bpf_kfunc void bpf_rcu_read_lock(void)
Since 20d59ee55172 ("libbpf: add bpf_core_cast() macro"), libbpf is now exporting a const arg version of bpf_rdonly_cast(). This causes the following conflicting type error when generating kfunc prototypes from BTF: In file included from skeleton/pid_iter.bpf.c:5: /home/dxu/dev/linux/tools/bpf/bpftool/bootstrap/libbpf/include/bpf/bpf_core_read.h:297:14: error: conflicting types for 'bpf_rdonly_cast' extern void *bpf_rdonly_cast(const void *obj__ign, __u32 btf_id__k) __ksym __weak; ^ ./vmlinux.h:135625:14: note: previous declaration is here extern void *bpf_rdonly_cast(void *obj__ign, u32 btf_id__k) __weak __ksym; This is b/c the kernel defines bpf_rdonly_cast() with non-const arg. Since const arg is more permissive and thus backwards compatible, we change the kernel definition as well to avoid conflicting type errors. Signed-off-by: Daniel Xu <dxu@dxuuu.xyz> --- kernel/bpf/helpers.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)