From cf4dcbae4799415fc5a85f9bb9f31bbf036f2994 Mon Sep 17 00:00:00 2001 From: Alexander Lobakin Date: Thu, 21 Apr 2022 00:38:58 +0000 Subject: [PATCH] bpftool: define a local bpf_perf_link to fix accessing its fields When building bpftool with !CONFIG_PERF_EVENTS: skeleton/pid_iter.bpf.c:47:14: error: incomplete definition of type 'struct bpf_perf_link' perf_link = container_of(link, struct bpf_perf_link, link); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ tools/bpf/bpftool/bootstrap/libbpf/include/bpf/bpf_helpers.h:74:22: note: expanded from macro 'container_of' ((type *)(__mptr - offsetof(type, member))); \ ^~~~~~~~~~~~~~~~~~~~~~ tools/bpf/bpftool/bootstrap/libbpf/include/bpf/bpf_helpers.h:68:60: note: expanded from macro 'offsetof' #define offsetof(TYPE, MEMBER) ((unsigned long)&((TYPE *)0)->MEMBER) ~~~~~~~~~~~^ skeleton/pid_iter.bpf.c:44:9: note: forward declaration of 'struct bpf_perf_link' struct bpf_perf_link *perf_link; ^ &bpf_perf_link is being defined and used only under the ifdef. Define struct bpf_perf_link___local with the `preserve_access_index` attribute inside the pid_iter BPF prog to allow compiling on any configs. CO-RE will substitute it with the real struct bpf_perf_link accesses later on. container_of() is not CO-REd, but it is a noop for bpf_perf_link <-> bpf_link and the local copy is a full mirror of the original structure. Fixes: cbdaf71f7e65 ("bpftool: Add bpf_cookie to link output") Suggested-by: Andrii Nakryiko Signed-off-by: Alexander Lobakin Signed-off-by: Quentin Monnet --- tools/bpf/bpftool/skeleton/pid_iter.bpf.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/src/skeleton/pid_iter.bpf.c b/src/skeleton/pid_iter.bpf.c index e2af8e5fb29e..3a4c4f7d83d8 100644 --- a/src/skeleton/pid_iter.bpf.c +++ b/src/skeleton/pid_iter.bpf.c @@ -15,6 +15,11 @@ enum bpf_obj_type { BPF_OBJ_BTF, }; +struct bpf_perf_link___local { + struct bpf_link link; + struct file *perf_file; +} __attribute__((preserve_access_index)); + struct perf_event___local { u64 bpf_cookie; } __attribute__((preserve_access_index)); @@ -45,10 +50,10 @@ static __always_inline __u32 get_obj_id(void *ent, enum bpf_obj_type type) /* could be used only with BPF_LINK_TYPE_PERF_EVENT links */ static __u64 get_bpf_cookie(struct bpf_link *link) { + struct bpf_perf_link___local *perf_link; struct perf_event___local *event; - struct bpf_perf_link *perf_link; - perf_link = container_of(link, struct bpf_perf_link, link); + perf_link = container_of(link, struct bpf_perf_link___local, link); event = BPF_CORE_READ(perf_link, perf_file, private_data); return BPF_CORE_READ(event, bpf_cookie); } -- 2.40.0