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bpftool: use a local copy of perf_event to fix accessing :: Bpf_cookie 

[ Upstream commit 4cbeeb0dc0 ]

When CONFIG_PERF_EVENTS is not set, struct perf_event remains empty.
However, the structure is being used by bpftool indirectly via BTF.
This leads to:

skeleton/pid_iter.bpf.c:49:30: error: no member named 'bpf_cookie' in 'struct perf_event'
        return BPF_CORE_READ(event, bpf_cookie);
               ~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~

...

skeleton/pid_iter.bpf.c:49:9: error: returning 'void' from a function with incompatible result type '__u64' (aka 'unsigned long long')
        return BPF_CORE_READ(event, bpf_cookie);
               ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Tools and samples can't use any CONFIG_ definitions, so the fields
used there should always be present.
Define struct perf_event___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 perf_event
accesses later on.

Fixes: cbdaf71f7e ("bpftool: Add bpf_cookie to link output")
Suggested-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexander Lobakin <alobakin@pm.me>
Signed-off-by: Quentin Monnet <quentin@isovalent.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20230707095425.168126-2-quentin@isovalent.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Alexander Lobakin 2023-07-07 10:54:22 +01:00 committed by Greg Kroah-Hartman
parent ff84349098
commit 564560f3ba
1 changed files with 5 additions and 1 deletions
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6
tools/bpf/bpftool/skeleton/pid_iter.bpf.c
View File

@ -15,6 +15,10 @@ enum bpf_obj_type {
BPF_OBJ_BTF,
};
struct perf_event___local {
u64 bpf_cookie;
} __attribute__((preserve_access_index));
extern const void bpf_link_fops __ksym;
extern const void bpf_map_fops __ksym;
extern const void bpf_prog_fops __ksym;
@ -41,8 +45,8 @@ 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 perf_event___local *event;
struct bpf_perf_link *perf_link;
struct perf_event *event;
perf_link = container_of(link, struct bpf_perf_link, link);
event = BPF_CORE_READ(perf_link, perf_file, private_data);