diff mbox series

[v2,bpf,01/11] bpftool: use a local copy of perf_event to fix accessing ::bpf_cookie

Message ID 20220421003152.339542-2-alobakin@pm.me (mailing list archive)
State Changes Requested
Delegated to: BPF
Headers show
Series bpf: random unpopular userspace fixes (32 bit et al) | expand

Checks

Context Check Description
bpf/vmtest-bpf-VM_Test-2 success Logs for Kernel LATEST on z15 + selftests
bpf/vmtest-bpf-PR success PR summary
bpf/vmtest-bpf-VM_Test-1 success Logs for Kernel LATEST on ubuntu-latest + selftests
netdev/tree_selection success Clearly marked for bpf, async
netdev/fixes_present success Fixes tag present in non-next series
netdev/subject_prefix success Link
netdev/cover_letter success Series has a cover letter
netdev/patch_count success Link
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 0 this patch: 0
netdev/cc_maintainers fail 3 blamed authors not CCed: yhs@fb.com 9erthalion6@gmail.com quentin@isovalent.com; 8 maintainers not CCed: 9erthalion6@gmail.com laoar.shao@gmail.com kafai@fb.com quentin@isovalent.com akpm@linux-foundation.org yhs@fb.com john.fastabend@gmail.com kpsingh@kernel.org
netdev/build_clang success Errors and warnings before: 0 this patch: 0
netdev/module_param success Was 0 now: 0
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/verify_fixes success Fixes tag looks correct
netdev/build_allmodconfig_warn success Errors and warnings before: 0 this patch: 0
netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 19 lines checked
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0

Commit Message

Alexander Lobakin April 21, 2022, 12:38 a.m. UTC 
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: cbdaf71f7e65 ("bpftool: Add bpf_cookie to link output")
Suggested-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexander Lobakin <alobakin@pm.me>
---
 tools/bpf/bpftool/skeleton/pid_iter.bpf.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

--
2.36.0
diff mbox series

Patch

diff --git a/tools/bpf/bpftool/skeleton/pid_iter.bpf.c b/tools/bpf/bpftool/skeleton/pid_iter.bpf.c
index eb05ea53afb1..e2af8e5fb29e 100644
--- a/tools/bpf/bpftool/skeleton/pid_iter.bpf.c
+++ b/tools/bpf/bpftool/skeleton/pid_iter.bpf.c
@@ -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);