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| author | Namhyung Kim <namhyung@kernel.org> | 2022-06-25 02:13:08 +0300 |
|---|---|---|
| committer | Arnaldo Carvalho de Melo <acme@redhat.com> | 2022-06-28 17:41:26 +0300 |
| commit | d6838ec44b4513280a3f43fcc402e246d543fb53 (patch) | |
| tree | cb12e505d57794c6937ffdd3ef28524e2e614e8c /tools | |
| parent | 941e3e7912696b9fbe3586083a7c2e102cee7a87 (diff) | |
| download | linux-d6838ec44b4513280a3f43fcc402e246d543fb53.tar.xz | |
perf offcpu: Fix build failure on old kernels
Old kernels have a 'struct task_struct' which contains a "state" field
and newer kernels have "__state" instead.
While the get_task_state() in the BPF code handles that in some way, it
assumed the current kernel has the new definition and it caused a build
error on old kernels.
We should not assume anything and access them carefully. Do not use
'task struct' directly access it instead using new and old definitions
in a row.
Fixes: edc41a1099c2d08c ("perf record: Enable off-cpu analysis with BPF")
Reported-by: Ian Rogers <irogers@google.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Blake Jones <blakejones@google.com>
Cc: Hao Luo <haoluo@google.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Milian Wolff <milian.wolff@kdab.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Song Liu <songliubraving@fb.com>
Cc: bpf@vger.kernel.org
Link: http://lore.kernel.org/lkml/20220624231313.367909-2-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Diffstat (limited to 'tools')
| -rw-r--r-- | tools/perf/util/bpf_skel/off_cpu.bpf.c | 20 |
1 files changed, 14 insertions, 6 deletions
diff --git a/tools/perf/util/bpf_skel/off_cpu.bpf.c b/tools/perf/util/bpf_skel/off_cpu.bpf.c index 792ae2847080..cc6d7fd55118 100644 --- a/tools/perf/util/bpf_skel/off_cpu.bpf.c +++ b/tools/perf/util/bpf_skel/off_cpu.bpf.c @@ -71,6 +71,11 @@ struct { __uint(max_entries, 1); } cgroup_filter SEC(".maps"); +/* new kernel task_struct definition */ +struct task_struct___new { + long __state; +} __attribute__((preserve_access_index)); + /* old kernel task_struct definition */ struct task_struct___old { long state; @@ -93,14 +98,17 @@ const volatile bool uses_cgroup_v1 = false; */ static inline int get_task_state(struct task_struct *t) { - if (bpf_core_field_exists(t->__state)) - return BPF_CORE_READ(t, __state); + /* recast pointer to capture new type for compiler */ + struct task_struct___new *t_new = (void *)t; - /* recast pointer to capture task_struct___old type for compiler */ - struct task_struct___old *t_old = (void *)t; + if (bpf_core_field_exists(t_new->__state)) { + return BPF_CORE_READ(t_new, __state); + } else { + /* recast pointer to capture old type for compiler */ + struct task_struct___old *t_old = (void *)t; - /* now use old "state" name of the field */ - return BPF_CORE_READ(t_old, state); + return BPF_CORE_READ(t_old, state); + } } static inline __u64 get_cgroup_id(struct task_struct *t) |