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authorNamhyung Kim <namhyung@kernel.org>2022-06-25 02:13:08 +0300
committerArnaldo Carvalho de Melo <acme@redhat.com>2022-06-28 17:41:26 +0300
commitd6838ec44b4513280a3f43fcc402e246d543fb53 (patch)
treecb12e505d57794c6937ffdd3ef28524e2e614e8c /tools
parent941e3e7912696b9fbe3586083a7c2e102cee7a87 (diff)
downloadlinux-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.c20
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)