[PATCH bpf] selftest/bpf: fix profiler test using CO-RE relocation for enums

[Andrii Nakryiko]

Instead of hard-coding invalid pids_cgrp_id, use Kconfig to detect the
presence of that enum value and CO-RE to capture its actual value in the
hosts's kernel.

Tested-by: Song Liu <songliubrav...@fb.com>
Fixes: 03d4d13fab3f ("selftests/bpf: Add profiler test")
Signed-off-by: Andrii Nakryiko <and...@kernel.org>
---
 tools/testing/selftests/bpf/progs/profiler.inc.h | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/tools/testing/selftests/bpf/progs/profiler.inc.h 
b/tools/testing/selftests/bpf/progs/profiler.inc.h
index 00578311a423..30982a7e4d0f 100644
--- a/tools/testing/selftests/bpf/progs/profiler.inc.h
+++ b/tools/testing/selftests/bpf/progs/profiler.inc.h
@@ -243,7 +243,10 @@ static ino_t get_inode_from_kernfs(struct kernfs_node* 
node)
        }
 }
 
-int pids_cgrp_id = 1;
+extern bool CONFIG_CGROUP_PIDS __kconfig __weak;
+enum cgroup_subsys_id___local {
+       pids_cgrp_id___local = 123, /* value doesn't matter */
+};
 
 static INLINE void* populate_cgroup_info(struct cgroup_data_t* cgroup_data,
                                         struct task_struct* task,
@@ -253,7 +256,9 @@ static INLINE void* populate_cgroup_info(struct 
cgroup_data_t* cgroup_data,
                BPF_CORE_READ(task, nsproxy, cgroup_ns, root_cset, dfl_cgrp, 
kn);
        struct kernfs_node* proc_kernfs = BPF_CORE_READ(task, cgroups, 
dfl_cgrp, kn);
 
-       if (ENABLE_CGROUP_V1_RESOLVER) {
+       if (ENABLE_CGROUP_V1_RESOLVER && CONFIG_CGROUP_PIDS) {
+               int cgrp_id = bpf_core_enum_value(enum cgroup_subsys_id___local,
+                                                 pids_cgrp_id___local);
 #ifdef UNROLL
 #pragma unroll
 #endif
@@ -262,7 +267,7 @@ static INLINE void* populate_cgroup_info(struct 
cgroup_data_t* cgroup_data,
                                BPF_CORE_READ(task, cgroups, subsys[i]);
                        if (subsys != NULL) {
                                int subsys_id = BPF_CORE_READ(subsys, ss, id);
-                               if (subsys_id == pids_cgrp_id) {
+                               if (subsys_id == cgrp_id) {
                                        proc_kernfs = BPF_CORE_READ(subsys, 
cgroup, kn);
                                        root_kernfs = BPF_CORE_READ(subsys, ss, 
root, kf_root, kn);
                                        break;
-- 
2.24.1