Re: [PATCH v2 bpf-next 3/4] selftests/bpf: Add profiler test

On Tue, Oct 13, 2020 at 12:56 PM Jiri Olsa [off-list ref] wrote:

On Thu, Oct 08, 2020 at 06:12:39PM -0700, Alexei Starovoitov wrote:

SNIP

quoted

+
+#ifdef UNROLL
+#pragma unroll
+#endif
+     for (int i = 0; i < MAX_CGROUPS_PATH_DEPTH; i++) {
+             filepart_length =
+                     bpf_probe_read_str(payload, MAX_PATH, BPF_CORE_READ(cgroup_node, name));
+             if (!cgroup_node)
+                     return payload;
+             if (cgroup_node == cgroup_root_node)
+                     *root_pos = payload - payload_start;
+             if (filepart_length <= MAX_PATH) {
+                     barrier_var(filepart_length);
+                     payload += filepart_length;
+             }
+             cgroup_node = BPF_CORE_READ(cgroup_node, parent);
+     }
+     return payload;
+}
+
+static ino_t get_inode_from_kernfs(struct kernfs_node* node)
+{
+     struct kernfs_node___52* node52 = (void*)node;
+
+     if (bpf_core_field_exists(node52->id.ino)) {
+             barrier_var(node52);
+             return BPF_CORE_READ(node52, id.ino);
+     } else {
+             barrier_var(node);
+             return (u64)BPF_CORE_READ(node, id);
+     }
+}
+
+int pids_cgrp_id = 1;

hi,
I'm getting compilation failure with this:

          CLNG-LLC [test_maps] profiler2.o
        In file included from progs/profiler2.c:6:
        progs/profiler.inc.h:246:5: error: redefinition of 'pids_cgrp_id' as different kind of symbol
        int pids_cgrp_id = 1;
            ^
        /home/jolsa/linux-qemu/tools/testing/selftests/bpf/tools/include/vmlinux.h:14531:2: note: previous definition is here
                pids_cgrp_id = 11,

Interesting.
You probably have CONFIG_CGROUP_PIDS in your .config?
I don't and bpf CI doesn't have it either, so this issue wasn't spotted earlier.

I can hard code 11, of course, but
but maybe Andrii has a cool way to use co-re to deal with this?
I think
"extern bool CONFIG_CGROUP_PIDS __kconfig"
won't work.
A good opportunity to try to use bpf_core_enum_value_exists() ?