libbpf-tools: fix readahead, support v5.10+ kernel

Signed-off-by: Wenbo Zhang <ethercflow@gmail.com>

libbpf-tools/readahead.bpf.c

@@ -26,8 +26,8 @@ struct {
 
 static struct hist hist;
 
-SEC("fentry/__do_page_cache_readahead")
-int BPF_PROG(do_page_cache_readahead)
+SEC("kprobe/do_page_cache_ra")
+int BPF_KPROBE(do_page_cache_ra)
 {
  u32 pid = bpf_get_current_pid_tgid();
  u64 one = 1;
@@ -53,8 +53,8 @@ int BPF_PROG(page_cache_alloc_ret, gfp_t gfp, struct page *ret)
  return 0;
 }
 
-SEC("fexit/__do_page_cache_readahead")
-int BPF_PROG(do_page_cache_readahead_ret)
+SEC("kretprobe/do_page_cache_ra")
+int BPF_KRETPROBE(do_page_cache_ra_ret)
 {
  u32 pid = bpf_get_current_pid_tgid();
 

libbpf-tools/readahead.c

@@ -97,13 +97,69 @@ int main(int argc, char **argv)
 
  obj = readahead_bpf__open_and_load();
  if (!obj) {
- fprintf(stderr, "failed to open and/or load BPF ojbect\n");
+ fprintf(stderr, "failed to open and/or load BPF object\n");
  return 1;
  }
 
- err = readahead_bpf__attach(obj);
+ /*
+ * Starting from v5.10-rc1 (8238287), __do_page_cache_readahead has
+ * renamed to do_page_cache_ra. We try to attach to do_page_cache_ra
+ * first, and if it fails, we try __do_page_cache_readahead again.
+ *
+ * If attach to do_page_cache_ra fails due to non-existence, you will
+ * see libbpf print related warn information. You can just ignore it.
+ */
+ obj->links.do_page_cache_ra =
+ bpf_program__attach_kprobe(obj->progs.do_page_cache_ra,
+ false,
+ "do_page_cache_ra");
+ err = libbpf_get_error(obj->links.do_page_cache_ra);
  if (err) {
- fprintf(stderr, "failed to attach BPF programs\n");
+ obj->links.do_page_cache_ra =
+ bpf_program__attach_kprobe(obj->progs.do_page_cache_ra,
+ false,
+ "__do_page_cache_readahead");
+ err = libbpf_get_error(obj->links.do_page_cache_ra);
+ if (err) {
+ fprintf(stderr, "failed to attach kprobe prog to "
+ "do_page_cache_ra or __do_page_cache_readahead\n");
+ goto cleanup;
+ }
+ }
+
+ obj->links.do_page_cache_ra_ret =
+ bpf_program__attach_kprobe(obj->progs.do_page_cache_ra_ret,
+ true,
+ "do_page_cache_ra");
+ err = libbpf_get_error(obj->links.do_page_cache_ra_ret);
+ if (err) {
+ obj->links.do_page_cache_ra_ret =
+ bpf_program__attach_kprobe(obj->progs.do_page_cache_ra_ret,
+ true,
+ "__do_page_cache_readahead");
+ err = libbpf_get_error(obj->links.do_page_cache_ra_ret);
+ if (err) {
+ fprintf(stderr, "failed to attach kretprobe prog to "
+ "do_page_cache_ra or __do_page_cache_readahead\n");
+ goto cleanup;
+ }
+ }
+
+ obj->links.page_cache_alloc_ret =
+ bpf_program__attach_trace(obj->progs.page_cache_alloc_ret);
+ err = libbpf_get_error(obj->links.page_cache_alloc_ret);
+ if (err) {
+ fprintf(stderr, "failed to attach to tracing prog to "
+ "page_dache_alloc\n");
+ goto cleanup;
+ }
+
+ obj->links.mark_page_accessed =
+ bpf_program__attach_trace(obj->progs.mark_page_accessed);
+ err = libbpf_get_error(obj->links.mark_page_accessed);
+ if (err) {
+ fprintf(stderr, "failed to attach to tracing prog to "
+ "mark_page_accessed\n");
  goto cleanup;
  }