Add kprobe and vmlinux example

examples/c-form/ex5.bpf.c

@@ -0,0 +1,32 @@
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+#include <bpf/bpf_core_read.h>
+
+// Map: key = struct request*, value = u64 timestamp
+struct {
+    __uint(type, BPF_MAP_TYPE_HASH);
+    __type(key, struct request *);
+    __type(value, u64);
+    __uint(max_entries, 1024);
+} start SEC(".maps");
+
+// Attach to kprobe for blk_start_request
+SEC("kprobe/blk_start_request")
+int BPF_KPROBE(trace_start, struct request *req)
+{
+    u64 ts = bpf_ktime_get_ns();
+    bpf_map_update_elem(&start, &req, &ts, BPF_ANY);
+    return 0;
+}
+
+// Optionally, attach also to blk_mq_start_request
+SEC("kprobe/blk_mq_start_request")
+int BPF_KPROBE(trace_start_mq, struct request *req)
+{
+    u64 ts = bpf_ktime_get_ns();
+    bpf_map_update_elem(&start, &req, &ts, BPF_ANY);
+    return 0;
+}
+
+char LICENSE[] SEC("license") = "GPL";