feat: Add initial implementation of struct_ops BPF program and kernel module with kfunc support

src/features/struct_ops/struct_ops.c

@@ -0,0 +1,76 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <signal.h>
+#include <unistd.h>
+#include <errno.h>
+
+#include "struct_ops.skel.h"  // Include the generated skeleton header
+
+static volatile bool exiting = false;
+
+// Signal handler for graceful termination
+void handle_signal(int sig) {
+    exiting = true;
+}
+
+int main(int argc, char **argv) {
+    struct struct_ops_bpf *skel;
+    int err;
+
+    // Handle SIGINT and SIGTERM for graceful shutdown
+    signal(SIGINT, handle_signal);
+
+    // Open the BPF application
+    skel = struct_ops_bpf__open();
+    if (!skel) {
+        fprintf(stderr, "Failed to open BPF skeleton\n");
+        return 1;
+    }
+
+    // Load & verify the BPF program
+    err = struct_ops_bpf__load(skel);
+    if (err) {
+        fprintf(stderr, "Failed to load and verify BPF skeleton: %d\n", err);
+        goto cleanup;
+    }
+
+    // Attach the BPF program (e.g., attach kprobe)
+    err = struct_ops_bpf__attach(skel);
+    if (err) {
+        fprintf(stderr, "Failed to attach BPF skeleton: %d\n", err);
+        goto cleanup;
+    }
+
+    printf("BPF program loaded and attached successfully. Press Ctrl-C to exit.\n");
+
+    // Optionally, read the trace_pipe to see bpf_printk outputs
+    FILE *trace_pipe = fopen("/sys/kernel/debug/tracing/trace_pipe", "r");
+    if (!trace_pipe) {
+        perror("fopen trace_pipe");
+        // Continue without reading trace_pipe
+    }
+
+    // Main loop
+    while (!exiting) {
+        if (trace_pipe) {
+            char buffer[256];
+            if (fgets(buffer, sizeof(buffer), trace_pipe)) {
+                printf("%s", buffer);
+            } else {
+                if (errno == EINTR)
+                    break;
+            }
+        } else {
+            // If trace_pipe is not available, just sleep
+            sleep(1);
+        }
+    }
+
+    if (trace_pipe)
+        fclose(trace_pipe);
+
+cleanup:
+    // Clean up and destroy the BPF program
+    struct_ops_bpf__destroy(skel);
+    return err < 0 ? -err : 0;
+}