Add some trace logs to BPF programs using ringbuf

Add some trace logs to BPF programs using ringbuf to give anybody at
least a fighting chance to understand where issues are. Retrieve them
by reading /sys/kernel/debug/tracing/trace_pipe.

Signed-off-by: Daniel Müller <[email protected]>

Author: d-e-s-o

libbpf-rs/tests/bin/ksyscall.bpf.o

@@ -13,11 +13,14 @@ int handle__ksyscall(pid_t pid, int sig) {
   int *value;
 
   value = bpf_ringbuf_reserve(&ringbuf, sizeof(int), 0);
-  if (value) {
-    *value = 1;
-    bpf_ringbuf_submit(value, 0);
+  if (!value) {
+    bpf_printk("handle__ksyscall: failed to reserve ring buffer space");
+    return 1;
   }
 
+  *value = 1;
+  bpf_ringbuf_submit(value, 0);
+  bpf_printk("handle__ksyscall: submitted ringbuf value");
   return 0;
 }
 

libbpf-rs/tests/bin/map_auto_pin.bpf.o

@@ -14,11 +14,14 @@ int handle__tracepoint(void *ctx)
     int *value;
 
     value = bpf_ringbuf_reserve(&ringbuf, sizeof(int), 0);
-    if (value) {
-        *value = 1;
-        bpf_ringbuf_submit(value, 0);
+    if (!value) {
+        bpf_printk("handle__tracepoint: failed to reserve ring buffer space");
+        return 1;
     }
 
+    *value = 1;
+    bpf_ringbuf_submit(value, 0);
+    bpf_printk("handle__tracepoint: submitted ringbuf value");
     return 0;
 }
 
@@ -28,11 +31,14 @@ int handle__tracepoint_with_cookie(void *ctx)
     int *value;
 
     value = bpf_ringbuf_reserve(&ringbuf, sizeof(int), 0);
-    if (value) {
-        *value = bpf_get_attach_cookie(ctx);
-        bpf_ringbuf_submit(value, 0);
+    if (!value) {
+        bpf_printk("handle__tracepoint_with_cookie: failed to reserve ring buffer space");
+        return 1;
     }
 
+    *value = bpf_get_attach_cookie(ctx);
+    bpf_printk("handle__tracepoint_with_cookie: cookie=%d", *value);
+    bpf_ringbuf_submit(value, 0);
     return 0;
 }
 

libbpf-rs/tests/bin/mapiter.bpf.o

@@ -15,11 +15,14 @@ int handle__uprobe(void *ctx)
     int *value;
 
     value = bpf_ringbuf_reserve(&ringbuf, sizeof(int), 0);
-    if (value) {
-        *value = 1;
-        bpf_ringbuf_submit(value, 0);
+    if (!value) {
+        bpf_printk("handle__uprobe: failed to reserve ring buffer space");
+        return 1;
     }
 
+    *value = 1;
+    bpf_ringbuf_submit(value, 0);
+    bpf_printk("handle__uprobe: submitted ringbuf value");
     return 0;
 }
 
@@ -29,11 +32,14 @@ int handle__uprobe_with_cookie(void *ctx)
     int *value;
 
     value = bpf_ringbuf_reserve(&ringbuf, sizeof(int), 0);
-    if (value) {
-        *value = bpf_get_attach_cookie(ctx);
-        bpf_ringbuf_submit(value, 0);
+    if (!value) {
+        bpf_printk("handle__uprobe_with_cookie: failed to reserve ring buffer space");
+        return 1;
     }
 
+    *value = bpf_get_attach_cookie(ctx);
+    bpf_printk("handle__uprobe_with_cookie: cookie=%d", *value);
+    bpf_ringbuf_submit(value, 0);
     return 0;
 }
 

libbpf-rs/tests/bin/percpu_map.bpf.o

@@ -15,11 +15,14 @@ int handle__usdt(void *ctx)
     int *value;
 
     value = bpf_ringbuf_reserve(&ringbuf, sizeof(int), 0);
-    if (value) {
-        *value = 1;
-        bpf_ringbuf_submit(value, 0);
+    if (!value) {
+        bpf_printk("handle__usdt: failed to reserve ring buffer space");
+        return 1;
     }
 
+    *value = 1;
+    bpf_ringbuf_submit(value, 0);
+    bpf_printk("handle__usdt: submitted ringbuf value");
     return 0;
 }
 
@@ -29,11 +32,14 @@ int handle__usdt_with_cookie(void *ctx)
     int *value;
 
     value = bpf_ringbuf_reserve(&ringbuf, sizeof(int), 0);
-    if (value) {
-        *value = bpf_usdt_cookie(ctx);
-        bpf_ringbuf_submit(value, 0);
+    if (!value) {
+        bpf_printk("handle__usdt_with_cookie: failed to reserve ring buffer space");
+        return 1;
     }
 
+    *value = bpf_usdt_cookie(ctx);
+    bpf_printk("handle__usdt_with_cookie: cookie=%d", *value);
+    bpf_ringbuf_submit(value, 0);
     return 0;
 }