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-rw-r--r--samples/bpf/tracex1_kern.c54
1 files changed, 54 insertions, 0 deletions
diff --git a/samples/bpf/tracex1_kern.c b/samples/bpf/tracex1_kern.c
new file mode 100644
index 000000000..ef30d2b35
--- /dev/null
+++ b/samples/bpf/tracex1_kern.c
@@ -0,0 +1,54 @@
+/* Copyright (c) 2013-2015 PLUMgrid, http://plumgrid.com
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of version 2 of the GNU General Public
+ * License as published by the Free Software Foundation.
+ */
+#include <linux/skbuff.h>
+#include <linux/netdevice.h>
+#include <uapi/linux/bpf.h>
+#include <linux/version.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+#define _(P) \
+ ({ \
+ typeof(P) val = 0; \
+ bpf_probe_read_kernel(&val, sizeof(val), &(P)); \
+ val; \
+ })
+
+/* kprobe is NOT a stable ABI
+ * kernel functions can be removed, renamed or completely change semantics.
+ * Number of arguments and their positions can change, etc.
+ * In such case this bpf+kprobe example will no longer be meaningful
+ */
+SEC("kprobe/__netif_receive_skb_core")
+int bpf_prog1(struct pt_regs *ctx)
+{
+ /* attaches to kprobe __netif_receive_skb_core,
+ * looks for packets on loobpack device and prints them
+ */
+ char devname[IFNAMSIZ];
+ struct net_device *dev;
+ struct sk_buff *skb;
+ int len;
+
+ /* non-portable! works for the given kernel only */
+ bpf_probe_read_kernel(&skb, sizeof(skb), (void *)PT_REGS_PARM1(ctx));
+ dev = _(skb->dev);
+ len = _(skb->len);
+
+ bpf_probe_read_kernel(devname, sizeof(devname), dev->name);
+
+ if (devname[0] == 'l' && devname[1] == 'o') {
+ char fmt[] = "skb %p len %d\n";
+ /* using bpf_trace_printk() for DEBUG ONLY */
+ bpf_trace_printk(fmt, sizeof(fmt), skb, len);
+ }
+
+ return 0;
+}
+
+char _license[] SEC("license") = "GPL";
+u32 _version SEC("version") = LINUX_VERSION_CODE;