v4.19.13 snapshot.
diff --git a/samples/bpf/tracex2_kern.c b/samples/bpf/tracex2_kern.c
new file mode 100644
index 0000000..5e11c20
--- /dev/null
+++ b/samples/bpf/tracex2_kern.c
@@ -0,0 +1,100 @@
+/* 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 <linux/version.h>
+#include <uapi/linux/bpf.h>
+#include "bpf_helpers.h"
+
+struct bpf_map_def SEC("maps") my_map = {
+ .type = BPF_MAP_TYPE_HASH,
+ .key_size = sizeof(long),
+ .value_size = sizeof(long),
+ .max_entries = 1024,
+};
+
+/* kprobe is NOT a stable ABI. If kernel internals change this bpf+kprobe
+ * example will no longer be meaningful
+ */
+SEC("kprobe/kfree_skb")
+int bpf_prog2(struct pt_regs *ctx)
+{
+ long loc = 0;
+ long init_val = 1;
+ long *value;
+
+ /* read ip of kfree_skb caller.
+ * non-portable version of __builtin_return_address(0)
+ */
+ BPF_KPROBE_READ_RET_IP(loc, ctx);
+
+ value = bpf_map_lookup_elem(&my_map, &loc);
+ if (value)
+ *value += 1;
+ else
+ bpf_map_update_elem(&my_map, &loc, &init_val, BPF_ANY);
+ return 0;
+}
+
+static unsigned int log2(unsigned int v)
+{
+ unsigned int r;
+ unsigned int shift;
+
+ r = (v > 0xFFFF) << 4; v >>= r;
+ shift = (v > 0xFF) << 3; v >>= shift; r |= shift;
+ shift = (v > 0xF) << 2; v >>= shift; r |= shift;
+ shift = (v > 0x3) << 1; v >>= shift; r |= shift;
+ r |= (v >> 1);
+ return r;
+}
+
+static unsigned int log2l(unsigned long v)
+{
+ unsigned int hi = v >> 32;
+ if (hi)
+ return log2(hi) + 32;
+ else
+ return log2(v);
+}
+
+struct hist_key {
+ char comm[16];
+ u64 pid_tgid;
+ u64 uid_gid;
+ u64 index;
+};
+
+struct bpf_map_def SEC("maps") my_hist_map = {
+ .type = BPF_MAP_TYPE_PERCPU_HASH,
+ .key_size = sizeof(struct hist_key),
+ .value_size = sizeof(long),
+ .max_entries = 1024,
+};
+
+SEC("kprobe/sys_write")
+int bpf_prog3(struct pt_regs *ctx)
+{
+ long write_size = PT_REGS_PARM3(ctx);
+ long init_val = 1;
+ long *value;
+ struct hist_key key;
+
+ key.index = log2l(write_size);
+ key.pid_tgid = bpf_get_current_pid_tgid();
+ key.uid_gid = bpf_get_current_uid_gid();
+ bpf_get_current_comm(&key.comm, sizeof(key.comm));
+
+ value = bpf_map_lookup_elem(&my_hist_map, &key);
+ if (value)
+ __sync_fetch_and_add(value, 1);
+ else
+ bpf_map_update_elem(&my_hist_map, &key, &init_val, BPF_ANY);
+ return 0;
+}
+char _license[] SEC("license") = "GPL";
+u32 _version SEC("version") = LINUX_VERSION_CODE;