samples/bpf/tracex4_kern.c

/* Copyright (c) 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/ptrace.h>
#include <linux/version.h>
#include <uapi/linux/bpf.h>
#include "bpf_helpers.h"

struct pair {
	u64 val;
	u64 ip;
};

struct bpf_map_def SEC("maps") my_map = {
	.type = BPF_MAP_TYPE_HASH,
	.key_size = sizeof(long),
	.value_size = sizeof(struct pair),
	.max_entries = 1000000,
};

/* kprobe is NOT a stable ABI. If kernel internals change this bpf+kprobe
 * example will no longer be meaningful
 */
SEC("kprobe/kmem_cache_free")
int bpf_prog1(struct pt_regs *ctx)
{
	long ptr = ctx->si;

	bpf_map_delete_elem(&my_map, &ptr);
	return 0;
}

SEC("kretprobe/kmem_cache_alloc_node")
int bpf_prog2(struct pt_regs *ctx)
{
	long ptr = ctx->ax;
	long ip = 0;

	/* get ip address of kmem_cache_alloc_node() caller */
	bpf_probe_read(&ip, sizeof(ip), (void *)(ctx->bp + sizeof(ip)));

	struct pair v = {
		.val = bpf_ktime_get_ns(),
		.ip = ip,
	};

	bpf_map_update_elem(&my_map, &ptr, &v, BPF_ANY);
	return 0;
}
char _license[] SEC("license") = "GPL";
u32 _version SEC("version") = LINUX_VERSION_CODE;