linux/samples/bpf/test_probe_write_user_kern.c
Daniel T. Lee 3677d0a131 samples: bpf: Refactor kprobe tracing programs with libbpf
For the problem of increasing fragmentation of the bpf loader programs,
instead of using bpf_loader.o, which is used in samples/bpf, this
commit refactors the existing kprobe tracing programs with libbbpf
bpf loader.

    - For kprobe events pointing to system calls, the SYSCALL() macro in
    trace_common.h was used.
    - Adding a kprobe event and attaching a bpf program to it was done
    through bpf_program_attach().
    - Instead of using the existing BPF MAP definition, MAP definition
    has been refactored with the new BTF-defined MAP format.

Signed-off-by: Daniel T. Lee <danieltimlee@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200823085334.9413-3-danieltimlee@gmail.com
2020-08-24 20:59:35 -07:00

57 lines
1.8 KiB
C

/* Copyright (c) 2016 Sargun Dhillon <sargun@sargun.me>
*
* 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>
#include <bpf/bpf_core_read.h>
#include "trace_common.h"
struct {
__uint(type, BPF_MAP_TYPE_HASH);
__type(key, struct sockaddr_in);
__type(value, struct sockaddr_in);
__uint(max_entries, 256);
} dnat_map SEC(".maps");
/* 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
*
* This example sits on a syscall, and the syscall ABI is relatively stable
* of course, across platforms, and over time, the ABI may change.
*/
SEC("kprobe/" SYSCALL(sys_connect))
int bpf_prog1(struct pt_regs *ctx)
{
struct pt_regs *real_regs = (struct pt_regs *)PT_REGS_PARM1_CORE(ctx);
void *sockaddr_arg = (void *)PT_REGS_PARM2_CORE(real_regs);
int sockaddr_len = (int)PT_REGS_PARM3_CORE(real_regs);
struct sockaddr_in new_addr, orig_addr = {};
struct sockaddr_in *mapped_addr;
if (sockaddr_len > sizeof(orig_addr))
return 0;
if (bpf_probe_read_user(&orig_addr, sizeof(orig_addr), sockaddr_arg) != 0)
return 0;
mapped_addr = bpf_map_lookup_elem(&dnat_map, &orig_addr);
if (mapped_addr != NULL) {
memcpy(&new_addr, mapped_addr, sizeof(new_addr));
bpf_probe_write_user(sockaddr_arg, &new_addr,
sizeof(new_addr));
}
return 0;
}
char _license[] SEC("license") = "GPL";
u32 _version SEC("version") = LINUX_VERSION_CODE;