From d0b2f91bede3bd5e3d24dd6803e56eee959c1797 Mon Sep 17 00:00:00 2001 From: André Fabian Silva Delgado Date: Thu, 20 Oct 2016 00:10:27 -0300 Subject: Linux-libre 4.8.2-gnu --- samples/bpf/test_probe_write_user_kern.c | 52 ++++++++++++++++++++++++++++++++ 1 file changed, 52 insertions(+) create mode 100644 samples/bpf/test_probe_write_user_kern.c (limited to 'samples/bpf/test_probe_write_user_kern.c') diff --git a/samples/bpf/test_probe_write_user_kern.c b/samples/bpf/test_probe_write_user_kern.c new file mode 100644 index 000000000..3a677c807 --- /dev/null +++ b/samples/bpf/test_probe_write_user_kern.c @@ -0,0 +1,52 @@ +/* Copyright (c) 2016 Sargun Dhillon + * + * 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 +#include +#include +#include +#include "bpf_helpers.h" + +struct bpf_map_def SEC("maps") dnat_map = { + .type = BPF_MAP_TYPE_HASH, + .key_size = sizeof(struct sockaddr_in), + .value_size = sizeof(struct sockaddr_in), + .max_entries = 256, +}; + +/* 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/sys_connect") +int bpf_prog1(struct pt_regs *ctx) +{ + struct sockaddr_in new_addr, orig_addr = {}; + struct sockaddr_in *mapped_addr; + void *sockaddr_arg = (void *)PT_REGS_PARM2(ctx); + int sockaddr_len = (int)PT_REGS_PARM3(ctx); + + if (sockaddr_len > sizeof(orig_addr)) + return 0; + + if (bpf_probe_read(&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; -- cgit v1.2.3-54-g00ecf