diff options
Diffstat (limited to 'samples/bpf/test_probe_write_user.bpf.c')
| -rw-r--r-- | samples/bpf/test_probe_write_user.bpf.c | 54 |
1 files changed, 54 insertions, 0 deletions
diff --git a/samples/bpf/test_probe_write_user.bpf.c b/samples/bpf/test_probe_write_user.bpf.c new file mode 100644 index 000000000000..a0f10c5ca273 --- /dev/null +++ b/samples/bpf/test_probe_write_user.bpf.c @@ -0,0 +1,54 @@ +/* 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 "vmlinux.h" +#include <string.h> +#include <linux/version.h> +#include <bpf/bpf_helpers.h> +#include <bpf/bpf_tracing.h> +#include <bpf/bpf_core_read.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("ksyscall/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; |