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Diffstat (limited to 'samples/bpf/test_probe_write_user.bpf.c')
-rw-r--r--samples/bpf/test_probe_write_user.bpf.c54
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;