cregit-Linux how code gets into the kernel

Release 4.14 samples/bpf/lwt_len_hist_kern.c

Directory: samples/bpf
/* Copyright (c) 2016 Thomas Graf <tgraf@tgraf.ch>
 *
 * 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.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * General Public License for more details.
 */

#include <uapi/linux/bpf.h>
#include <uapi/linux/if_ether.h>
#include <uapi/linux/ip.h>
#include <uapi/linux/in.h>
#include "bpf_helpers.h"


# define printk(fmt, ...)						\
		({                                                      \
                        char ____fmt[] = fmt;                           \
                        bpf_trace_printk(____fmt, sizeof(____fmt),      \
                                     ##__VA_ARGS__);                    \
                })


struct bpf_elf_map {
	
__u32 type;
	
__u32 size_key;
	
__u32 size_value;
	
__u32 max_elem;
	
__u32 flags;
	
__u32 id;
	
__u32 pinning;
};

struct bpf_elf_map SEC("maps") lwt_len_hist_map = {
	.type = BPF_MAP_TYPE_PERCPU_HASH,
	.size_key = sizeof(__u64),
	.size_value = sizeof(__u64),
	.pinning = 2,
	.max_elem = 1024,
};


static unsigned int log2(unsigned int v) { unsigned int r; unsigned int shift; r = (v > 0xFFFF) << 4; v >>= r; shift = (v > 0xFF) << 3; v >>= shift; r |= shift; shift = (v > 0xF) << 2; v >>= shift; r |= shift; shift = (v > 0x3) << 1; v >>= shift; r |= shift; r |= (v >> 1); return r; }

Contributors

PersonTokensPropCommitsCommitProp
Thomas Graf98100.00%1100.00%
Total98100.00%1100.00%


static unsigned int log2l(unsigned long v) { unsigned int hi = v >> 32; if (hi) return log2(hi) + 32; else return log2(v); }

Contributors

PersonTokensPropCommitsCommitProp
Thomas Graf38100.00%1100.00%
Total38100.00%1100.00%

SEC("len_hist")
int do_len_hist(struct __sk_buff *skb) { __u64 *value, key, init_val = 1; key = log2l(skb->len); value = bpf_map_lookup_elem(&lwt_len_hist_map, &key); if (value) __sync_fetch_and_add(value, 1); else bpf_map_update_elem(&lwt_len_hist_map, &key, &init_val, BPF_ANY); return BPF_OK; }

Contributors

PersonTokensPropCommitsCommitProp
Thomas Graf69100.00%1100.00%
Total69100.00%1100.00%

char _license[] SEC("license") = "GPL";

Overall Contributors

PersonTokensPropCommitsCommitProp
Thomas Graf312100.00%1100.00%
Total312100.00%1100.00%
Directory: samples/bpf
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