samples/bpf: Add counting example for kfree_skb() function calls and the write() syscall
this example has two probes in one C file that attach to different kprove events and use two different maps. 1st probe is x64 specific equivalent of dropmon. It attaches to kfree_skb, retrevies 'ip' address of kfree_skb() caller and counts number of packet drops at that 'ip' address. User space prints 'location - count' map every second. 2nd probe attaches to kprobe:sys_write and computes a histogram of different write sizes Usage: $ sudo tracex2 location 0xffffffff81695995 count 1 location 0xffffffff816d0da9 count 2 location 0xffffffff81695995 count 2 location 0xffffffff816d0da9 count 2 location 0xffffffff81695995 count 3 location 0xffffffff816d0da9 count 2 557145+0 records in 557145+0 records out 285258240 bytes (285 MB) copied, 1.02379 s, 279 MB/s syscall write() stats byte_size : count distribution 1 -> 1 : 3 | | 2 -> 3 : 0 | | 4 -> 7 : 0 | | 8 -> 15 : 0 | | 16 -> 31 : 2 | | 32 -> 63 : 3 | | 64 -> 127 : 1 | | 128 -> 255 : 1 | | 256 -> 511 : 0 | | 512 -> 1023 : 1118968 |************************************* | Ctrl-C at any time. Kernel will auto cleanup maps and programs $ addr2line -ape ./bld_x64/vmlinux 0xffffffff81695995 0xffffffff816d0da9 0xffffffff81695995: ./bld_x64/../net/ipv4/icmp.c:1038 0xffffffff816d0da9: ./bld_x64/../net/unix/af_unix.c:1231 Signed-off-by: Alexei Starovoitov <ast@plumgrid.com> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Daniel Borkmann <daniel@iogearbox.net> Cc: David S. Miller <davem@davemloft.net> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Link: http://lkml.kernel.org/r/1427312966-8434-8-git-send-email-ast@plumgrid.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Alexei Starovoitov
Ingo Molnar
parent
b896c4f95a
commit
d822a19268
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@ -7,6 +7,7 @@ hostprogs-y += sock_example
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hostprogs-y += sockex1
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hostprogs-y += sockex2
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hostprogs-y += tracex1
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hostprogs-y += tracex2
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test_verifier-objs := test_verifier.o libbpf.o
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test_maps-objs := test_maps.o libbpf.o
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@ -14,12 +15,14 @@ sock_example-objs := sock_example.o libbpf.o
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sockex1-objs := bpf_load.o libbpf.o sockex1_user.o
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sockex2-objs := bpf_load.o libbpf.o sockex2_user.o
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tracex1-objs := bpf_load.o libbpf.o tracex1_user.o
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tracex2-objs := bpf_load.o libbpf.o tracex2_user.o
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# Tell kbuild to always build the programs
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always := $(hostprogs-y)
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always += sockex1_kern.o
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always += sockex2_kern.o
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always += tracex1_kern.o
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always += tracex2_kern.o
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HOSTCFLAGS += -I$(objtree)/usr/include
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@ -27,6 +30,7 @@ HOSTCFLAGS_bpf_load.o += -I$(objtree)/usr/include -Wno-unused-variable
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HOSTLOADLIBES_sockex1 += -lelf
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HOSTLOADLIBES_sockex2 += -lelf
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HOSTLOADLIBES_tracex1 += -lelf
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HOSTLOADLIBES_tracex2 += -lelf
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# point this to your LLVM backend with bpf support
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LLC=$(srctree)/tools/bpf/llvm/bld/Debug+Asserts/bin/llc
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@ -0,0 +1,86 @@
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/* Copyright (c) 2013-2015 PLUMgrid, http://plumgrid.com
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of version 2 of the GNU General Public
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* License as published by the Free Software Foundation.
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*/
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#include <linux/skbuff.h>
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#include <linux/netdevice.h>
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#include <linux/version.h>
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#include <uapi/linux/bpf.h>
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#include "bpf_helpers.h"
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struct bpf_map_def SEC("maps") my_map = {
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.type = BPF_MAP_TYPE_HASH,
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.key_size = sizeof(long),
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.value_size = sizeof(long),
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.max_entries = 1024,
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};
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/* kprobe is NOT a stable ABI. If kernel internals change this bpf+kprobe
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* example will no longer be meaningful
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*/
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SEC("kprobe/kfree_skb")
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int bpf_prog2(struct pt_regs *ctx)
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{
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long loc = 0;
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long init_val = 1;
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long *value;
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/* x64 specific: read ip of kfree_skb caller.
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* non-portable version of __builtin_return_address(0)
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*/
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bpf_probe_read(&loc, sizeof(loc), (void *)ctx->sp);
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value = bpf_map_lookup_elem(&my_map, &loc);
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if (value)
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*value += 1;
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else
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bpf_map_update_elem(&my_map, &loc, &init_val, BPF_ANY);
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return 0;
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}
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static unsigned int log2(unsigned int v)
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{
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unsigned int r;
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unsigned int shift;
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r = (v > 0xFFFF) << 4; v >>= r;
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shift = (v > 0xFF) << 3; v >>= shift; r |= shift;
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shift = (v > 0xF) << 2; v >>= shift; r |= shift;
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shift = (v > 0x3) << 1; v >>= shift; r |= shift;
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r |= (v >> 1);
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return r;
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}
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static unsigned int log2l(unsigned long v)
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{
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unsigned int hi = v >> 32;
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if (hi)
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return log2(hi) + 32;
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else
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return log2(v);
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}
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struct bpf_map_def SEC("maps") my_hist_map = {
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.type = BPF_MAP_TYPE_ARRAY,
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.key_size = sizeof(u32),
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.value_size = sizeof(long),
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.max_entries = 64,
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};
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SEC("kprobe/sys_write")
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int bpf_prog3(struct pt_regs *ctx)
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{
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long write_size = ctx->dx; /* arg3 */
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long init_val = 1;
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long *value;
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u32 index = log2l(write_size);
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value = bpf_map_lookup_elem(&my_hist_map, &index);
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if (value)
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__sync_fetch_and_add(value, 1);
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return 0;
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}
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char _license[] SEC("license") = "GPL";
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u32 _version SEC("version") = LINUX_VERSION_CODE;
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@ -0,0 +1,95 @@
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#include <stdio.h>
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#include <unistd.h>
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#include <stdlib.h>
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#include <signal.h>
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#include <linux/bpf.h>
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#include "libbpf.h"
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#include "bpf_load.h"
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#define MAX_INDEX 64
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#define MAX_STARS 38
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static void stars(char *str, long val, long max, int width)
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{
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int i;
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for (i = 0; i < (width * val / max) - 1 && i < width - 1; i++)
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str[i] = '*';
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if (val > max)
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str[i - 1] = '+';
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str[i] = '\0';
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}
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static void print_hist(int fd)
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{
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int key;
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long value;
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long data[MAX_INDEX] = {};
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char starstr[MAX_STARS];
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int i;
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int max_ind = -1;
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long max_value = 0;
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for (key = 0; key < MAX_INDEX; key++) {
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bpf_lookup_elem(fd, &key, &value);
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data[key] = value;
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if (value && key > max_ind)
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max_ind = key;
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if (value > max_value)
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max_value = value;
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}
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printf(" syscall write() stats\n");
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printf(" byte_size : count distribution\n");
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for (i = 1; i <= max_ind + 1; i++) {
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stars(starstr, data[i - 1], max_value, MAX_STARS);
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printf("%8ld -> %-8ld : %-8ld |%-*s|\n",
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(1l << i) >> 1, (1l << i) - 1, data[i - 1],
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MAX_STARS, starstr);
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}
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}
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static void int_exit(int sig)
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{
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print_hist(map_fd[1]);
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exit(0);
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}
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int main(int ac, char **argv)
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{
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char filename[256];
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long key, next_key, value;
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FILE *f;
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int i;
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snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
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signal(SIGINT, int_exit);
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/* start 'ping' in the background to have some kfree_skb events */
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f = popen("ping -c5 localhost", "r");
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(void) f;
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/* start 'dd' in the background to have plenty of 'write' syscalls */
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f = popen("dd if=/dev/zero of=/dev/null count=5000000", "r");
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(void) f;
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if (load_bpf_file(filename)) {
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printf("%s", bpf_log_buf);
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return 1;
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}
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for (i = 0; i < 5; i++) {
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key = 0;
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while (bpf_get_next_key(map_fd[0], &key, &next_key) == 0) {
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bpf_lookup_elem(map_fd[0], &next_key, &value);
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printf("location 0x%lx count %ld\n", next_key, value);
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key = next_key;
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}
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if (key)
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printf("\n");
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sleep(1);
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}
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print_hist(map_fd[1]);
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return 0;
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}
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