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samples/bpf: Add counting example for kfree_skb() function calls and the write() syscall

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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 2015-03-25 12:49:24 -07:00 • committed by Ingo Molnar
parent b896c4f95a
commit d822a19268
3 changed files with 185 additions and 0 deletions
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86
samples/bpf/tracex2_kern.c Normal file
View file

@ -0,0 +1,86 @@
/* Copyright (c) 2013-2015 PLUMgrid, http://plumgrid.com
*
* 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 <linux/skbuff.h>
#include <linux/netdevice.h>
#include <linux/version.h>
#include <uapi/linux/bpf.h>
#include "bpf_helpers.h"
struct bpf_map_def SEC("maps") my_map = {
.type = BPF_MAP_TYPE_HASH,
.key_size = sizeof(long),
.value_size = sizeof(long),
.max_entries = 1024,
};
/* kprobe is NOT a stable ABI. If kernel internals change this bpf+kprobe
* example will no longer be meaningful
*/
SEC("kprobe/kfree_skb")
int bpf_prog2(struct pt_regs *ctx)
{
long loc = 0;
long init_val = 1;
long *value;
/* x64 specific: read ip of kfree_skb caller.
* non-portable version of __builtin_return_address(0)
*/
bpf_probe_read(&loc, sizeof(loc), (void *)ctx->sp);
value = bpf_map_lookup_elem(&my_map, &loc);
if (value)
*value += 1;
else
bpf_map_update_elem(&my_map, &loc, &init_val, BPF_ANY);
return 0;
}
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;
}
static unsigned int log2l(unsigned long v)
{
unsigned int hi = v >> 32;
if (hi)
return log2(hi) + 32;
else
return log2(v);
}
struct bpf_map_def SEC("maps") my_hist_map = {
.type = BPF_MAP_TYPE_ARRAY,
.key_size = sizeof(u32),
.value_size = sizeof(long),
.max_entries = 64,
};
SEC("kprobe/sys_write")
int bpf_prog3(struct pt_regs *ctx)
{
long write_size = ctx->dx; /* arg3 */
long init_val = 1;
long *value;
u32 index = log2l(write_size);
value = bpf_map_lookup_elem(&my_hist_map, &index);
if (value)
__sync_fetch_and_add(value, 1);
return 0;
}
char _license[] SEC("license") = "GPL";
u32 _version SEC("version") = LINUX_VERSION_CODE;