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authorAlexei Starovoitov <ast@plumgrid.com>2015-03-25 12:49:24 -0700
committerIngo Molnar <mingo@kernel.org>2015-04-02 13:25:50 +0200
commitd822a192684912c80950d28a0b7adc96261e957c (patch)
tree5686f28d7d36ed9577af6e565f0cdd8c8fbedc65 /samples
parentb896c4f95ab4052d6bad3acde95167d30242a84f (diff)
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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>
Diffstat (limited to 'samples')
-rw-r--r--samples/bpf/Makefile4
-rw-r--r--samples/bpf/tracex2_kern.c86
-rw-r--r--samples/bpf/tracex2_user.c95
3 files changed, 185 insertions, 0 deletions
diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
index 51f6f01e5a3a..6dd272143733 100644
--- a/samples/bpf/Makefile
+++ b/samples/bpf/Makefile
@@ -7,6 +7,7 @@ hostprogs-y += sock_example
hostprogs-y += sockex1
hostprogs-y += sockex2
hostprogs-y += tracex1
+hostprogs-y += tracex2
test_verifier-objs := test_verifier.o libbpf.o
test_maps-objs := test_maps.o libbpf.o
@@ -14,12 +15,14 @@ sock_example-objs := sock_example.o libbpf.o
sockex1-objs := bpf_load.o libbpf.o sockex1_user.o
sockex2-objs := bpf_load.o libbpf.o sockex2_user.o
tracex1-objs := bpf_load.o libbpf.o tracex1_user.o
+tracex2-objs := bpf_load.o libbpf.o tracex2_user.o
# Tell kbuild to always build the programs
always := $(hostprogs-y)
always += sockex1_kern.o
always += sockex2_kern.o
always += tracex1_kern.o
+always += tracex2_kern.o
HOSTCFLAGS += -I$(objtree)/usr/include
@@ -27,6 +30,7 @@ HOSTCFLAGS_bpf_load.o += -I$(objtree)/usr/include -Wno-unused-variable
HOSTLOADLIBES_sockex1 += -lelf
HOSTLOADLIBES_sockex2 += -lelf
HOSTLOADLIBES_tracex1 += -lelf
+HOSTLOADLIBES_tracex2 += -lelf
# point this to your LLVM backend with bpf support
LLC=$(srctree)/tools/bpf/llvm/bld/Debug+Asserts/bin/llc
diff --git a/samples/bpf/tracex2_kern.c b/samples/bpf/tracex2_kern.c
new file mode 100644
index 000000000000..19ec1cfc45db
--- /dev/null
+++ b/samples/bpf/tracex2_kern.c
@@ -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;
diff --git a/samples/bpf/tracex2_user.c b/samples/bpf/tracex2_user.c
new file mode 100644
index 000000000000..91b8d0896fbb
--- /dev/null
+++ b/samples/bpf/tracex2_user.c
@@ -0,0 +1,95 @@
+#include <stdio.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <signal.h>
+#include <linux/bpf.h>
+#include "libbpf.h"
+#include "bpf_load.h"
+
+#define MAX_INDEX 64
+#define MAX_STARS 38
+
+static void stars(char *str, long val, long max, int width)
+{
+ int i;
+
+ for (i = 0; i < (width * val / max) - 1 && i < width - 1; i++)
+ str[i] = '*';
+ if (val > max)
+ str[i - 1] = '+';
+ str[i] = '\0';
+}
+
+static void print_hist(int fd)
+{
+ int key;
+ long value;
+ long data[MAX_INDEX] = {};
+ char starstr[MAX_STARS];
+ int i;
+ int max_ind = -1;
+ long max_value = 0;
+
+ for (key = 0; key < MAX_INDEX; key++) {
+ bpf_lookup_elem(fd, &key, &value);
+ data[key] = value;
+ if (value && key > max_ind)
+ max_ind = key;
+ if (value > max_value)
+ max_value = value;
+ }
+
+ printf(" syscall write() stats\n");
+ printf(" byte_size : count distribution\n");
+ for (i = 1; i <= max_ind + 1; i++) {
+ stars(starstr, data[i - 1], max_value, MAX_STARS);
+ printf("%8ld -> %-8ld : %-8ld |%-*s|\n",
+ (1l << i) >> 1, (1l << i) - 1, data[i - 1],
+ MAX_STARS, starstr);
+ }
+}
+static void int_exit(int sig)
+{
+ print_hist(map_fd[1]);
+ exit(0);
+}
+
+int main(int ac, char **argv)
+{
+ char filename[256];
+ long key, next_key, value;
+ FILE *f;
+ int i;
+
+ snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
+
+ signal(SIGINT, int_exit);
+
+ /* start 'ping' in the background to have some kfree_skb events */
+ f = popen("ping -c5 localhost", "r");
+ (void) f;
+
+ /* start 'dd' in the background to have plenty of 'write' syscalls */
+ f = popen("dd if=/dev/zero of=/dev/null count=5000000", "r");
+ (void) f;
+
+ if (load_bpf_file(filename)) {
+ printf("%s", bpf_log_buf);
+ return 1;
+ }
+
+ for (i = 0; i < 5; i++) {
+ key = 0;
+ while (bpf_get_next_key(map_fd[0], &key, &next_key) == 0) {
+ bpf_lookup_elem(map_fd[0], &next_key, &value);
+ printf("location 0x%lx count %ld\n", next_key, value);
+ key = next_key;
+ }
+ if (key)
+ printf("\n");
+ sleep(1);
+ }
+ print_hist(map_fd[1]);
+
+ return 0;
+}