semantically this example is the same as dropmon.c which has eBPF in assembler.
In this example both eBPF and user space are in C:
ex2_kern.c - C code that will compile into eBPF and will
be attached to kfree_skb event
ex2_user.c - corresponding user space part that iterates the map
populated by in-kernel eBPF code
Usage:
$ sudo ex2 ex2_kern.o
Should see:
writing bpf-5 -> /sys/kernel/debug/tracing/events/skb/kfree_skb/filter
location 0xffffffff816efc67 count 1
location 0xffffffff815d8030 count 1
location 0xffffffff816efc67 count 3
location 0xffffffff815d8030 count 4
location 0xffffffff816efc67 count 9
location 0xffffffff815d8030 count 7
location 0xffffffff816efc67 count 15
location 0xffffffff815d8030 count 10
location 0xffffffff816efc67 count 23
location 0xffffffff815d8030 count 13
location 0xffffffff816efc67 count 29
Ctrl-C at any time. Kernel will auto cleanup maps and programs
Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxxxx>
---
samples/bpf/Makefile | 6 ++++--
samples/bpf/ex2_kern.c | 29 +++++++++++++++++++++++++++++
samples/bpf/ex2_user.c | 28 ++++++++++++++++++++++++++++
3 files changed, 61 insertions(+), 2 deletions(-)
create mode 100644 samples/bpf/ex2_kern.c
create mode 100644 samples/bpf/ex2_user.c
diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
index c97f408fcd6d..b865a5df5c60 100644
--- a/samples/bpf/Makefile
+++ b/samples/bpf/Makefile
@@ -2,19 +2,21 @@
obj- := dummy.o
# List of programs to build
-hostprogs-y := sock_example dropmon ex1
+hostprogs-y := sock_example dropmon ex1 ex2
sock_example-objs := sock_example.o libbpf.o
dropmon-objs := dropmon.o libbpf.o
ex1-objs := bpf_load.o libbpf.o ex1_user.o
+ex2-objs := bpf_load.o libbpf.o ex2_user.o
# Tell kbuild to always build the programs
-always := $(hostprogs-y) ex1_kern.o
+always := $(hostprogs-y) ex1_kern.o ex2_kern.o
HOSTCFLAGS += -I$(objtree)/usr/include
HOSTCFLAGS_bpf_load.o += -I$(objtree)/usr/include -Wno-unused-variable
HOSTLOADLIBES_ex1 += -lelf
+HOSTLOADLIBES_ex2 += -lelf
LLC=$(srctree)/tools/bpf/llvm/bld/Debug+Asserts/bin/llc
diff --git a/samples/bpf/ex2_kern.c b/samples/bpf/ex2_kern.c
new file mode 100644
index 000000000000..b4a8e73a3f9d
--- /dev/null
+++ b/samples/bpf/ex2_kern.c
@@ -0,0 +1,29 @@
+#include <linux/skbuff.h>
+#include <linux/netdevice.h>
+#include <uapi/linux/bpf.h>
+#include <trace/bpf_trace.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,
+};
+
+SEC("events/skb/kfree_skb")
+int bpf_prog2(struct bpf_context *ctx)
+{
+ long loc = ctx->arg2;
+ long init_val = 1;
+ void *value;
+
+ value = bpf_map_lookup_elem(&my_map, &loc);
+ if (value)
+ (*(long *) value) += 1;
+ else
+ bpf_map_update_elem(&my_map, &loc, &init_val);
+ return 0;
+}
+
+char license[] SEC("license") = "GPL";
diff --git a/samples/bpf/ex2_user.c b/samples/bpf/ex2_user.c
new file mode 100644
index 000000000000..8b0fc91f83ca
--- /dev/null
+++ b/samples/bpf/ex2_user.c
@@ -0,0 +1,28 @@
+#include <stdio.h>
+#include <unistd.h>
+#include <linux/bpf.h>
+#include "libbpf.h"
+#include "bpf_load.h"
+
+int main(int ac, char **argv)
+{
+ long key, next_key, value;
+ int i;
+
+ if (load_bpf_file(argv[1]))
+ return 1;
+
+ for (i = 0; i < 10; 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);
+ }
+
+ return 0;
+}
--
1.7.9.5
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