ex1_kern.c - C program which will be compiled into eBPF
to filter netif_receive_skb events on skb->dev->name == "lo"
ex1_user.c - corresponding user space component that
forever reads /sys/.../trace_pipe
Usage:
$ sudo ex1
should see:
writing bpf-4 -> /sys/kernel/debug/tracing/events/net/netif_receive_skb/filter
ping-25476 [001] ..s3 5639.718218: __netif_receive_skb_core: skb 4d51700 dev
b9e6000
ping-25476 [001] ..s3 5639.718262: __netif_receive_skb_core: skb 4d51400 dev
b9e6000
ping-25476 [002] ..s3 5640.716233: __netif_receive_skb_core: skb 5d06500 dev
b9e6000
ping-25476 [002] ..s3 5640.716272: __netif_receive_skb_core: skb 5d06300 dev
b9e6000
Ctrl-C at any time, kernel will auto cleanup
Signed-off-by: Alexei Starovoitov <a...@plumgrid.com>
---
samples/bpf/Makefile | 15 +++++++++++++--
samples/bpf/ex1_kern.c | 27 +++++++++++++++++++++++++++
samples/bpf/ex1_user.c | 24 ++++++++++++++++++++++++
3 files changed, 64 insertions(+), 2 deletions(-)
create mode 100644 samples/bpf/ex1_kern.c
create mode 100644 samples/bpf/ex1_user.c
diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
index caf1ab93b37c..c97f408fcd6d 100644
--- a/samples/bpf/Makefile
+++ b/samples/bpf/Makefile
@@ -2,12 +2,23 @@
obj- := dummy.o
# List of programs to build
-hostprogs-y := sock_example dropmon
+hostprogs-y := sock_example dropmon ex1
sock_example-objs := sock_example.o libbpf.o
dropmon-objs := dropmon.o libbpf.o
+ex1-objs := bpf_load.o libbpf.o ex1_user.o
# Tell kbuild to always build the programs
-always := $(hostprogs-y)
+always := $(hostprogs-y) ex1_kern.o
HOSTCFLAGS += -I$(objtree)/usr/include
+
+HOSTCFLAGS_bpf_load.o += -I$(objtree)/usr/include -Wno-unused-variable
+HOSTLOADLIBES_ex1 += -lelf
+
+LLC=$(srctree)/tools/bpf/llvm/bld/Debug+Asserts/bin/llc
+
+%.o: %.c
+ clang $(NOSTDINC_FLAGS) $(LINUXINCLUDE) $(EXTRA_CFLAGS) \
+ -D__KERNEL__ -Wno-unused-value -Wno-pointer-sign \
+ -O2 -emit-llvm -c $< -o -| $(LLC) -o $@
diff --git a/samples/bpf/ex1_kern.c b/samples/bpf/ex1_kern.c
new file mode 100644
index 000000000000..05a06cccaadb
--- /dev/null
+++ b/samples/bpf/ex1_kern.c
@@ -0,0 +1,27 @@
+#include <linux/skbuff.h>
+#include <linux/netdevice.h>
+#include <uapi/linux/bpf.h>
+#include <trace/bpf_trace.h>
+#include "bpf_helpers.h"
+
+SEC("events/net/netif_receive_skb")
+int bpf_prog1(struct bpf_context *ctx)
+{
+ /*
+ * attaches to /sys/kernel/debug/tracing/events/net/netif_receive_skb
+ * prints events for loobpack device only
+ */
+ char devname[] = "lo";
+ struct net_device *dev;
+ struct sk_buff *skb = 0;
+
+ skb = (struct sk_buff *) ctx->arg1;
+ dev = bpf_fetch_ptr(&skb->dev);
+ if (bpf_memcmp(dev->name, devname, 2) == 0) {
+ char fmt[] = "skb %x dev %x\n";
+ bpf_printk(fmt, sizeof(fmt), skb, dev);
+ }
+ return 0;
+}
+
+char license[] SEC("license") = "GPL";
diff --git a/samples/bpf/ex1_user.c b/samples/bpf/ex1_user.c
new file mode 100644
index 000000000000..e85c1b483f57
--- /dev/null
+++ b/samples/bpf/ex1_user.c
@@ -0,0 +1,24 @@
+#include <stdio.h>
+#include <linux/bpf.h>
+#include "libbpf.h"
+#include "bpf_load.h"
+
+int main(int ac, char **argv)
+{
+ FILE *f;
+ char filename[256];
+
+ snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
+
+ if (load_bpf_file(filename)) {
+ printf("%s", bpf_log_buf);
+ return 1;
+ }
+
+ f = popen("ping -c5 localhost", "r");
+ (void) f;
+
+ read_trace_pipe();
+
+ return 0;
+}
--
1.7.9.5
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