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Date: Tue, 27 Jan 2015 20:06:09 -0800
From: Alexei Starovoitov <ast@...mgrid.com>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: Ingo Molnar <mingo@...nel.org>, Namhyung Kim <namhyung@...nel.org>,
Arnaldo Carvalho de Melo <acme@...radead.org>,
Jiri Olsa <jolsa@...hat.com>,
Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
linux-api@...r.kernel.org, netdev@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: [PATCH v2 linux-trace 4/8] samples: bpf: simple tracing example in C
tracex1_kern.c - C program which will be compiled into eBPF
to filter netif_receive_skb events on skb->dev->name == "lo"
The programs returns 1 to continue storing an event into trace buffer
and returns 0 - to discard an event.
tracex1_user.c - corresponding user space component that
forever reads /sys/.../trace_pipe
Usage:
$ sudo tracex1
should see:
writing bpf-4 -> /sys/kernel/debug/tracing/events/net/netif_receive_skb/filter
ping-364 [000] ..s2 8.089771: netif_receive_skb: dev=lo skbaddr=ffff88000dfcc100 len=84
ping-364 [000] ..s2 8.089889: netif_receive_skb: dev=lo skbaddr=ffff88000dfcc900 len=84
Ctrl-C at any time, kernel will auto cleanup
Signed-off-by: Alexei Starovoitov <ast@...mgrid.com>
---
samples/bpf/Makefile | 4 +++
samples/bpf/bpf_helpers.h | 14 +++++++++++
samples/bpf/bpf_load.c | 59 +++++++++++++++++++++++++++++++++++++++-----
samples/bpf/bpf_load.h | 3 +++
samples/bpf/tracex1_kern.c | 28 +++++++++++++++++++++
samples/bpf/tracex1_user.c | 24 ++++++++++++++++++
6 files changed, 126 insertions(+), 6 deletions(-)
create mode 100644 samples/bpf/tracex1_kern.c
create mode 100644 samples/bpf/tracex1_user.c
diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
index 789691374562..da28e1b6d3a6 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 += dropmon
+hostprogs-y += tracex1
dropmon-objs := dropmon.o libbpf.o
test_verifier-objs := test_verifier.o libbpf.o
@@ -14,17 +15,20 @@ test_maps-objs := test_maps.o libbpf.o
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
# Tell kbuild to always build the programs
always := $(hostprogs-y)
always += sockex1_kern.o
always += sockex2_kern.o
+always += tracex1_kern.o
HOSTCFLAGS += -I$(objtree)/usr/include
HOSTCFLAGS_bpf_load.o += -I$(objtree)/usr/include -Wno-unused-variable
HOSTLOADLIBES_sockex1 += -lelf
HOSTLOADLIBES_sockex2 += -lelf
+HOSTLOADLIBES_tracex1 += -lelf
# point this to your LLVM backend with bpf support
LLC=$(srctree)/tools/bpf/llvm/bld/Debug+Asserts/bin/llc
diff --git a/samples/bpf/bpf_helpers.h b/samples/bpf/bpf_helpers.h
index ca0333146006..9c385c2eacf8 100644
--- a/samples/bpf/bpf_helpers.h
+++ b/samples/bpf/bpf_helpers.h
@@ -15,6 +15,20 @@ static int (*bpf_map_update_elem)(void *map, void *key, void *value,
(void *) BPF_FUNC_map_update_elem;
static int (*bpf_map_delete_elem)(void *map, void *key) =
(void *) BPF_FUNC_map_delete_elem;
+static void *(*bpf_fetch_ptr)(void *unsafe_ptr) =
+ (void *) BPF_FUNC_fetch_ptr;
+static unsigned long long (*bpf_fetch_u64)(void *unsafe_ptr) =
+ (void *) BPF_FUNC_fetch_u64;
+static unsigned int (*bpf_fetch_u32)(void *unsafe_ptr) =
+ (void *) BPF_FUNC_fetch_u32;
+static unsigned short (*bpf_fetch_u16)(void *unsafe_ptr) =
+ (void *) BPF_FUNC_fetch_u16;
+static unsigned char (*bpf_fetch_u8)(void *unsafe_ptr) =
+ (void *) BPF_FUNC_fetch_u8;
+static int (*bpf_memcmp)(void *unsafe_ptr, void *safe_ptr, int size) =
+ (void *) BPF_FUNC_memcmp;
+static unsigned long long (*bpf_ktime_get_ns)(void) =
+ (void *) BPF_FUNC_ktime_get_ns;
/* llvm builtin functions that eBPF C program may use to
* emit BPF_LD_ABS and BPF_LD_IND instructions
diff --git a/samples/bpf/bpf_load.c b/samples/bpf/bpf_load.c
index 1831d236382b..788ac51c1024 100644
--- a/samples/bpf/bpf_load.c
+++ b/samples/bpf/bpf_load.c
@@ -14,6 +14,8 @@
#include "bpf_helpers.h"
#include "bpf_load.h"
+#define DEBUGFS "/sys/kernel/debug/tracing/"
+
static char license[128];
static bool processed_sec[128];
int map_fd[MAX_MAPS];
@@ -22,15 +24,18 @@ int prog_cnt;
static int load_and_attach(const char *event, struct bpf_insn *prog, int size)
{
- int fd;
bool is_socket = strncmp(event, "socket", 6) == 0;
+ enum bpf_prog_type prog_type;
+ char path[256] = DEBUGFS;
+ char fmt[32];
+ int fd, event_fd, err;
- if (!is_socket)
- /* tracing events tbd */
- return -1;
+ if (is_socket)
+ prog_type = BPF_PROG_TYPE_SOCKET_FILTER;
+ else
+ prog_type = BPF_PROG_TYPE_TRACING_FILTER;
- fd = bpf_prog_load(BPF_PROG_TYPE_SOCKET_FILTER,
- prog, size, license);
+ fd = bpf_prog_load(prog_type, prog, size, license);
if (fd < 0) {
printf("bpf_prog_load() err=%d\n%s", errno, bpf_log_buf);
@@ -39,6 +44,28 @@ static int load_and_attach(const char *event, struct bpf_insn *prog, int size)
prog_fd[prog_cnt++] = fd;
+ if (is_socket)
+ return 0;
+
+ snprintf(fmt, sizeof(fmt), "bpf-%d", fd);
+
+ strcat(path, event);
+ strcat(path, "/filter");
+
+ printf("writing %s -> %s\n", fmt, path);
+
+ event_fd = open(path, O_WRONLY, 0);
+ if (event_fd < 0) {
+ printf("failed to open event %s\n", event);
+ return -1;
+ }
+
+ err = write(event_fd, fmt, strlen(fmt));
+ if (err < 0) {
+ printf("write to '%s' failed '%s'\n", event, strerror(errno));
+ return -1;
+ }
+
return 0;
}
@@ -201,3 +228,23 @@ int load_bpf_file(char *path)
close(fd);
return 0;
}
+
+void read_trace_pipe(void)
+{
+ int trace_fd;
+
+ trace_fd = open(DEBUGFS "trace_pipe", O_RDONLY, 0);
+ if (trace_fd < 0)
+ return;
+
+ while (1) {
+ static char buf[4096];
+ ssize_t sz;
+
+ sz = read(trace_fd, buf, sizeof(buf));
+ if (sz) {
+ buf[sz] = 0;
+ puts(buf);
+ }
+ }
+}
diff --git a/samples/bpf/bpf_load.h b/samples/bpf/bpf_load.h
index 27789a34f5e6..d154fc2b0535 100644
--- a/samples/bpf/bpf_load.h
+++ b/samples/bpf/bpf_load.h
@@ -21,4 +21,7 @@ extern int prog_fd[MAX_PROGS];
*/
int load_bpf_file(char *path);
+/* forever reads /sys/.../trace_pipe */
+void read_trace_pipe(void);
+
#endif
diff --git a/samples/bpf/tracex1_kern.c b/samples/bpf/tracex1_kern.c
new file mode 100644
index 000000000000..7849ceb4bce6
--- /dev/null
+++ b/samples/bpf/tracex1_kern.c
@@ -0,0 +1,28 @@
+#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)
+ /* print event using default tracepoint format */
+ return 1;
+
+ /* drop event */
+ return 0;
+}
+
+char _license[] SEC("license") = "GPL";
diff --git a/samples/bpf/tracex1_user.c b/samples/bpf/tracex1_user.c
new file mode 100644
index 000000000000..e85c1b483f57
--- /dev/null
+++ b/samples/bpf/tracex1_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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