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authorAlexei Starovoitov <ast@plumgrid.com>2015-03-25 12:49:23 -0700
committerIngo Molnar <mingo@kernel.org>2015-04-02 13:25:50 +0200
commitb896c4f95ab4052d6bad3acde95167d30242a84f (patch)
tree8c18a3ca9f2b389823d7181db606fa3c8d2eccc7 /samples/bpf/bpf_load.c
parent9c959c863f8217a2ff3d7c296e8223654d240569 (diff)
downloadlinux-b896c4f95ab4052d6bad3acde95167d30242a84f.tar.gz
samples/bpf: Add simple non-portable kprobe filter example
tracex1_kern.c - C program compiled into BPF. It attaches to kprobe:netif_receive_skb() When skb->dev->name == "lo", it prints sample debug message into trace_pipe via bpf_trace_printk() helper function. tracex1_user.c - corresponding user space component that: - loads BPF program via bpf() syscall - opens kprobes:netif_receive_skb event via perf_event_open() syscall - attaches the program to event via ioctl(event_fd, PERF_EVENT_IOC_SET_BPF, prog_fd); - prints from trace_pipe Note, this BPF program is non-portable. It must be recompiled with current kernel headers. kprobe is not a stable ABI and BPF+kprobe scripts may no longer be meaningful when kernel internals change. No matter in what way the kernel changes, neither the kprobe, nor the BPF program can ever crash or corrupt the kernel, assuming the kprobes, perf and BPF subsystem has no bugs. The verifier will detect that the program is using bpf_trace_printk() and the kernel will print 'this is a DEBUG kernel' warning banner, which means that bpf_trace_printk() should be used for debugging of the BPF program only. Usage: $ sudo tracex1 ping-19826 [000] d.s2 63103.382648: : skb ffff880466b1ca00 len 84 ping-19826 [000] d.s2 63103.382684: : skb ffff880466b1d300 len 84 ping-19826 [000] d.s2 63104.382533: : skb ffff880466b1ca00 len 84 ping-19826 [000] d.s2 63104.382594: : skb ffff880466b1d300 len 84 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/1427312966-8434-7-git-send-email-ast@plumgrid.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'samples/bpf/bpf_load.c')
-rw-r--r--samples/bpf/bpf_load.c125
1 files changed, 117 insertions, 8 deletions
diff --git a/samples/bpf/bpf_load.c b/samples/bpf/bpf_load.c
index 1831d236382b..38dac5a53b51 100644
--- a/samples/bpf/bpf_load.c
+++ b/samples/bpf/bpf_load.c
@@ -8,29 +8,70 @@
#include <unistd.h>
#include <string.h>
#include <stdbool.h>
+#include <stdlib.h>
#include <linux/bpf.h>
#include <linux/filter.h>
+#include <linux/perf_event.h>
+#include <sys/syscall.h>
+#include <sys/ioctl.h>
+#include <sys/mman.h>
+#include <poll.h>
#include "libbpf.h"
#include "bpf_helpers.h"
#include "bpf_load.h"
+#define DEBUGFS "/sys/kernel/debug/tracing/"
+
static char license[128];
+static int kern_version;
static bool processed_sec[128];
int map_fd[MAX_MAPS];
int prog_fd[MAX_PROGS];
+int event_fd[MAX_PROGS];
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;
-
- if (!is_socket)
- /* tracing events tbd */
+ bool is_kprobe = strncmp(event, "kprobe/", 7) == 0;
+ bool is_kretprobe = strncmp(event, "kretprobe/", 10) == 0;
+ enum bpf_prog_type prog_type;
+ char buf[256];
+ int fd, efd, err, id;
+ struct perf_event_attr attr = {};
+
+ attr.type = PERF_TYPE_TRACEPOINT;
+ attr.sample_type = PERF_SAMPLE_RAW;
+ attr.sample_period = 1;
+ attr.wakeup_events = 1;
+
+ if (is_socket) {
+ prog_type = BPF_PROG_TYPE_SOCKET_FILTER;
+ } else if (is_kprobe || is_kretprobe) {
+ prog_type = BPF_PROG_TYPE_KPROBE;
+ } else {
+ printf("Unknown event '%s'\n", event);
return -1;
+ }
+
+ if (is_kprobe || is_kretprobe) {
+ if (is_kprobe)
+ event += 7;
+ else
+ event += 10;
+
+ snprintf(buf, sizeof(buf),
+ "echo '%c:%s %s' >> /sys/kernel/debug/tracing/kprobe_events",
+ is_kprobe ? 'p' : 'r', event, event);
+ err = system(buf);
+ if (err < 0) {
+ printf("failed to create kprobe '%s' error '%s'\n",
+ event, strerror(errno));
+ return -1;
+ }
+ }
- fd = bpf_prog_load(BPF_PROG_TYPE_SOCKET_FILTER,
- prog, size, license);
+ fd = bpf_prog_load(prog_type, prog, size, license, kern_version);
if (fd < 0) {
printf("bpf_prog_load() err=%d\n%s", errno, bpf_log_buf);
@@ -39,6 +80,41 @@ static int load_and_attach(const char *event, struct bpf_insn *prog, int size)
prog_fd[prog_cnt++] = fd;
+ if (is_socket)
+ return 0;
+
+ strcpy(buf, DEBUGFS);
+ strcat(buf, "events/kprobes/");
+ strcat(buf, event);
+ strcat(buf, "/id");
+
+ efd = open(buf, O_RDONLY, 0);
+ if (efd < 0) {
+ printf("failed to open event %s\n", event);
+ return -1;
+ }
+
+ err = read(efd, buf, sizeof(buf));
+ if (err < 0 || err >= sizeof(buf)) {
+ printf("read from '%s' failed '%s'\n", event, strerror(errno));
+ return -1;
+ }
+
+ close(efd);
+
+ buf[err] = 0;
+ id = atoi(buf);
+ attr.config = id;
+
+ efd = perf_event_open(&attr, -1/*pid*/, 0/*cpu*/, -1/*group_fd*/, 0);
+ if (efd < 0) {
+ printf("event %d fd %d err %s\n", id, efd, strerror(errno));
+ return -1;
+ }
+ event_fd[prog_cnt - 1] = efd;
+ ioctl(efd, PERF_EVENT_IOC_ENABLE, 0);
+ ioctl(efd, PERF_EVENT_IOC_SET_BPF, fd);
+
return 0;
}
@@ -135,6 +211,9 @@ int load_bpf_file(char *path)
if (gelf_getehdr(elf, &ehdr) != &ehdr)
return 1;
+ /* clear all kprobes */
+ i = system("echo \"\" > /sys/kernel/debug/tracing/kprobe_events");
+
/* scan over all elf sections to get license and map info */
for (i = 1; i < ehdr.e_shnum; i++) {
@@ -149,6 +228,14 @@ int load_bpf_file(char *path)
if (strcmp(shname, "license") == 0) {
processed_sec[i] = true;
memcpy(license, data->d_buf, data->d_size);
+ } else if (strcmp(shname, "version") == 0) {
+ processed_sec[i] = true;
+ if (data->d_size != sizeof(int)) {
+ printf("invalid size of version section %zd\n",
+ data->d_size);
+ return 1;
+ }
+ memcpy(&kern_version, data->d_buf, sizeof(int));
} else if (strcmp(shname, "maps") == 0) {
processed_sec[i] = true;
if (load_maps(data->d_buf, data->d_size))
@@ -178,7 +265,8 @@ int load_bpf_file(char *path)
if (parse_relo_and_apply(data, symbols, &shdr, insns))
continue;
- if (memcmp(shname_prog, "events/", 7) == 0 ||
+ if (memcmp(shname_prog, "kprobe/", 7) == 0 ||
+ memcmp(shname_prog, "kretprobe/", 10) == 0 ||
memcmp(shname_prog, "socket", 6) == 0)
load_and_attach(shname_prog, insns, data_prog->d_size);
}
@@ -193,7 +281,8 @@ int load_bpf_file(char *path)
if (get_sec(elf, i, &ehdr, &shname, &shdr, &data))
continue;
- if (memcmp(shname, "events/", 7) == 0 ||
+ if (memcmp(shname, "kprobe/", 7) == 0 ||
+ memcmp(shname, "kretprobe/", 10) == 0 ||
memcmp(shname, "socket", 6) == 0)
load_and_attach(shname, data->d_buf, data->d_size);
}
@@ -201,3 +290,23 @@ 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 > 0) {
+ buf[sz] = 0;
+ puts(buf);
+ }
+ }
+}