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| author | Alexei Starovoitov | 2015-03-25 20:49:23 +0100 |
|---|---|---|
| committer | Ingo Molnar | 2015-04-02 13:25:50 +0200 |
| commit | b896c4f95ab4052d6bad3acde95167d30242a84f (patch) | |
| tree | 8c18a3ca9f2b389823d7181db606fa3c8d2eccc7 /samples/bpf/bpf_load.h | |
| parent | tracing: Allow BPF programs to call bpf_trace_printk() (diff) | |
| download | kernel-qcow2-linux-b896c4f95ab4052d6bad3acde95167d30242a84f.tar.gz kernel-qcow2-linux-b896c4f95ab4052d6bad3acde95167d30242a84f.tar.xz kernel-qcow2-linux-b896c4f95ab4052d6bad3acde95167d30242a84f.zip | |
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.h')
| -rw-r--r-- | samples/bpf/bpf_load.h | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/samples/bpf/bpf_load.h b/samples/bpf/bpf_load.h index 27789a34f5e6..cbd7c2b532b9 100644 --- a/samples/bpf/bpf_load.h +++ b/samples/bpf/bpf_load.h @@ -6,6 +6,7 @@ extern int map_fd[MAX_MAPS]; extern int prog_fd[MAX_PROGS]; +extern int event_fd[MAX_PROGS]; /* parses elf file compiled by llvm .c->.o * . parses 'maps' section and creates maps via BPF syscall @@ -21,4 +22,6 @@ extern int prog_fd[MAX_PROGS]; */ int load_bpf_file(char *path); +void read_trace_pipe(void); + #endif |