Commit Graph

3 Commits

Author SHA1 Message Date
Daniel Borkmann 02413cabd6 bpf, samples: don't zero data when not needed
Remove the zero initialization in the sample programs where appropriate.
Note that this is an optimization which is now possible, old programs
still doing the zero initialization are just fine as well. Also, make
sure we don't have padding issues when we don't memset() the entire
struct anymore.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
2016-04-14 21:40:42 -04:00
Michael Holzheu d912557b34 samples: bpf: enable trace samples for s390x
The trace bpf samples do not compile on s390x because they use x86
specific fields from the "pt_regs" structure.

Fix this and access the fields via new PT_REGS macros.

Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Acked-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2015-07-08 15:17:45 -07:00
Alexei Starovoitov b896c4f95a 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>
2015-04-02 13:25:50 +02:00