Eric Lee / smarc-fsl-linux-kernel

09 Mar, 2016

1 commit

02 Apr, 2015

1 commit

  • b896c4f95   samples/bpf: Add simple non-portable kprobe filter example ... Browse Code »

    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
    Cc: Arnaldo Carvalho de Melo
    Cc: Arnaldo Carvalho de Melo
    Cc: Daniel Borkmann
    Cc: David S. Miller
    Cc: Jiri Olsa
    Cc: Linus Torvalds
    Cc: Masami Hiramatsu
    Cc: Namhyung Kim
    Cc: Peter Zijlstra
    Cc: Peter Zijlstra
    Cc: Steven Rostedt
    Link: http://lkml.kernel.org/r/1427312966-8434-7-git-send-email-ast@plumgrid.com
    Signed-off-by: Ingo Molnar

    Alexei Starovoitov
     

06 Dec, 2014

1 commit

  • 249b812d8   samples: bpf: elf_bpf file loader ... Browse Code »

    simple .o parser and loader using BPF syscall.
    .o is a standard ELF generated by LLVM backend

    It parses elf file compiled by llvm .c->.o
    - parses 'maps' section and creates maps via BPF syscall
    - parses 'license' section and passes it to syscall
    - parses elf relocations for BPF maps and adjusts BPF_LD_IMM64 insns
    by storing map_fd into insn->imm and marking such insns as BPF_PSEUDO_MAP_FD
    - loads eBPF programs via BPF syscall

    One ELF file can contain multiple BPF programs.

    int load_bpf_file(char *path);
    populates prog_fd[] and map_fd[] with FDs received from bpf syscall

    bpf_helpers.h - helper functions available to eBPF programs written in C

    Signed-off-by: Alexei Starovoitov
    Signed-off-by: David S. Miller

    Alexei Starovoitov