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bpf: add a bpf_override_function helper

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Error injection is sloppy and very ad-hoc.  BPF could fill this niche
perfectly with it's kprobe functionality.  We could make sure errors are
only triggered in specific call chains that we care about with very
specific situations.  Accomplish this with the bpf_override_funciton
helper.  This will modify the probe'd callers return value to the
specified value and set the PC to an override function that simply
returns, bypassing the originally probed function.  This gives us a nice
clean way to implement systematic error injection for all of our code
paths.

Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Josef Bacik <jbacik@fb.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Josef Bacik 2017-11-07 15:28:42 -05:00 • committed by David S. Miller
parent 54985120a1
commit dd0bb688ea
15 changed files with 133 additions and 9 deletions
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7
kernel/events/core.c
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@ -8171,6 +8171,13 @@ static int perf_event_set_bpf_prog(struct perf_event *event, u32 prog_fd)
return -EINVAL;
}
/* Kprobe override only works for kprobes, not uprobes. */
if (prog->kprobe_override &&
!(event->tp_event->flags & TRACE_EVENT_FL_KPROBE)) {
bpf_prog_put(prog);
return -EINVAL;
}
if (is_tracepoint || is_syscall_tp) {
int off = trace_event_get_offsets(event->tp_event);