Messages in this thread | | | Subject | Re: [PATCH 0/2][v5] Add the ability to do BPF directed error injection | From | Alexei Starovoitov <> | Date | Wed, 8 Nov 2017 06:43:25 +0900 |
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On 11/8/17 5:28 AM, Josef Bacik wrote: > I'm sending this through Dave since it'll conflict with other BPF changes in his > tree, but since it touches tracing as well Dave would like a review from > somebody on the tracing side. > > v4->v5: > - disallow kprobe_override programs from being put in the prog map array so we > don't tail call into something we didn't check. This allows us to make the > normal path still fast without a bunch of percpu operations.
looks great to me. Peter, could you please review x86 bits?
> v3->v4: > - fix a build error found by kbuild test bot (I didn't wait long enough > apparently.) > - Added a warning message as per Daniels suggestion. > > v2->v3: > - added a ->kprobe_override flag to bpf_prog. > - added some sanity checks to disallow attaching bpf progs that have > ->kprobe_override set that aren't for ftrace kprobes. > - added the trace_kprobe_ftrace helper to check if the trace_event_call is a > ftrace kprobe. > - renamed bpf_kprobe_state to bpf_kprobe_override, fixed it so we only read this > value in the kprobe path, and thus only write to it if we're overriding or > clearing the override. > > v1->v2: > - moved things around to make sure that bpf_override_return could really only be > used for an ftrace kprobe. > - killed the special return values from trace_call_bpf. > - renamed pc_modified to bpf_kprobe_state so bpf_override_return could tell if > it was being called from an ftrace kprobe context. > - reworked the logic in kprobe_perf_func to take advantage of bpf_kprobe_state. > - updated the test as per Alexei's review. > > - Original message - > > A lot of our error paths are not well tested because we have no good way of > injecting errors generically. Some subystems (block, memory) have ways to > inject errors, but they are random so it's hard to get reproduceable results. > > With BPF we can add determinism to our error injection. We can use kprobes and > other things to verify we are injecting errors at the exact case we are trying > to test. This patch gives us the tool to actual do the error injection part. > It is very simple, we just set the return value of the pt_regs we're given to > whatever we provide, and then override the PC with a dummy function that simply > returns. > > Right now this only works on x86, but it would be simple enough to expand to > other architectures. Thanks, > > Josef >
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