| Message ID | 1511385814-20863-1-git-send-email-josef@toxicpanda.com |
|---|---|
| Headers | show |
| Series | Add the ability to do BPF directed error injection | expand |
On Wed, Nov 22, 2017 at 04:23:29PM -0500, Josef Bacik wrote: > This is hopefully the final version, I've addressed the comment by Igno and > added his Acks. > > v6->v7: > - moved the opt-in macro to bpf.h out of kprobes.h. Thanks Josef! All patches look great to me. We'll probably take them all into bpf-next.git to start testing together with other bpf changes and when net-next reopens will send them to Dave. Then optionally can send pull-req for the first patch only to tip if Ingo thinks that there can be conflicts with the work happening in parallel on kprobe/x86 bits. This way hopefully there will be no conflicts during the next merge window. Makes sense? > v5->v6: > - add BPF_ALLOW_ERROR_INJECTION() tagging for functions that will support this > feature. This way only functions that opt-in will be allowed to be > overridden. > - added a btrfs patch to allow error injection for open_ctree() so that the bpf > sample actually works. > > 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. > > 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
On 11/22/2017 10:23 PM, Josef Bacik wrote: > This is hopefully the final version, I've addressed the comment by Igno and > added his Acks. > > v6->v7: > - moved the opt-in macro to bpf.h out of kprobes.h. > > v5->v6: > - add BPF_ALLOW_ERROR_INJECTION() tagging for functions that will support this > feature. This way only functions that opt-in will be allowed to be > overridden. > - added a btrfs patch to allow error injection for open_ctree() so that the bpf > sample actually works. > > 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. > > 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, Ok, given the remaining feedback from Ingo was addressed and therefore the series acked, I've applied it to bpf-next tree, thanks Josef.