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.
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| @@ -677,6 +677,10 @@ union bpf_attr { · 676 unmodified lines | ||
| 677 | 677 | * @buf: buf to fill |
| 678 | 678 | * @buf_size: size of the buf |
| 679 | 679 | * Return : 0 on success or negative error code |
| 680 | + * | |
| 681 | + * int bpf_override_return(pt_regs, rc) | |
| 682 | + * @pt_regs: pointer to struct pt_regs | |
| 683 | + * @rc: the return value to set | |
| 680 | 684 | */ |
| 681 | 685 | #define __BPF_FUNC_MAPPER(FN) \ |
| 682 | 686 | FN(unspec), \ |
| @@ -736,7 +740,8 @@ union bpf_attr { · 53 unmodified lines | ||
| 736 | 740 | FN(xdp_adjust_meta), \ |
| 737 | 741 | FN(perf_event_read_value), \ |
| 738 | 742 | FN(perf_prog_read_value), \ |
| 739 | − FN(getsockopt), | |
| 743 | + FN(getsockopt), \ | |
| 744 | + FN(override_return), | |
| 740 | 745 | |
| 741 | 746 | /* integer value in 'imm' field of BPF_CALL instruction selects which helper |
| 742 | 747 | * function eBPF program intends to call |