553a8f2f42
Josef Bacik says: ==================== This is the same as v8, just rebased onto the bpf tree. v8->v9: - rebased onto the bpf tree. v7->v8: - removed the _ASM_KPROBE_ERROR_INJECT since it was not needed. 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, Josef ==================== In patch "bpf: add a bpf_override_function helper" Alexei moved "ifdef CONFIG_BPF_KPROBE_OVERRIDE" few lines to fail program loading when kprobe_override is not available instead of failing at run-time. Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
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README
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.