bpf, x86/unwind/orc: Support reliable unwinding through BPF stack frames #6452
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Introduce a bpf_has_frame_pointer() helper that uwninders can call to determine whether a given instruction pointer is within the valid frame pointer region of a BPF JIT program or trampoline (i.e., after the prologue, before the epilogue). This will enable livepatch (with the ORC unwinder) to reliably unwind through BPF JIT frames. Signed-off-by: Josh Poimboeuf <[email protected]> Acked-by: Song Liu <[email protected]>
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BPF JIT programs and trampolines use a frame pointer, so the current ORC unwinder strategy of falling back to frame pointers (when an ORC entry is missing) usually works in practice when unwinding through BPF JIT stack frames. However, that frame pointer fallback is just a guess, so the unwind gets marked unreliable for live patching, which can cause livepatch transition stalls. Make the common case reliable by calling the bpf_has_frame_pointer() helper to detect the valid frame pointer region of BPF JIT programs and trampolines. Fixes: ee9f8fc ("x86/unwind: Add the ORC unwinder") Reported-by: Andrey Grodzovsky <[email protected]> Closes: https://lore.kernel.org/[email protected] Signed-off-by: Josh Poimboeuf <[email protected]> Acked-by: Song Liu <[email protected]>
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Pull request for series with
subject: bpf, x86/unwind/orc: Support reliable unwinding through BPF stack frames
version: 1
url: https://patchwork.kernel.org/project/netdevbpf/list/?series=1029826