Re: [PATCH bpf-next 1/2] bpf, x86: patch tail-call fentry slot on non-IBT JITs
From: Alexei Starovoitov <hidden>
Date: 2026-03-27 14:24:26
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On Fri, Mar 27, 2026 at 7:16 AM Takeru Hayasaka [off-list ref] wrote:
x86 tail-call fentry patching mirrors CALL text pokes to the tail-call landing slot. The helper that locates that mirrored slot assumes an ENDBR-prefixed landing, which works on IBT JITs but fails on non-IBT JITs where the landing starts directly with the 5-byte patch slot.
tailcalls are deprecated. We should go the other way and disable them ibt jit instead. The less interaction between fentry and tailcall the better. pw-bot: cr