The following commit has been merged into the x86/core branch of tip: Commit-ID: 9e1db76f44de4d9439e48c9ef61e5d457395202b Gitweb: https://git.kernel.org/tip/9e1db76f44de4d9439e48c9ef61e5d457395202b Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx> AuthorDate: Fri, 11 Mar 2022 10:44:37 +01:00 Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx> CommitterDate: Fri, 11 Mar 2022 13:05:08 +01:00 x86,bpf: Fix bpf_arch_text_poke() Alexei reported that BPF direct trampolines are no longer working with IBT=y builds. Ensure that bpf_arch_text_poke() can find the NOP callsite emitted by emit_prologue(). Fixes: 2f6f7bf13ab6 ("x86/ibt,bpf: Add ENDBR instructions to prologue and trampoline") Reported-by: Alexei Starovoitov <alexei.starovoitov@xxxxxxxxx> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> Link: https://lore.kernel.org/r/YionV0%2bv%2fcUBiOh0@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx --- arch/x86/net/bpf_jit_comp.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c index 159b79f..f071c03 100644 --- a/arch/x86/net/bpf_jit_comp.c +++ b/arch/x86/net/bpf_jit_comp.c @@ -395,6 +395,13 @@ int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type t, /* BPF poking in modules is not supported */ return -EINVAL; + /* + * See emit_prologue(), for IBT builds the trampoline hook is preceded + * with an ENDBR instruction. + */ + if (is_endbr(*(u32 *)ip)) + ip += ENDBR_INSN_SIZE; + return __bpf_arch_text_poke(ip, t, old_addr, new_addr, true); }
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