x86,bpf: Avoid IBT objtool warning
Clang can inline emit_indirect_jump() and then folds constants, which results in: | vmlinux.o: warning: objtool: emit_bpf_dispatcher()+0x6a4: relocation to !ENDBR: .text.__x86.indirect_thunk+0x40 | vmlinux.o: warning: objtool: emit_bpf_dispatcher()+0x67d: relocation to !ENDBR: .text.__x86.indirect_thunk+0x40 | vmlinux.o: warning: objtool: emit_bpf_tail_call_indirect()+0x386: relocation to !ENDBR: .text.__x86.indirect_thunk+0x20 | vmlinux.o: warning: objtool: emit_bpf_tail_call_indirect()+0x35d: relocation to !ENDBR: .text.__x86.indirect_thunk+0x20 Suppress the optimization such that it must emit a code reference to the __x86_indirect_thunk_array[] base. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Alexei Starovoitov <ast@kernel.org> Link: https://lkml.kernel.org/r/20220405075531.GB30877@worktop.programming.kicks-ass.net
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@ -412,6 +412,7 @@ static void emit_indirect_jump(u8 **pprog, int reg, u8 *ip)
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EMIT_LFENCE();
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EMIT_LFENCE();
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EMIT2(0xFF, 0xE0 + reg);
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EMIT2(0xFF, 0xE0 + reg);
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} else if (cpu_feature_enabled(X86_FEATURE_RETPOLINE)) {
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} else if (cpu_feature_enabled(X86_FEATURE_RETPOLINE)) {
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OPTIMIZER_HIDE_VAR(reg);
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emit_jump(&prog, &__x86_indirect_thunk_array[reg], ip);
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emit_jump(&prog, &__x86_indirect_thunk_array[reg], ip);
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} else
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} else
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#endif
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#endif
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