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arm64: bpf: add extra pass to handle faulty codegen
Code generation functions in arch/arm64/kernel/insn.c previously BUG_ON invalid parameters. Following change of that behavior, now we need to handle the error case where AARCH64_BREAK_FAULT is returned. Instead of error-handling on every emit() in JIT, we add a new validation pass at the end of JIT compilation. There's no point in running JITed code at run-time only to trap due to AARCH64_BREAK_FAULT. Instead, we drop this failed JIT compilation and allow the system to gracefully fallback on the BPF interpreter. Signed-off-by: Zi Shen Lim <zlim.lnx@gmail.com> Suggested-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: David S. Miller <davem@davemloft.net>
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@ -1,7 +1,7 @@
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/*
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* BPF JIT compiler for ARM64
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*
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* Copyright (C) 2014-2015 Zi Shen Lim <zlim.lnx@gmail.com>
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* Copyright (C) 2014-2016 Zi Shen Lim <zlim.lnx@gmail.com>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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@ -737,6 +737,20 @@ static int build_body(struct jit_ctx *ctx)
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return 0;
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}
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static int validate_code(struct jit_ctx *ctx)
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{
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int i;
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for (i = 0; i < ctx->idx; i++) {
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u32 a64_insn = le32_to_cpu(ctx->image[i]);
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if (a64_insn == AARCH64_BREAK_FAULT)
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return -1;
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}
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return 0;
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}
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static inline void bpf_flush_icache(void *start, void *end)
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{
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flush_icache_range((unsigned long)start, (unsigned long)end);
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@ -799,6 +813,12 @@ void bpf_int_jit_compile(struct bpf_prog *prog)
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build_epilogue(&ctx);
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/* 3. Extra pass to validate JITed code. */
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if (validate_code(&ctx)) {
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bpf_jit_binary_free(header);
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goto out;
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}
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/* And we're done. */
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if (bpf_jit_enable > 1)
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bpf_jit_dump(prog->len, image_size, 2, ctx.image);
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