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Commit 42ff712b authored by Zi Shen Lim's avatar Zi Shen Lim Committed by David S. Miller
Browse files

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: default avatarZi Shen Lim <zlim.lnx@gmail.com>
Suggested-by: default avatarAlexei Starovoitov <ast@kernel.org>
Acked-by: default avatarAlexei Starovoitov <ast@kernel.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent c94ae4f7

arch/arm64/net/bpf_jit_comp.c

+21 −1
Original line number Diff line number Diff line 
/*

 * BPF JIT compiler for ARM64

 *

 * Copyright (C) 2014-2015 Zi Shen Lim <zlim.lnx@gmail.com>

 * Copyright (C) 2014-2016 Zi Shen Lim <zlim.lnx@gmail.com>

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License version 2 as
@@ -737,6 +737,20 @@ static int build_body(struct jit_ctx *ctx) 
	return 0;

}



static int validate_code(struct jit_ctx *ctx)

{

	int i;



	for (i = 0; i < ctx->idx; i++) {

		u32 a64_insn = le32_to_cpu(ctx->image[i]);



		if (a64_insn == AARCH64_BREAK_FAULT)

			return -1;

	}



	return 0;

}



static inline void bpf_flush_icache(void *start, void *end)

{

	flush_icache_range((unsigned long)start, (unsigned long)end);
@@ -799,6 +813,12 @@ void bpf_int_jit_compile(struct bpf_prog *prog) 


	build_epilogue(&ctx);



	/* 3. Extra pass to validate JITed code. */

	if (validate_code(&ctx)) {

		bpf_jit_binary_free(header);

		goto out;

	}



	/* And we're done. */

	if (bpf_jit_enable > 1)

		bpf_jit_dump(prog->len, image_size, 2, ctx.image);