| Message ID | 1452756802-16511-2-git-send-email-zlim.lnx@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Wed, Jan 13, 2016 at 11:33:22PM -0800, Zi Shen Lim wrote: > 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> Looks good to me. Acked-by: Alexei Starovoitov <ast@kernel.org> technically it's a bug fix, though the shift problem is already mitigated. Will, any comments?
From: Zi Shen Lim <zlim.lnx@gmail.com> Date: Wed, 13 Jan 2016 23:33:22 -0800 > 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> Applied.
diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c index d6a53ef..d66bc1f 100644 --- a/arch/arm64/net/bpf_jit_comp.c +++ b/arch/arm64/net/bpf_jit_comp.c @@ -1,7 +1,7 @@ /* * 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 @@ -726,6 +726,20 @@ 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); @@ -788,6 +802,12 @@ 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);
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> --- Per discussion here: http://www.spinics.net/lists/arm-kernel/msg474179.html arch/arm64/net/bpf_jit_comp.c | 22 +++++++++++++++++++++- 1 file changed, 21 insertions(+), 1 deletion(-)