From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [PATCH v2 net] bpf: x86: fix epilogue generation for eBPF programs Date: Fri, 05 Dec 2014 21:24:33 -0800 (PST) Message-ID: <20141205.212433.750912400773154348.davem@davemloft.net> References: <1417301173-23691-1-git-send-email-ast@plumgrid.com> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: zlim.lnx@gmail.com, edumazet@google.com, dborkman@redhat.com, hpa@zytor.com, tglx@linutronix.de, mingo@kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org To: ast@plumgrid.com Return-path: In-Reply-To: <1417301173-23691-1-git-send-email-ast@plumgrid.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org From: Alexei Starovoitov Date: Sat, 29 Nov 2014 14:46:13 -0800 > classic BPF has a restriction that last insn is always BPF_RET. > eBPF doesn't have BPF_RET instruction and this restriction. > It has BPF_EXIT insn which can appear anywhere in the program > one or more times and it doesn't have to be last insn. > Fix eBPF JIT to emit epilogue when first BPF_EXIT is seen > and all other BPF_EXIT instructions will be emitted as jump. > > Since jump offset to epilogue is computed as: > jmp_offset = ctx->cleanup_addr - addrs[i] > we need to change type of cleanup_addr to signed to compute the offset as: > (long long) ((int)20 - (int)30) > instead of: > (long long) ((unsigned int)20 - (int)30) > > Fixes: 622582786c9e ("net: filter: x86: internal BPF JIT") > Signed-off-by: Alexei Starovoitov Applied, thanks.