From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ferruh Yigit Subject: Re: [PATCH v1] net/tap: explain how to compile eBPF C file Date: Wed, 4 Jul 2018 20:47:49 +0100 Message-ID: <48f3aef6-765d-66d4-305c-541bd2aa3eb7@intel.com> References: <1528733172-24747-1-git-send-email-ophirmu@mellanox.com> <3694221.zYt2n70HGy@xps> <2FAE2DE7-DB89-42F8-9010-E522187248AD@intel.com> <2475252.9oVMbiDvHd@xps> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Cc: "dev@dpdk.org" , Pascal Mazon , Olga Shern To: Ophir Munk , "Wiles, Keith" , Thomas Monjalon Return-path: Received: from mga07.intel.com (mga07.intel.com [134.134.136.100]) by dpdk.org (Postfix) with ESMTP id 982C51BEB9 for ; Wed, 4 Jul 2018 21:47:53 +0200 (CEST) In-Reply-To: Content-Language: en-US List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" On 6/12/2018 3:02 PM, Ophir Munk wrote: > Please note that other than cloning iproute2 we also need to install clang and llvm tools versions 3.7 and upper. > Not sure there are clang and llvm packages of the required versions for the common distributions. > I compiled the tools source code and installed them manually. Hi Keith, Thomas, What do you suggest on this patch? The "tap_bpf_program.c" is already withing the tap pmd this patch improves the doc about how to compile it, although it may not be so user friendly as Keith pointed, I believe better to get doc improvement here. And there is a code update "+#include "bpf_api.h", which includes a iproute2 header, I am not sure about this one and how to manage this dependency. > >> -----Original Message----- >> From: Wiles, Keith [mailto:keith.wiles@intel.com] >> Sent: Tuesday, June 12, 2018 4:53 PM >> To: Thomas Monjalon >> Cc: dev@dpdk.org; Ophir Munk ; Pascal Mazon >> ; Olga Shern >> Subject: Re: [dpdk-dev] [PATCH v1] net/tap: explain how to compile eBPF C >> file >> >> >> >>> On Jun 12, 2018, at 8:44 AM, Thomas Monjalon >> wrote: >>> >>> 12/06/2018 15:33, Wiles, Keith: >>>> >>>>> On Jun 12, 2018, at 7:58 AM, Thomas Monjalon >> wrote: >>>>> >>>>> 12/06/2018 14:36, Wiles, Keith: >>>>>> >>>>>>> On Jun 12, 2018, at 7:26 AM, Thomas Monjalon >> wrote: >>>>>>> >>>>>>> 11/06/2018 18:35, Wiles, Keith: >>>>>>>> >>>>>>>>> On Jun 11, 2018, at 11:06 AM, Ophir Munk >> wrote: >>>>>>>>> >>>>>>>>> This commit explains how to manually compile the C source file >>>>>>>>> tap_bpf_program.c into an ELF file using the clang compiler. >>>>>>>>> The code in tap_bpf_program.c requires definitions found in >>>>>>>>> iproute2 source code. This commit suggests cloning the iproute2 >>>>>>>>> git tree and include its path in the clang command. It also adds >>>>>>>>> inclusion of file bpf_api.h (required for eBPF definitions) >>>>>>>>> which is located in iproute2 source tree. For more details refer to >> TAP documentation. >>>>>>>>> This commit is related to commits [1] and [2]. >>>>>>>> >>>>>>>> Normally I would have suggested that eBPF be disable in the TAP >> driver as it requires external code and programs, but that ship has sailed. >>>>>>> >>>>>>> The external programs are required only to generate new >>>>>>> instructions, changing the behaviour of the BPF program. >>>>>>> Currently, the instructions for RSS behaviour are provided. >>>>>>> >>>>>>>> I would like to see building the tap_bpf_program.o as a target in the >> Makefile, this way the developer can just run the ‘make bpf_program’ target >> and it would be simpler and less error prone. >>>>> >>>>> As explained in the documentation, for now there is a dependency on >>>>> iproute2 for the compilation of this BPF program. >>>>> So we cannot make it as simple as a "make command". >>>>> Probably that we can rework it to change the dependency. >>>>> I heard there are some good BPF libraries available now? >>>> >>>> Well the dependence of iproute2 is really no different then requiring say >> libnuma, they just have to pull the code first to type the ‘make bpf_program’ >> right? >>> >>> The iproute2 dependency is different because it is not a library. >>> The .h file is never packaged. >>> So we need to download the sources and set -I to this directory. >> >> To eliminate the -I problem the clone could be done inside the tap directory >> and -I ./iproute2/include used, right? >> The make target could even clone the code into the tap directory, which >> means we can solve these problems you are pointing out. >> >> Go ahead and do what you want here, but making it harder for the developer >> should not be our normally mode of operation. >> >>> >>> >>>> If that is the case then a make target make sense to me. If iproute2 is not >> found then an error, right? >>> >>> >>>>>>> For this to happen, we need to improve the tools. >>>>>> >>>>>> In what way do we need to improve the tools and which tools are we >> talking about. Building the .o file below appears to be a simple set of >> command lines. I have a question in my original email about what tool. >>>>> >>>>> The .o file is only the an intermediate file. >>>>> The next step (numbered as 5 in this patch) is to extract the >>>>> section of BPF instructions to be uploaded in the kernel. >>>>> This step must be done by a "tool". Ophir did it by hacking tc, but >>>>> it is not upstreamed yet. >>>>> There could be other ways (possibly easier) to achieve the same result. >>>> >>>> Please change the doc to reflect the tool is not upstreamed yet and the >> developer needs to figure out how to extract the data from the binary. >>>> >>>> I used objdump -j l3_l4 -s tap_bpf_program.o and got a hex dump of >>>> the l3_l4 section >>>> >>>> 0000 bf160000 00000000 61681000 00000000 ... >>>> >>>> Someone schooled in the art of Python coding should be able to >>>> convert that output to a ‘C’ data array. :-) >>>> >>>>> >>>>>>> It is a work in progress. >>>>> >>>>> Contributions are welcome. >>>>> >>>>>>> This is a very first step to use Linux BPF with DPDK. >>>>>>> If there are more interests, we should really streamline its usage >>>>>>> for all parts of DPDK which runs on top of some kernel code. >>>>>> >>>>>> streamlining other parts of DPDK would be nice, but we are now talking >> about the tap/eBPF patch. >>>> >>>> Regards, >>>> Keith >> >> Regards, >> Keith >