From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arnaldo Carvalho de Melo Subject: Re: [PATCH bpf-next v5 00/10] BTF: BPF Type Format Date: Thu, 14 Jun 2018 14:18:06 -0300 Message-ID: <20180614171806.GG30043@kernel.org> References: <20180607190510.qtj7gq4wbfewcn4g@kafai-mbp> <20180607193029.GG17292@kernel.org> <20180607200701.bvsjzoq56rnggwfd@kafai-mbp> <20180612203124.GB22039@kernel.org> <20180612204126.GC22039@kernel.org> <20180613232638.yyhktiovl6oeawgt@kafai-mbp> <20180614150334.GF30043@kernel.org> <20180614162227.r72d7wk57unfhqvo@kafai-mbp.dhcp.thefacebook.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: netdev@vger.kernel.org, Alexei Starovoitov , Daniel Borkmann , kernel-team@fb.com, Wang Nan , Jiri Olsa , Namhyung Kim , Ingo Molnar To: Martin KaFai Lau Return-path: Received: from mail.kernel.org ([198.145.29.99]:41392 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754819AbeFNRSK (ORCPT ); Thu, 14 Jun 2018 13:18:10 -0400 Content-Disposition: inline In-Reply-To: <20180614162227.r72d7wk57unfhqvo@kafai-mbp.dhcp.thefacebook.com> Sender: netdev-owner@vger.kernel.org List-ID: Em Thu, Jun 14, 2018 at 09:22:27AM -0700, Martin KaFai Lau escreveu: > On Thu, Jun 14, 2018 at 12:03:34PM -0300, Arnaldo Carvalho de Melo wrote: > > > > > > > 1. The tools/testing/selftests/bpf/Makefile has the CLANG_FLAGS and > > > > > > LLC_FLAGS needed to compile the bpf prog. It requires a new > > > > > > "-mattr=dwarf" llc option which was added to the future > > > > > > llvm 7.0. > > [ ... ] > > > I tried it, but it didn't work, see: > > > > [root@jouet bpf]# cat hello.c > > #include "stdio.h" > > > > int syscall_enter(openat)(void *ctx) > > { > > puts("Hello, world\n"); > > return 0; > > } > > [root@jouet bpf]# trace -e openat,hello.c touch /tmp/kafai > > clang-6.0: error: unknown argument: '-mattr=dwarf' > "-mattr=dwarf" is currently a llc only option. > > tools/testing/selftests/bpf/Makefile has example on how to pipe clang to llc. > e.g.: > clang -g -O2 -target bpf -emit-llvm -c hello.c -o - | llc -march=bpf -mcpu=generic -mattr=dwarfris -filetype=obj -o hello.o Ok, so I'll probably add a llvm.opts .perfconfig entry that, if present will tell tools/perf/util/llvm-utils.c that piping the output of clang to llvm, so that we can use llvm specific options, needs to be done. Probably, for the time being I'll check for -g in llvm.clang-opt and if it is there, set up the piping... Just out of curiosity, is there any plan to have this as a clang option? Just to finish this thing here, lemme try a slightly modified version of your command line: [root@jouet bpf]# clang -D__KERNEL__ -D__NR_CPUS__=4 -DLINUX_VERSION_CODE=0x41100 -g -nostdinc -isystem /usr/lib/gcc/x86_64-redhat-linux/7/include -I/home/acme/git/linux/arch/x86/include -I./arch/x86/include/generated -I/home/acme/git/linux/include -I./include -I/home/acme/git/linux/arch/x86/include/uapi -I./arch/x86/include/generated/uapi -I/home/acme/git/linux/include/uapi -I./include/generated/uapi -include /home/acme/git/linux/include/linux/kconfig.h -I/home/acme/lib/include/perf/bpf -Wno-unused-value -Wno-pointer-sign -working-directory /lib/modules/4.17.0-rc5/build -c /home/acme/bpf/hello.c -target bpf -emit-llvm -O2 -o - | llc -march=bpf -mcpu=generic -mattr=dwarfris -filetype=obj -o hello2.o [root@jouet bpf]# [root@jouet bpf]# file hello2.o hello2.o: ELF 64-bit LSB relocatable, *unknown arch 0xf7* version 1 (SYSV), with debug_info, not stripped [root@jouet bpf]# pahole hello2.o struct bpf_map_def { unsigned int type; /* 0 4 */ unsigned int key_size; /* 4 4 */ unsigned int value_size; /* 8 4 */ unsigned int max_entries; /* 12 4 */ /* size: 16, cachelines: 1, members: 4 */ /* last cacheline: 16 bytes */ }; [root@jouet bpf]# Finally works, thanks. Thanks, - Arnaldo > > ERROR: unable to compile hello.c > > Hint: Check error message shown above. > > Hint: You can also pre-compile it into .o using: > > clang -target bpf -O2 -c hello.c > > with proper -I and -D options. > > event syntax error: 'hello.c' > > \___ Failed to load hello.c from source: Error when compiling BPF scriptlet > > > > (add -v to see detail) > > Run 'perf list' for a list of valid events > > > > Usage: perf trace [] [] > > or: perf trace [] -- [] > > or: perf trace record [] [] > > or: perf trace record [] -- [] > > > > -e, --event event/syscall selector. use 'perf list' to list available events > > [root@jouet bpf]# > > > > The full command line with that is: > > > > [root@jouet bpf]# trace -v -e openat,hello.c touch /tmp/kafai |& grep mattr > > set env: CLANG_OPTIONS=-g -mattr=dwarf > > llvm compiling command : /usr/local/bin/clang -D__KERNEL__ -D__NR_CPUS__=4 -DLINUX_VERSION_CODE=0x41100 -g -mattr=dwarf -nostdinc -isystem /usr/lib/gcc/x86_64-redhat-linux/7/include -I/home/acme/git/linux/arch/x86/include -I./arch/x86/include/generated -I/home/acme/git/linux/include -I./include -I/home/acme/git/linux/arch/x86/include/uapi -I./arch/x86/include/generated/uapi -I/home/acme/git/linux/include/uapi -I./include/generated/uapi -include /home/acme/git/linux/include/linux/kconfig.h -I/home/acme/lib/include/perf/bpf -Wno-unused-value -Wno-pointer-sign -working-directory /lib/modules/4.17.0-rc5/build -c /home/acme/bpf/hello.c -target bpf -O2 -o - > > clang-6.0: error: unknown argument: '-mattr=dwarf' > > [root@jouet bpf]# > > > > This is with these llvm and clang trees: > > > > [root@jouet llvm]# git log --oneline -5 > > 98c78e82f54 (HEAD -> master, origin/master, origin/HEAD) [asan] Instrument comdat globals on COFF targets > > 6ad988b5998 [DAGCombiner] clean up comments; NFC > > a735ba5b795 [X86][SSE] Support v8i16/v16i16 rotations > > 1503b9f6fe8 [x86] add tests for node-level FMF; NFC > > 4a49826736f [x86] regenerate test checks; NFC > > [root@jouet llvm]# > > > > [root@jouet llvm]# cd tools/clang/ > > [root@jouet clang]# git log --oneline -5 > > 8c873daccc (HEAD -> master, origin/master, origin/HEAD) [X86] Add builtins for vpermq/vpermpd instructions to enable target feature checking. > > a344be6ba4 [X86] Change immediate type for some builtins from char to int. > > dcdd53793e [CUDA] Fix emission of constant strings in sections > > a90c85acaf [X86] Add builtins for shufps and shufpd to enable target feature and immediate range checking. > > ff71c0eccc [X86] Add builtins for pshufd, pshuflw, and pshufhw to enable target feature and immediate range checking. > > [root@jouet clang]# > > > > [root@jouet clang]# git log | grep mattr=dwarf > > [root@jouet clang]# cd - > > /home/acme/git.tmp/git/llvm > > [root@jouet llvm]# git log | grep mattr=dwarf > > bpf: introduce -mattr=dwarfris to disable DwarfUsesRelocationsAcrossSections > > This patch introduces a new flag -mattr=dwarfris > > [root@jouet llvm]# > > > > Humm, so its -mattr=dwarfris and not -attr=dwarf? > > > > Didn't help :-\ > > > > commit 0e0047f8c9ada2f0fe0c5f01579a80e2455b8df5 > > Author: Yonghong Song > > Date: Thu Mar 1 23:04:59 2018 +0000 > > > > bpf: introduce -mattr=dwarfris to disable DwarfUsesRelocationsAcrossSections > > > > Commit e4507fb8c94b ("bpf: disable DwarfUsesRelocationsAcrossSections") > > disables MCAsmInfo DwarfUsesRelocationsAcrossSections unconditionally > > so that dwarf will not use cross section (between dwarf and symbol table) > > relocations. This new debug format enables pahole to dump structures > > correctly as libdwarves.so does not have BPF backend support yet. > > > > This new debug format, however, breaks bcc (https://github.com/iovisor/bcc) > > source debug output as llvm in-memory Dwarf support has some issues to > > handle it. More specifically, with DwarfUsesRelocationsAcrossSections > > disabled, JIT compiler does not generate .debug_abbrev and Dwarf > > DIE (debug info entry) processing is not happy about this. > > > > This patch introduces a new flag -mattr=dwarfris > > (dwarf relocation in section) to disable DwarfUsesRelocationsAcrossSections. > > DwarfUsesRelocationsAcrossSections is true by default. > > > > Signed-off-by: Yonghong Song > > > > git-svn-id: https://urldefense.proofpoint.com/v2/url?u=https-3A__llvm.org_svn_llvm-2Dproject_llvm_trunk-40326505&d=DwIBAg&c=5VD0RTtNlTh3ycd41b3MUw&r=VQnoQ7LvghIj0gVEaiQSUw&m=LO28-RE-2ZJTXto_gff4BgnxXkbUq8d2CEz1jD_wDl4&s=VCR3pGVfY54-OsZ3BqRsOr3FF5JVyltwbnbzu30_4EY&e= 91177308-0d34-0410-b5e6-96231b3b80d8 > > > >