From mboxrd@z Thu Jan 1 00:00:00 1970 From: Martin KaFai Lau Subject: Re: [PATCH bpf-next v5 00/10] BTF: BPF Type Format Date: Thu, 7 Jun 2018 13:07:01 -0700 Message-ID: <20180607200701.bvsjzoq56rnggwfd@kafai-mbp> References: <20180607190510.qtj7gq4wbfewcn4g@kafai-mbp> <20180607193029.GG17292@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Cc: , Alexei Starovoitov , Daniel Borkmann , , Wang Nan , Jiri Olsa , Namhyung Kim , Ingo Molnar To: Arnaldo Carvalho de Melo Return-path: Received: from mx0b-00082601.pphosted.com ([67.231.153.30]:43722 "EHLO mx0b-00082601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751037AbeFGUHv (ORCPT ); Thu, 7 Jun 2018 16:07:51 -0400 Content-Disposition: inline In-Reply-To: <20180607193029.GG17292@kernel.org> Sender: netdev-owner@vger.kernel.org List-ID: On Thu, Jun 07, 2018 at 04:30:29PM -0300, Arnaldo Carvalho de Melo wrote: > Em Thu, Jun 07, 2018 at 12:05:10PM -0700, Martin KaFai Lau escreveu: > > On Thu, Jun 07, 2018 at 11:03:37AM -0300, Arnaldo Carvalho de Melo wrote: > > > Em Thu, Jun 07, 2018 at 10:54:01AM -0300, Arnaldo Carvalho de Melo escreveu: > > > > Em Tue, Jun 05, 2018 at 02:25:48PM -0700, Martin KaFai Lau escreveu: > > > > > [ btw, the latest commit (1 commit) should be 94a11b59e592 ]. > > > > So, the commit log message for the pahole patch is non-existent: > > > > https://github.com/iamkafai/pahole/commit/94a11b59e5920908085bfc8d24c92f95c8ffceaf > > > > we should do better in describing what is done and how, I'm staring > > > with a message you sent to the kernel part: > > > -- > > > This patch introduces BPF Type Format (BTF). > > > > BTF (BPF Type Format) is the meta data format which describes > > > the data types of BPF program/map. Hence, it basically focus > > > on the C programming language which the modern BPF is primary > > > using. The first use case is to provide a generic pretty print > > > capability for a BPF map. > > > I will add details in the next github respin/push. > > Ok, but I can do that if there is nothing else to do in the code at this > stage :-) > > > > Now I'm going to do the step-by-step guide on testing the feature just > > > introduced, and will try to convert from dwarf to BTF and back, compare > > > the pahole output for types encoded in DWARF and BTF, etc. > > > > If you have something ressembling this already, please share. > > > The pahole only has the encoder part. I tested with the verbose output > > from the "pahole -V -J". Loading the btf to the kernel is also tested. > > Ok, so here it goes my first stab at testing, using perf's BPF > integration: > > [root@jouet bpf]# cat hello.c > #include "stdio.h" > > int syscall_enter(openat)(void *ctx) > { > puts("Hello, world\n"); > return 0; > } > [root@jouet bpf]# cat ~/.perfconfig > [llvm] > dump-obj = true > [root@jouet bpf]# perf trace -e open*,hello.c touch /tmp/hello.BTF > LLVM: dumping hello.o > 0.017 ( ): __bpf_stdout__:Hello, world > 0.019 ( 0.011 ms): touch/28147 openat(dfd: CWD, filename: /etc/ld.so.cache, flags: CLOEXEC ) = 3 > 0.053 ( ): __bpf_stdout__:Hello, world > 0.055 ( 0.011 ms): touch/28147 openat(dfd: CWD, filename: /lib64/libc.so.6, flags: CLOEXEC ) = 3 > 0.354 ( 0.012 ms): touch/28147 open(filename: /usr/lib/locale/locale-archive, flags: CLOEXEC ) = 3 > 0.411 ( ): __bpf_stdout__:Hello, world > 0.412 ( 0.198 ms): touch/28147 openat(dfd: CWD, filename: /tmp/hello.BTF, flags: CREAT|NOCTTY|NONBLOCK|WRONLY, mode: IRUGO|IWUGO) = 3 > [root@jouet bpf]# > [root@jouet bpf]# file hello.o > hello.o: ELF 64-bit LSB relocatable, *unknown arch 0xf7* version 1 (SYSV), not stripped > [root@jouet bpf]# pahole --btf_encode hello.o > pahole: hello.o: No debugging information found > [root@jouet bpf]# > > [root@jouet bpf]# readelf -s hello.o > > Symbol table '.symtab' contains 5 entries: > Num: Value Size Type Bind Vis Ndx Name > 0: 0000000000000000 0 NOTYPE LOCAL DEFAULT UND > 1: 0000000000000000 0 NOTYPE GLOBAL DEFAULT 7 __bpf_stdout__ > 2: 0000000000000000 0 NOTYPE GLOBAL DEFAULT 5 _license > 3: 0000000000000000 0 NOTYPE GLOBAL DEFAULT 6 _version > 4: 0000000000000000 0 NOTYPE GLOBAL DEFAULT 3 syscall_enter_openat > [root@jouet bpf]# > [root@jouet bpf]# readelf -SW hello.o > There are 10 section headers, starting at offset 0x1f8: > > Section Headers: > [Nr] Name Type Address Off Size ES Flg Lk Inf Al > [ 0] NULL 0000000000000000 000000 000000 00 0 0 0 > [ 1] .strtab STRTAB 0000000000000000 000178 00007f 00 0 0 1 > [ 2] .text PROGBITS 0000000000000000 000040 000000 00 AX 0 0 4 > [ 3] syscalls:sys_enter_openat PROGBITS 0000000000000000 000040 000088 00 AX 0 0 8 > [ 4] .relsyscalls:sys_enter_openat REL 0000000000000000 000168 000010 10 9 3 8 > [ 5] license PROGBITS 0000000000000000 0000c8 000004 00 WA 0 0 1 > [ 6] version PROGBITS 0000000000000000 0000cc 000004 00 WA 0 0 4 > [ 7] maps PROGBITS 0000000000000000 0000d0 000010 00 WA 0 0 4 > [ 8] .rodata.str1.1 PROGBITS 0000000000000000 0000e0 00000e 01 AMS 0 0 1 > [ 9] .symtab SYMTAB 0000000000000000 0000f0 000078 18 1 1 8 > Key to Flags: > W (write), A (alloc), X (execute), M (merge), S (strings), I (info), > L (link order), O (extra OS processing required), G (group), T (TLS), > C (compressed), x (unknown), o (OS specific), E (exclude), > p (processor specific) > [root@jouet bpf]# > > Humm, lemme try something, add -g to clang-opt: > > [root@jouet bpf]# cat ~/.perfconfig > [llvm] > dump-obj = true > clang-opt = -g > [root@jouet bpf]# perf trace -e open*,hello.c touch /tmp/hello.BTF > LLVM: dumping hello.o > 0.185 ( ): __bpf_stdout__:Hello, world > 0.188 ( 0.009 ms): touch/19670 openat(dfd: CWD, filename: /etc/ld.so.cache, flags: CLOEXEC ) = 3 > 0.219 ( ): __bpf_stdout__:Hello, world > 0.220 ( 0.011 ms): touch/19670 openat(dfd: CWD, filename: /lib64/libc.so.6, flags: CLOEXEC ) = 3 > 0.480 ( 0.095 ms): touch/19670 open(filename: /usr/lib/locale/locale-archive, flags: CLOEXEC ) = 3 > 0.624 ( ): __bpf_stdout__:Hello, world > 0.626 ( 0.011 ms): touch/19670 openat(dfd: CWD, filename: /tmp/hello.BTF, flags: CREAT|NOCTTY|NONBLOCK|WRONLY, mode: IRUGO|IWUGO) = 3 > [root@jouet bpf]# file hello.o > hello.o: ELF 64-bit LSB relocatable, *unknown arch 0xf7* version 1 (SYSV), with debug_info, not stripped > [root@jouet bpf]# > > Much better: > > [root@jouet bpf]# readelf -SW hello.o > There are 25 section headers, starting at offset 0xc70: > > Section Headers: > [Nr] Name Type Address Off Size ES Flg Lk Inf Al > [ 0] NULL 0000000000000000 000000 000000 00 0 0 0 > [ 1] .strtab STRTAB 0000000000000000 000b50 000119 00 0 0 1 > [ 2] .text PROGBITS 0000000000000000 000040 000000 00 AX 0 0 4 > [ 3] syscalls:sys_enter_openat PROGBITS 0000000000000000 000040 000088 00 AX 0 0 8 > [ 4] .relsyscalls:sys_enter_openat REL 0000000000000000 000910 000010 10 24 3 8 > [ 5] license PROGBITS 0000000000000000 0000c8 000004 00 WA 0 0 1 > [ 6] version PROGBITS 0000000000000000 0000cc 000004 00 WA 0 0 4 > [ 7] maps PROGBITS 0000000000000000 0000d0 000010 00 WA 0 0 4 > [ 8] .rodata.str1.1 PROGBITS 0000000000000000 0000e0 00000e 01 AMS 0 0 1 > [ 9] .debug_str PROGBITS 0000000000000000 0000ee 00010e 01 MS 0 0 1 > [10] .debug_loc PROGBITS 0000000000000000 0001fc 000023 00 0 0 1 > [11] .debug_abbrev PROGBITS 0000000000000000 00021f 0000e3 00 0 0 1 > [12] .debug_info PROGBITS 0000000000000000 000302 00015e 00 0 0 1 > [13] .rel.debug_info REL 0000000000000000 000920 0001e0 10 24 12 8 > [14] .debug_ranges PROGBITS 0000000000000000 000460 000030 00 0 0 1 > [15] .debug_macinfo PROGBITS 0000000000000000 000490 000001 00 0 0 1 > [16] .debug_pubnames PROGBITS 0000000000000000 000491 00006e 00 0 0 1 > [17] .rel.debug_pubnames REL 0000000000000000 000b00 000010 10 24 16 8 > [18] .debug_pubtypes PROGBITS 0000000000000000 0004ff 00005a 00 0 0 1 > [19] .rel.debug_pubtypes REL 0000000000000000 000b10 000010 10 24 18 8 > [20] .debug_frame PROGBITS 0000000000000000 000560 000028 00 0 0 8 > [21] .rel.debug_frame REL 0000000000000000 000b20 000020 10 24 20 8 > [22] .debug_line PROGBITS 0000000000000000 000588 00006e 00 0 0 1 > [23] .rel.debug_line REL 0000000000000000 000b40 000010 10 24 22 8 > [24] .symtab SYMTAB 0000000000000000 0005f8 000318 18 1 29 8 > Key to Flags: > W (write), A (alloc), X (execute), M (merge), S (strings), I (info), > L (link order), O (extra OS processing required), G (group), T (TLS), > C (compressed), x (unknown), o (OS specific), E (exclude), > p (processor specific) > [root@jouet bpf]# > > [root@jouet bpf]# readelf -s hello.o > > Symbol table '.symtab' contains 33 entries: > Num: Value Size Type Bind Vis Ndx Name > 0: 0000000000000000 0 NOTYPE LOCAL DEFAULT UND > 1: 0000000000000000 0 NOTYPE LOCAL DEFAULT 9 > 2: 000000000000002d 0 NOTYPE LOCAL DEFAULT 9 > 3: 0000000000000044 0 NOTYPE LOCAL DEFAULT 9 > 4: 0000000000000053 0 NOTYPE LOCAL DEFAULT 9 > 5: 000000000000005c 0 NOTYPE LOCAL DEFAULT 9 > 6: 0000000000000061 0 NOTYPE LOCAL DEFAULT 9 > 7: 000000000000006a 0 NOTYPE LOCAL DEFAULT 9 > 8: 0000000000000073 0 NOTYPE LOCAL DEFAULT 9 > 9: 0000000000000077 0 NOTYPE LOCAL DEFAULT 9 > 10: 0000000000000086 0 NOTYPE LOCAL DEFAULT 9 > 11: 000000000000008b 0 NOTYPE LOCAL DEFAULT 9 > 12: 0000000000000098 0 NOTYPE LOCAL DEFAULT 9 > 13: 00000000000000a1 0 NOTYPE LOCAL DEFAULT 9 > 14: 00000000000000ac 0 NOTYPE LOCAL DEFAULT 9 > 15: 00000000000000b8 0 NOTYPE LOCAL DEFAULT 9 > 16: 00000000000000c4 0 NOTYPE LOCAL DEFAULT 9 > 17: 00000000000000d6 0 NOTYPE LOCAL DEFAULT 9 > 18: 00000000000000e8 0 NOTYPE LOCAL DEFAULT 9 > 19: 00000000000000fd 0 NOTYPE LOCAL DEFAULT 9 > 20: 0000000000000101 0 NOTYPE LOCAL DEFAULT 9 > 21: 0000000000000107 0 NOTYPE LOCAL DEFAULT 9 > 22: 0000000000000000 0 SECTION LOCAL DEFAULT 3 > 23: 0000000000000000 0 SECTION LOCAL DEFAULT 10 > 24: 0000000000000000 0 SECTION LOCAL DEFAULT 11 > 25: 0000000000000000 0 SECTION LOCAL DEFAULT 12 > 26: 0000000000000000 0 SECTION LOCAL DEFAULT 14 > 27: 0000000000000000 0 SECTION LOCAL DEFAULT 20 > 28: 0000000000000000 0 SECTION LOCAL DEFAULT 22 > 29: 0000000000000000 0 NOTYPE GLOBAL DEFAULT 7 __bpf_stdout__ > 30: 0000000000000000 0 NOTYPE GLOBAL DEFAULT 5 _license > 31: 0000000000000000 0 NOTYPE GLOBAL DEFAULT 6 _version > 32: 0000000000000000 0 NOTYPE GLOBAL DEFAULT 3 syscall_enter_openat > [root@jouet bpf]# > > Progress: > > [root@jouet bpf]# pahole --btf_encode hello.o > sh: llvm-objcopy: command not found > Failed to encode BTF > [root@jouet bpf]# > > [acme@jouet perf]$ llvm- > llvm-ar llvm-cov llvm-dis llvm-lib llvm-modextract llvm-profdata llvm-split > llvm-as llvm-c-test llvm-dlltool llvm-link llvm-mt llvm-ranlib llvm-stress > llvm-bcanalyzer llvm-cvtres llvm-dsymutil llvm-lto llvm-nm llvm-readelf llvm-strings > llvm-cat llvm-cxxdump llvm-dwarfdump llvm-lto2 llvm-objdump llvm-readobj llvm-symbolizer > llvm-config llvm-cxxfilt llvm-dwp llvm-mc llvm-opt-report llvm-rtdyld llvm-tblgen > llvm-config-64 llvm-diff llvm-extract llvm-mcmarkup llvm-pdbutil llvm-size llvm-xray > [acme@jouet perf]$ llvm- > > So this must be available in a newer llvm version? Which one? I should have put in the details in my last email or in the commit message, my bad. 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. Hence, I have been using the llvm's master in github which also has the llvm-objcopy. 2. The kernel's btf part only focus on the BPF map. Hence, the testing bpf program should have the map's key and map's value. e.g. tools/testing/selftests/bpf/test_btf_haskv.c > > [root@jouet bpf]# clang -v > clang version 5.0.1 (tags/RELEASE_501/final) > Target: x86_64-unknown-linux-gnu > Thread model: posix > InstalledDir: /usr/bin > Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-redhat-linux/7 > Found candidate GCC installation: /usr/lib/gcc/x86_64-redhat-linux/7 > Selected GCC installation: /usr/bin/../lib/gcc/x86_64-redhat-linux/7 > Candidate multilib: .;@m64 > Candidate multilib: 32;@m32 > Selected multilib: .;@m64 > [root@jouet bpf]# > > [acme@jouet perf]$ rpm -q clang llvm > clang-5.0.1-5.fc27.x86_64 > llvm-5.0.1-6.fc27.x86_64 > [acme@jouet perf]$ > [root@jouet bpf]# clang -v > clang version 5.0.1 (tags/RELEASE_501/final) > Target: x86_64-unknown-linux-gnu > Thread model: posix > InstalledDir: /usr/bin > Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-redhat-linux/7 > Found candidate GCC installation: /usr/lib/gcc/x86_64-redhat-linux/7 > Selected GCC installation: /usr/bin/../lib/gcc/x86_64-redhat-linux/7 > Candidate multilib: .;@m64 > Candidate multilib: 32;@m32 > Selected multilib: .;@m64 > [root@jouet bpf]# > > [acme@jouet perf]$ rpm -q clang llvm > clang-5.0.1-5.fc27.x86_64 > llvm-5.0.1-6.fc27.x86_64 > [acme@jouet perf]$ > > - Arnaldo