Date:   Fri, 10 Jun 2022 11:45:48 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     Jiri Olsa <jolsa@...nel.org>, Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        "linux-perf-use." <linux-perf-users@...r.kernel.org>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        Ian Rogers <irogers@...gle.com>
Subject: Re: [PATCHv4 bpf-next 0/2] perf tools: Fix prologue generation

On Fri, Jun 10, 2022 at 11:34 AM Arnaldo Carvalho de Melo
<acme@...nel.org> wrote:
>
> Em Thu, Jun 09, 2022 at 01:31:52PM -0700, Andrii Nakryiko escreveu:
> > On Fri, Jun 3, 2022 at 1:45 PM Jiri Olsa <jolsa@...nel.org> wrote:
> > >
> > > hi,
> > > sending change we discussed some time ago [1] to get rid of
> > > some deprecated functions we use in perf prologue code.
> > >
> > > Despite the gloomy discussion I think the final code does
> > > not look that bad ;-)
> > >
> > > This patchset removes following libbpf functions from perf:
> > >   bpf_program__set_prep
> > >   bpf_program__nth_fd
> > >   struct bpf_prog_prep_result
> > >
> > > v4 changes:
> > >   - fix typo [Andrii]
> > >
> > > v3 changes:
> > >   - removed R0/R1 zero init in libbpf_prog_prepare_load_fn,
> > >     because it's not needed [Andrii]
> > >   - rebased/post on top of bpf-next/master which now has
> > >     all the needed perf/core changes
> > >
> > > v2 changes:
> > >   - use fallback section prog handler, so we don't need to
> > >     use section prefix [Andrii]
> > >   - realloc prog->insns array in bpf_program__set_insns [Andrii]
> > >   - squash patch 1 from previous version with
> > >     bpf_program__set_insns change [Daniel]
> > >   - patch 3 already merged [Arnaldo]
> > >   - added more comments
> > >
> > > thanks,
> > > jirka
> > >
> >
> > Arnaldo, can I get an ack from you for this patch set? Thank you!
>
> So, before these patches:
>
> [acme@...co perf-urgent]$ git log --oneline -5
> 22905f78d181f446 (HEAD) libperf evsel: Open shouldn't leak fd on failure
> a3c6da3dbd4bdf9c perf test: Fix "perf stat CSV output linter" test on s390
> 785cb9e85e8ba66f perf unwind: Fix uninitialized variable
> 874c8ca1e60b2c56 netfs: Fix gcc-12 warning by embedding vfs inode in netfs_i_context
> 3d9f55c57bc3659f Merge tag 'fs_for_v5.19-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs
> [acme@...co perf-urgent]$ sudo su -
> [root@...co ~]# perf -v
> perf version 5.19.rc1.g22905f78d181
> [root@...co ~]# perf test 42
>  42: BPF filter                                                      :
>  42.1: Basic BPF filtering                                           : Ok
>  42.2: BPF pinning                                                   : Ok
>  42.3: BPF prologue generation                                       : Ok
> [root@...co ~]#
>
> And after:
>
> [acme@...co perf-urgent]$ git log --oneline -5
> f8ec656242acf2de (HEAD -> perf/urgent) perf tools: Rework prologue generation code
> a750a8dd7e5d2d4b perf tools: Register fallback libbpf section handler
> d28f2a8ad42af160 libperf evsel: Open shouldn't leak fd on failure
> a3c6da3dbd4bdf9c perf test: Fix "perf stat CSV output linter" test on s390
> 785cb9e85e8ba66f perf unwind: Fix uninitialized variable
> [acme@...co perf-urgent]$ sudo su -
> [root@...co ~]# perf -v
> perf version 5.19.rc1.gf8ec656242ac
> [root@...co ~]# perf test 42
>  42: BPF filter                                                      :
>  42.1: Basic BPF filtering                                           : FAILED!
>  42.2: BPF pinning                                                   : FAILED!
>  42.3: BPF prologue generation                                       : Ok
> [root@...co ~]#
>
> Jiri, can you try reproducing these? Do this require some other work
> that is in bpf-next/master? Lemme try...
>
> Further details:
>
> [acme@...co perf-urgent]$ clang -v
> clang version 13.0.0 (five:git/llvm-project d667b96c98438edcc00ec85a3b151ac2dae862f3)
> Target: x86_64-unknown-linux-gnu
> Thread model: posix
> InstalledDir: /usr/local/bin
> Found candidate GCC installation: /usr/lib/gcc/x86_64-redhat-linux/12
> Selected GCC installation: /usr/lib/gcc/x86_64-redhat-linux/12
> Candidate multilib: .;@m64
> Candidate multilib: 32;@m32
> Selected multilib: .;@m64
> [acme@...co perf-urgent]$ cat /etc/fedora-release
> Fedora release 36 (Thirty Six)
> [acme@...co perf-urgent]$ gcc -v
> Using built-in specs.
> COLLECT_GCC=/usr/bin/gcc
> COLLECT_LTO_WRAPPER=/usr/libexec/gcc/x86_64-redhat-linux/12/lto-wrapper
> OFFLOAD_TARGET_NAMES=nvptx-none
> OFFLOAD_TARGET_DEFAULT=1
> Target: x86_64-redhat-linux
> Configured with: ../configure --enable-bootstrap --enable-languages=c,c++,fortran,objc,obj-c++,ada,go,d,lto --prefix=/usr --mandir=/usr/share/man --infodir=/usr/share/info --with-bugurl=http://bugzilla.redhat.com/bugzilla --enable-shared --enable-threads=posix --enable-checking=release --enable-multilib --with-system-zlib --enable-__cxa_atexit --disable-libunwind-exceptions --enable-gnu-unique-object --enable-linker-build-id --with-gcc-major-version-only --enable-libstdcxx-backtrace --with-linker-hash-style=gnu --enable-plugin --enable-initfini-array --with-isl=/builddir/build/BUILD/gcc-12.1.1-20220507/obj-x86_64-redhat-linux/isl-install --enable-offload-targets=nvptx-none --without-cuda-driver --enable-offload-defaulted --enable-gnu-indirect-function --enable-cet --with-tune=generic --with-arch_32=i686 --build=x86_64-redhat-linux --with-build-config=bootstrap-lto --enable-link-serialization=1
> Thread model: posix
> Supported LTO compression algorithms: zlib zstd
> gcc version 12.1.1 20220507 (Red Hat 12.1.1-1) (GCC)
> [acme@...co perf-urgent]$
>
> [root@...co ~]# perf test -v 42
>  42: BPF filter                                                      :
>  42.1: Basic BPF filtering                                           :
> --- start ---
> test child forked, pid 638881
> Kernel build dir is set to /lib/modules/5.17.11-300.fc36.x86_64/build
> set env: KBUILD_DIR=/lib/modules/5.17.11-300.fc36.x86_64/build
> unset env: KBUILD_OPTS
> include option is set to -nostdinc -I./arch/x86/include -I./arch/x86/include/generated  -I./include -I./arch/x86/include/uapi -I./arch/x86/include/generated/uapi -I./include/uapi -I./include/generated/uapi -include ./include/linux/compiler-version.h -include ./include/linux/kconfig.h
> set env: NR_CPUS=8
> set env: LINUX_VERSION_CODE=0x5110b
> set env: CLANG_EXEC=/usr/lib64/ccache/clang
> set env: CLANG_OPTIONS=-xc -g
> set env: KERNEL_INC_OPTIONS=-nostdinc -I./arch/x86/include -I./arch/x86/include/generated  -I./include -I./arch/x86/include/uapi -I./arch/x86/include/generated/uapi -I./include/uapi -I./include/generated/uapi -include ./include/linux/compiler-version.h -include ./include/linux/kconfig.h
> set env: PERF_BPF_INC_OPTIONS=-I/home/acme/lib/perf/include/bpf
> set env: WORKING_DIR=/lib/modules/5.17.11-300.fc36.x86_64/build
> set env: CLANG_SOURCE=-
> llvm compiling command template: echo '// SPDX-License-Identifier: GPL-2.0
> /*
>  * bpf-script-example.c
>  * Test basic LLVM building
>  */
> #ifndef LINUX_VERSION_CODE
> # error Need LINUX_VERSION_CODE
> # error Example: for 4.2 kernel, put 'clang-opt="-DLINUX_VERSION_CODE=0x40200" into llvm section of ~/.perfconfig'
> #endif
> #define BPF_ANY 0
> #define BPF_MAP_TYPE_ARRAY 2
> #define BPF_FUNC_map_lookup_elem 1
> #define BPF_FUNC_map_update_elem 2
>
> static void *(*bpf_map_lookup_elem)(void *map, void *key) =
>         (void *) BPF_FUNC_map_lookup_elem;
> static void *(*bpf_map_update_elem)(void *map, void *key, void *value, int flags) =
>         (void *) BPF_FUNC_map_update_elem;
>
> struct bpf_map_def {
>         unsigned int type;
>         unsigned int key_size;
>         unsigned int value_size;
>         unsigned int max_entries;
> };
>
> #define SEC(NAME) __attribute__((section(NAME), used))
> struct bpf_map_def SEC("maps") flip_table = {
>         .type = BPF_MAP_TYPE_ARRAY,
>         .key_size = sizeof(int),
>         .value_size = sizeof(int),
>         .max_entries = 1,
> };
>
> SEC("func=do_epoll_wait")
> int bpf_func__SyS_epoll_pwait(void *ctx)
> {
>         int ind =0;
>         int *flag = bpf_map_lookup_elem(&flip_table, &ind);
>         int new_flag;
>         if (!flag)
>                 return 0;
>         /* flip flag and store back */
>         new_flag = !*flag;
>         bpf_map_update_elem(&flip_table, &ind, &new_flag, BPF_ANY);
>         return new_flag;
> }
> char _license[] SEC("license") = "GPL";
> int _version SEC("version") = LINUX_VERSION_CODE;
> ' | $CLANG_EXEC -D__KERNEL__ -D__NR_CPUS__=$NR_CPUS -DLINUX_VERSION_CODE=$LINUX_VERSION_CODE $CLANG_OPTIONS $PERF_BPF_INC_OPTIONS $KERNEL_INC_OPTIONS -Wno-unused-value -Wno-pointer-sign -working-directory $WORKING_DIR -c "$CLANG_SOURCE" -target bpf $CLANG_EMIT_LLVM -O2 -o - $LLVM_OPTIONS_PIPE
> llvm compiling command : echo '// SPDX-License-Identifier: GPL-2.0
> /*
>  * bpf-script-example.c
>  * Test basic LLVM building
>  */
> #ifndef LINUX_VERSION_CODE
> # error Need LINUX_VERSION_CODE
> # error Example: for 4.2 kernel, put 'clang-opt=-DLINUX_VERSION_CODE=0x40200 into llvm section of ~/.perfconfig'
> #endif
> #define BPF_ANY 0
> #define BPF_MAP_TYPE_ARRAY 2
> #define BPF_FUNC_map_lookup_elem 1
> #define BPF_FUNC_map_update_elem 2
>
> static void *(*bpf_map_lookup_elem)(void *map, void *key) =
>         (void *) BPF_FUNC_map_lookup_elem;
> static void *(*bpf_map_update_elem)(void *map, void *key, void *value, int flags) =
>         (void *) BPF_FUNC_map_update_elem;
>
> struct bpf_map_def {
>         unsigned int type;
>         unsigned int key_size;
>         unsigned int value_size;
>         unsigned int max_entries;
> };
>
> #define SEC(NAME) __attribute__((section(NAME), used))
> struct bpf_map_def SEC(maps) flip_table = {
>         .type = BPF_MAP_TYPE_ARRAY,
>         .key_size = sizeof(int),
>         .value_size = sizeof(int),
>         .max_entries = 1,
> };
>
> SEC(func=do_epoll_wait)
> int bpf_func__SyS_epoll_pwait(void *ctx)
> {
>         int ind =0;
>         int *flag = bpf_map_lookup_elem(&flip_table, &ind);
>         int new_flag;
>         if (!flag)
>                 return 0;
>         /* flip flag and store back */
>         new_flag = !*flag;
>         bpf_map_update_elem(&flip_table, &ind, &new_flag, BPF_ANY);
>         return new_flag;
> }
> char _license[] SEC(license) = GPL;
> int _version SEC(version) = LINUX_VERSION_CODE;
> ' | /usr/lib64/ccache/clang -D__KERNEL__ -D__NR_CPUS__=8 -DLINUX_VERSION_CODE=0x5110b -xc -g -I/home/acme/lib/perf/include/bpf -nostdinc -I./arch/x86/include -I./arch/x86/include/generated  -I./include -I./arch/x86/include/uapi -I./arch/x86/include/generated/uapi -I./include/uapi -I./include/generated/uapi -include ./include/linux/compiler-version.h -include ./include/linux/kconfig.h  -Wno-unused-value -Wno-pointer-sign -working-directory /lib/modules/5.17.11-300.fc36.x86_64/build -c - -target bpf  -O2 -o -
> libbpf: loading object '[basic_bpf_test]' from buffer
> libbpf: elf: section(3) func=do_epoll_wait, size 192, link 0, flags 6, type=1
> libbpf: sec 'func=do_epoll_wait': found program 'bpf_func__SyS_epoll_pwait' at insn offset 0 (0 bytes), code size 24 insns (192 bytes)
> libbpf: elf: section(4) .relfunc=do_epoll_wait, size 32, link 22, flags 0, type=9
> libbpf: elf: section(5) maps, size 16, link 0, flags 3, type=1
> libbpf: elf: section(6) license, size 4, link 0, flags 3, type=1
> libbpf: license of [basic_bpf_test] is GPL
> libbpf: elf: section(7) version, size 4, link 0, flags 3, type=1
> libbpf: kernel version of [basic_bpf_test] is 5110b
> libbpf: elf: section(13) .BTF, size 576, link 0, flags 0, type=1
> libbpf: elf: section(15) .BTF.ext, size 256, link 0, flags 0, type=1
> libbpf: elf: section(22) .symtab, size 336, link 1, flags 0, type=2
> libbpf: looking for externs among 14 symbols...
> libbpf: collected 0 externs total
> libbpf: elf: found 1 legacy map definitions (16 bytes) in [basic_bpf_test]
> libbpf: map 'flip_table' (legacy): legacy map definitions are deprecated, use BTF-defined maps instead
> libbpf: map 'flip_table' (legacy): at sec_idx 5, offset 0.
> libbpf: map 11 is "flip_table"
> libbpf: Use of BPF_ANNOTATE_KV_PAIR is deprecated, use BTF-defined maps in .maps section instead
> libbpf: map:flip_table container_name:____btf_map_flip_table cannot be found in BTF. Missing BPF_ANNOTATE_KV_PAIR?
> libbpf: sec '.relfunc=do_epoll_wait': collecting relocation for section(3) 'func=do_epoll_wait'
> libbpf: sec '.relfunc=do_epoll_wait': relo #0: insn #4 against 'flip_table'
> libbpf: prog 'bpf_func__SyS_epoll_pwait': found map 0 (flip_table, sec 5, off 0) for insn #4
> libbpf: sec '.relfunc=do_epoll_wait': relo #1: insn #17 against 'flip_table'
> libbpf: prog 'bpf_func__SyS_epoll_pwait': found map 0 (flip_table, sec 5, off 0) for insn #17
> bpf: config program 'func=do_epoll_wait'
> symbol:do_epoll_wait file:(null) line:0 offset:0 return:0 lazy:(null)
> bpf: config 'func=do_epoll_wait' is ok
> Looking at the vmlinux_path (8 entries long)
> symsrc__init: build id mismatch for vmlinux.
> Using /usr/lib/debug/lib/modules/5.17.11-300.fc36.x86_64/vmlinux for symbols
> Open Debuginfo file: /usr/lib/debug/.build-id/f2/26f5d75e6842add57095a0615a1e5c16783dd7.debug
> Try to find probe point from debuginfo.
> Matched function: do_epoll_wait [38063fb]
> Probe point found: do_epoll_wait+0
> Found 1 probe_trace_events.
> Opening /sys/kernel/tracing//kprobe_events write=1
> Opening /sys/kernel/tracing//README write=0
> Writing event: p:perf_bpf_probe/func _text+3943040
> libbpf: map 'flip_table': created successfully, fd=4
> libbpf: prog 'bpf_func__SyS_epoll_pwait': BPF program load failed: Invalid argument
> libbpf: prog 'bpf_func__SyS_epoll_pwait': -- BEGIN PROG LOAD LOG --
> Invalid insn code at line_info[11].insn_off

Mismatched line_info.

Jiri, I think we need to clear func_info and line_info in
bpf_program__set_insns() because at that point func/line info can be
mismatched and won't correspond to the actual set of instructions.

Arnaldo, thanks for testing and providing details!

> processed 0 insns (limit 1000000) max_states_per_insn 0 total_states 0 peak_states 0 mark_read 0
> -- END PROG LOAD LOG --
> libbpf: failed to load program 'bpf_func__SyS_epoll_pwait'
> libbpf: failed to load object '[basic_bpf_test]'
> bpf: load objects failed: err=-22: (Invalid argument)
> Failed to add events selected by BPF
> Opening /sys/kernel/tracing//kprobe_events write=1
> Opening /sys/kernel/tracing//uprobe_events write=1
> Parsing probe_events: p:perf_bpf_probe/func _text+3943040
> Group:perf_bpf_probe Event:func probe:p
> Writing event: -:perf_bpf_probe/func
> test child finished with -1

[...]

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