Date:   Mon, 9 Mar 2020 16:23:43 -0300
From:   Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>
To:     Nick Desaulniers <ndesaulniers@...gle.com>
Cc:     Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Clark Williams <williams@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-perf-users@...r.kernel.org,
        Ilie Halip <ilie.halip@...il.com>,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Igor Lubashev <ilubashe@...mai.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Peter Zijlstra <peterz@...radead.org>,
        clang-built-linux <clang-built-linux@...glegroups.com>
Subject: Re: [PATCH 3/6] perf python: Fix clang detection when using
 CC=clang-version

Em Mon, Mar 09, 2020 at 11:58:33AM -0700, Nick Desaulniers escreveu:
> On Mon, Mar 9, 2020 at 11:53 AM Arnaldo Carvalho de Melo
> <acme@...nel.org> wrote:
> >
> > From: Ilie Halip <ilie.halip@...il.com>
> >
> > Currently, the setup.py script detects the clang compiler only when invoked
> > with CC=clang. But when using a specific version (e.g. CC=clang-11), this
> > doesn't work correctly and wrong compiler flags are set, leading to build
> > errors.
> >
> > To properly detect clang, invoke the compiler with -v and check the output.
> > The first line should start with "clang version ...".
> >
> > Committer testing:
> >
> >   $ make CC=clang-9 O=/tmp/build/perf -C tools/perf install-bin
> >   <SNIP>
> >   $ readelf -wi /tmp/build/perf/python/perf.cpython-37m-x86_64-linux-gnu.so | grep DW_AT_producer | head -1
> >     <c>   DW_AT_producer    : (indirect string, offset: 0x0): clang version 9.0.1 (Fedora 9.0.1-2.fc31) /usr/bin/clang-9 -Wno-unused-result -Wsign-compare -D DYNAMIC_ANNOTATIONS_ENABLED=1 -D NDEBUG -O2 -g -pipe -Wall -Werror=format-security -Wp,-D_FORTIFY_SOURCE=2 -Wp,-D_GLIBCXX_ASSERTIONS -fexceptions -fstack-protector-strong -grecord-command-line -m64 -mtune=generic -fasynchronous-unwind-tables -fcf-protection=full -D _GNU_SOURCE -fPIC -fwrapv -Wbad-function-cast -Wdeclaration-after-statement -Wformat-security -Wformat-y2k -Winit-self -Wmissing-declarations -Wmissing-prototypes -Wnested-externs -Wno-system-headers -Wold-style-definition -Wpacked -Wredundant-decls -Wstrict-prototypes -Wswitch-default -Wswitch-enum -Wundef -Wwrite-strings -Wformat -Wshadow -D HAVE_ARCH_X86_64_SUPPORT -I /tmp/build/perf/arch/x86/include/generated -D HAVE_SYSCALL_TABLE_SUPPORT -D HAVE_PERF_REGS_SUPPORT -D HAVE_ARCH_REGS_QUERY_REGISTER_OFFSET -Werror -O3 -fno-omit-frame-pointer -ggdb3 -funwind-tables -Wall -Wextra -std=gnu99 -fstack-protector-all -D _FORTIFY_SOURCE=2 -D _LARGEFILE64_SOURCE -D _FILE_OFFSET_BITS=64 -D _GNU_SOURCE -I /home/acme/git/perf/tools/lib/perf/include -I /home/acme/git/perf/tools/perf/util/include -I /home/acme/git/perf/tools/perf/arch/x86/include -I /home/acme/git/perf/tools/include/ -I /home/acme/git/perf/tools/arch/x86/include/uapi -I /home/acme/git/perf/tools/include/uapi -I /home/acme/git/perf/tools/arch/x86/include/ -I /home/acme/git/perf/tools/arch/x86/ -I /tmp/build/perf//util -I /tmp/build/perf/ -I /home/acme/git/perf/tools/perf/util -I /home/acme/git/perf/tools/perf -I /home/acme/git/perf/tools/lib/ -D HAVE_PTHREAD_ATTR_SETAFFINITY_NP -D HAVE_PTHREAD_BARRIER -D HAVE_EVENTFD -D HAVE_GET_CURRENT_DIR_NAME -D HAVE_GETTID -D HAVE_DWARF_GETLOCATIONS_SUPPORT -D HAVE_GLIBC_SUPPORT -D HAVE_AIO_SUPPORT -D HAVE_SCHED_GETCPU_SUPPORT -D HAVE_SETNS_SUPPORT -D HAVE_LIBELF_SUPPORT -D HAVE_LIBELF_MMAP_SUPPORT -D HAVE_ELF_GETPHDRNUM_SUPPORT -D HAVE_GELF_GETNOTE_SUPPORT -D HAVE_ELF_GETSHDRSTRNDX_SUPPORT -D HAVE_DWARF_SUPPORT -D HAVE_LIBBPF_SUPPORT -D HAVE_BPF_PROLOGUE -D HAVE_SDT_EVENT -D HAVE_JITDUMP -D HAVE_DWARF_UNWIND_SUPPORT -D NO_LIBUNWIND_DEBUG_FRAME -D HAVE_LIBUNWIND_SUPPORT -D HAVE_LIBCRYPTO_SUPPORT -D HAVE_SLANG_SUPPORT -D HAVE_GTK2_SUPPORT -D NO_LIBPERL -D HAVE_TIMERFD_SUPPORT -D HAVE_LIBPYTHON_SUPPORT -D HAVE_CPLUS_DEMANGLE_SUPPORT -D HAVE_LIBBFD_SUPPORT -D HAVE_ZLIB_SUPPORT -D HAVE_LZMA_SUPPORT -D HAVE_ZSTD_SUPPORT -D HAVE_LIBCAP_SUPPORT -D HAVE_BACKTRACE_SUPPORT -D HAVE_LIBNUMA_SUPPORT -D HAVE_KVM_STAT_SUPPORT -D DISASM_FOUR_ARGS_SIGNATURE -D HAVE_LIBBABELTRACE_SUPPORT -D HAVE_AUXTRACE_SUPPORT -D HAVE_JVMTI_CMLR -I /tmp/build/perf/ -fPIC -I util/include -I /usr/include/python3.7m -c /home/acme/git/perf/tools/perf/util/python.c -o /tmp/build/perf/python_ext_build/tmp/home/acme/git/perf/tools/perf/util/python.o -Wbad-function-cast -Wdeclaration-after-statement -Wformat-security -Wformat-y2k -Winit-self -Wmissing-declarations -Wmissing-prototypes -Wnested-externs -Wno-system-headers -Wold-style-definition -Wpacked -Wredundant-decls -Wstrict-prototypes -Wswitch-default -Wswitch-enum -Wundef -Wwrite-strings -Wformat -Wshadow -D HAVE_ARCH_X86_64_SUPPORT -I /tmp/build/perf/arch/x86/include/generated -D HAVE_SYSCALL_TABLE_SUPPORT -D HAVE_PERF_REGS_SUPPORT -D HAVE_ARCH_REGS_QUERY_REGISTER_OFFSET -Werror -O3 -fno-omit-frame-pointer -ggdb3 -funwind-tables -Wall -Wextra -std=gnu99 -fstack-protector-all -D _FORTIFY_SOURCE=2 -D _LARGEFILE64_SOURCE -D _FILE_OFFSET_BITS=64 -D _GNU_SOURCE -I /home/acme/git/perf/tools/lib/perf/include -I /home/acme/git/perf/tools/perf/util/include -I /home/acme/git/perf/tools/perf/arch/x86/include -I /home/acme/git/perf/tools/include/ -I /home/acme/git/perf/tools/arch/x86/include/uapi -I /home/acme/git/perf/tools/include/uapi -I /home/acme/git/perf/tools/arch/x86/include/ -I /home/acme/git/perf/tools/arch/x86/ -I /tmp/build/perf//util -I /tmp/build/perf/ -I /home/acme/git/perf/tools/perf/util -I /home/acme/git/perf/tools/perf -I /home/acme/git/perf/tools/lib/ -D HAVE_PTHREAD_ATTR_SETAFFINITY_NP -D HAVE_PTHREAD_BARRIER -D HAVE_EVENTFD -D HAVE_GET_CURRENT_DIR_NAME -D HAVE_GETTID -D HAVE_DWARF_GETLOCATIONS_SUPPORT -D HAVE_GLIBC_SUPPORT -D HAVE_AIO_SUPPORT -D HAVE_SCHED_GETCPU_SUPPORT -D HAVE_SETNS_SUPPORT -D HAVE_LIBELF_SUPPORT -D HAVE_LIBELF_MMAP_SUPPORT -D HAVE_ELF_GETPHDRNUM_SUPPORT -D HAVE_GELF_GETNOTE_SUPPORT -D HAVE_ELF_GETSHDRSTRNDX_SUPPORT -D HAVE_DWARF_SUPPORT -D HAVE_LIBBPF_SUPPORT -D HAVE_BPF_PROLOGUE -D HAVE_SDT_EVENT -D HAVE_JITDUMP -D HAVE_DWARF_UNWIND_SUPPORT -D NO_LIBUNWIND_DEBUG_FRAME -D HAVE_LIBUNWIND_SUPPORT -D HAVE_LIBCRYPTO_SUPPORT -D HAVE_SLANG_SUPPORT -D HAVE_GTK2_SUPPORT -D NO_LIBPERL -D HAVE_TIMERFD_SUPPORT -D HAVE_LIBPYTHON_SUPPORT -D HAVE_CPLUS_DEMANGLE_SUPPORT -D HAVE_LIBBFD_SUPPORT -D HAVE_ZLIB_SUPPORT -D HAVE_LZMA_SUPPORT -D HAVE_ZSTD_SUPPORT -D HAVE_LIBCAP_SUPPORT -D HAVE_BACKTRACE_SUPPORT -D HAVE_LIBNUMA_SUPPORT -D HAVE_KVM_STAT_SUPPORT -D DISASM_FOUR_ARGS_SIGNATURE -D HAVE_LIBBABELTRACE_SUPPORT -D HAVE_AUXTRACE_SUPPORT -D HAVE_JVMTI_CMLR -I /tmp/build/perf/ -fno-strict-aliasing -Wno-write-strings -Wno-unused-parameter -Wno-redundant-decls
> 
> Sorry for not speaking up sooner, but if you don't want to include
> that mass of command line options above, I generally check which
> toolchain has been used to produce a binary via:
> $ readelf --string-dump=.comment <foo>
> which may be more concise, but sometimes we strip out the `.comment`
> section from binaries.

Well, this doesn't produce what I needed, see:

[root@...e ~]# readelf --string-dump=.comment /tmp/build/perf/python/perf.cpython-37m-x86_64-linux-gnu.so

String dump of section '.comment':
  [     0]  GCC: (GNU) 9.2.1 20190827 (Red Hat 9.2.1-1)

[root@...e ~]#

See the part below, where I need to look at what compiler flags were
used to build the python build, like -fcf-protection.

- Arnaldo

 
> >   $
> >
> > And here is how tools/perf/util/setup.py checks if the used clang has
> > options that the distro specific python extension building compiler
> > defaults:
> >
> >   if cc_is_clang:
> >       from distutils.sysconfig import get_config_vars
> >       vars = get_config_vars()
> >       for var in ('CFLAGS', 'OPT'):
> >           vars[var] = sub("-specs=[^ ]+", "", vars[var])
> >           if not clang_has_option("-mcet"):
> >               vars[var] = sub("-mcet", "", vars[var])
> >           if not clang_has_option("-fcf-protection"):
> >               vars[var] = sub("-fcf-protection", "", vars[var])
> >           if not clang_has_option("-fstack-clash-protection"):
> >               vars[var] = sub("-fstack-clash-protection", "", vars[var])
> >           if not clang_has_option("-fstack-protector-strong"):
> >               vars[var] = sub("-fstack-protector-strong", "", vars[var])
> >
> > So "-fcf-protection=full" is used, clang-9 has this option and thus it
> > was kept, the perf python extension was built with it and the build
> > completed successfully.
> >
> > Link: https://github.com/ClangBuiltLinux/linux/issues/903
> > Signed-off-by: Ilie Halip <ilie.halip@...il.com>
> > Tested-by: Arnaldo Carvalho de Melo <acme@...hat.com>
> > Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
> > Cc: Igor Lubashev <ilubashe@...mai.com>
> > Cc: Jiri Olsa <jolsa@...hat.com>
> > Cc: Mark Rutland <mark.rutland@....com>
> > Cc: Namhyung Kim <namhyung@...nel.org>
> > Cc: Peter Zijlstra <peterz@...radead.org>
> > Cc: clang-built-linux@...glegroups.com
> > Link: http://lore.kernel.org/lkml/20200309085618.14307-1-ilie.halip@gmail.com
> > Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
> > ---
> >  tools/perf/util/setup.py | 10 ++++++----
> >  1 file changed, 6 insertions(+), 4 deletions(-)
> >
> > diff --git a/tools/perf/util/setup.py b/tools/perf/util/setup.py
> > index aa344a163eaf..8a065a6f9713 100644
> > --- a/tools/perf/util/setup.py
> > +++ b/tools/perf/util/setup.py
> > @@ -2,11 +2,13 @@ from os import getenv
> >  from subprocess import Popen, PIPE
> >  from re import sub
> >
> > +cc = getenv("CC")
> > +cc_is_clang = b"clang version" in Popen([cc, "-v"], stderr=PIPE).stderr.readline()
> > +
> >  def clang_has_option(option):
> > -    return [o for o in Popen(['clang', option], stderr=PIPE).stderr.readlines() if b"unknown argument" in o] == [ ]
> > +    return [o for o in Popen([cc, option], stderr=PIPE).stderr.readlines() if b"unknown argument" in o] == [ ]
> >
> > -cc = getenv("CC")
> > -if cc == "clang":
> > +if cc_is_clang:
> >      from distutils.sysconfig import get_config_vars
> >      vars = get_config_vars()
> >      for var in ('CFLAGS', 'OPT'):
> > @@ -40,7 +42,7 @@ class install_lib(_install_lib):
> >  cflags = getenv('CFLAGS', '').split()
> >  # switch off several checks (need to be at the end of cflags list)
> >  cflags += ['-fno-strict-aliasing', '-Wno-write-strings', '-Wno-unused-parameter', '-Wno-redundant-decls' ]
> > -if cc != "clang":
> > +if not cc_is_clang:
> >      cflags += ['-Wno-cast-function-type' ]
> >
> >  src_perf  = getenv('srctree') + '/tools/perf'
> > --
> > 2.21.1
> >
> > --
> > You received this message because you are subscribed to the Google Groups "Clang Built Linux" group.
> > To unsubscribe from this group and stop receiving emails from it, send an email to clang-built-linux+unsubscribe@...glegroups.com.
> > To view this discussion on the web visit https://groups.google.com/d/msgid/clang-built-linux/20200309185323.22583-4-acme%40kernel.org.
> 
> 
> 
> -- 
> Thanks,
> ~Nick Desaulniers

-- 

- Arnaldo

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