Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
MIME-Version: 1.0
References: <20230311065753.3012826-1-irogers@google.com> <20230311065753.3012826-10-irogers@google.com>
 <f8298af8-4d29-5cbd-cb5f-d33b3fdd641c@arm.com> <CAP-5=fV3HPjXqHm1m-HB3rJU=emV16bUby1Xt-5x4+zjdPRnsg@mail.gmail.com>
In-Reply-To: <CAP-5=fV3HPjXqHm1m-HB3rJU=emV16bUby1Xt-5x4+zjdPRnsg@mail.gmail.com>
From:   Ian Rogers <irogers@google.com>
Date:   Thu, 30 Mar 2023 12:03:53 -0700
Message-ID: <CAP-5=fWYHyJbZicrsj6UnOBVTFX8NheL+GPGQbC8NMQv2G1WcA@mail.gmail.com>
Subject: Re: [PATCH v1 09/13] perf symbol: Add abi::__cxa_demangle C++
 demangling support
To:     James Clark <james.clark@arm.com>
Cc:     Arnaldo Carvalho de Melo <acme@kernel.org>,
        Stephane Eranian <eranian@google.com>,
        Mark Rutland <mark.rutland@arm.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Jiri Olsa <jolsa@kernel.org>,
        Namhyung Kim <namhyung@kernel.org>,
        Nathan Chancellor <nathan@kernel.org>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Tom Rix <trix@redhat.com>,
        Roberto Sassu <roberto.sassu@huawei.com>,
        Quentin Monnet <quentin@isovalent.com>,
        Andres Freund <andres@anarazel.de>,
        Tiezhu Yang <yangtiezhu@loongson.cn>,
        Pavithra Gurushankar <gpavithrasha@gmail.com>,
        Yang Jihong <yangjihong1@huawei.com>,
        Adrian Hunter <adrian.hunter@intel.com>,
        Leo Yan <leo.yan@linaro.org>,
        =?UTF-8?Q?Martin_Li=C5=A1ka?= <mliska@suse.cz>,
        linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org,
        llvm@lists.linux.dev, Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Precedence: bulk

On Thu, Mar 30, 2023 at 9:50=E2=80=AFAM Ian Rogers <irogers@google.com> wro=
te:
>
> On Thu, Mar 30, 2023 at 7:08=E2=80=AFAM James Clark <james.clark@arm.com>=
 wrote:
> >
> >
> >
> > On 11/03/2023 06:57, Ian Rogers wrote:
> > > Refactor C++ demangling out of symbol-elf into its own files similar
> > > to other languages. Add abi::__cxa_demangle support. As the other
> > > demanglers are not shippable with distributions, this brings back C++
> > > demangling in a common case. It isn't perfect as the support for
> > > optionally demangling arguments and modifiers isn't present.
> > >
> > > Signed-off-by: Ian Rogers <irogers@google.com>
> > > ---
> > >  tools/perf/Makefile.config       | 29 +++++++++---------
> > >  tools/perf/util/Build            |  1 +
> > >  tools/perf/util/demangle-cxx.cpp | 50 ++++++++++++++++++++++++++++++=
++
> > >  tools/perf/util/demangle-cxx.h   | 16 ++++++++++
> > >  tools/perf/util/symbol-elf.c     | 37 +++++------------------
> > >  5 files changed, 88 insertions(+), 45 deletions(-)
> > >  create mode 100644 tools/perf/util/demangle-cxx.cpp
> > >  create mode 100644 tools/perf/util/demangle-cxx.h
> > >
> > > diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
> > > index 5756498248e0..fdeca45cf15f 100644
> > > --- a/tools/perf/Makefile.config
> > > +++ b/tools/perf/Makefile.config
> > > @@ -906,6 +906,7 @@ ifdef BUILD_NONDISTRO
> > >    endif
> > >
> > >    CFLAGS +=3D -DHAVE_LIBBFD_SUPPORT
> > > +  CXXFLAGS +=3D -DHAVE_LIBBFD_SUPPORT
> > >    ifeq ($(feature-libbfd-buildid), 1)
> > >      CFLAGS +=3D -DHAVE_LIBBFD_BUILDID_SUPPORT
> > >    else
> > > @@ -913,26 +914,24 @@ ifdef BUILD_NONDISTRO
> > >    endif
> > >  endif
> > >
> > > -ifdef NO_DEMANGLE
> > > -  CFLAGS +=3D -DNO_DEMANGLE
> > > -else
> > > +ifndef NO_DEMANGLE
> > > +  $(call feature_check,cxa-demangle)
> > > +  ifeq ($(feature-cxa-demangle), 1)
> > > +    EXTLIBS +=3D -lstdc++
> >
> > Hi Ian,
> >
> > I think cross compilation for arm on x86 isn't working after this chang=
e
> > (at least on Ubuntu).
> >
> > Even with all of the arm64 libstdc++ stuff installed, you can only link
> > to it using g++, but the perf build tries to link to it using gcc. Not
> > sure it's some quirk with the search paths on Ubuntu or something else:
> >
> >   $ aarch64-linux-gnu-gcc -lstdc++
> >
> >    /usr/lib/gcc-cross/aarch64-linux-gnu/12/../../../../aarch64-linux-
> > gnu/bin/ld: cannot find -lstdc++: No such file or directory
> >   collect2: error: ld returned 1 exit status
> >
> > g++ gets further:
> >
> >   $ aarch64-linux-gnu-g++ -lstdc++
> >
> >   ...
> >   (.text+0x20): undefined reference to `main'
> > collect2: error: ld returned 1 exit status
> >
> > At the end of the perf build it looks like something similar is
> > happening (with all the non interesting bits deleted):
> >
> >    $ make ARCH=3Darm64 CROSS_COMPILE=3Daarch64-linux-gnu- -C tools/perf
> > NO_BPF_SKEL=3D1 V=3D1
> >
> >   aarch64-linux-gnu-gcc ... -o perf
> >
> > /usr/lib/gcc-cross/aarch64-linux-gnu/12/../../../../aarch64-linux-gnu/b=
in/ld:
> > cannot find -lstdc++: No such file or directory
> >
> > If I build with NO_DEMANGLE=3D1 then the build works, but I think it wo=
uld
> > at be best to autodetect rather than have to do this. Or maybe even lin=
k
> > at the end with g++ if we're going to use libstdc++?
>
> Hi James,
>
> sorry for the problems you are having, I'll see if I can get a repo. I
> did add a feature test with this change in the same set:
> https://lore.kernel.org/lkml/20230311065753.3012826-9-irogers@google.com/
> So it should be feature testing and only enabling when
> HAVE_CXA_DEMANGLE_SUPPORT is present. Obviously something is up, so
> I'll have a think about it.
>
> Thanks,
> Ian

Sorry to say I couldn't repro on Debian:

$ make ARCH=3Darm64 CROSS_COMPILE=3Daarch64-linux-gnu- -C tools/perf
NO_LIBELF=3D1 NO_LIBTRACEEVENT=3D1
make: Entering directory '/home/irogers/kernel.org/tools/perf'
 BUILD:   Doing 'make -j16' parallel build
Warning: Kernel ABI header at 'tools/include/uapi/linux/in.h' differs
from latest version at 'include/uapi/linux/in.h'
diff -u tools/include/uapi/linux/in.h include/uapi/linux/in.h
Warning: Kernel ABI header at
'tools/arch/x86/include/asm/cpufeatures.h' differs from latest version
at 'arch/x86/include/asm/cpufeatures.h'
diff -u tools/arch/x86/include/asm/cpufeatures.h
arch/x86/include/asm/cpufeatures.h
Warning: Kernel ABI header at
'tools/arch/arm64/include/uapi/asm/perf_regs.h' differs from latest
version at 'arch/arm64/include/uapi/asm/perf_regs.h'
diff -u tools/arch/arm64/include/uapi/asm/perf_regs.h
arch/arm64/include/uapi/asm/perf_regs.h
Warning: Kernel ABI header at 'tools/include/linux/coresight-pmu.h'
differs from latest version at 'include/linux/coresight-pmu.h'
diff -u tools/include/linux/coresight-pmu.h include/linux/coresight-pmu.h
Makefile.config:588: No sys/sdt.h found, no SDT events are defined,
please install systemtap-sdt-devel or systemtap-sdt-dev
Makefile.config:679: Disabling post unwind, no support found.
Makefile.config:747: No libcrypto.h found, disables jitted code
injection, please install openssl-devel or libssl-dev
Makefile.config:759: slang not found, disables TUI support. Please
install slang-devel, libslang-devor libslang2-dev
Makefile.config:806: Missing perl devel files. Disabling perl
scripting support, please install perl-ExtUtils-Embed/libperl-dev
Makefile.config:846: No 'Python.h' was found: disables Python support
- please install python-devel/python-dev
Makefile.config:951: No liblzma found, disables xz kernel module
decompression, please install xz-devel/liblzma-dev
Makefile.config:964: No libzstd found, disables trace compression,
please install libzstd-dev[el] and/or set LIBZSTD_DIR
Makefile.config:975: No libcap found, disables capability support,
please install libcap-devel/libcap-dev
Makefile.config:988: No numa.h found, disables 'perf bench numa mem'
benchmark, please install numactl-devel/libnuma-devel/libnuma-dev
Makefile.config:1047: No libbabeltrace found, disables 'perf data' CTF
format support, please install
libbabeltrace-dev[el]/libbabeltrace-ctf-dev
Makefile.config:1138: libpfm4 not found, disables libpfm4 support.
Please install libpfm4-dev

Auto-detecting system features:
...                                   dwarf: [ OFF ]
...                      dwarf_getlocations: [ OFF ]
...                                   glibc: [ on  ]
...                                  libbfd: [ OFF ]
...                          libbfd-buildid: [ OFF ]
...                                  libcap: [ OFF ]
...                                  libelf: [ OFF ]
...                                 libnuma: [ OFF ]
...                  numa_num_possible_cpus: [ OFF ]
...                                 libperl: [ OFF ]
...                               libpython: [ OFF ]
...                               libcrypto: [ OFF ]
...                               libunwind: [ OFF ]
...                      libdw-dwarf-unwind: [ OFF ]
...                                    zlib: [ OFF ]
...                                    lzma: [ OFF ]
...                               get_cpuid: [ OFF ]
...                                     bpf: [ on  ]
...                                  libaio: [ on  ]
...                                 libzstd: [ OFF ]

 INSTALL libsubcmd_headers
 INSTALL libsymbol_headers
 INSTALL libapi_headers
 INSTALL libperf_headers
 FLEX    util/parse-events-flex.c
 FLEX    util/pmu-flex.c
 CC      util/pmu-bison.o
 FLEX    util/expr-flex.c
 CC      util/expr-bison.o
 CXX     util/demangle-cxx.o
 CC      util/demangle-ocaml.o
 CC      util/demangle-java.o
 CC      util/demangle-rust.o
 CC      util/perf-hooks.o
 CC      util/parse-events.o
 CC      util/parse-events-flex.o
 CC      util/pmu.o
 CC      util/pmu-flex.o
 CC      util/expr-flex.o
 CC      util/expr.o
 LD      util/perf-in.o
 LD      perf-in.o
 LINK    perf
make: Leaving directory '.../tools/perf'

Thanks,
Ian

> > Thanks
> > James
> >
> > > +    CFLAGS +=3D -DHAVE_CXA_DEMANGLE_SUPPORT
> > > +    CXXFLAGS +=3D -DHAVE_CXA_DEMANGLE_SUPPORT
> > > +  endif
> > >    ifdef BUILD_NONDISTRO
> > >      ifeq ($(filter -liberty,$(EXTLIBS)),)
> > > -      ifdef HAVE_CPLUS_DEMANGLE_SUPPORT
> > > +      $(call feature_check,cplus-demangle)
> > > +      ifeq ($(feature-cplus-demangle), 1)
> > >          EXTLIBS +=3D -liberty
> > > -      else
> > > -        $(call feature_check,cplus-demangle)
> > > -        ifeq ($(feature-cplus-demangle), 1)
> > > -          EXTLIBS +=3D -liberty
> > > -        endif
> > >        endif
> > >      endif
> > > -  endif
> > > -
> > > -  ifneq ($(filter -liberty,$(EXTLIBS)),)
> > > -    CFLAGS +=3D -DHAVE_CPLUS_DEMANGLE_SUPPORT
> > > -  else
> > > -    CFLAGS +=3D -DNO_DEMANGLE
> > > +    ifneq ($(filter -liberty,$(EXTLIBS)),)
> > > +      CFLAGS +=3D -DHAVE_CPLUS_DEMANGLE_SUPPORT
> > > +      CXXFLAGS +=3D -DHAVE_CPLUS_DEMANGLE_SUPPORT
> > > +    endif
> > >    endif
> > >  endif
> > >
> > > diff --git a/tools/perf/util/Build b/tools/perf/util/Build
> > > index 918b501f9bd8..8607575183a9 100644
> > > --- a/tools/perf/util/Build
> > > +++ b/tools/perf/util/Build
> > > @@ -211,6 +211,7 @@ perf-$(CONFIG_ZSTD) +=3D zstd.o
> > >
> > >  perf-$(CONFIG_LIBCAP) +=3D cap.o
> > >
> > > +perf-y +=3D demangle-cxx.o
> > >  perf-y +=3D demangle-ocaml.o
> > >  perf-y +=3D demangle-java.o
> > >  perf-y +=3D demangle-rust.o
> > > diff --git a/tools/perf/util/demangle-cxx.cpp b/tools/perf/util/deman=
gle-cxx.cpp
> > > new file mode 100644
> > > index 000000000000..8708bcafd370
> > > --- /dev/null
> > > +++ b/tools/perf/util/demangle-cxx.cpp
> > > @@ -0,0 +1,50 @@
> > > +// SPDX-License-Identifier: GPL-2.0
> > > +#include "demangle-cxx.h"
> > > +#include <stdlib.h>
> > > +#include <string.h>
> > > +#include <linux/compiler.h>
> > > +
> > > +#ifdef HAVE_LIBBFD_SUPPORT
> > > +#define PACKAGE 'perf'
> > > +#include <bfd.h>
> > > +#endif
> > > +
> > > +#ifdef HAVE_CXA_DEMANGLE_SUPPORT
> > > +#include <cxxabi.h>
> > > +#endif
> > > +
> > > +#if defined(HAVE_LIBBFD_SUPPORT) || defined(HAVE_CPLUS_DEMANGLE_SUPP=
ORT)
> > > +#ifndef DMGL_PARAMS
> > > +#define DMGL_PARAMS     (1 << 0)  /* Include function args */
> > > +#define DMGL_ANSI       (1 << 1)  /* Include const, volatile, etc */
> > > +#endif
> > > +#endif
> > > +
> > > +/*
> > > + * Demangle C++ function signature
> > > + *
> > > + * Note: caller is responsible for freeing demangled string
> > > + */
> > > +extern "C"
> > > +char *cxx_demangle_sym(const char *str, bool params __maybe_unused,
> > > +                       bool modifiers __maybe_unused)
> > > +{
> > > +#ifdef HAVE_LIBBFD_SUPPORT
> > > +        int flags =3D (params ? DMGL_PARAMS : 0) | (modifiers ? DMGL=
_ANSI : 0);
> > > +
> > > +        return bfd_demangle(NULL, str, flags);
> > > +#elif defined(HAVE_CPLUS_DEMANGLE_SUPPORT)
> > > +        int flags =3D (params ? DMGL_PARAMS : 0) | (modifiers ? DMGL=
_ANSI : 0);
> > > +
> > > +        return cplus_demangle(str, flags);
> > > +#elif defined(HAVE_CXA_DEMANGLE_SUPPORT)
> > > +        size_t len =3D strlen(str);
> > > +        char *output =3D (char*)malloc(len);
> > > +        int status;
> > > +
> > > +        output =3D abi::__cxa_demangle(str, output, &len, &status);
> > > +        return output;
> > > +#else
> > > +        return NULL;
> > > +#endif
> > > +}
> > > diff --git a/tools/perf/util/demangle-cxx.h b/tools/perf/util/demangl=
e-cxx.h
> > > new file mode 100644
> > > index 000000000000..26b5b66c0b4e
> > > --- /dev/null
> > > +++ b/tools/perf/util/demangle-cxx.h
> > > @@ -0,0 +1,16 @@
> > > +/* SPDX-License-Identifier: GPL-2.0 */
> > > +#ifndef __PERF_DEMANGLE_CXX
> > > +#define __PERF_DEMANGLE_CXX 1
> > > +
> > > +#ifdef __cplusplus
> > > +extern "C" {
> > > +#endif
> > > +
> > > +char *cxx_demangle_sym(const char *str, bool params, bool modifiers)=
;
> > > +
> > > +#ifdef __cplusplus
> > > +}
> > > +#endif
> > > +
> > > +
> > > +#endif /* __PERF_DEMANGLE_CXX */
> > > diff --git a/tools/perf/util/symbol-elf.c b/tools/perf/util/symbol-el=
f.c
> > > index 41882ae8452e..c0a2de42c51b 100644
> > > --- a/tools/perf/util/symbol-elf.c
> > > +++ b/tools/perf/util/symbol-elf.c
> > > @@ -12,6 +12,7 @@
> > >  #include "maps.h"
> > >  #include "symbol.h"
> > >  #include "symsrc.h"
> > > +#include "demangle-cxx.h"
> > >  #include "demangle-ocaml.h"
> > >  #include "demangle-java.h"
> > >  #include "demangle-rust.h"
> > > @@ -25,6 +26,11 @@
> > >  #include <symbol/kallsyms.h>
> > >  #include <internal/lib.h>
> > >
> > > +#ifdef HAVE_LIBBFD_SUPPORT
> > > +#define PACKAGE 'perf'
> > > +#include <bfd.h>
> > > +#endif
> > > +
> > >  #ifndef EM_AARCH64
> > >  #define EM_AARCH64   183  /* ARM 64 bit */
> > >  #endif
> > > @@ -45,34 +51,6 @@
> > >
> > >  typedef Elf64_Nhdr GElf_Nhdr;
> > >
> > > -#ifndef DMGL_PARAMS
> > > -#define DMGL_NO_OPTS     0              /* For readability... */
> > > -#define DMGL_PARAMS      (1 << 0)       /* Include function args */
> > > -#define DMGL_ANSI        (1 << 1)       /* Include const, volatile, =
etc */
> > > -#endif
> > > -
> > > -#ifdef HAVE_LIBBFD_SUPPORT
> > > -#define PACKAGE 'perf'
> > > -#include <bfd.h>
> > > -#else
> > > -#ifdef HAVE_CPLUS_DEMANGLE_SUPPORT
> > > -extern char *cplus_demangle(const char *, int);
> > > -
> > > -static inline char *bfd_demangle(void __maybe_unused *v, const char =
*c, int i)
> > > -{
> > > -     return cplus_demangle(c, i);
> > > -}
> > > -#else
> > > -#ifdef NO_DEMANGLE
> > > -static inline char *bfd_demangle(void __maybe_unused *v,
> > > -                              const char __maybe_unused *c,
> > > -                              int __maybe_unused i)
> > > -{
> > > -     return NULL;
> > > -}
> > > -#endif
> > > -#endif
> > > -#endif
> > >
> > >  #ifndef HAVE_ELF_GETPHDRNUM_SUPPORT
> > >  static int elf_getphdrnum(Elf *elf, size_t *dst)
> > > @@ -295,7 +273,6 @@ static bool want_demangle(bool is_kernel_sym)
> > >
> > >  static char *demangle_sym(struct dso *dso, int kmodule, const char *=
elf_name)
> > >  {
> > > -     int demangle_flags =3D verbose > 0 ? (DMGL_PARAMS | DMGL_ANSI) =
: DMGL_NO_OPTS;
> > >       char *demangled =3D NULL;
> > >
> > >       /*
> > > @@ -306,7 +283,7 @@ static char *demangle_sym(struct dso *dso, int km=
odule, const char *elf_name)
> > >       if (!want_demangle(dso->kernel || kmodule))
> > >           return demangled;
> > >
> > > -     demangled =3D bfd_demangle(NULL, elf_name, demangle_flags);
> > > +     demangled =3D cxx_demangle_sym(elf_name, verbose > 0, verbose >=
 0);
> > >       if (demangled =3D=3D NULL) {
> > >               demangled =3D ocaml_demangle_sym(elf_name);
> > >               if (demangled =3D=3D NULL) {