linux-kernel - Re: [PATCH v1 0/5] Support dynamic opening of capstone and libLLVM

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Message-ID: <CAP-5=fX8aoEKaFKzdJowq6q470GfpzX-vWTASJEDx3=LHumChA@mail.gmail.com>
Date: Mon, 20 Jan 2025 10:01:55 -0800
From: Ian Rogers <irogers@...gle.com>
To: Nick Desaulniers <ndesaulniers@...gle.com>, Bill Wendling <morbo@...gle.com>, 
	linux-perf-users <linux-perf-users@...r.kernel.org>, llvm@...ts.linux.dev
Cc: Peter Zijlstra <peterz@...radead.org>, Dmitry Vyukov <dvyukov@...gle.com>, 
	"Masami Hiramatsu (Google)" <mhiramat@...nel.org>, Kajol Jain <kjain@...ux.ibm.com>, 
	Ingo Molnar <mingo@...hat.com>, Arnaldo Carvalho de Melo <acme@...nel.org>, Namhyung Kim <namhyung@...nel.org>, 
	Mark Rutland <mark.rutland@....com>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, 
	Adrian Hunter <adrian.hunter@...el.com>, Kan Liang <kan.liang@...ux.intel.com>, 
	Nathan Chancellor <nathan@...nel.org>, Justin Stitt <justinstitt@...gle.com>, 
	"Steinar H. Gunderson" <sesse@...gle.com>, Charlie Jenkins <charlie@...osinc.com>, 
	Changbin Du <changbin.du@...wei.com>, James Clark <james.clark@...aro.org>, 
	Athira Rajeev <atrajeev@...ux.vnet.ibm.com>, Li Huafei <lihuafei1@...wei.com>, 
	Andi Kleen <ak@...ux.intel.com>, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1 0/5] Support dynamic opening of capstone and libLLVM

On Mon, Jan 20, 2025 at 9:32 AM Ian Rogers <irogers@...gle.com> wrote:
>
> Linking against libcapstone and libLLVM can be a significant increase
> in dependencies and size of memory footprint. For something like `perf
> record` the disassembler and addr2line functionality won't be
> used. Support dynamically loading these libraries using dlopen and
> then calling the appropriate functions found using dlsym.
>
> The patch series:
> 1) moves the capstone and LLVM code to their own C files,
> 2) simplifies a little the capstone code,
> 3) adds perf_ variants of the functions that will either directly call
>    the function or use dlsym to discover it.
>
> The addr2line LLVM functionality is written in C++. To avoid linking
> against libLLVM for this, a new LIBLLVM_DYNAMIC option is added where
> the C++ code with the libLLVM dependency will be built into a
> libperf-llvm.so and that dlsym-ed and called against.

A question for the LLVM folks longer term, could the
llvm/DebugInfo/Symbolize/Symbolize.h functionality be added to the
llvm-c API (ie the not C++ one) for the sake of perf's use using dlsym
for its addr2line implementation? This would enable the
libperf-llvm.so library added in these patches to be removed and
libLLVM.so used in its place.

Thanks,
Ian


> Ian Rogers (5):
>   perf capstone: Move capstone functionality into its own file
>   perf llvm: Move llvm functionality into its own file
>   perf capstone: Remove open_capstone_handle
>   perf capstone: Support for dlopen-ing libcapstone.so
>   perf llvm: Support for dlopen-ing libLLVM.so
>
>  tools/perf/Makefile.config         |  13 +
>  tools/perf/Makefile.perf           |  23 +-
>  tools/perf/builtin-script.c        |   2 -
>  tools/perf/tests/make              |   2 +
>  tools/perf/util/Build              |   4 +-
>  tools/perf/util/capstone.c         | 723 +++++++++++++++++++++++++++++
>  tools/perf/util/capstone.h         |  24 +
>  tools/perf/util/disasm.c           | 612 +-----------------------
>  tools/perf/util/disasm.h           |   2 +
>  tools/perf/util/llvm-c-helpers.cpp | 113 ++++-
>  tools/perf/util/llvm.c             | 537 +++++++++++++++++++++
>  tools/perf/util/llvm.h             |  24 +
>  tools/perf/util/print_insn.c       | 117 +----
>  tools/perf/util/srcline.c          |  65 +--
>  tools/perf/util/srcline.h          |   6 +
>  15 files changed, 1481 insertions(+), 786 deletions(-)
>  create mode 100644 tools/perf/util/capstone.c
>  create mode 100644 tools/perf/util/capstone.h
>  create mode 100644 tools/perf/util/llvm.c
>  create mode 100644 tools/perf/util/llvm.h
>
> --
> 2.48.0.rc2.279.g1de40edade-goog
>