Re: [PATCH v6 00/15] Support dynamic opening of capstone/llvm

[Arnaldo Carvalho de Melo <acme@kernel.org>]

On Mon, Sep 29, 2025 at 12:07:50PM -0700, Ian Rogers wrote:
> Linking against libcapstone and libLLVM can be a significant increase
> in dependencies and file size if building statically. 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.

Got the first 5 patches of this series cherry-picked, will test it all
and then consider from 6 onwards.

- Arnaldo
 
> The patch series:
> 1) moves the capstone, LLVM and libbfd 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;
> 4) adds BPF JIT disassembly support to in memory disassemblers (LLVM
>    and capstone) by just directing them at the BPF info linear JIT
>    instructions (note this doesn't support source lines);
> 5) adds fallback to srcline's addr2line so that llvm_addr2line is
>    tried first, then the deprecated libbfd and then the forked command
>    tried next, moving the code for forking out of the main srcline.c
>    file in the process.
> 
> 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. Ideally LLVM
> would extend their C API to avoid this.
> 
> v6: Refactor the libbfd along with capstone and LLVM, previous patch
>     series had tried to avoid this by just removing the deprecated
>     BUILD_NONDISTRO code. Remove the libtracefs removal into its own
>     patch.
> v5: Rebase and comment typo fix.
> v4: Rebase and addition of a patch removing an unused struct variable.
> v3: Add srcline addr2line fallback trying LLVM first then forking a
>     process. This came up in conversation with Steinar Gunderson
>     <sesse@google.com>.
>     Tweak the cover letter message to try to address Andi Kleen's
>     <ak@linux.intel.com> feedback that the series doesn't really
>     achieve anything.
> v2: Add mangling of the function names in libperf-llvm.so to avoid
>     potential infinite recursion. Add BPF JIT disassembly support to
>     LLVM and capstone. Add/rebase the BUILD_NONDISTRO cleanup onto the
>     series from:
>     https://lore.kernel.org/lkml/20250111202851.1075338-1-irogers@google.com/
>     Some other minor additional clean up.
> 
> Ian Rogers (15):
>   perf map: Constify objdump offset/address conversion APIs
>   perf capstone: Move capstone functionality into its own file
>   perf llvm: Move llvm functionality into its own file
>   perf libbfd: Move libbfd functionality to 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
>   perf llvm: Mangle libperf-llvm.so function names
>   perf dso: Move read_symbol from llvm/capstone to dso
>   perf dso: Support BPF programs in dso__read_symbol
>   perf llvm: Disassemble cleanup
>   perf dso: Clean up read_symbol error handling
>   perf disasm: Make ins__scnprintf and ins__is_nop static
>   perf srcline: Fallback between addr2line implementations
>   perf disasm: Remove unused evsel from annotate_args
> 
>  tools/perf/Makefile.config         |  14 +
>  tools/perf/Makefile.perf           |  24 +-
>  tools/perf/builtin-script.c        |   2 -
>  tools/perf/tests/make              |   2 +
>  tools/perf/util/Build              |   7 +-
>  tools/perf/util/addr2line.c        | 439 ++++++++++++++++
>  tools/perf/util/addr2line.h        |  20 +
>  tools/perf/util/annotate.c         |   1 -
>  tools/perf/util/capstone.c         | 682 +++++++++++++++++++++++++
>  tools/perf/util/capstone.h         |  24 +
>  tools/perf/util/config.c           |   2 +-
>  tools/perf/util/disasm.c           | 645 ++----------------------
>  tools/perf/util/disasm.h           |   6 +-
>  tools/perf/util/disasm_bpf.c       | 195 --------
>  tools/perf/util/disasm_bpf.h       |  12 -
>  tools/perf/util/dso.c              | 112 +++++
>  tools/perf/util/dso.h              |   4 +
>  tools/perf/util/libbfd.c           | 600 ++++++++++++++++++++++
>  tools/perf/util/libbfd.h           |  83 ++++
>  tools/perf/util/llvm-c-helpers.cpp | 120 ++++-
>  tools/perf/util/llvm-c-helpers.h   |  24 +-
>  tools/perf/util/llvm.c             | 484 ++++++++++++++++++
>  tools/perf/util/llvm.h             |  21 +
>  tools/perf/util/map.c              |  19 +-
>  tools/perf/util/map.h              |   6 +-
>  tools/perf/util/print_insn.c       | 117 +----
>  tools/perf/util/srcline.c          | 772 ++---------------------------
>  tools/perf/util/srcline.h          |   9 +-
>  tools/perf/util/symbol-elf.c       | 100 +---
>  tools/perf/util/symbol.c           | 131 -----
>  30 files changed, 2745 insertions(+), 1932 deletions(-)
>  create mode 100644 tools/perf/util/addr2line.c
>  create mode 100644 tools/perf/util/addr2line.h
>  create mode 100644 tools/perf/util/capstone.c
>  create mode 100644 tools/perf/util/capstone.h
>  delete mode 100644 tools/perf/util/disasm_bpf.c
>  delete mode 100644 tools/perf/util/disasm_bpf.h
>  create mode 100644 tools/perf/util/libbfd.c
>  create mode 100644 tools/perf/util/libbfd.h
>  create mode 100644 tools/perf/util/llvm.c
>  create mode 100644 tools/perf/util/llvm.h
> 
> -- 
> 2.51.0.570.gb178f27e6d-goog
>