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

Arnaldo Carvalho de Melo
2025-10-02T18:45:10Z

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
>