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

Ian Rogers
2025-09-29T19:08:23Z

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.

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

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2.51.0.570.gb178f27e6d-goog