Re: [PATCH v7 00/11] Capstone/llvm improvements + dlopen support

[Ian Rogers]

On Mon, Oct 6, 2025 at 11:41 AM Arnaldo Carvalho de Melo
<acme@xxxxxxxxxx> wrote:
>
> On Mon, Oct 06, 2025 at 03:39:13PM -0300, Arnaldo Carvalho de Melo wrote:
> > On Sun, Oct 05, 2025 at 02:22:01PM -0700, Ian Rogers wrote:
> > > v7: Refactor now the first 5 patches, that largely moved code around,
> > >     have landed. Move the dlopen code to the end of the series so that
> > >     the first 8 patches can be picked improving capstone/LLVM support
>
> > So I tentatively picked the first 8 patches, will test it now, hopefully
> > we can go with it to have BPF annotation...
>
> > Wait, will try to fix this one:
>
> > ⬢ [acme@toolbx perf-tools-next]$ git log --oneline -1 ; time make -C tools/perf build-test
> >                  make_static: cd . && make LDFLAGS=-static NO_PERF_READ_VDSO32=1 NO_PERF_READ_VDSOX32=1 NO_JVMTI=1 NO_LIBTRACEEVENT=1 NO_LIBELF=1 -j32  DESTDIR=/tmp/tmp.w26bDGykTM
> > cd . && make LDFLAGS=-static NO_PERF_READ_VDSO32=1 NO_PERF_READ_VDSOX32=1 NO_JVMTI=1 NO_LIBTRACEEVENT=1 NO_LIBELF=1 -j32 DESTDIR=/tmp/tmp.w26bDGykTM
> >   BUILD:   Doing 'make -j32' parallel build
> > <SNIP>
> > Auto-detecting system features:
> > ...                                   libdw: [ OFF ]
> > ...                                   glibc: [ on  ]
> > ...                                  libelf: [ OFF ]
> > ...                                 libnuma: [ OFF ]
> > ...                  numa_num_possible_cpus: [ OFF ]
> > ...                               libpython: [ OFF ]
> > ...                             libcapstone: [ OFF ]
> > ...                               llvm-perf: [ OFF ]
> > ...                                    zlib: [ OFF ]
> > ...                                    lzma: [ OFF ]
> > ...                               get_cpuid: [ on  ]
> > ...                                     bpf: [ on  ]
> > ...                                  libaio: [ on  ]
> > ...                                 libzstd: [ OFF ]
> > <SNIP>
> >  CC      tests/api-io.o
> >   CC      util/sha1.o
> >   CC      util/smt.o
> >   LD      util/intel-pt-decoder/perf-util-in.o
> >   CC      tests/demangle-java-test.o
> >   CC      util/strbuf.o
> >   CC      util/string.o
> >   CC      tests/demangle-ocaml-test.o
> >   CC      util/strlist.o
> >   CC      tests/demangle-rust-v0-test.o
> >   CC      tests/pfm.o
> >   CC      tests/parse-metric.o
> >   CC      util/strfilter.o
> >   CC      tests/pe-file-parsing.o
> > util/llvm.c: In function ‘init_llvm’:
> > util/llvm.c:78:17: error: implicit declaration of function ‘LLVMInitializeAllTargetInfos’ [-Wimplicit-function-declaration]
> >    78 |                 LLVMInitializeAllTargetInfos();
> >       |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > util/llvm.c:79:17: error: implicit declaration of function ‘LLVMInitializeAllTargetMCs’ [-Wimplicit-function-declaration]
> >    79 |                 LLVMInitializeAllTargetMCs();
> >       |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~
> > util/llvm.c:80:17: error: implicit declaration of function ‘LLVMInitializeAllDisassemblers’ [-Wimplicit-function-declaration]
> >    80 |                 LLVMInitializeAllDisassemblers();
> >       |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > util/llvm.c: At top level:
> > util/llvm.c:73:13: error: ‘init_llvm’ defined but not used [-Werror=unused-function]
> >    73 | static void init_llvm(void)
> >       |             ^~~~~~~~~
> > cc1: all warnings being treated as errors
> >   CC      tests/expand-cgroup.o
> >   CC      util/top.o
> >   CC      tests/perf-time-to-tsc.o
> >   CC      util/usage.o
> > make[6]: *** [/home/acme/git/perf-tools-next/tools/build/Makefile.build:86: util/llvm.o] Error 1
> > make[6]: *** Waiting for unfinished jobs....
> >   CC      tests/dlfilter-test.o
> >   CC      tests/sigtrap.o
> >   CC      tests/event_groups.o
>
> Guess this will be enough:
>
> diff --git a/tools/perf/util/llvm.c b/tools/perf/util/llvm.c
> index 565cad1969e5e51f..2ebf1f5f65bf77c7 100644
> --- a/tools/perf/util/llvm.c
> +++ b/tools/perf/util/llvm.c
> @@ -70,6 +70,7 @@ int llvm__addr2line(const char *dso_name __maybe_unused, u64 addr __maybe_unused
>  #endif
>  }
>
> +#ifdef HAVE_LIBLLVM_SUPPORT
>  static void init_llvm(void)
>  {
>         static bool init;
> @@ -90,7 +91,6 @@ static void init_llvm(void)
>   * should add some textual annotation for after the instruction. The caller
>   * will use this information to add the actual annotation.
>   */
> -#ifdef HAVE_LIBLLVM_SUPPORT
>  struct symbol_lookup_storage {
>         u64 branch_addr;
>         u64 pcrel_load_addr;

Ah crap. Yeah, it's a PITA trying to keep LLVM and not LLVM builds
happy. perf_LLVM* fixes this by possibly always punting to the
dlopen/dlsym version when HAVE_LIBLLVM_SUPPORT isn't there - hence a
lot of the comments I've been making. I forgot to rebuild without
libLLVM and so missed needing the extra #ifdefs. I agree with the fix
but the fix can be removed in the (now) later patches that use
dlopen/dlsym.

Thanks,
Ian