Re: [PATCH v2 4/6] tools/build: Allow versioning LLVM readelf

[Ian Rogers]

On Mon, May 18, 2026 at 2:04 AM James Clark <james.clark@xxxxxxxxxx> wrote:
>
> Documentation/kbuild/llvm.rst mentions that readelf is included in the
> LLVM toolchain, but it's not currently included in this block.
>
> Add it so that LLVM=... options also apply to readelf. Users in tools/
> were Perf which was hardcoding it, and another was the BPF makefile.
> Both already include Makefile.include so convert them to use the new
> variable.
>
> It also didn't have the cross compile prefix, so either readelf didn't
> mind opening cross binaries, or it wasn't working for cross builds.
>
> Signed-off-by: James Clark <james.clark@xxxxxxxxxx>

For the tools/perf/Makefile.perf part of this change.

Reviewed-by: Ian Rogers <irogers@xxxxxxxxxx>

Thanks for the cleanup!
Ian

> ---
>  tools/lib/bpf/Makefile         | 8 ++++----
>  tools/perf/Makefile.perf       | 1 -
>  tools/scripts/Makefile.include | 2 ++
>  3 files changed, 6 insertions(+), 5 deletions(-)
>
> diff --git a/tools/lib/bpf/Makefile b/tools/lib/bpf/Makefile
> index 168140f8e646..180dca9c57c8 100644
> --- a/tools/lib/bpf/Makefile
> +++ b/tools/lib/bpf/Makefile
> @@ -114,12 +114,12 @@ PC_FILE           := $(addprefix $(OUTPUT),$(PC_FILE))
>
>  TAGS_PROG := $(if $(shell which etags 2>/dev/null),etags,ctags)
>
> -GLOBAL_SYM_COUNT = $(shell readelf -s --wide $(BPF_IN_SHARED) | \
> +GLOBAL_SYM_COUNT = $(shell $(READELF) -s --wide $(BPF_IN_SHARED) | \
>                            cut -d "@" -f1 | sed 's/_v[0-9]_[0-9]_[0-9].*//' | \
>                            sed 's/\[.*\]//' | \
>                            awk '/GLOBAL/ && /DEFAULT/ && !/UND|ABS/ {print $$NF}' | \
>                            sort -u | wc -l)
> -VERSIONED_SYM_COUNT = $(shell readelf --dyn-syms --wide $(OUTPUT)libbpf.so | \
> +VERSIONED_SYM_COUNT = $(shell $(READELF) --dyn-syms --wide $(OUTPUT)libbpf.so | \
>                               sed 's/\[.*\]//' | \
>                               awk '/GLOBAL/ && /DEFAULT/ && !/UND|ABS/ {print $$NF}' | \
>                               grep -Eo '[^ ]+@LIBBPF_' | cut -d@ -f1 | sort -u | wc -l)
> @@ -182,12 +182,12 @@ check_abi: $(OUTPUT)libbpf.so $(VERSION_SCRIPT)
>                      "versioned symbols in $^ ($(VERSIONED_SYM_COUNT))." \
>                      "Please make sure all LIBBPF_API symbols are"       \
>                      "versioned in $(VERSION_SCRIPT)." >&2;              \
> -               readelf -s --wide $(BPF_IN_SHARED) |                     \
> +               $(READELF) -s --wide $(BPF_IN_SHARED) |                  \
>                     cut -d "@" -f1 | sed 's/_v[0-9]_[0-9]_[0-9].*//' |   \
>                     sed 's/\[.*\]//' |                                   \
>                     awk '/GLOBAL/ && /DEFAULT/ && !/UND/ {print $$NF}'|  \
>                     sort -u > $(OUTPUT)libbpf_global_syms.tmp;           \
> -               readelf --dyn-syms --wide $(OUTPUT)libbpf.so |           \
> +               $(READELF) --dyn-syms --wide $(OUTPUT)libbpf.so |                \
>                     sed 's/\[.*\]//' |                                   \
>                     awk '/GLOBAL/ && /DEFAULT/ && !/UND|ABS/ {print $$NF}'|  \
>                     grep -Eo '[^ ]+@LIBBPF_' | cut -d@ -f1 |             \
> diff --git a/tools/perf/Makefile.perf b/tools/perf/Makefile.perf
> index 0aba14f22a06..63276bf55856 100644
> --- a/tools/perf/Makefile.perf
> +++ b/tools/perf/Makefile.perf
> @@ -215,7 +215,6 @@ FLEX    ?= flex
>  BISON   ?= bison
>  STRIP   = strip
>  AWK     = awk
> -READELF ?= readelf
>
>  # include Makefile.config by default and rule out
>  # non-config cases
> diff --git a/tools/scripts/Makefile.include b/tools/scripts/Makefile.include
> index e81e5b479c56..380ad84ac51e 100644
> --- a/tools/scripts/Makefile.include
> +++ b/tools/scripts/Makefile.include
> @@ -73,6 +73,7 @@ ifneq ($(LLVM),)
>    $(call allow-override,LLC,$(LLVM_PREFIX)llc$(LLVM_SUFFIX))
>    $(call allow-override,LLVM_CONFIG,$(LLVM_PREFIX)llvm-config$(LLVM_SUFFIX))
>    $(call allow-override,LLVM_OBJCOPY,$(LLVM_PREFIX)llvm-objcopy$(LLVM_SUFFIX))
> +  $(call allow-override,READELF,$(LLVM_PREFIX)llvm-readelf$(LLVM_SUFFIX))
>  else
>    # Allow setting various cross-compile vars or setting CROSS_COMPILE as a prefix.
>    $(call allow-override,CC,$(CROSS_COMPILE)gcc)
> @@ -80,6 +81,7 @@ else
>    $(call allow-override,LD,$(CROSS_COMPILE)ld)
>    $(call allow-override,CXX,$(CROSS_COMPILE)g++)
>    $(call allow-override,STRIP,$(CROSS_COMPILE)strip)
> +  $(call allow-override,READELF,$(CROSS_COMPILE)readelf)
>
>    # Host versions aren't prefixed
>    $(call allow-override,HOSTAR,ar)
>
> --
> 2.34.1
>