[PATCH v4 0/4] tools/build: Allow versioning of all LLVM tools

[PATCH v4 0/4] tools/build: Allow versioning of all LLVM tools

[James Clark]

I ran into the build issue mentioned in the first commit, because using
an option like LLVM=-15 is a documented way to build [1], but only
some of the LLVM tools defined in tools/ support this.

After fixing that, a lot of other tidyups fell out. I didn't go too far,
for example some selftests include tools/testing/selftests/lib.mk which
reimplements some of the LLVM_SUFFIX stuff, but other selftests include
tools/scripts/Makefile.include and I stopped before touching the former.
Some other non build scripts hard code toolchains and I didn't touch
those either, this change is only focused on things that already
include Makefile.include.

[1]: Documentation/kbuild/llvm.rst

Signed-off-by: James Clark <james.clark@linaro.org>
---
Changes in v4:
- Drop "tools/build: selftests: Allow versioning LLVM lld", clang
  already picks the correct sibling lld version. (Sashiko)
- Link to v3: https://lore.kernel.org/r/20260715-james-perf-llvm-version-v3-0-8854bfe5af7e@linaro.org

Changes in v3:
- Add warning for empty $USE_LD
- Use $HOSTREADELF in bpf Makefile
- Rebase on v7.2-rc3
- Link to v2: https://lore.kernel.org/r/20260518-james-perf-llvm-version-v2-0-f12cc4f031d8@linaro.org

Changes in v2:
- Fix selftests/bpf build. LLD needs to take the full path to be used
  with -fuse-ld=
- Link to v1: https://lore.kernel.org/r/20260514-james-perf-llvm-version-v1-0-6cac1a9a4c8d@linaro.org

---
James Clark (4):
      tools/build: Allow versioning of all LLVM tools defined in Makefile.include
      tools/build: Indent if else blocks
      tools/build: Allow versioning LLVM readelf
      tools/build: selftests: Remove some duplicate toolchain definitions

 tools/bpf/resolve_btfids/Makefile    |  3 --
 tools/lib/api/Makefile               |  4 --
 tools/lib/bpf/Makefile               |  8 ++--
 tools/lib/subcmd/Makefile            |  4 --
 tools/lib/symbol/Makefile            |  4 --
 tools/perf/Makefile.perf             |  7 ----
 tools/scripts/Makefile.include       | 77 ++++++++++++++++++++----------------
 tools/testing/selftests/bpf/Makefile |  1 -
 8 files changed, 46 insertions(+), 62 deletions(-)
---
base-commit: a13c140cc289c0b7b3770bce5b3ad42ab35074aa
change-id: 20260511-james-perf-llvm-version-43ab1cb5bc7d

Best regards,
-- 
James Clark <james.clark@linaro.org>

[PATCH v4 1/4] tools/build: Allow versioning of all LLVM tools defined in Makefile.include

[James Clark]

The version of LLVM tools can be given on the build command with
LLVM=-15, but this isn't applied to all tools. For example $(CC) gets
versioned, but $(CLANG) doesn't. This causes a Perf build with LTO=1 to
fail with an error about mixed clang versions:

 ld.lld: error: libperf/core.o: Unknown attribute kind (86)
   (Producer: 'LLVM18.1.8' Reader: 'LLVM 15.0.7')

This file has two "ifneq ($(LLVM),)" blocks adjacent to each other, so
merge these blocks making it obvious that all tools should be versioned
consistently and there is nothing special about each block.

This also reveals that ?= and "allow-override" are used inconsistently
between the blocks. "allow-override" is technically only required for
builtin variables, but isn't only used on them, and doesn't do any harm
if used on a non-builtin. Make them all "allow-override" for
consistency. The only functional difference this will cause is if there
is a file level definition of one of the variables followed by an
"#include of Makefile.include" which will now overwrite. But this isn't
done and in a later commit some of the duplicate definitions will be
removed for good measure.

There are also some other LLVM tools that are not defined here and will
be moved in a later commit.

Signed-off-by: James Clark <james.clark@linaro.org>
---
 tools/scripts/Makefile.include | 37 ++++++++++++++++++++-----------------
 1 file changed, 20 insertions(+), 17 deletions(-)

diff --git a/tools/scripts/Makefile.include b/tools/scripts/Makefile.include
index 41971a68972dda218714d6b95b1d9d92349285c3..7022e78208a236604a681d45b1ff4f2128f412e5 100644
--- a/tools/scripts/Makefile.include
+++ b/tools/scripts/Makefile.include
@@ -61,10 +61,18 @@ $(error Invalid value for LLVM, see Documentation/kbuild/llvm.rst)
 endif
 
 $(call allow-override,CC,$(LLVM_PREFIX)clang$(LLVM_SUFFIX))
+$(call allow-override,CLANG,$(LLVM_PREFIX)clang$(LLVM_SUFFIX))
+$(call allow-override,HOSTCC,$(LLVM_PREFIX)clang$(LLVM_SUFFIX))
 $(call allow-override,AR,$(LLVM_PREFIX)llvm-ar$(LLVM_SUFFIX))
+$(call allow-override,HOSTAR,$(LLVM_PREFIX)llvm-ar$(LLVM_SUFFIX))
 $(call allow-override,LD,$(LLVM_PREFIX)ld.lld$(LLVM_SUFFIX))
+$(call allow-override,HOSTLD,$(LLVM_PREFIX)ld.lld$(LLVM_SUFFIX))
 $(call allow-override,CXX,$(LLVM_PREFIX)clang++$(LLVM_SUFFIX))
 $(call allow-override,STRIP,$(LLVM_PREFIX)llvm-strip$(LLVM_SUFFIX))
+$(call allow-override,LLVM_STRIP,$(LLVM_PREFIX)llvm-strip$(LLVM_SUFFIX))
+$(call allow-override,LLC,$(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))
 else
 # Allow setting various cross-compile vars or setting CROSS_COMPILE as a prefix.
 $(call allow-override,CC,$(CROSS_COMPILE)gcc)
@@ -72,26 +80,21 @@ $(call allow-override,AR,$(CROSS_COMPILE)ar)
 $(call allow-override,LD,$(CROSS_COMPILE)ld)
 $(call allow-override,CXX,$(CROSS_COMPILE)g++)
 $(call allow-override,STRIP,$(CROSS_COMPILE)strip)
-endif
-
-CC_NO_CLANG := $(shell $(CC) -dM -E -x c /dev/null | grep -Fq "__clang__"; echo $$?)
 
-ifneq ($(LLVM),)
-HOSTAR  ?= $(LLVM_PREFIX)llvm-ar$(LLVM_SUFFIX)
-HOSTCC  ?= $(LLVM_PREFIX)clang$(LLVM_SUFFIX)
-HOSTLD  ?= $(LLVM_PREFIX)ld.lld$(LLVM_SUFFIX)
-else
-HOSTAR  ?= ar
-HOSTCC  ?= gcc
-HOSTLD  ?= ld
+# Host versions aren't prefixed
+$(call allow-override,HOSTAR,ar)
+$(call allow-override,HOSTCC,gcc)
+$(call allow-override,HOSTLD,ld)
+
+# Some tools still require Clang, LLC and/or LLVM utils
+$(call allow-override,CLANG,clang)
+$(call allow-override,LLC,llc)
+$(call allow-override,LLVM_CONFIG,llvm-config)
+$(call allow-override,LLVM_OBJCOPY,llvm-objcopy)
+$(call allow-override,LLVM_STRIP,llvm-strip)
 endif
 
-# Some tools require Clang, LLC and/or LLVM utils
-CLANG		?= clang
-LLC		?= llc
-LLVM_CONFIG	?= llvm-config
-LLVM_OBJCOPY	?= llvm-objcopy
-LLVM_STRIP	?= llvm-strip
+CC_NO_CLANG := $(shell $(CC) -dM -E -x c /dev/null | grep -Fq "__clang__"; echo $$?)
 
 # Some tools require bpftool
 SYSTEM_BPFTOOL	?= bpftool

-- 
2.34.1

[PATCH v4 2/4] tools/build: Indent if else blocks

[James Clark]

These blocks are quite big and unreadable without indentation. Indent
them.

No functional changes intended.

Signed-off-by: James Clark <james.clark@linaro.org>
---
 tools/scripts/Makefile.include | 76 +++++++++++++++++++++---------------------
 1 file changed, 38 insertions(+), 38 deletions(-)

diff --git a/tools/scripts/Makefile.include b/tools/scripts/Makefile.include
index 7022e78208a236604a681d45b1ff4f2128f412e5..e81e5b479c563321e458b2a7ad8fca2b4607a254 100644
--- a/tools/scripts/Makefile.include
+++ b/tools/scripts/Makefile.include
@@ -52,46 +52,46 @@ define allow-override
 endef
 
 ifneq ($(LLVM),)
-ifneq ($(filter %/,$(LLVM)),)
-LLVM_PREFIX := $(LLVM)
-else ifneq ($(filter -%,$(LLVM)),)
-LLVM_SUFFIX := $(LLVM)
-else ifneq ($(LLVM),1)
-$(error Invalid value for LLVM, see Documentation/kbuild/llvm.rst)
-endif
+  ifneq ($(filter %/,$(LLVM)),)
+    LLVM_PREFIX := $(LLVM)
+  else ifneq ($(filter -%,$(LLVM)),)
+    LLVM_SUFFIX := $(LLVM)
+  else ifneq ($(LLVM),1)
+    $(error Invalid value for LLVM, see Documentation/kbuild/llvm.rst)
+  endif
 
-$(call allow-override,CC,$(LLVM_PREFIX)clang$(LLVM_SUFFIX))
-$(call allow-override,CLANG,$(LLVM_PREFIX)clang$(LLVM_SUFFIX))
-$(call allow-override,HOSTCC,$(LLVM_PREFIX)clang$(LLVM_SUFFIX))
-$(call allow-override,AR,$(LLVM_PREFIX)llvm-ar$(LLVM_SUFFIX))
-$(call allow-override,HOSTAR,$(LLVM_PREFIX)llvm-ar$(LLVM_SUFFIX))
-$(call allow-override,LD,$(LLVM_PREFIX)ld.lld$(LLVM_SUFFIX))
-$(call allow-override,HOSTLD,$(LLVM_PREFIX)ld.lld$(LLVM_SUFFIX))
-$(call allow-override,CXX,$(LLVM_PREFIX)clang++$(LLVM_SUFFIX))
-$(call allow-override,STRIP,$(LLVM_PREFIX)llvm-strip$(LLVM_SUFFIX))
-$(call allow-override,LLVM_STRIP,$(LLVM_PREFIX)llvm-strip$(LLVM_SUFFIX))
-$(call allow-override,LLC,$(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))
+  $(call allow-override,CC,$(LLVM_PREFIX)clang$(LLVM_SUFFIX))
+  $(call allow-override,CLANG,$(LLVM_PREFIX)clang$(LLVM_SUFFIX))
+  $(call allow-override,HOSTCC,$(LLVM_PREFIX)clang$(LLVM_SUFFIX))
+  $(call allow-override,AR,$(LLVM_PREFIX)llvm-ar$(LLVM_SUFFIX))
+  $(call allow-override,HOSTAR,$(LLVM_PREFIX)llvm-ar$(LLVM_SUFFIX))
+  $(call allow-override,LD,$(LLVM_PREFIX)ld.lld$(LLVM_SUFFIX))
+  $(call allow-override,HOSTLD,$(LLVM_PREFIX)ld.lld$(LLVM_SUFFIX))
+  $(call allow-override,CXX,$(LLVM_PREFIX)clang++$(LLVM_SUFFIX))
+  $(call allow-override,STRIP,$(LLVM_PREFIX)llvm-strip$(LLVM_SUFFIX))
+  $(call allow-override,LLVM_STRIP,$(LLVM_PREFIX)llvm-strip$(LLVM_SUFFIX))
+  $(call allow-override,LLC,$(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$(LLVM_SUFFIX))
 else
-# Allow setting various cross-compile vars or setting CROSS_COMPILE as a prefix.
-$(call allow-override,CC,$(CROSS_COMPILE)gcc)
-$(call allow-override,AR,$(CROSS_COMPILE)ar)
-$(call allow-override,LD,$(CROSS_COMPILE)ld)
-$(call allow-override,CXX,$(CROSS_COMPILE)g++)
-$(call allow-override,STRIP,$(CROSS_COMPILE)strip)
-
-# Host versions aren't prefixed
-$(call allow-override,HOSTAR,ar)
-$(call allow-override,HOSTCC,gcc)
-$(call allow-override,HOSTLD,ld)
-
-# Some tools still require Clang, LLC and/or LLVM utils
-$(call allow-override,CLANG,clang)
-$(call allow-override,LLC,llc)
-$(call allow-override,LLVM_CONFIG,llvm-config)
-$(call allow-override,LLVM_OBJCOPY,llvm-objcopy)
-$(call allow-override,LLVM_STRIP,llvm-strip)
+  # Allow setting various cross-compile vars or setting CROSS_COMPILE as a prefix.
+  $(call allow-override,CC,$(CROSS_COMPILE)gcc)
+  $(call allow-override,AR,$(CROSS_COMPILE)ar)
+  $(call allow-override,LD,$(CROSS_COMPILE)ld)
+  $(call allow-override,CXX,$(CROSS_COMPILE)g++)
+  $(call allow-override,STRIP,$(CROSS_COMPILE)strip)
+
+  # Host versions aren't prefixed
+  $(call allow-override,HOSTAR,ar)
+  $(call allow-override,HOSTCC,gcc)
+  $(call allow-override,HOSTLD,ld)
+
+  # Some tools still require Clang, LLC and/or LLVM utils
+  $(call allow-override,CLANG,clang)
+  $(call allow-override,LLC,llc)
+  $(call allow-override,LLVM_CONFIG,llvm-config)
+  $(call allow-override,LLVM_OBJCOPY,llvm-objcopy)
+  $(call allow-override,LLVM_STRIP,llvm-strip)
 endif
 
 CC_NO_CLANG := $(shell $(CC) -dM -E -x c /dev/null | grep -Fq "__clang__"; echo $$?)

-- 
2.34.1

[PATCH v4 3/4] tools/build: Allow versioning LLVM readelf

[James Clark]

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
variables.

Where readelf wasn't doing anything arch specific, use HOSTREADELF
because it's more likely to be installed.

Reviewed-by: Ian Rogers <irogers@google.com>
Signed-off-by: James Clark <james.clark@linaro.org>
---
 tools/lib/bpf/Makefile         | 8 ++++----
 tools/perf/Makefile.perf       | 1 -
 tools/scripts/Makefile.include | 4 ++++
 3 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/tools/lib/bpf/Makefile b/tools/lib/bpf/Makefile
index eca584fb061e16013e76827e4203f6be0477a73e..269fe21fc8da73083367b3c122bdd2b718e12bc5 100644
--- a/tools/lib/bpf/Makefile
+++ b/tools/lib/bpf/Makefile
@@ -115,12 +115,12 @@ 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 $(HOSTREADELF) -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 $(HOSTREADELF) --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)
@@ -183,12 +183,12 @@ 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) |			 \
+		$(HOSTREADELF) -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 |		 \
+		$(HOSTREADELF) --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 476b8dcaef58cb1f3fa75f46a647c2cfe2352767..4d0d7ae02e06b117487a17691c4e62a138428ac5 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 e81e5b479c563321e458b2a7ad8fca2b4607a254..46a3872b87624a7bf475d9b42a3e471f36789dfd 100644
--- a/tools/scripts/Makefile.include
+++ b/tools/scripts/Makefile.include
@@ -73,6 +73,8 @@ 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))
+  $(call allow-override,HOSTREADELF,$(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)
@@ -80,11 +82,13 @@ 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)
   $(call allow-override,HOSTCC,gcc)
   $(call allow-override,HOSTLD,ld)
+  $(call allow-override,HOSTREADELF,readelf)
 
   # Some tools still require Clang, LLC and/or LLVM utils
   $(call allow-override,CLANG,clang)

-- 
2.34.1

[PATCH v4 4/4] tools/build: selftests: Remove some duplicate toolchain definitions

[James Clark]

Try to remove some, but not all duplicate toolchain definitions. In
these instances, their makefiles already include
tools/scripts/Makefile.include which defines these in a consistent way.

STRIP is the only one that was set with an '=', but I don't think it
was significant so that difference can be dropped.

Signed-off-by: James Clark <james.clark@linaro.org>
---
 tools/bpf/resolve_btfids/Makefile    | 3 ---
 tools/lib/api/Makefile               | 4 ----
 tools/lib/subcmd/Makefile            | 4 ----
 tools/lib/symbol/Makefile            | 4 ----
 tools/perf/Makefile.perf             | 6 ------
 tools/testing/selftests/bpf/Makefile | 1 -
 6 files changed, 22 deletions(-)

diff --git a/tools/bpf/resolve_btfids/Makefile b/tools/bpf/resolve_btfids/Makefile
index 7672208f65e4bc245c03603634d3aa0093a91096..6fdb6302e0a28e9166175822f42cfbb4f4eb24e5 100644
--- a/tools/bpf/resolve_btfids/Makefile
+++ b/tools/bpf/resolve_btfids/Makefile
@@ -20,9 +20,6 @@ HOST_OVERRIDES := AR="$(HOSTAR)" CC="$(HOSTCC)" LD="$(HOSTLD)" ARCH="$(HOSTARCH)
 		  CROSS_COMPILE="" CLANG_CROSS_FLAGS="" EXTRA_CFLAGS="$(HOSTCFLAGS)"
 
 RM      ?= rm
-HOSTCC  ?= gcc
-HOSTLD  ?= ld
-HOSTAR  ?= ar
 HOSTPKG_CONFIG ?= pkg-config
 CROSS_COMPILE =
 
diff --git a/tools/lib/api/Makefile b/tools/lib/api/Makefile
index 8665c799e0fa7155016e8bc6968ebe76a90e1d13..a228fdb5adba8d7f8282688964a9751a06cb0c79 100644
--- a/tools/lib/api/Makefile
+++ b/tools/lib/api/Makefile
@@ -9,10 +9,6 @@ srctree := $(patsubst %/,%,$(dir $(srctree)))
 #$(info Determined 'srctree' to be $(srctree))
 endif
 
-CC ?= $(CROSS_COMPILE)gcc
-AR ?= $(CROSS_COMPILE)ar
-LD ?= $(CROSS_COMPILE)ld
-
 MAKEFLAGS += --no-print-directory
 
 INSTALL = install
diff --git a/tools/lib/subcmd/Makefile b/tools/lib/subcmd/Makefile
index 8703ab487b68c89406fed575217b57f58e71fb01..9f1ddcf0504d993249991e0af4589db1072465d1 100644
--- a/tools/lib/subcmd/Makefile
+++ b/tools/lib/subcmd/Makefile
@@ -9,10 +9,6 @@ srctree := $(patsubst %/,%,$(dir $(srctree)))
 #$(info Determined 'srctree' to be $(srctree))
 endif
 
-CC ?= $(CROSS_COMPILE)gcc
-LD ?= $(CROSS_COMPILE)ld
-AR ?= $(CROSS_COMPILE)ar
-
 RM = rm -f
 
 MAKEFLAGS += --no-print-directory
diff --git a/tools/lib/symbol/Makefile b/tools/lib/symbol/Makefile
index 426b845edfaccf56f7c246c281a549c18d0f3919..d692abe8add6e243d7b024fe556cc0983eb4b443 100644
--- a/tools/lib/symbol/Makefile
+++ b/tools/lib/symbol/Makefile
@@ -9,10 +9,6 @@ srctree := $(patsubst %/,%,$(dir $(srctree)))
 #$(info Determined 'srctree' to be $(srctree))
 endif
 
-CC ?= $(CROSS_COMPILE)gcc
-AR ?= $(CROSS_COMPILE)ar
-LD ?= $(CROSS_COMPILE)ld
-
 MAKEFLAGS += --no-print-directory
 
 INSTALL = install
diff --git a/tools/perf/Makefile.perf b/tools/perf/Makefile.perf
index 4d0d7ae02e06b117487a17691c4e62a138428ac5..ca67d4b6fc38367c63123332360ccf27102fc086 100644
--- a/tools/perf/Makefile.perf
+++ b/tools/perf/Makefile.perf
@@ -174,11 +174,6 @@ endef
 
 LD += $(EXTRA_LDFLAGS)
 
-HOSTCC  ?= gcc
-HOSTLD  ?= ld
-HOSTAR  ?= ar
-CLANG   ?= clang
-
 # Some distros provide the command $(CROSS_COMPILE)pkg-config for
 # searching packges installed with Multiarch. Use it for cross
 # compilation if it is existed.
@@ -213,7 +208,6 @@ FIND    = find
 INSTALL = install
 FLEX    ?= flex
 BISON   ?= bison
-STRIP   = strip
 AWK     = awk
 
 # include Makefile.config by default and rule out
diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index b642ee489ea64046a9b19852780c3a6f009cbd82..a1a4ae76365955f8f7c1193a03e74bef0d344f9c 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -3,7 +3,6 @@ include ../../../build/Build.include
 include ../../../scripts/Makefile.arch
 include ../../../scripts/Makefile.include
 
-CXX ?= $(CROSS_COMPILE)g++
 OBJCOPY ?= $(CROSS_COMPILE)objcopy
 
 CURDIR := $(abspath .)

-- 
2.34.1

Re: [PATCH v4 0/4] tools/build: Allow versioning of all LLVM tools

[Ian Rogers]

On Wed, Jul 15, 2026 at 7:54 AM James Clark <james.clark@linaro.org> wrote:
>
> I ran into the build issue mentioned in the first commit, because using
> an option like LLVM=-15 is a documented way to build [1], but only
> some of the LLVM tools defined in tools/ support this.
>
> After fixing that, a lot of other tidyups fell out. I didn't go too far,
> for example some selftests include tools/testing/selftests/lib.mk which
> reimplements some of the LLVM_SUFFIX stuff, but other selftests include
> tools/scripts/Makefile.include and I stopped before touching the former.
> Some other non build scripts hard code toolchains and I didn't touch
> those either, this change is only focused on things that already
> include Makefile.include.
>
> [1]: Documentation/kbuild/llvm.rst
>
> Signed-off-by: James Clark <james.clark@linaro.org>

For the series:

Reviewed-by: Ian Rogers <irogers@google.com>

Thanks,
Ian

> ---
> Changes in v4:
> - Drop "tools/build: selftests: Allow versioning LLVM lld", clang
>   already picks the correct sibling lld version. (Sashiko)
> - Link to v3: https://lore.kernel.org/r/20260715-james-perf-llvm-version-v3-0-8854bfe5af7e@linaro.org
>
> Changes in v3:
> - Add warning for empty $USE_LD
> - Use $HOSTREADELF in bpf Makefile
> - Rebase on v7.2-rc3
> - Link to v2: https://lore.kernel.org/r/20260518-james-perf-llvm-version-v2-0-f12cc4f031d8@linaro.org
>
> Changes in v2:
> - Fix selftests/bpf build. LLD needs to take the full path to be used
>   with -fuse-ld=
> - Link to v1: https://lore.kernel.org/r/20260514-james-perf-llvm-version-v1-0-6cac1a9a4c8d@linaro.org
>
> ---
> James Clark (4):
>       tools/build: Allow versioning of all LLVM tools defined in Makefile.include
>       tools/build: Indent if else blocks
>       tools/build: Allow versioning LLVM readelf
>       tools/build: selftests: Remove some duplicate toolchain definitions
>
>  tools/bpf/resolve_btfids/Makefile    |  3 --
>  tools/lib/api/Makefile               |  4 --
>  tools/lib/bpf/Makefile               |  8 ++--
>  tools/lib/subcmd/Makefile            |  4 --
>  tools/lib/symbol/Makefile            |  4 --
>  tools/perf/Makefile.perf             |  7 ----
>  tools/scripts/Makefile.include       | 77 ++++++++++++++++++++----------------
>  tools/testing/selftests/bpf/Makefile |  1 -
>  8 files changed, 46 insertions(+), 62 deletions(-)
> ---
> base-commit: a13c140cc289c0b7b3770bce5b3ad42ab35074aa
> change-id: 20260511-james-perf-llvm-version-43ab1cb5bc7d
>
> Best regards,
> --
> James Clark <james.clark@linaro.org>
>

Re: [PATCH v4 3/4] tools/build: Allow versioning LLVM readelf

[Ihor Solodrai]

On 7/15/26 7:53 AM, James Clark 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
> variables.
> 
> Where readelf wasn't doing anything arch specific, use HOSTREADELF
> because it's more likely to be installed.
> 
> Reviewed-by: Ian Rogers <irogers@google.com>
> Signed-off-by: James Clark <james.clark@linaro.org>
> ---
>  tools/lib/bpf/Makefile         | 8 ++++----
>  tools/perf/Makefile.perf       | 1 -
>  tools/scripts/Makefile.include | 4 ++++
>  3 files changed, 8 insertions(+), 5 deletions(-)
> 
> diff --git a/tools/lib/bpf/Makefile b/tools/lib/bpf/Makefile
> index eca584fb061e16013e76827e4203f6be0477a73e..269fe21fc8da73083367b3c122bdd2b718e12bc5 100644
> --- a/tools/lib/bpf/Makefile
> +++ b/tools/lib/bpf/Makefile
> @@ -115,12 +115,12 @@ 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 $(HOSTREADELF) -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 $(HOSTREADELF) --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)
> @@ -183,12 +183,12 @@ 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) |			 \
> +		$(HOSTREADELF) -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 |		 \
> +		$(HOSTREADELF) --dyn-syms --wide $(OUTPUT)libbpf.so |	 \

Acked-by: Ihor Solodrai <ihor.solodrai@linux.dev>

Thanks!

>  		    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 476b8dcaef58cb1f3fa75f46a647c2cfe2352767..4d0d7ae02e06b117487a17691c4e62a138428ac5 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 e81e5b479c563321e458b2a7ad8fca2b4607a254..46a3872b87624a7bf475d9b42a3e471f36789dfd 100644
> --- a/tools/scripts/Makefile.include
> +++ b/tools/scripts/Makefile.include
> @@ -73,6 +73,8 @@ 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))
> +  $(call allow-override,HOSTREADELF,$(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)
> @@ -80,11 +82,13 @@ 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)
>    $(call allow-override,HOSTCC,gcc)
>    $(call allow-override,HOSTLD,ld)
> +  $(call allow-override,HOSTREADELF,readelf)
>  
>    # Some tools still require Clang, LLC and/or LLVM utils
>    $(call allow-override,CLANG,clang)
> 

Re: [PATCH v4 4/4] tools/build: selftests: Remove some duplicate toolchain definitions

[Ihor Solodrai]

On 7/15/26 7:53 AM, James Clark wrote:
> Try to remove some, but not all duplicate toolchain definitions. In
> these instances, their makefiles already include
> tools/scripts/Makefile.include which defines these in a consistent way.
> 
> STRIP is the only one that was set with an '=', but I don't think it
> was significant so that difference can be dropped.
> 
> Signed-off-by: James Clark <james.clark@linaro.org>
> ---
>  tools/bpf/resolve_btfids/Makefile    | 3 ---
>  tools/lib/api/Makefile               | 4 ----
>  tools/lib/subcmd/Makefile            | 4 ----
>  tools/lib/symbol/Makefile            | 4 ----
>  tools/perf/Makefile.perf             | 6 ------
>  tools/testing/selftests/bpf/Makefile | 1 -
>  6 files changed, 22 deletions(-)
> 
> diff --git a/tools/bpf/resolve_btfids/Makefile b/tools/bpf/resolve_btfids/Makefile
> index 7672208f65e4bc245c03603634d3aa0093a91096..6fdb6302e0a28e9166175822f42cfbb4f4eb24e5 100644
> --- a/tools/bpf/resolve_btfids/Makefile
> +++ b/tools/bpf/resolve_btfids/Makefile
> @@ -20,9 +20,6 @@ HOST_OVERRIDES := AR="$(HOSTAR)" CC="$(HOSTCC)" LD="$(HOSTLD)" ARCH="$(HOSTARCH)
>  		  CROSS_COMPILE="" CLANG_CROSS_FLAGS="" EXTRA_CFLAGS="$(HOSTCFLAGS)"
>  
>  RM      ?= rm
> -HOSTCC  ?= gcc
> -HOSTLD  ?= ld
> -HOSTAR  ?= ar

Acked-by: Ihor Solodrai <ihor.solodrai@linux.dev>

>  HOSTPKG_CONFIG ?= pkg-config
>  CROSS_COMPILE =
>  
> [...]
>