[PATCH 0/6] tools/build: Allow versioning of all LLVM tools

[PATCH 0/6] 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>
---
James Clark (6):
      tools/build: Allow versioning of all LLVM tools defined in Makefile.include
      tools/build: Indent if else blocks
      selftests: Remove unused LLD variable
      tools/build: Allow versioning LLVM readelf
      tools/build: selftests: Allow versioning LLVM lld
      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 |  9 ++---
 tools/testing/selftests/hid/Makefile |  7 ----
 9 files changed, 50 insertions(+), 73 deletions(-)
---
base-commit: 09d355618f7ccc27ffc7fc668b2e232872962079
change-id: 20260511-james-perf-llvm-version-43ab1cb5bc7d

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

[PATCH 1/6] 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 41971a68972d..7022e78208a2 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 2/6] 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 7022e78208a2..e81e5b479c56 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 3/6] selftests: Remove unused LLD variable

[James Clark]

This file was mostly copied from selftests/bpf/Makefile, but the LLD
variable is not used here. Also, this copied block didn't get the same
fixes as the original one did later.

Remove it to avoid confusion and so future fixes don't have to be in two
places.

Signed-off-by: James Clark <james.clark@linaro.org>
---
 tools/testing/selftests/hid/Makefile | 7 -------
 1 file changed, 7 deletions(-)

diff --git a/tools/testing/selftests/hid/Makefile b/tools/testing/selftests/hid/Makefile
index 50ec9e0406ab..96071b4800e8 100644
--- a/tools/testing/selftests/hid/Makefile
+++ b/tools/testing/selftests/hid/Makefile
@@ -105,13 +105,6 @@ $(MAKE_DIRS):
 	$(call msg,MKDIR,,$@)
 	$(Q)mkdir -p $@
 
-# LLVM's ld.lld doesn't support all the architectures, so use it only on x86
-ifeq ($(SRCARCH),x86)
-LLD := lld
-else
-LLD := ld
-endif
-
 DEFAULT_BPFTOOL := $(HOST_SCRATCH_DIR)/sbin/bpftool
 
 TEST_GEN_PROGS_EXTENDED += $(DEFAULT_BPFTOOL)

-- 
2.34.1

[PATCH 4/6] 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
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@linaro.org>
---
 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

[PATCH 5/6] tools/build: selftests: Allow versioning LLVM lld

[James Clark]

Building with LLVM=... could result in a different version of lld being
used than the main toolchain for liburandom_read.so because it's
hardcoded to "lld" in this makefile.

Make it consistent with the rest of the LLVM toolchain by adding an LLD
variable to Makefile.include. Keep the fallback for other architectures
in tools/testing/selftests/bpf/Makefile as it seems like it's something
specific to this make rule and shouldn't be global.

Clang accepts either a full path or "ld.lld-15" style inputs to
-fuse-ld= so this will work with LLD defined the same way as the other
LLVM tools. However, for full paths, we need to use ".../ld.lld" instead
of the generic driver "lld", but I don't think the original use of "lld"
was significant as this is always a linux build.

Signed-off-by: James Clark <james.clark@linaro.org>
---
 tools/scripts/Makefile.include       | 2 ++
 tools/testing/selftests/bpf/Makefile | 8 ++++----
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/tools/scripts/Makefile.include b/tools/scripts/Makefile.include
index 380ad84ac51e..5c2d505cba62 100644
--- a/tools/scripts/Makefile.include
+++ b/tools/scripts/Makefile.include
@@ -67,6 +67,7 @@ ifneq ($(LLVM),)
   $(call allow-override,HOSTAR,$(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))
+  $(call allow-override,LLD,$(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))
@@ -91,6 +92,7 @@ else
   # Some tools still require Clang, LLC and/or LLVM utils
   $(call allow-override,CLANG,clang)
   $(call allow-override,LLC,llc)
+  $(call allow-override,LLD,ld.lld)
   $(call allow-override,LLVM_CONFIG,llvm-config)
   $(call allow-override,LLVM_OBJCOPY,llvm-objcopy)
   $(call allow-override,LLVM_STRIP,llvm-strip)
diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index 6ef6872adbc3..44ba829e5d4d 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -245,9 +245,9 @@ $(OUTPUT)/%:%.c
 
 # LLVM's ld.lld doesn't support all the architectures, so use it only on x86
 ifeq ($(SRCARCH),$(filter $(SRCARCH),x86 riscv))
-LLD := lld
+USE_LD := $(LLD)
 else
-LLD := $(shell command -v $(LD))
+USE_LD := $(shell command -v $(LD))
 endif
 
 # Filter out -static for liburandom_read.so and its dependent targets so that static builds
@@ -258,7 +258,7 @@ $(OUTPUT)/liburandom_read.so: urandom_read_lib1.c urandom_read_lib2.c liburandom
 		     $(filter-out -static,$(CFLAGS) $(LDFLAGS)) \
 		     $(filter %.c,$^) $(filter-out -static,$(LDLIBS)) \
 		     -Wno-unused-command-line-argument \
-		     -fuse-ld=$(LLD) -Wl,-znoseparate-code -Wl,--build-id=sha1 \
+		     -fuse-ld=$(USE_LD) -Wl,-znoseparate-code -Wl,--build-id=sha1 \
 		     -Wl,--version-script=liburandom_read.map \
 		     -fPIC -shared -o $@
 
@@ -268,7 +268,7 @@ $(OUTPUT)/urandom_read: urandom_read.c urandom_read_aux.c $(OUTPUT)/liburandom_r
 		     $(filter-out -static,$(CFLAGS) $(LDFLAGS)) $(filter %.c,$^) \
 		     -Wno-unused-command-line-argument \
 		     -lurandom_read $(filter-out -static,$(LDLIBS)) -L$(OUTPUT) \
-		     -fuse-ld=$(LLD) -Wl,-znoseparate-code -Wl,--build-id=sha1 \
+		     -fuse-ld=$(USE_LD) -Wl,-znoseparate-code -Wl,--build-id=sha1 \
 		     -Wl,-rpath=. -o $@
 
 $(OUTPUT)/sign-file: ../../../../scripts/sign-file.c

-- 
2.34.1

[PATCH 6/6] 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 7672208f65e4..6fdb6302e0a2 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 8665c799e0fa..a228fdb5adba 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 8703ab487b68..9f1ddcf0504d 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 426b845edfac..d692abe8add6 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 63276bf55856..948abfd2ee8d 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 44ba829e5d4d..b3e356c34479 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 1/6] tools/build: Allow versioning of all LLVM tools defined in Makefile.include

[bot+bpf-ci]

[-- Attachment #1: Type: text/plain, Size: 1862 bytes --]

> tools/build: Allow versioning of all LLVM tools defined in Makefile.include
>
> 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>

This looks like a bug fix that corrects inconsistent LLVM tool versioning
introduced in an earlier commit. Should this include:

  Fixes: e9c281928c24 ("kbuild: Make $(LLVM) more flexible")


---
AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md

CI run summary: https://github.com/kernel-patches/bpf/actions/runs/25853166705

Re: [PATCH 1/6] tools/build: Allow versioning of all LLVM tools defined in Makefile.include

[James Clark]

On 14/05/2026 11:02 am, bot+bpf-ci@kernel.org wrote:
>> tools/build: Allow versioning of all LLVM tools defined in Makefile.include
>>
>> 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>
> 
> This looks like a bug fix that corrects inconsistent LLVM tool versioning
> introduced in an earlier commit. Should this include:
> 
>    Fixes: e9c281928c24 ("kbuild: Make $(LLVM) more flexible")
> 
> 
> ---
> AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
> See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md
> 
> CI run summary: https://github.com/kernel-patches/bpf/actions/runs/25853166705

I did consider a fixes tag, but the only real bug is with Perf and 
LTO=1, and building it in this way has obviously never worked, so you 
could also argue this is new behavior.

I think it's quite and edge case and has some risk to break other tools 
if backported so I left the tag off.

Re: [PATCH 5/6] tools/build: selftests: Allow versioning LLVM lld

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] Using `-fuse-ld=ld.lld` breaks compilation of BPF selftests with GCC.
--

commit 18e1876d18fad631b521da817483ba47293a9020
Author: James Clark <james.clark@linaro.org>

tools/build: selftests: Allow versioning LLVM lld

This commit updates Makefile.include to add an LLD variable, matching the
rest of the LLVM toolchain. It modifies the BPF selftests Makefile to use
this new LLD variable instead of hardcoding lld.

> diff --git a/tools/scripts/Makefile.include b/tools/scripts/Makefile.include
> index 380ad84ac51e6..5c2d505cba62b 100644
> --- a/tools/scripts/Makefile.include
> +++ b/tools/scripts/Makefile.include
[ ... ]
> @@ -91,6 +92,7 @@ else
>    # Some tools still require Clang, LLC and/or LLVM utils
>    $(call allow-override,CLANG,clang)
>    $(call allow-override,LLC,llc)
> +  $(call allow-override,LLD,ld.lld)

Could setting LLD to ld.lld when not using LLVM cause issues for BPF
selftests compilation with GCC?

>    $(call allow-override,LLVM_CONFIG,llvm-config)
>    $(call allow-override,LLVM_OBJCOPY,llvm-objcopy)
>    $(call allow-override,LLVM_STRIP,llvm-strip)
> diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
> index 6ef6872adbc3e..44ba829e5d4dd 100644
> --- a/tools/testing/selftests/bpf/Makefile
> +++ b/tools/testing/selftests/bpf/Makefile
> @@ -245,9 +245,9 @@ $(OUTPUT)/%:%.c
>  
>  # LLVM's ld.lld doesn't support all the architectures, so use it only on x86
>  ifeq ($(SRCARCH),$(filter $(SRCARCH),x86 riscv))
> -LLD := lld
> +USE_LD := $(LLD)
>  else
> -LLD := $(shell command -v $(LD))
> +USE_LD := $(shell command -v $(LD))
>  endif
>  
>  # Filter out -static for liburandom_read.so and its dependent targets so that static builds
> @@ -258,7 +258,7 @@ $(OUTPUT)/liburandom_read.so: urandom_read_lib1.c urandom_read_lib2.c liburandom
>  		     $(filter-out -static,$(CFLAGS) $(LDFLAGS)) \
>  		     $(filter %.c,$^) $(filter-out -static,$(LDLIBS)) \
>  		     -Wno-unused-command-line-argument \
> -		     -fuse-ld=$(LLD) -Wl,-znoseparate-code -Wl,--build-id=sha1 \
> +		     -fuse-ld=$(USE_LD) -Wl,-znoseparate-code -Wl,--build-id=sha1 \

When LLVM=1 is not set, CC defaults to gcc. The Makefile uses
$(CC) ... -fuse-ld=$(USE_LD) to link liburandom_read.so.

Because USE_LD evaluates to ld.lld, gcc receives -fuse-ld=ld.lld.

However, GCC's command-line option parser is strictly hardcoded to accept
only specific linker names (lld, bfd, gold, mold). It does not recognize
-fuse-ld=ld.lld or absolute paths, and fails with an error like:

gcc: error: unrecognized command-line option '-fuse-ld=ld.lld'; did you mean '-fuse-ld=lld'?

Does this regression break the default GCC build of BPF selftests on x86
and riscv architectures?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260514-james-perf-llvm-version-v1-0-6cac1a9a4c8d@linaro.org?part=5