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From c7f38ebb54f2dcf7588052b0b8189b8e87cb7eff Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Toke=20H=C3=B8iland-J=C3=B8rgensen?= <toke@redhat.com>
Date: Fri, 14 Mar 2025 11:30:01 +0100
Subject: [PATCH] Get rid of llc and use clang to build BPF object files
directly
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
It turns out we pass both -S and -c to clang, which has become an error
starting from clang 20. The two-stage build using 'clang -S' followed by
llc was used in the early days of BPF development, but these days, clang
is perfectly happy to produce BPF object files directly.
So use this opportunity to get rid of llc entirely, and simplify the BPF
object build rules while we're add it, by moving all of the -W* defines
to BPF_CFLAGS.
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
---
.github/scripts/run_tests_in_vm.sh | 2 +-
.github/workflows/covscan.yml | 1 -
.github/workflows/selftests.yml | 1 -
configure | 6 +-----
lib/common.mk | 12 +-----------
lib/defines.mk | 4 +++-
lib/libxdp/Makefile | 12 +-----------
lib/libxdp/tests/Makefile | 12 +-----------
lib/util/Makefile | 12 +-----------
packaging/rpm/xdp-tools.spec | 1 -
10 files changed, 9 insertions(+), 54 deletions(-)
diff --git a/configure b/configure
index 6a57528..6b0fd27 100755
--- a/configure
+++ b/configure
@@ -61,7 +61,6 @@ check_toolchain()
: ${CC=gcc}
: ${OBJCOPY=objcopy}
: ${CLANG=clang}
- : ${LLC=llc}
: ${M4=m4}
: ${EMACS=emacs}
: ${BPFTOOL=bpftool}
@@ -70,9 +69,8 @@ check_toolchain()
: ${ARCH_NAME=}
CLANG=$(find_tool clang "$CLANG")
- LLC=$(find_tool llc "$LLC")
- for TOOL in $PKG_CONFIG $CC $LD $OBJCOPY $CLANG $LLC $M4; do
+ for TOOL in $PKG_CONFIG $CC $LD $OBJCOPY $CLANG $M4; do
if [ ! $(command -v ${TOOL} 2>/dev/null) ]; then
echo "*** ERROR: Cannot find tool ${TOOL}" ;
exit 1;
@@ -131,7 +129,6 @@ check_toolchain()
echo "CC:=${CC}" >>$CONFIG
echo "OBJCOPY:=${OBJCOPY}" >>$CONFIG
echo "CLANG:=${CLANG}" >>$CONFIG
- echo "LLC:=${LLC}" >>$CONFIG
echo "M4:=${M4}" >>$CONFIG
echo "EMACS:=${EMACS}" >>$CONFIG
echo "ARCH_INCLUDES:=$ARCH_INCLUDES" >> $CONFIG
@@ -447,7 +444,6 @@ endif
ifeq (\$(VERBOSE), 0)
QUIET_CC = @echo ' CC '\$@;
QUIET_CLANG = @echo ' CLANG '\$@;
- QUIET_LLC = @echo ' LLC '\$@;
QUIET_LINK = @echo ' LINK '\$@;
QUIET_INSTALL = @echo ' INSTALL '\$@;
QUIET_M4 = @echo ' M4 '\$@;
diff --git a/lib/common.mk b/lib/common.mk
index dfac249..ce24c48 100644
--- a/lib/common.mk
+++ b/lib/common.mk
@@ -108,17 +108,7 @@ $(ALL_EXEC_TARGETS): %: %.c $(OBJECT_LIBBPF) $(OBJECT_LIBXDP) $(LIBMK) $(LIB_OB
$< $(USER_EXTRA_C) $(LDLIBS)
$(XDP_OBJ): %.o: %.c $(KERN_USER_H) $(EXTRA_DEPS) $(BPF_HEADERS) $(LIBMK)
- $(QUIET_CLANG)$(CLANG) -S \
- -target $(BPF_TARGET) \
- -D __BPF_TRACING__ \
- $(BPF_CFLAGS) \
- -Wall \
- -Wno-unused-value \
- -Wno-pointer-sign \
- -Wno-compare-distinct-pointer-types \
- -Werror \
- -O2 -emit-llvm -c -g -o ${@:.o=.ll} $<
- $(QUIET_LLC)$(LLC) -march=$(BPF_TARGET) -filetype=obj -o $@ ${@:.o=.ll}
+ $(QUIET_CLANG)$(CLANG) -target $(BPF_TARGET) $(BPF_CFLAGS) -O2 -c -g -o $@ $<
$(BPF_SKEL_H): %.skel.h: %.bpf.o
$(QUIET_GEN)$(BPFTOOL) gen skeleton $< name $(notdir ${@:.skel.h=}) > $@
diff --git a/lib/defines.mk b/lib/defines.mk
index f3ff3d3..e86b206 100644
--- a/lib/defines.mk
+++ b/lib/defines.mk
@@ -1,5 +1,7 @@
CFLAGS ?= -O2 -g
-BPF_CFLAGS ?= -Wno-visibility
+BPF_CFLAGS ?= -Wall -Wno-unused-value -Wno-pointer-sign \
+ -Wno-compare-distinct-pointer-types \
+ -Wno-visibility -Werror -fno-stack-protector
BPF_TARGET ?= bpf
HAVE_FEATURES :=
diff --git a/lib/libxdp/Makefile b/lib/libxdp/Makefile
index c3336f2..4716fb0 100644
--- a/lib/libxdp/Makefile
+++ b/lib/libxdp/Makefile
@@ -135,17 +135,7 @@ $(EMBEDDED_XDP_OBJS): %.embed.o: %.o
$(Q)$(OBJCOPY) --rename-section .data=.rodata,alloc,load,readonly,data,contents $@
$(XDP_OBJS): %.o: %.c $(BPF_HEADERS) $(LIBMK)
- $(QUIET_CLANG)$(CLANG) -S \
- -target $(BPF_TARGET) \
- -D __BPF_TRACING__ \
- $(BPF_CFLAGS) \
- -Wall \
- -Wno-unused-value \
- -Wno-pointer-sign \
- -Wno-compare-distinct-pointer-types \
- -Werror \
- -O2 -emit-llvm -c -g -o ${@:.o=.ll} $<
- $(QUIET_LLC)$(LLC) -march=$(BPF_TARGET) -filetype=obj -o $@ ${@:.o=.ll}
+ $(QUIET_CLANG)$(CLANG) -target $(BPF_TARGET) $(BPF_CFLAGS) -O2 -c -g -o $@ $<
.PHONY: man
ifeq ($(EMACS),)
|
