diff mbox series

[bpf-next,4/6] bpftool: Enable cross-building with clang

Message ID 20211122192019.1277299-5-jean-philippe@linaro.org (mailing list archive)
State Changes Requested
Delegated to: BPF
Headers show
Series tools/bpf: Enable cross-building with clang | expand

Checks

Context Check Description
netdev/tree_selection success Clearly marked for bpf-next
netdev/apply fail Patch does not apply to bpf-next
bpf/vmtest-bpf-next-PR fail merge-conflict

Commit Message

Jean-Philippe Brucker Nov. 22, 2021, 7:20 p.m. UTC 
Cross-building using clang requires passing the "-target" flag rather
than using the CROSS_COMPILE prefix. Makefile.include transforms
CROSS_COMPILE into CLANG_CROSS_FLAGS, and adds that to CFLAGS. Filter
out the cross flags for the bootstrap bpftool, and erase the
CROSS_COMPILE flag for the bootstrap libbpf.

Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
---
 tools/bpf/bpftool/Makefile | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

Comments

Andrii Nakryiko Nov. 29, 2021, 11:53 p.m. UTC | #1 
On Mon, Nov 22, 2021 at 11:23 AM Jean-Philippe Brucker
<jean-philippe@linaro.org> wrote:
>
> Cross-building using clang requires passing the "-target" flag rather
> than using the CROSS_COMPILE prefix. Makefile.include transforms
> CROSS_COMPILE into CLANG_CROSS_FLAGS, and adds that to CFLAGS. Filter
> out the cross flags for the bootstrap bpftool, and erase the
> CROSS_COMPILE flag for the bootstrap libbpf.
>
> Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
> ---
>  tools/bpf/bpftool/Makefile | 13 +++++++------
>  1 file changed, 7 insertions(+), 6 deletions(-)
>
> diff --git a/tools/bpf/bpftool/Makefile b/tools/bpf/bpftool/Makefile
> index 42eb8eee3d89..b0f3e17d981a 100644
> --- a/tools/bpf/bpftool/Makefile
> +++ b/tools/bpf/bpftool/Makefile
> @@ -57,7 +57,7 @@ $(LIBBPF_INTERNAL_HDRS): $(LIBBPF_HDRS_DIR)/%.h: $(BPF_DIR)/%.h | $(LIBBPF_HDRS_
>  $(LIBBPF_BOOTSTRAP): $(wildcard $(BPF_DIR)/*.[ch] $(BPF_DIR)/Makefile) | $(LIBBPF_BOOTSTRAP_OUTPUT)
>         $(Q)$(MAKE) -C $(BPF_DIR) OUTPUT=$(LIBBPF_BOOTSTRAP_OUTPUT) \
>                 DESTDIR=$(LIBBPF_BOOTSTRAP_DESTDIR) prefix= \
> -               ARCH= CC=$(HOSTCC) LD=$(HOSTLD) $@ install_headers
> +               ARCH= CROSS_COMPILE= CC=$(HOSTCC) LD=$(HOSTLD) $@ install_headers
>
>  $(LIBBPF_BOOTSTRAP_INTERNAL_HDRS): $(LIBBPF_BOOTSTRAP_HDRS_DIR)/%.h: $(BPF_DIR)/%.h | $(LIBBPF_BOOTSTRAP_HDRS_DIR)
>         $(call QUIET_INSTALL, $@)
> @@ -152,6 +152,9 @@ CFLAGS += -DHAVE_LIBBFD_SUPPORT
>  SRCS += $(BFD_SRCS)
>  endif
>
> +HOST_CFLAGS = $(subst -I$(LIBBPF_INCLUDE),-I$(LIBBPF_BOOTSTRAP_INCLUDE),\
> +               $(filter-out $(CLANG_CROSS_FLAGS),$(CFLAGS)))

Isn't this dangerous? CLANG_CROSS_FLAGS are treated as space-separated
array of values, so if you have something like '-I whatever' it will
actually filter out unrelated -Is from CFLAGS, no? I'd rather subst
into empty string instead, just like we do for LIBBPF_INCLUDE.

> +
>  BPFTOOL_BOOTSTRAP := $(BOOTSTRAP_OUTPUT)bpftool
>
>  BOOTSTRAP_OBJS = $(addprefix $(BOOTSTRAP_OUTPUT),main.o common.o json_writer.o gen.o btf.o xlated_dumper.o btf_dumper.o disasm.o)
> @@ -202,7 +205,7 @@ endif
>  CFLAGS += $(if $(BUILD_BPF_SKELS),,-DBPFTOOL_WITHOUT_SKELETONS)
>
>  $(BOOTSTRAP_OUTPUT)disasm.o: $(srctree)/kernel/bpf/disasm.c
> -       $(QUIET_CC)$(HOSTCC) $(CFLAGS) -c -MMD $< -o $@
> +       $(QUIET_CC)$(HOSTCC) $(HOST_CFLAGS) -c -MMD $< -o $@
>
>  $(OUTPUT)disasm.o: $(srctree)/kernel/bpf/disasm.c
>         $(QUIET_CC)$(CC) $(CFLAGS) -c -MMD $< -o $@
> @@ -213,15 +216,13 @@ ifneq ($(feature-zlib), 1)
>  endif
>
>  $(BPFTOOL_BOOTSTRAP): $(BOOTSTRAP_OBJS) $(LIBBPF_BOOTSTRAP)
> -       $(QUIET_LINK)$(HOSTCC) $(CFLAGS) $(LDFLAGS) $(BOOTSTRAP_OBJS) $(LIBS_BOOTSTRAP) -o $@
> +       $(QUIET_LINK)$(HOSTCC) $(HOST_CFLAGS) $(LDFLAGS) $(BOOTSTRAP_OBJS) $(LIBS_BOOTSTRAP) -o $@
>
>  $(OUTPUT)bpftool: $(OBJS) $(LIBBPF)
>         $(QUIET_LINK)$(CC) $(CFLAGS) $(LDFLAGS) $(OBJS) $(LIBS) -o $@
>
>  $(BOOTSTRAP_OUTPUT)%.o: %.c $(LIBBPF_BOOTSTRAP_INTERNAL_HDRS) | $(BOOTSTRAP_OUTPUT)
> -       $(QUIET_CC)$(HOSTCC) \
> -               $(subst -I$(LIBBPF_INCLUDE),-I$(LIBBPF_BOOTSTRAP_INCLUDE),$(CFLAGS)) \
> -               -c -MMD $< -o $@
> +       $(QUIET_CC)$(HOSTCC) $(HOST_CFLAGS) -c -MMD $< -o $@
>
>  $(OUTPUT)%.o: %.c
>         $(QUIET_CC)$(CC) $(CFLAGS) -c -MMD $< -o $@
> --
> 2.33.1
>
diff mbox series

Patch

diff --git a/tools/bpf/bpftool/Makefile b/tools/bpf/bpftool/Makefile
index 42eb8eee3d89..b0f3e17d981a 100644
--- a/tools/bpf/bpftool/Makefile
+++ b/tools/bpf/bpftool/Makefile
@@ -57,7 +57,7 @@  $(LIBBPF_INTERNAL_HDRS): $(LIBBPF_HDRS_DIR)/%.h: $(BPF_DIR)/%.h | $(LIBBPF_HDRS_
 $(LIBBPF_BOOTSTRAP): $(wildcard $(BPF_DIR)/*.[ch] $(BPF_DIR)/Makefile) | $(LIBBPF_BOOTSTRAP_OUTPUT)
 	$(Q)$(MAKE) -C $(BPF_DIR) OUTPUT=$(LIBBPF_BOOTSTRAP_OUTPUT) \
 		DESTDIR=$(LIBBPF_BOOTSTRAP_DESTDIR) prefix= \
-		ARCH= CC=$(HOSTCC) LD=$(HOSTLD) $@ install_headers
+		ARCH= CROSS_COMPILE= CC=$(HOSTCC) LD=$(HOSTLD) $@ install_headers
 
 $(LIBBPF_BOOTSTRAP_INTERNAL_HDRS): $(LIBBPF_BOOTSTRAP_HDRS_DIR)/%.h: $(BPF_DIR)/%.h | $(LIBBPF_BOOTSTRAP_HDRS_DIR)
 	$(call QUIET_INSTALL, $@)
@@ -152,6 +152,9 @@  CFLAGS += -DHAVE_LIBBFD_SUPPORT
 SRCS += $(BFD_SRCS)
 endif
 
+HOST_CFLAGS = $(subst -I$(LIBBPF_INCLUDE),-I$(LIBBPF_BOOTSTRAP_INCLUDE),\
+		$(filter-out $(CLANG_CROSS_FLAGS),$(CFLAGS)))
+
 BPFTOOL_BOOTSTRAP := $(BOOTSTRAP_OUTPUT)bpftool
 
 BOOTSTRAP_OBJS = $(addprefix $(BOOTSTRAP_OUTPUT),main.o common.o json_writer.o gen.o btf.o xlated_dumper.o btf_dumper.o disasm.o)
@@ -202,7 +205,7 @@  endif
 CFLAGS += $(if $(BUILD_BPF_SKELS),,-DBPFTOOL_WITHOUT_SKELETONS)
 
 $(BOOTSTRAP_OUTPUT)disasm.o: $(srctree)/kernel/bpf/disasm.c
-	$(QUIET_CC)$(HOSTCC) $(CFLAGS) -c -MMD $< -o $@
+	$(QUIET_CC)$(HOSTCC) $(HOST_CFLAGS) -c -MMD $< -o $@
 
 $(OUTPUT)disasm.o: $(srctree)/kernel/bpf/disasm.c
 	$(QUIET_CC)$(CC) $(CFLAGS) -c -MMD $< -o $@
@@ -213,15 +216,13 @@  ifneq ($(feature-zlib), 1)
 endif
 
 $(BPFTOOL_BOOTSTRAP): $(BOOTSTRAP_OBJS) $(LIBBPF_BOOTSTRAP)
-	$(QUIET_LINK)$(HOSTCC) $(CFLAGS) $(LDFLAGS) $(BOOTSTRAP_OBJS) $(LIBS_BOOTSTRAP) -o $@
+	$(QUIET_LINK)$(HOSTCC) $(HOST_CFLAGS) $(LDFLAGS) $(BOOTSTRAP_OBJS) $(LIBS_BOOTSTRAP) -o $@
 
 $(OUTPUT)bpftool: $(OBJS) $(LIBBPF)
 	$(QUIET_LINK)$(CC) $(CFLAGS) $(LDFLAGS) $(OBJS) $(LIBS) -o $@
 
 $(BOOTSTRAP_OUTPUT)%.o: %.c $(LIBBPF_BOOTSTRAP_INTERNAL_HDRS) | $(BOOTSTRAP_OUTPUT)
-	$(QUIET_CC)$(HOSTCC) \
-		$(subst -I$(LIBBPF_INCLUDE),-I$(LIBBPF_BOOTSTRAP_INCLUDE),$(CFLAGS)) \
-		-c -MMD $< -o $@
+	$(QUIET_CC)$(HOSTCC) $(HOST_CFLAGS) -c -MMD $< -o $@
 
 $(OUTPUT)%.o: %.c
 	$(QUIET_CC)$(CC) $(CFLAGS) -c -MMD $< -o $@