Re: [PATCH v1] tools/resolve_btfids: Tidy host CFLAGS forcing

[Jiri Olsa <olsajiri@gmail.com>]

On Wed, Feb 01, 2023 at 11:00:02AM +0100, Jiri Olsa wrote:
> On Tue, Jan 31, 2023 at 05:50:15PM -0800, Ian Rogers wrote:
> > Avoid passing CROSS_COMPILE to submakes and ensure CFLAGS is forced to
> > HOSTCFLAGS for submake builds. This fixes problems with cross
> > compilation.
> > 
> > Tidy to not unnecessarily modify/export CFLAGS, make the override for
> > prepare and build clearer.
> > 
> > Fixes: 13e07691a16f ("tools/resolve_btfids: Alter how HOSTCC is forced")
> > Reported-by: Nathan Chancellor <nathan@kernel.org>
> > Signed-off-by: Ian Rogers <irogers@google.com>
> 
> hum, that seems to build just the fixdep and skip the resolve_btfids binary
> 
> make[1]: Entering directory '/home/jolsa/kernel/linux-qemu/build'
>   GEN     Makefile
>   CALL    ../scripts/checksyscalls.sh
>   DESCEND bpf/resolve_btfids
>   HOSTCC  /home/jolsa/kernel/linux-qemu/build/tools/bpf/resolve_btfids/fixdep.o
>   HOSTLD  /home/jolsa/kernel/linux-qemu/build/tools/bpf/resolve_btfids/fixdep-in.o
>   LINK    /home/jolsa/kernel/linux-qemu/build/tools/bpf/resolve_btfids/fixdep
>   UPD     include/generated/utsversion.h
>   CC      init/version-timestamp.o
>   LD      .tmp_vmlinux.btf
>   BTF     .btf.vmlinux.bin.o
> die__process_unit: DW_TAG_label (0xa) @ <0x4f0d4> not handled!
> 
>   ...
> 
> die__process_unit: DW_TAG_label (0xa) @ <0xaf91cc3> not handled!
> die__process_unit: DW_TAG_label (0xa) @ <0xb032fa7> not handled!
>   LD      .tmp_vmlinux.kallsyms1
>   NM      .tmp_vmlinux.kallsyms1.syms
>   KSYMS   .tmp_vmlinux.kallsyms1.S
>   AS      .tmp_vmlinux.kallsyms1.S
>   LD      .tmp_vmlinux.kallsyms2
>   NM      .tmp_vmlinux.kallsyms2.syms
>   KSYMS   .tmp_vmlinux.kallsyms2.S
>   AS      .tmp_vmlinux.kallsyms2.S
>   LD      .tmp_vmlinux.kallsyms3
>   NM      .tmp_vmlinux.kallsyms3.syms
>   KSYMS   .tmp_vmlinux.kallsyms3.S
>   AS      .tmp_vmlinux.kallsyms3.S
>   LD      vmlinux
>   BTFIDS  vmlinux
> ../scripts/link-vmlinux.sh: line 277: ./tools/bpf/resolve_btfids/resolve_btfids: No such file or directory
> make[2]: *** [../scripts/Makefile.vmlinux:35: vmlinux] Error 127
> make[2]: *** Deleting file 'vmlinux'
> make[1]: *** [/home/jolsa/kernel/linux-qemu/Makefile:1264: vmlinux] Error 2
> make[1]: Leaving directory '/home/jolsa/kernel/linux-qemu/build'
> make: *** [Makefile:242: __sub-make] Error 2
> 
> we actually have the hostprogs support in tools/build and we use it for
> fixdep, I think we should use it also here, I'll check

it doesn't look that bad.. the change below fixes the build for me,
perhaps we should do that for all the host tools

jirka


---
diff --git a/tools/bpf/resolve_btfids/Build b/tools/bpf/resolve_btfids/Build
index ae82da03f9bf..077de3829c72 100644
--- a/tools/bpf/resolve_btfids/Build
+++ b/tools/bpf/resolve_btfids/Build
@@ -1,3 +1,5 @@
+hostprogs := resolve_btfids
+
 resolve_btfids-y += main.o
 resolve_btfids-y += rbtree.o
 resolve_btfids-y += zalloc.o
@@ -7,4 +9,4 @@ resolve_btfids-y += str_error_r.o
 
 $(OUTPUT)%.o: ../../lib/%.c FORCE
 	$(call rule_mkdir)
-	$(call if_changed_dep,cc_o_c)
+	$(call if_changed_dep,host_cc_o_c)
diff --git a/tools/bpf/resolve_btfids/Makefile b/tools/bpf/resolve_btfids/Makefile
index daed388aa5d7..de513fd08535 100644
--- a/tools/bpf/resolve_btfids/Makefile
+++ b/tools/bpf/resolve_btfids/Makefile
@@ -22,6 +22,9 @@ HOST_OVERRIDES := AR="$(HOSTAR)" CC="$(HOSTCC)" LD="$(HOSTLD)" ARCH="$(HOSTARCH)
 		  EXTRA_CFLAGS="$(HOSTCFLAGS) $(KBUILD_HOSTCFLAGS)"
 
 RM      ?= rm
+HOSTCC  ?= gcc
+HOSTLD  ?= ld
+HOSTAR  ?= ar
 CROSS_COMPILE =
 
 OUTPUT ?= $(srctree)/tools/bpf/resolve_btfids/
@@ -64,7 +67,7 @@ $(BPFOBJ): $(wildcard $(LIBBPF_SRC)/*.[ch] $(LIBBPF_SRC)/Makefile) | $(LIBBPF_OU
 LIBELF_FLAGS := $(shell $(HOSTPKG_CONFIG) libelf --cflags 2>/dev/null)
 LIBELF_LIBS  := $(shell $(HOSTPKG_CONFIG) libelf --libs 2>/dev/null || echo -lelf)
 
-CFLAGS += -g \
+HOSTCFLAGS += -g \
           -I$(srctree)/tools/include \
           -I$(srctree)/tools/include/uapi \
           -I$(LIBBPF_INCLUDE) \
@@ -73,7 +76,7 @@ CFLAGS += -g \
 
 LIBS = $(LIBELF_LIBS) -lz
 
-export srctree OUTPUT CFLAGS Q
+export srctree OUTPUT HOSTCFLAGS Q HOSTCC HOSTLD HOSTAR
 include $(srctree)/tools/build/Makefile.include
 
 $(BINARY_IN): fixdep FORCE prepare | $(OUTPUT)