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

[Ian Rogers]

On Wed, Feb 1, 2023 at 2:43 AM Jiri Olsa <olsajiri@xxxxxxxxx> wrote:
>
> 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@xxxxxxxxxx>
> > > Signed-off-by: Ian Rogers <irogers@xxxxxxxxxx>
> >
> > 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

I don't mind this. The fixdep vs all thing is just cause by the
ordering in the Makefile, you can fix by specifying the target or add
this patch:
```
--- a/tools/bpf/resolve_btfids/Makefile
+++ b/tools/bpf/resolve_btfids/Makefile
@@ -58,11 +58,11 @@ HOST_OVERRIDES_BUILD := $(HOST_OVERRIDES_PREPARE) \

LIBS = $(LIBELF_LIBS) -lz

+all: $(BINARY)
+
export srctree OUTPUT Q
include $(srctree)/tools/build/Makefile.include

-all: $(BINARY)
-
prepare: $(BPFOBJ) $(SUBCMDOBJ)

$(OUTPUT) $(OUTPUT)/libsubcmd $(LIBBPF_OUT):
```

Should we do this and the hostprogs migration as a follow up? There
isn't that much use of hostprogs in tools, but I like that your change
will show HOSTCC rather than CC during compilation. If we use
hostprogs can we just avoid the overrides altogether?

Thanks,
Ian

>
> ---
> 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)