Subject: Re: linux-next: build warning after merge of the bpf-next tree

From: Stephen Rothwell <[email-masked]>
Date: Tue, 14 Jul 2020 20:33:41 +1000

Hi Jiri,

On Tue, 14 Jul 2020 11:00:48 +0200 Jiri Olsa <[email-masked]> wrote:
>
> On Tue, Jul 14, 2020 at 12:16:08PM +1000, Stephen Rothwell wrote:
> > 
> > After merging the bpf-next tree, today's linux-next build (powerpc
> > ppc64_defconfig) produced this warning:
> > 
> > ld: warning: orphan section `.BTF_ids' from `kernel/trace/bpf_trace.o' being placed in section `.BTF_ids'
> > ld: warning: orphan section `.BTF_ids' from `kernel/bpf/btf.o' being placed in section `.BTF_ids'
> > ld: warning: orphan section `.BTF_ids' from `kernel/bpf/stackmap.o' being placed in section `.BTF_ids'
> > ld: warning: orphan section `.BTF_ids' from `net/core/filter.o' being placed in section `.BTF_ids'
> > ld: warning: orphan section `.BTF_ids' from `kernel/trace/bpf_trace.o' being placed in section `.BTF_ids'
> > ld: warning: orphan section `.BTF_ids' from `kernel/bpf/btf.o' being placed in section `.BTF_ids'
> > ld: warning: orphan section `.BTF_ids' from `kernel/bpf/stackmap.o' being placed in section `.BTF_ids'
> > ld: warning: orphan section `.BTF_ids' from `net/core/filter.o' being placed in section `.BTF_ids'
> > ld: warning: orphan section `.BTF_ids' from `kernel/trace/bpf_trace.o' being placed in section `.BTF_ids'
> > ld: warning: orphan section `.BTF_ids' from `kernel/bpf/btf.o' being placed in section `.BTF_ids'
> > ld: warning: orphan section `.BTF_ids' from `kernel/bpf/stackmap.o' being placed in section `.BTF_ids'
> > ld: warning: orphan section `.BTF_ids' from `net/core/filter.o' being placed in section `.BTF_ids'
> > 
> > Presumably ntroduced by the merge of the resolve_btfids branch.  
> 
> missing one more #ifdef.. chage below fixes it for me,
> it's squashed with the fix for the arm build, I'll post 
> both fixes today
> 
> thanks,
> jirka
> 
> 
> ---
> diff --git a/include/linux/btf_ids.h b/include/linux/btf_ids.h
> index fe019774f8a7..2f9754a4ab2b 100644
> --- a/include/linux/btf_ids.h
> +++ b/include/linux/btf_ids.h
> @@ -3,6 +3,8 @@
>  #ifndef _LINUX_BTF_IDS_H
>  #define _LINUX_BTF_IDS_H
>  
> +#ifdef CONFIG_DEBUG_INFO_BTF
> +
>  #include <linux/compiler.h> /* for __PASTE */
>  
>  /*
> @@ -21,7 +23,7 @@
>  asm(							\
>  ".pushsection " BTF_IDS_SECTION ",\"a\";       \n"	\
>  ".local " #symbol " ;                          \n"	\
> -".type  " #symbol ", @object;                  \n"	\
> +".type  " #symbol ", STT_OBJECT;               \n"	\
>  ".size  " #symbol ", 4;                        \n"	\
>  #symbol ":                                     \n"	\
>  ".zero 4                                       \n"	\
> @@ -83,5 +85,12 @@ asm(							\
>  ".zero 4                                       \n"	\
>  ".popsection;                                  \n");
>  
> +#else
> +
> +#define BTF_ID_LIST(name) u32 name[5];
> +#define BTF_ID(prefix, name)
> +#define BTF_ID_UNUSED
> +
> +#endif /* CONFIG_DEBUG_INFO_BTF */
>  
>  #endif
> diff --git a/tools/bpf/resolve_btfids/Makefile b/tools/bpf/resolve_btfids/Makefile
> index 948378ca73d4..a88cd4426398 100644
> --- a/tools/bpf/resolve_btfids/Makefile
> +++ b/tools/bpf/resolve_btfids/Makefile
> @@ -16,6 +16,20 @@ else
>    MAKEFLAGS=--no-print-directory
>  endif
>  
> +# always use the host compiler
> +ifneq ($(LLVM),)
> +HOSTAR  ?= llvm-ar
> +HOSTCC  ?= clang
> +HOSTLD  ?= ld.lld
> +else
> +HOSTAR  ?= ar
> +HOSTCC  ?= gcc
> +HOSTLD  ?= ld
> +endif
> +AR       = $(HOSTAR)
> +CC       = $(HOSTCC)
> +LD       = $(HOSTLD)
> +
>  OUTPUT ?= $(srctree)/tools/bpf/resolve_btfids/
>  
>  LIBBPF_SRC := $(srctree)/tools/lib/bpf/
> 

Thanks for the quick response.  However, in the mean time the bpf-next
tree has been merged into the net-next tree, so these fixes will be
needed there ASAP.

-- 
Cheers,
Stephen Rothwell