linux-kernel - Re: [PATCH -next] arm32/boot/compressed: Force hidden visibility for all symbol references

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Message-ID: <CAMj1kXH5agoCW0gONDZAodHQKANgrix=pE4e5YuHKgR=GwTRwA@mail.gmail.com>
Date: Fri, 24 Jan 2025 15:00:10 +0100
From: Ard Biesheuvel <ardb@...nel.org>
To: Yuntao Liu <liuyuntao12@...wei.com>, Linus Walleij <linus.walleij@...aro.org>
Cc: linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, 
	linux@...linux.org.uk, ruanjinjie@...wei.com, kees@...nel.org, 
	masahiroy@...nel.org
Subject: Re: [PATCH -next] arm32/boot/compressed: Force hidden visibility for
 all symbol references

On Fri, 24 Jan 2025 at 09:31, Yuntao Liu <liuyuntao12@...wei.com> wrote:
>
> Eliminate all GOT entries in the decompressor binary, by forcing hidden
> visibility for all symbol references, which informs the compiler that
> such references will be resolved at link time without the need for
> allocating GOT entries.
>
> Include linux/hidden.h in Makefile, like x86, for the
> hidden visibility attribute.
>
> Signed-off-by: Yuntao Liu <liuyuntao12@...wei.com>

Doesn't this break appended DTB?

> ---
>  arch/arm/boot/compressed/Makefile | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/arch/arm/boot/compressed/Makefile b/arch/arm/boot/compressed/Makefile
> index 945b5975fce2..d8a17760ad29 100644
> --- a/arch/arm/boot/compressed/Makefile
> +++ b/arch/arm/boot/compressed/Makefile
> @@ -93,6 +93,9 @@ targets       := vmlinux vmlinux.lds piggy_data piggy.o \
>                  head.o $(OBJS)
>
>  KBUILD_CFLAGS += -DDISABLE_BRANCH_PROFILING
> +ifneq ($(CONFIG_LD_IS_LLD),y)
> +KBUILD_CFLAGS += -include $(srctree)/include/linux/hidden.h
> +endif
>

Why not for LLD?


>  ccflags-y := -fpic $(call cc-option,-mno-single-pic-base,) -fno-builtin \
>              -I$(srctree)/scripts/dtc/libfdt -fno-stack-protector \
> --
> 2.34.1
>