linux-kernel - Re: [RFC] Don't create sframes during build

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Message-ID: <b3db475e-e84d-4056-9420-bc0acc8b9fe5@debian.org>
Date: Thu, 4 Sep 2025 16:02:42 +0200
From: Matthias Klose <doko@...ian.org>
To: Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-kbuild@...r.kernel.org
Cc: Arnd Bergmann <arnd@...db.de>, Josh Poimboeuf <jpoimboe@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Nathan Chancellor
 <nathan@...nel.org>,
        Nicolas Schier <nicolas.schier@...ux.dev>,
        Binutils <binutils@...rceware.org>
Subject: Re: [RFC] Don't create sframes during build

[ CCing binutils@...rceware.org ]

On 9/4/25 15:18, Sebastian Andrzej Siewior wrote:
> Hi,
> 
> gcc in Debian, starting with 15.2.0-2, 14.3.0-6 enables sframe
> generation. Unless options like -ffreestanding are passed. Since this
> isn't done, there are a few warnings during compile

If there are other options when sframe shouldn't be enabled, please tell.

Gentoo chose another approach, enabling sframe unconditionally in gas, 
unless disabled by --gsframe=no.

> | crypto/chacha.o: warning: objtool: .sframe+0x30: data relocation to !ENDBR: chacha_stream_xor+0x0
> | crypto/chacha.o: warning: objtool: .sframe+0x94: data relocation to !ENDBR: crypto_xchacha_crypt+0x0
> 
> followed by warnings at the end
> 
> |   AR      vmlinux.a
> |   LD      vmlinux.o
> | vmlinux.o: warning: objtool: .sframe+0x15c: data relocation to !ENDBR: repair_env_string+0x0
> | vmlinux.o: warning: objtool: .sframe+0x1c0: data relocation to !ENDBR: run_init_process+0x0
> | vmlinux.o: warning: objtool: .sframe+0x1d4: data relocation to !ENDBR: try_to_run_init_process+0x0
> | vmlinux.o: warning: objtool: .sframe+0x1e8: data relocation to !ENDBR: rcu_read_unlock+0x0
> …
> | vmlinux.o: warning: objtool: .sframe+0x12765c: data relocation to !ENDBR: get_eff_addr_reg+0x0
> | vmlinux.o: warning: objtool: .sframe+0x1276ac: data relocation to !ENDBR: get_seg_base_limit+0x0
> |   OBJCOPY modules.builtin.modinfo
> 
> followed by a boom
> |   LD      .tmp_vmlinux1
> | ld: error: unplaced orphan section `.sframe' from `vmlinux.o'
> 
> We could drop the sframe during the final link but this does not get rid
> of the objtool warnings so we would have to ignore them. But we don't
> need it. So what about the following:
> 
> diff --git a/Makefile b/Makefile
> --- a/Makefile
> +++ b/Makefile
> @@ -886,6 +886,8 @@ ifdef CONFIG_CC_IS_GCC
>   KBUILD_CFLAGS	+= $(call cc-option,--param=allow-store-data-races=0)
>   KBUILD_CFLAGS	+= $(call cc-option,-fno-allow-store-data-races)
>   endif
> +# No sframe generation for kernel if enabled by default
> +KBUILD_CFLAGS	+= $(call cc-option,-Xassembler --gsframe=no)
>   
>   ifdef CONFIG_READABLE_ASM
>   # Disable optimizations that make assembler listings hard to read.
This is what I chose for package builds that need disablement of sframe.