linux-kernel - Re: [tip:x86/urgent] x86: linker script: avoid ALIGN statements inside output sections

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Date:	Tue, 28 Apr 2009 10:14:55 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	linux-kernel@...r.kernel.org, mingo@...hat.com, hpa@...or.com,
	hpa@...icro.com, tglx@...utronix.de, hpa@...ux.intel.com,
	jeremy.fitzhardinge@...rix.com
Cc:	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:x86/urgent] x86: linker script: avoid ALIGN statements
	inside output sections


* tip-bot for H. Peter Anvin <hpa@...icro.com> wrote:

> Commit-ID:  c707f31e2e6af2d37bc742c31be0c7e96946c71f
> Gitweb:     http://git.kernel.org/tip/c707f31e2e6af2d37bc742c31be0c7e96946c71f
> Author:     H. Peter Anvin <hpa@...icro.com>
> AuthorDate: Mon, 27 Apr 2009 13:09:45 -0700
> Committer:  H. Peter Anvin <hpa@...icro.com>
> CommitDate: Mon, 27 Apr 2009 13:09:45 -0700
> 
> x86: linker script: avoid ALIGN statements inside output sections
> 
> ALIGN statements inside output sections means that the alignment 
> padding ends up part of the section.  This causes real problems 
> when the section is otherwise empty.  ALIGN can be done either 
> before the output section or as part of the output section header; 
> the latter has the advantage that the alignment information is 
> propagated into the appropriate ELF headers.
> 
> Without this patch, we produce invalid kernels in certain 
> configurations involving X86_VSMP.
> 
> Reported-and-tested-by: Thomas Gleixner <tglx@...utronix.de>
> Cc: Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>
> Signed-off-by: H. Peter Anvin <hpa@...ux.intel.com>
> 
> 
> ---
>  arch/x86/kernel/vmlinux_32.lds.S |   45 +++++++++++++++-----------------
>  arch/x86/kernel/vmlinux_64.lds.S |   52 +++++++++++++++++--------------------
>  2 files changed, 45 insertions(+), 52 deletions(-)
> 
> diff --git a/arch/x86/kernel/vmlinux_32.lds.S b/arch/x86/kernel/vmlinux_32.lds.S
> index 62ad500..7197db8 100644
> --- a/arch/x86/kernel/vmlinux_32.lds.S
> +++ b/arch/x86/kernel/vmlinux_32.lds.S
> @@ -37,8 +37,7 @@ SECTIONS
>    } :text = 0x9090
>  
>    /* read-only */
> -  .text : AT(ADDR(.text) - LOAD_OFFSET) {
> -	. = ALIGN(PAGE_SIZE); /* not really needed, already page aligned */
> +  .text : AT(ADDR(.text) - LOAD_OFFSET) ALIGN(PAGE_SIZE) {
>  	*(.text.page_aligned)
>  	TEXT_TEXT
>  	SCHED_TEXT
> @@ -52,8 +51,8 @@ SECTIONS
>  
>    NOTES :text :note
>  
> -  . = ALIGN(16);		/* Exception table */
> -  __ex_table : AT(ADDR(__ex_table) - LOAD_OFFSET) {
> +  /* Exception table */
> +  __ex_table : AT(ADDR(__ex_table) - LOAD_OFFSET) ALIGN(16) {


this construct breaks older toolchains:

/opt/crosstool/gcc-4.2.3-glibc-2.3.6/x86_64-unknown-linux-gnu/bin/x86_64-unknown-linux-gnu-ld:arch/x86/kernel/vmlinux.lds:138: 
parse error

titan:~/tip> 
/opt/crosstool/gcc-4.2.3-glibc-2.3.6/x86_64-unknown-linux-gnu/bin/x86_64-unknown-linux-gnu-ld -v
GNU ld version 2.16.1

this is what it does not like:

 __ex_table : AT(ADDR(__ex_table) - 0xffffffff80000000) ALIGN(16) {

config attached.

	Ingo

View attachment "config" of type "text/plain" (65257 bytes)