linux-kernel - Re: [PATCH 1/2] arc: rename xCCM sections so they are not merged in global .data/.text

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Message-ID: <6d3a6876-402f-c237-f9a2-88aad3179ead@synopsys.com>
Date:   Thu, 22 Dec 2016 16:25:13 -0800
From:   Vineet Gupta <Vineet.Gupta1@...opsys.com>
To:     Alexey Brodkin <Alexey.Brodkin@...opsys.com>,
        "linux-snps-arc@...ts.infradead.org" 
        <linux-snps-arc@...ts.infradead.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Igor Guryanov" <Igor.Guryanov@...opsys.com>
Subject: Re: [PATCH 1/2] arc: rename xCCM sections so they are not merged in
 global .data/.text

On 12/22/2016 06:09 AM, Alexey Brodkin wrote:
> If Linux kernel is compiled with "-ffunction-sections" each function is placed in
> its own section named ".text.function_name". This is required for
> discarding of not-used functions during final linkage. But in the end
> all ".text.XXX" sections are merged in the global ".text" section of
> vmlinux Elf.
>
> The same happens with data sections when "-fdata-sections" are used.
>
> That means our ".data.arcfp" and ".text.arcfp" sections get silently
> merged in global ".data" and ".text" sections even though we want to
> put them in separate memory regions in case ICCM and/or DCCM exist in
> the ARC core.
>
> Solution is as simple as addition of one extra period in section name.
>
> Signed-off-by: Alexey Brodkin <abrodkin@...opsys.com>
> Cc: Igor Guryanov <guryanov@...opsys.com>
> Cc: stable@...r.kernel.org

For stable backport -I think there is no point in CC'ing them initially.
Better to make a note in the patch and conclude at the time of patch review and I
can in the end add the CC tag so this gets pulled automatically w/o CC'ing the
stable mailing list at all !

> ---
>  arch/arc/include/asm/linkage.h | 6 +++---
>  arch/arc/kernel/vmlinux.lds.S  | 8 ++++----
>  2 files changed, 7 insertions(+), 7 deletions(-)
>
> diff --git a/arch/arc/include/asm/linkage.h b/arch/arc/include/asm/linkage.h
> index b29f1a9fd6f7..3a5f13d65ee1 100644
> --- a/arch/arc/include/asm/linkage.h
> +++ b/arch/arc/include/asm/linkage.h
> @@ -28,7 +28,7 @@
>  /* annotation for data we want in DCCM - if enabled in .config */
>  .macro ARCFP_CODE
>  #ifdef CONFIG_ARC_HAS_ICCM
> -	.section .text.arcfp, "ax",@progbits
> +	.section .text..arcfp, "ax",@progbits

Why not turn this around and call it arcfp.text and arcfp.data etc - just like
done for other special sections such as sched, cpuidle, lock... Just so we are
consistent with normal kernel convention !

>  #else
>  	.section .text, "ax",@progbits
>  #endif
> @@ -47,13 +47,13 @@
>  #else	/* !__ASSEMBLY__ */
>  
>  #ifdef CONFIG_ARC_HAS_ICCM
> -#define __arcfp_code __attribute__((__section__(".text.arcfp")))
> +#define __arcfp_code __attribute__((__section__(".text..arcfp")))
>  #else
>  #define __arcfp_code __attribute__((__section__(".text")))
>  #endif
>  
>  #ifdef CONFIG_ARC_HAS_DCCM
> -#define __arcfp_data __attribute__((__section__(".data.arcfp")))
> +#define __arcfp_data __attribute__((__section__(".data..arcfp")))
>  #else
>  #define __arcfp_data __attribute__((__section__(".data")))
>  #endif
> diff --git a/arch/arc/kernel/vmlinux.lds.S b/arch/arc/kernel/vmlinux.lds.S
> index f35ed578e007..f69ae479ee73 100644
> --- a/arch/arc/kernel/vmlinux.lds.S
> +++ b/arch/arc/kernel/vmlinux.lds.S
> @@ -37,8 +37,8 @@ SECTIONS
>  	}
>  
>  #ifdef CONFIG_ARC_HAS_ICCM
> -	.text.arcfp : {
> -		*(.text.arcfp)
> +	.text..arcfp : {
> +		*(.text..arcfp)
>  		. = ALIGN(CONFIG_ARC_ICCM_SZ * 1024);
>  	}
>  #endif
> @@ -151,8 +151,8 @@ SECTIONS
>  #ifdef CONFIG_ARC_HAS_DCCM
>  	. = CONFIG_ARC_DCCM_BASE;
>  	__arc_dccm_base = .;
> -	.data.arcfp : {
> -		*(.data.arcfp)
> +	.data..arcfp : {
> +		*(.data..arcfp)
>  	}
>  	. = ALIGN(CONFIG_ARC_DCCM_SZ * 1024);
>  #endif