linux-kernel - Re: [PATCH] [MIPS] Place __kernel_entry at the beginning of text section

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Message-ID: <66daf1a8-efb7-4fef-92cd-eb680c7832fa@alliedtelesis.co.nz>
Date: Tue, 26 Nov 2024 12:42:31 +1300
From: Chris Packham <chris.packham@...iedtelesis.co.nz>
To: Rong Xu <xur@...gle.com>, Thomas Bogendoerfer
 <tsbogend@...ha.franken.de>, Masahiro Yamada <masahiroy@...nel.org>,
 Klara Modin <klarasmodin@...il.com>,
 Christophe Leroy <christophe.leroy@...roup.eu>,
 Michael Ellerman <mpe@...erman.id.au>, Nicolas Schier <nicolas@...sle.eu>,
 "Maciej W. Rozycki" <macro@...am.me.uk>, linux-mips@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] [MIPS] Place __kernel_entry at the beginning of text
 section

On 26/11/24 12:09, Rong Xu wrote:
> Mark __kernel_entry as ".head.text" and place HEAD_TEXT before
> TEXT_TEXT in the linker script. This ensures that __kernel_entry
> will be placed at the beginning of text section.
>
> Drop mips from scripts/head-object-list.txt.
>
> Signed-off-by: Rong Xu <xur@...gle.com>
> Reported-by: Chris Packham <chris.packham@...iedtelesis.co.nz>

Works for me on my RTL9302C based board

Tested-by: Chris Packham <chris.packham@...iedtelesis.co.nz>

> ---
>   arch/mips/kernel/head.S        | 1 +
>   arch/mips/kernel/vmlinux.lds.S | 1 +
>   scripts/head-object-list.txt   | 1 -
>   3 files changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/arch/mips/kernel/head.S b/arch/mips/kernel/head.S
> index e90695b2b60e..6d5fc498c6f9 100644
> --- a/arch/mips/kernel/head.S
> +++ b/arch/mips/kernel/head.S
> @@ -26,6 +26,7 @@
>   
>   #include <kernel-entry-init.h>
>   
> +	__HEAD

I'm not and expert on any of this but... should this go below the 
setup_c0_status_* macros (just before the CONFIG_NO_EXCEPT_FILL) line? I 
don't think it makes any actual difference but as a reader it feels more 
logical that the __HEAD annotation is applying to the .fill and 
__kernel_entry.

>   	/*
>   	 * For the moment disable interrupts, mark the kernel mode and
>   	 * set ST0_KX so that the CPU does not spit fire when using
> diff --git a/arch/mips/kernel/vmlinux.lds.S b/arch/mips/kernel/vmlinux.lds.S
> index d575f945d422..c9c1ba85ac7b 100644
> --- a/arch/mips/kernel/vmlinux.lds.S
> +++ b/arch/mips/kernel/vmlinux.lds.S
> @@ -62,6 +62,7 @@ SECTIONS
>   	_text = .;	/* Text and read-only data */
>   	_stext = .;
>   	.text : {
> +		HEAD_TEXT
>   		TEXT_TEXT
>   		SCHED_TEXT
>   		LOCK_TEXT
> diff --git a/scripts/head-object-list.txt b/scripts/head-object-list.txt
> index fd5d00bac447..f12b4a7b8406 100644
> --- a/scripts/head-object-list.txt
> +++ b/scripts/head-object-list.txt
> @@ -23,7 +23,6 @@ arch/m68k/coldfire/head.o
>   arch/m68k/kernel/head.o
>   arch/m68k/kernel/sun3-head.o
>   arch/microblaze/kernel/head.o
> -arch/mips/kernel/head.o
>   arch/nios2/kernel/head.o
>   arch/openrisc/kernel/head.o
>   arch/parisc/kernel/head.o
>
> base-commit: 3596c721c4348b2a964e43f9296a0c01509ba927