[PATCH] arm64: move kimage_vaddr to .rodata

[PATCH] arm64: move kimage_vaddr to .rodata

[Rémi Denis-Courmont]

From: Remi Denis-Courmont <remi.denis.courmont@huawei.com>

This datum is not referenced from .idmap.text: it does not need to be
mapped in idmap. Lets move it to .rodata as it is never written to after
early boot of the primary CPU.
(Maybe .data.ro_after_init would be cleaner though?)

Signed-off-by: Rémi Denis-Courmont <remi@remlab.net>
---
 arch/arm64/kernel/head.S | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index 6e08ee2b4d55..8e5c0e0040e4 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -457,17 +457,19 @@ SYM_FUNC_START_LOCAL(__primary_switched)
 	b	start_kernel
 SYM_FUNC_END(__primary_switched)
 
+	.pushsection ".rodata", "a"
+SYM_DATA_START(kimage_vaddr)
+	.quad		_text - TEXT_OFFSET
+SYM_DATA_END(kimage_vaddr)
+EXPORT_SYMBOL(kimage_vaddr)
+	.popsection
+
 /*
  * end early head section, begin head code that is also used for
  * hotplug and needs to have the same protections as the text region
  */
 	.section ".idmap.text","awx"
 
-SYM_DATA_START(kimage_vaddr)
-	.quad		_text - TEXT_OFFSET
-SYM_DATA_END(kimage_vaddr)
-EXPORT_SYMBOL(kimage_vaddr)
-
 /*
  * If we're fortunate enough to boot at EL2, ensure that the world is
  * sane before dropping to EL1.
-- 
2.25.1

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Re: [PATCH] arm64: move kimage_vaddr to .rodata

[Mark Rutland]

On Thu, Mar 12, 2020 at 11:40:02AM +0200, Rémi Denis-Courmont wrote:
> From: Remi Denis-Courmont <remi.denis.courmont@huawei.com>
> 
> This datum is not referenced from .idmap.text: it does not need to be
> mapped in idmap. Lets move it to .rodata as it is never written to after
> early boot of the primary CPU.
> (Maybe .data.ro_after_init would be cleaner though?)

Can we move this into arch/arm64/mm/mmu.c, where we already have
kimage_voffset:

| u64 kimage_voffset __ro_after_init;
| EXPORT_SYMBOL(kimage_voffset);

... or is it not possible to initialize kimage_vaddr correctly in C?

Thanks,
Mark.

> 
> Signed-off-by: Rémi Denis-Courmont <remi@remlab.net>
> ---
>  arch/arm64/kernel/head.S | 12 +++++++-----
>  1 file changed, 7 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
> index 6e08ee2b4d55..8e5c0e0040e4 100644
> --- a/arch/arm64/kernel/head.S
> +++ b/arch/arm64/kernel/head.S
> @@ -457,17 +457,19 @@ SYM_FUNC_START_LOCAL(__primary_switched)
>  	b	start_kernel
>  SYM_FUNC_END(__primary_switched)
>  
> +	.pushsection ".rodata", "a"
> +SYM_DATA_START(kimage_vaddr)
> +	.quad		_text - TEXT_OFFSET
> +SYM_DATA_END(kimage_vaddr)
> +EXPORT_SYMBOL(kimage_vaddr)
> +	.popsection
> +
>  /*
>   * end early head section, begin head code that is also used for
>   * hotplug and needs to have the same protections as the text region
>   */
>  	.section ".idmap.text","awx"
>  
> -SYM_DATA_START(kimage_vaddr)
> -	.quad		_text - TEXT_OFFSET
> -SYM_DATA_END(kimage_vaddr)
> -EXPORT_SYMBOL(kimage_vaddr)
> -
>  /*
>   * If we're fortunate enough to boot at EL2, ensure that the world is
>   * sane before dropping to EL1.
> -- 
> 2.25.1
> 
> 
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
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Re: [PATCH] arm64: move kimage_vaddr to .rodata

[Remi Denis-Courmont]

Le 2020-03-12 18:40, Mark Rutland a écrit :
> On Thu, Mar 12, 2020 at 11:40:02AM +0200, Rémi Denis-Courmont wrote:
>> From: Remi Denis-Courmont <remi.denis.courmont@huawei.com>
>> 
>> This datum is not referenced from .idmap.text: it does not need to be
>> mapped in idmap. Lets move it to .rodata as it is never written to 
>> after
>> early boot of the primary CPU.
>> (Maybe .data.ro_after_init would be cleaner though?)
> 
> Can we move this into arch/arm64/mm/mmu.c, where we already have
> kimage_voffset:
> 
> | u64 kimage_voffset __ro_after_init;
> | EXPORT_SYMBOL(kimage_voffset);
> 
> ... or is it not possible to initialize kimage_vaddr correctly in C?

Good question... I'll check tomorrow.

-- 
Rémi Denis-Courmont
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Re: [PATCH] arm64: move kimage_vaddr to .rodata

[Will Deacon]

On Thu, Mar 12, 2020 at 11:40:02AM +0200, Rémi Denis-Courmont wrote:
> From: Remi Denis-Courmont <remi.denis.courmont@huawei.com>
> 
> This datum is not referenced from .idmap.text: it does not need to be
> mapped in idmap. Lets move it to .rodata as it is never written to after
> early boot of the primary CPU.
> (Maybe .data.ro_after_init would be cleaner though?)
> 
> Signed-off-by: Rémi Denis-Courmont <remi@remlab.net>
> ---
>  arch/arm64/kernel/head.S | 12 +++++++-----
>  1 file changed, 7 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
> index 6e08ee2b4d55..8e5c0e0040e4 100644
> --- a/arch/arm64/kernel/head.S
> +++ b/arch/arm64/kernel/head.S
> @@ -457,17 +457,19 @@ SYM_FUNC_START_LOCAL(__primary_switched)
>  	b	start_kernel
>  SYM_FUNC_END(__primary_switched)
>  
> +	.pushsection ".rodata", "a"
> +SYM_DATA_START(kimage_vaddr)
> +	.quad		_text - TEXT_OFFSET
> +SYM_DATA_END(kimage_vaddr)
> +EXPORT_SYMBOL(kimage_vaddr)
> +	.popsection
> +
>  /*
>   * end early head section, begin head code that is also used for
>   * hotplug and needs to have the same protections as the text region
>   */
>  	.section ".idmap.text","awx"
>  
> -SYM_DATA_START(kimage_vaddr)
> -	.quad		_text - TEXT_OFFSET
> -SYM_DATA_END(kimage_vaddr)
> -EXPORT_SYMBOL(kimage_vaddr)

Acked-by: Will Deacon <will@kernel.org>

Will
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Re: [PATCH] arm64: move kimage_vaddr to .rodata

[Catalin Marinas]

On Thu, Mar 12, 2020 at 11:40:02AM +0200, Rémi Denis-Courmont wrote:
> From: Remi Denis-Courmont <remi.denis.courmont@huawei.com>
> 
> This datum is not referenced from .idmap.text: it does not need to be
> mapped in idmap. Lets move it to .rodata as it is never written to after
> early boot of the primary CPU.
> (Maybe .data.ro_after_init would be cleaner though?)
> 
> Signed-off-by: Rémi Denis-Courmont <remi@remlab.net>

Queued for 5.7. Thanks.

-- 
Catalin
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