Re: [PATCH 2/4] arm: mmu: traverse reserved mem map as uncached

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

Hello,

On 11/2/20 10:30 AM, Rouven Czerwinski wrote:
> Traverse the reserved memory map and map areas which are marked with
> uncached as uncached (and thus noexec).
> 
> Signed-off-by: Rouven Czerwinski <r.czerwinski@pengutronix.de>
> ---
>  arch/arm/cpu/mmu.c | 14 ++++++++++++++
>  include/of.h       |  5 +++++
>  2 files changed, 19 insertions(+)
> 
> diff --git a/arch/arm/cpu/mmu.c b/arch/arm/cpu/mmu.c
> index 6af228505d..5974e1e38a 100644
> --- a/arch/arm/cpu/mmu.c
> +++ b/arch/arm/cpu/mmu.c
> @@ -17,6 +17,7 @@
>  #include <memory.h>
>  #include <asm/system_info.h>
>  #include <asm/sections.h>
> +#include <of.h>
>  
>  #include "mmu.h"
>  
> @@ -393,6 +394,8 @@ static void vectors_init(void)
>  void __mmu_init(bool mmu_on)
>  {
>  	struct memory_bank *bank;
> +	struct of_reserve_map *res_map;
> +	int i;
>  
>  	arm_set_cache_functions();
>  
> @@ -453,6 +456,17 @@ void __mmu_init(bool mmu_on)
>  		__mmu_cache_flush();
>  	}
>  
> +	res_map = of_get_reserve_map();
> +	if (res_map) {
> +		for (i = 0; i < res_map->num_entries; i++) {
> +			if (res_map->uncached & BIT(i)) {
> +				create_sections(ttb, res_map->start[i],
> +						res_map->end[i],
> +						PMD_SECT_DEF_UNCACHED);

PMD_SECT_DEF_UNCACHED does _not_ include PMD_SECT_XN. See create_flat_mapping()
Also, code earlier does __mmu_cache_flush() after each create_sections.
Don't we need this here as well? (Or is it not needed at all?)

> +			}
> +		}
> +	}
> +
>  	__mmu_cache_on();
>  }
>  
> diff --git a/include/of.h b/include/of.h
> index 5d7f54fb36..3d8c26f319 100644
> --- a/include/of.h
> +++ b/include/of.h
> @@ -1042,6 +1042,11 @@ static inline int of_firmware_load_overlay(struct device_node *overlay, const ch
>  {
>  	return -ENOSYS;
>  }
> +
> +static inline struct of_reserve_map *of_get_reserve_map(void)
> +{
> +	return NULL;
> +}

This should results in an error because a static declaration follows a non-static
one. You need to move the extern of_get_reserve_map into the #ifdef as well.

>  #endif
>  
>  #endif /* __OF_H */
> 

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