Re: [PATCH] mmu: move MAP_RO definition into global mmu.h header

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

Hi,

On 1/5/26 9:47 AM, Ahmad Fatoum wrote:
> To allow generic code to remap memory as read-only, let's add the
> definition to the global header.
> 
> On platforms other than ARM, mapping R/O will just be cached R/W.
> 
> Signed-off-by: Ahmad Fatoum <a.fatoum@barebox.org>

Please disregard in favor of Sascha's version. I think it's better to
just let it fail on unsupported architectures instead of mapping it to
MAP_CACHED.

Cheers,
Ahmad

> ---
>  arch/Kconfig              | 3 +++
>  arch/arm/Kconfig          | 1 +
>  arch/arm/cpu/mmu-common.c | 4 ++--
>  arch/arm/cpu/mmu-common.h | 3 +--
>  arch/arm/cpu/mmu_32.c     | 4 ++--
>  arch/arm/cpu/mmu_64.c     | 2 +-
>  include/mmu.h             | 6 ++++++
>  7 files changed, 16 insertions(+), 7 deletions(-)
> 
> diff --git a/arch/Kconfig b/arch/Kconfig
> index ca9aa25a9c4b..3daba5239740 100644
> --- a/arch/Kconfig
> +++ b/arch/Kconfig
> @@ -62,6 +62,9 @@ config ARCH_DMA_DEFAULT_COHERENT
>  config ARCH_HAS_DMA_WRITE_COMBINE
>  	bool
>  
> +config ARCH_HAS_RO_MAPPINGS
> +	bool
> +
>  config ARCH_HAS_ASAN_FIBER_API
>  	bool
>  
> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> index 5123e9b1402c..d9b1f5de1fa7 100644
> --- a/arch/arm/Kconfig
> +++ b/arch/arm/Kconfig
> @@ -17,6 +17,7 @@ config ARM
>  	select HAVE_ARCH_BOOTM_OFTREE
>  	select HW_HAS_PCI
>  	select ARCH_HAS_DMA_WRITE_COMBINE
> +	select ARCH_HAS_RO_MAPPINGS
>  	select HAVE_EFI_LOADER if MMU # for payload unaligned accesses
>  	default y
>  
> diff --git a/arch/arm/cpu/mmu-common.c b/arch/arm/cpu/mmu-common.c
> index a1431c0ff461..6db85fa9c7d4 100644
> --- a/arch/arm/cpu/mmu-common.c
> +++ b/arch/arm/cpu/mmu-common.c
> @@ -22,7 +22,7 @@ const char *map_type_tostr(maptype_t map_type)
>  
>  	switch (map_type) {
>  	case ARCH_MAP_CACHED_RWX:	return "RWX";
> -	case ARCH_MAP_CACHED_RO:	return "RO";
> +	case MAP_RO:			return "RO";
>  	case MAP_CACHED:		return "CACHED";
>  	case MAP_UNCACHED:		return "UNCACHED";
>  	case MAP_CODE:			return "CODE";
> @@ -158,7 +158,7 @@ static void mmu_remap_memory_banks(void)
>  	}
>  
>  	remap_range((void *)code_start, code_size, MAP_CODE);
> -	remap_range((void *)rodata_start, rodata_size, ARCH_MAP_CACHED_RO);
> +	remap_range((void *)rodata_start, rodata_size, MAP_RO);
>  
>  	setup_trap_pages();
>  }
> diff --git a/arch/arm/cpu/mmu-common.h b/arch/arm/cpu/mmu-common.h
> index a111e15a21b4..39332d8f5a98 100644
> --- a/arch/arm/cpu/mmu-common.h
> +++ b/arch/arm/cpu/mmu-common.h
> @@ -12,7 +12,6 @@
>  #include <linux/bits.h>
>  
>  #define ARCH_MAP_CACHED_RWX	MAP_ARCH(2)
> -#define ARCH_MAP_CACHED_RO	MAP_ARCH(3)
>  
>  #define ARCH_MAP_FLAG_PAGEWISE	BIT(31)
>  
> @@ -32,7 +31,7 @@ static inline maptype_t arm_mmu_maybe_skip_permissions(maptype_t map_type)
>  	switch (map_type & MAP_TYPE_MASK) {
>  	case MAP_CODE:
>  	case MAP_CACHED:
> -	case ARCH_MAP_CACHED_RO:
> +	case MAP_RO:
>  		return ARCH_MAP_CACHED_RWX;
>  	default:
>  		return map_type;
> diff --git a/arch/arm/cpu/mmu_32.c b/arch/arm/cpu/mmu_32.c
> index 912d14e8cf82..d41ebcfb7fe4 100644
> --- a/arch/arm/cpu/mmu_32.c
> +++ b/arch/arm/cpu/mmu_32.c
> @@ -304,7 +304,7 @@ static uint32_t get_pte_flags(maptype_t map_type)
>  		switch (map_type & MAP_TYPE_MASK) {
>  		case ARCH_MAP_CACHED_RWX:
>  			return PTE_FLAGS_CACHED_V7_RWX;
> -		case ARCH_MAP_CACHED_RO:
> +		case MAP_RO:
>  			return PTE_FLAGS_CACHED_RO_V7;
>  		case MAP_CACHED:
>  			return PTE_FLAGS_CACHED_V7;
> @@ -320,7 +320,7 @@ static uint32_t get_pte_flags(maptype_t map_type)
>  		}
>  	} else {
>  		switch (map_type & MAP_TYPE_MASK) {
> -		case ARCH_MAP_CACHED_RO:
> +		case MAP_RO:
>  		case MAP_CODE:
>  			return PTE_FLAGS_CACHED_RO_V4;
>  		case ARCH_MAP_CACHED_RWX:
> diff --git a/arch/arm/cpu/mmu_64.c b/arch/arm/cpu/mmu_64.c
> index 56c6a21f2b2a..006b2b29478f 100644
> --- a/arch/arm/cpu/mmu_64.c
> +++ b/arch/arm/cpu/mmu_64.c
> @@ -159,7 +159,7 @@ static unsigned long get_pte_attrs(maptype_t map_type)
>  		return attrs_xn() | MEM_ALLOC_WRITECOMBINE;
>  	case MAP_CODE:
>  		return CACHED_MEM | PTE_BLOCK_RO;
> -	case ARCH_MAP_CACHED_RO:
> +	case MAP_RO:
>  		return attrs_xn() | CACHED_MEM | PTE_BLOCK_RO;
>  	case ARCH_MAP_CACHED_RWX:
>  		return CACHED_MEM;
> diff --git a/include/mmu.h b/include/mmu.h
> index f79619808829..7d87885a5cb4 100644
> --- a/include/mmu.h
> +++ b/include/mmu.h
> @@ -16,6 +16,12 @@
>  #define MAP_WRITECOMBINE	MAP_UNCACHED
>  #endif
>  
> +#ifdef CONFIG_ARCH_HAS_RO_MAPPINGS
> +#define MAP_RO			5
> +#else
> +#define MAP_RO			MAP_CACHED
> +#endif
> +
>  #define MAP_TYPE_MASK	0xFFFF
>  #define MAP_ARCH(x)	((u16)~(x))
>  

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