Re: [PATCH] mmu: explicitly map executable non-SDRAM regions with MAP_CODE

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

On 20.06.25 14:45, Sascha Hauer wrote:
> On Wed, Jun 18, 2025 at 02:36:42PM +0200, Ahmad Fatoum wrote:
>> So far we have been setting eXecute Never on MAP_UNCACHED regions and
>> left it out for the default MAP_CACHED region.
>>
>> We have at least three places, which depend on this to remap non-SDRAM
>> regions executable, so ROM code or newly uploaded code can be run.
>>
>> Switch them over to use a new MAP_CODE mapping type. For now, this is
>> equivalent to MAP_CACHED, but with the addition of W^X support in
>> barebox, this will be required to avoid a prefetch abort when MMU
>> attributes are used.
>>
>> Signed-off-by: Ahmad Fatoum <a.fatoum@barebox.org>
>> ---
>> Sascha, I think this should be ordered before your MMU patches to avoid
>> the known regressions. Let's see what else there is. :)
>> ---
>>  arch/arm/mach-imx/romapi.c | 3 ++-
>>  drivers/firmware/socfpga.c | 3 ++-
>>  drivers/hab/habv4.c        | 2 +-
>>  include/mmu.h              | 1 +
>>  4 files changed, 6 insertions(+), 3 deletions(-)
>>
>> diff --git a/arch/arm/mach-imx/romapi.c b/arch/arm/mach-imx/romapi.c
>> index 10af42f28a76..a4143d372ae8 100644
>> --- a/arch/arm/mach-imx/romapi.c
>> +++ b/arch/arm/mach-imx/romapi.c
>> @@ -299,7 +299,8 @@ void imx93_bootsource(void)
>>  		goto out;
>>  	}
>>  
>> -	arch_remap_range((void *)rom.start, rom.start, resource_size(&rom), MAP_CACHED);
>> +	/* TODO: restore uncached mapping once we no longer need this? */
>> +	arch_remap_range((void *)rom.start, rom.start, resource_size(&rom), MAP_CODE);
>>  
>>  	OPTIMIZER_HIDE_VAR(rom_api);
>>  
>> diff --git a/drivers/firmware/socfpga.c b/drivers/firmware/socfpga.c
>> index 0f7d11abb588..4b10ca009798 100644
>> --- a/drivers/firmware/socfpga.c
>> +++ b/drivers/firmware/socfpga.c
>> @@ -353,7 +353,8 @@ static int socfpga_fpgamgr_program_finish(struct firmware_handler *fh)
>>  		return status;
>>  	}
>>  
>> -	remap_range((void *)CYCLONE5_OCRAM_ADDRESS, PAGE_SIZE, MAP_CACHED);
>> +	/* TODO: restore uncached mapping once we no longer need this? */
>> +	remap_range((void *)CYCLONE5_OCRAM_ADDRESS, PAGE_SIZE, MAP_CODE);
> 
> This is done before the code is copied to this page. I moved it after
> the fncpy call to avoid writing to readonly memory.

fncpy calls memcpy internally though, so we should either leave the MAP_CACHED
as is and add a further MAP_CODE after the fncpy or introduce a fncpy_toio
that calls memcpy_toio internally.

What do you think?

> While at it I also added the remapping to MAP_UNCACHED.

Thanks,
Ahmad

> 
> Sascha
> 


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