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

[Sascha Hauer]

On Fri, Jun 20, 2025 at 05:45:45PM +0200, Ahmad Fatoum wrote:
> 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 at 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.
> 
Ok, changed that to:

	remap_range((void *)CYCLONE5_OCRAM_ADDRESS, PAGE_SIZE, MAP_CACHED);

	fncpy();

	remap_range((void *)CYCLONE5_OCRAM_ADDRESS, PAGE_SIZE, MAP_CODE);

	ocram_func()

	remap_range((void *)CYCLONE5_OCRAM_ADDRESS, PAGE_SIZE, MAP_UNCACHED);

Sascha

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