Re: [PATCH 10/27] ARM: i.MX: Drop HAB workaround

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

On 12.05.23 13:09, Sascha Hauer wrote:
> The i.MX HAB code on i.MX6 has to jump into ROM which happens to start
> at 0x0. To make that possible we used to map the ROM cached and jumped
> to it before the MMU is initialized. Instead, remap the ROM as needed
> in the HAB code so that we can safely jump into ROM with MMU enabled.
> 
> Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
> ---
>  arch/arm/cpu/mmu-early_32.c | 7 -------
>  drivers/hab/habv4.c         | 9 ++++++++-
>  2 files changed, 8 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/arm/cpu/mmu-early_32.c b/arch/arm/cpu/mmu-early_32.c
> index 07c5917e6a..94bde44c9b 100644
> --- a/arch/arm/cpu/mmu-early_32.c
> +++ b/arch/arm/cpu/mmu-early_32.c
> @@ -58,12 +58,5 @@ void mmu_early_enable(unsigned long membase, unsigned long memsize,
>  	/* maps main memory as cachable */
>  	map_region(membase, memsize, PMD_SECT_DEF_CACHED);
>  
> -	/*
> -	 * With HAB enabled we call into the ROM code later in imx6_hab_get_status().
> -	 * Map the ROM cached which has the effect that the XN bit is not set.
> -	 */
> -	if (IS_ENABLED(CONFIG_HABV4) && IS_ENABLED(CONFIG_ARCH_IMX6))
> -		map_region(0x0, SZ_1M, PMD_SECT_DEF_CACHED);
> -
>  	__mmu_cache_on();
>  }
> diff --git a/drivers/hab/habv4.c b/drivers/hab/habv4.c
> index 252e38f655..d2494db114 100644
> --- a/drivers/hab/habv4.c
> +++ b/drivers/hab/habv4.c
> @@ -11,6 +11,9 @@
>  #include <hab.h>
>  #include <init.h>
>  #include <types.h>
> +#include <mmu.h>
> +#include <zero_page.h>
> +#include <linux/sizes.h>
>  #include <linux/arm-smccc.h>
>  #include <asm/cache.h>
>  
> @@ -613,12 +616,16 @@ static int init_imx6_hab_get_status(void)
>  		/* can happen in multi-image builds and is not an error */
>  		return 0;
>  
> +	arch_remap_range(0x0, SZ_1M, MAP_CACHED);

This affects SZ_1M bytes.

> +
>  	/*
>  	 * Nobody will check the return value if there were HAB errors, but the
>  	 * initcall will fail spectaculously with a strange error message.
>  	 */
>  	imx6_hab_get_status();
>  
> +	zero_page_faulting();

This affects only 4K. The rest of the 1M can now be speculated into :/

> +
>  	return 0;
>  }
>  
> @@ -627,7 +634,7 @@ static int init_imx6_hab_get_status(void)
>   * which will no longer be accessible when the MMU sets the zero page to
>   * faulting.
>   */
> -postconsole_initcall(init_imx6_hab_get_status);
> +postmmu_initcall(init_imx6_hab_get_status);
>  
>  int imx28_hab_get_status(void)
>  {

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