Re: [PATCH v3 2/2] vdso: Introduce vdso/page.h

["Arnd Bergmann" <arnd@arndb.de>]

On Thu, Oct 3, 2024, at 15:29, Vincenzo Frascino wrote:
> The VDSO implementation includes headers from outside of the
> vdso/ namespace.
>
> Introduce vdso/page.h to make sure that the generic library
> uses only the allowed namespace.
>
> Note: on a 32-bit architecture UL is an unsigned 32 bit long. Hence when
> it supports 64-bit phys_addr_t we might end up in situation in which the
> top 32 bit are cleared. To prevent this issue this patch provides
> separate macros for PAGE_MASK.
>
> Cc: Arnd Bergmann <arnd@arndb.de>
> Cc: Andy Lutomirski <luto@kernel.org>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Jason A. Donenfeld <Jason@zx2c4.com>
> Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>

Looks good to me. I would apply this to the asm-generic
tree for 6.13, but there is one small detail I'm unsure
about:

> +#if defined(CONFIG_PHYS_ADDR_T_64BIT)
> +#define PAGE_MASK	(~((1 << CONFIG_PAGE_SHIFT) - 1))
> +#else
> +#define PAGE_MASK	(~(PAGE_SIZE-1))
> +#endif

We only want the #if branch for 32-bit architectures, right?

On 64-bit ones, CONFIG_PHYS_ADDR_T_64BIT is always set, so
I think that is unnecessary change from the existing version,
even though it should be harmless.

     Arnd