[PATCH v2 2/2] riscv: Define TASK_SIZE_MAX for __access_ok()

[Arnd Bergmann]

On Wed, Mar 27, 2024, at 15:38, Samuel Holland wrote:
> TASK_SIZE_MAX should be set to a constant value, at least the largest
> valid userspace address under any runtime configuration. This optimizes
> the check in __access_ok(), which no longer needs to compute the runtime
> value of TASK_SIZE. The check does not need to be exact, as long as it
> accepts all valid userspace addresses and rejects all valid kernel
> addresses; well-behaved programs will never fail the access_ok() check.
>
> For RISC-V, which requires all virtual addresses to be sign extended,
> the optimal choice is LONG_MAX because it simplifies the limit
> comparison to a sign bit test.
>
> This removes about half of the references to pgtable_l[45]_enabled.
>
> Signed-off-by: Samuel Holland <samuel.holland at sifive.com>

Reviewed-by: Arnd Bergmann <arnd at arndb.de>