Re: [PATCH V4 8/8] riscv: Add config of thread stack size

Arnd Bergmann
2022-09-20T07:16:48Z

On Tue, Sep 20, 2022, at 2:46 AM, Guo Ren wrote:

>
> How about this one: (only THREAD_SIZE, no THREAD_ORDER&SHIFT.)
>
> -
> /* thread information allocation */
> -#ifdef CONFIG_64BIT
> -#define THREAD_SIZE_ORDER (2 + KASAN_STACK_ORDER)
> -#else
> -#define THREAD_SIZE_ORDER (1 + KASAN_STACK_ORDER)
> -#endif
> -#define THREAD_SIZE (PAGE_SIZE << THREAD_SIZE_ORDER)
> +#define THREAD_SIZE CONFIG_THREAD_SIZE

So far looks fine.

>
> /*
> * By aligning VMAP'd stacks to 2 * THREAD_SIZE, we can detect overflow by
> - * checking sp & (1 << THREAD_SHIFT), which we can do cheaply in the entry
> - * assembly.
> + * checking sp & THREAD_SIZE, which we can do cheaply in the entry assembly.
> */
> #ifdef CONFIG_VMAP_STACK
> #define THREAD_ALIGN (2 * THREAD_SIZE)
> @@ -36,7 +24,6 @@
> #define THREAD_ALIGN THREAD_SIZE
> #endif

The THREAD_ALIGN does not, this only works for power-of-two numbers of
THREAD_SIZE,

> diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S
> index 426529b84db0..1e35fb3bdae5 100644
> --- a/arch/riscv/kernel/entry.S
> +++ b/arch/riscv/kernel/entry.S
> @@ -29,8 +29,8 @@ _restore_kernel_tpsp:
>
> #ifdef CONFIG_VMAP_STACK
> addi sp, sp, -(PT_SIZE_ON_STACK)
> - srli sp, sp, THREAD_SHIFT
> - andi sp, sp, 0x1
> + srli sp, sp, PAGE_SHIFT
> + andi sp, sp, (THREAD_SIZE >> PAGE_SHIFT)

I think this needs to use THREAD_ALIGN, not THREAD_SIZE.

Arnd