lkml.org 
[lkml]   [2019]   [Dec]   [2]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] arm64/kernel/entry: refine comment of stack overflow check
On Mon, Dec 02, 2019 at 07:37:02PM +0800, Heyi Guo wrote:
> Stack overflow checking can be done by testing
> sp & (1 << THREAD_SHIFT)
> only for the stacks are aligned to (2 << THREAD_SHIFT) with size of
> (1 << THREAD_SIZE), and this is the case when CONFIG_VMAP_STACK is
> set.

Good point, I was sloppy with this comment.

>
> Fix the code comment to avoid confusion.
>
> Signed-off-by: Heyi Guo <guoheyi@huawei.com>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will@kernel.org>
> ---
> arch/arm64/kernel/entry.S | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
> index cf3bd2976e57..9e8ba507090f 100644
> --- a/arch/arm64/kernel/entry.S
> +++ b/arch/arm64/kernel/entry.S
> @@ -76,7 +76,8 @@ alternative_else_nop_endif
> #ifdef CONFIG_VMAP_STACK
> /*
> * Test whether the SP has overflowed, without corrupting a GPR.
> - * Task and IRQ stacks are aligned to (1 << THREAD_SHIFT).
> + * Task and IRQ stacks are aligned to (2 << THREAD_SHIFT) with size of
> + * (1 << THREAD_SHIFT).
> */

Can we make that:

Task and IRQ stacks are aligned so that SP & (1 << THREAD_SHIFT)
should always be zero.

... which I think is a bit clearer.

With that wording:

Acked-by: Mark Rutland <mark.rutland@arm.com>

Mark.

> add sp, sp, x0 // sp' = sp + x0
> sub x0, sp, x0 // x0' = sp' - x0 = (sp + x0) - x0 = sp
> --
> 2.19.1
>

\
 
 \ /
  Last update: 2019-12-02 13:35    [W:0.052 / U:3.104 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site