linux-kernel - Re: [PATCH 4/7] x86/entry: Increase entry

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Date:   Fri, 19 Jun 2020 11:10:45 +0800
From:   Lai Jiangshan <jiangshanlai+lkml@...il.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Josh Poimboeuf <jpoimboe@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>, X86 ML <x86@...nel.org>,
        dvyukov@...gle.com, elver@...gle.com, andreyknvl@...gle.com,
        mark.rutland@....com, mhelsley@...are.com,
        Steven Rostedt <rostedt@...dmis.org>, jthierry@...hat.com,
        mbenes@...e.cz, Andy Lutomirski <luto@...capital.net>
Subject: Re: [PATCH 4/7] x86/entry: Increase entry_stack size to a full page

On Fri, Jun 19, 2020 at 4:37 AM Peter Zijlstra <peterz@...radead.org> wrote:
>
> Marco crashed in bad_iret with a Clang11/KCSAN build due to
> overflowing the stack. Now that we run C code on it, expand it to a
> full page.

Some of my experimental code also once got crashed due to overflowing
the stack. I'm glad to have the stack expanded, thanks.

Reviewed-by: Lai Jiangshan <jiangshanlai@...il.com>

>
> Suggested-by: Andy Lutomirski <luto@...capital.net>
> Reported-by: Marco Elver <elver@...gle.com>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> ---
>  arch/x86/include/asm/processor.h |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> --- a/arch/x86/include/asm/processor.h
> +++ b/arch/x86/include/asm/processor.h
> @@ -370,7 +370,7 @@ struct x86_hw_tss {
>  #define IO_BITMAP_OFFSET_INVALID       (__KERNEL_TSS_LIMIT + 1)
>
>  struct entry_stack {
> -       unsigned long           words[64];
> +       char    stack[PAGE_SIZE];
>  };
>
>  struct entry_stack_page {
>
>