linux-kernel - Re: [PATCH 1/1] arm64: use IRQ_STACK_SIZE instead of THREAD

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Date:   Fri, 31 Jul 2020 16:32:01 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     Maninder Singh <maninder1.s@...sung.com>
Cc:     catalin.marinas@....com, will@...nel.org, james.morse@....com,
        akpm@...ux-foundation.org, Dave.Martin@....com,
        0x7f454c46@...il.com, peterz@...radead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        a.sahrawat@...sung.com, v.narang@...sung.com
Subject: Re: [PATCH 1/1] arm64: use IRQ_STACK_SIZE instead of THREAD_SIZE for
 irq stack

On Fri, Jul 31, 2020 at 05:19:50PM +0530, Maninder Singh wrote:
> IRQ_STACK_SIZE can be made different from THREAD_SIZE,

While that's true in theory, IRQ_STACK_SIZE is defined as:

|  #define IRQ_STACK_SIZE          THREAD_SIZE

... which *must* be the case or the overflow detction will either miss
some overflows, or spuriously detect overflows where there are none.

Pleased beware if you are changing this locally.

> and as IRQ_STACK_SIZE is used while irq stack allocation,
> same define should be used while printing information of irq stack.
> 
> Signed-off-by: Maninder Singh <maninder1.s@...sung.com>

Regardless of the above, it is best to use the more specific mnemonic,
so:

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

I'll leave it to Catalin and Will to pick this up.

Mark.

> ---
>  arch/arm64/kernel/traps.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
> index 47f651d..13ebd5c 100644
> --- a/arch/arm64/kernel/traps.c
> +++ b/arch/arm64/kernel/traps.c
> @@ -855,7 +855,7 @@ asmlinkage void handle_bad_stack(struct pt_regs *regs)
>  	pr_emerg("Task stack:     [0x%016lx..0x%016lx]\n",
>  		 tsk_stk, tsk_stk + THREAD_SIZE);
>  	pr_emerg("IRQ stack:      [0x%016lx..0x%016lx]\n",
> -		 irq_stk, irq_stk + THREAD_SIZE);
> +		 irq_stk, irq_stk + IRQ_STACK_SIZE);
>  	pr_emerg("Overflow stack: [0x%016lx..0x%016lx]\n",
>  		 ovf_stk, ovf_stk + OVERFLOW_STACK_SIZE);
>  
> -- 
> 1.9.1
>