Re: [PATCH v2 16/21] arm64: entry: Implement EL1t exception handlers for overflow stack

[Jinjie Ruan]

在 2026/9/19 0:14, Will Deacon 写道:
> In preparation for using EL1t to handle exceptions taken whilst running
> on the overflow stack, implement some simple wrappers around the EL1h
> handlers which perform a best-effort stack overflow check before
> proceeding.
> 
> Cc: Mark Rutland <mark.rutland@xxxxxxx>
> Signed-off-by: Will Deacon <will@xxxxxxxxxx>
> ---
>  arch/arm64/kernel/entry-common.c | 43 +++++++++++++++++++++++++++++---
>  1 file changed, 39 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/arm64/kernel/entry-common.c b/arch/arm64/kernel/entry-common.c
> index 72c03ccea59f..9738142780df 100644
> --- a/arch/arm64/kernel/entry-common.c
> +++ b/arch/arm64/kernel/entry-common.c
> @@ -327,10 +327,45 @@ static void debug_exception_exit(struct pt_regs *regs)
>  }
>  NOKPROBE_SYMBOL(debug_exception_exit);
>  
> -UNHANDLED(el1t, 64, sync)
> -UNHANDLED(el1t, 64, irq)
> -UNHANDLED(el1t, 64, fiq)
> -UNHANDLED(el1t, 64, error)
> +static void noinstr el1t_64_check_overflow_stack(struct pt_regs *regs)
> +{
> +	unsigned long sp = kernel_stack_pointer(regs) - sizeof(*regs);
> +	unsigned long ovf_stack = (unsigned long)this_cpu_ptr(overflow_stack);
> +
> +	/*
> +	 * We're in big trouble if we've overflowed the overflow stack
> +	 * so perform a best-effort check before we proceed. If our SP
> +	 * is outside of the overflow stack for this CPU then presumably
> +	 * we're already corrupting memory, so park ourselves here in an
> +	 * attempt to contain the damage.
> +	 */
> +	if (sp < ovf_stack || sp > ovf_stack + OVERFLOW_STACK_SIZE)
> +		cpu_park_loop();

Reviewed-by: Jinjie Ruan <ruanjinjie@xxxxxxxxxx>

> +}
> +
> +asmlinkage void noinstr el1t_64_sync_handler(struct pt_regs *regs)
> +{
> +	el1t_64_check_overflow_stack(regs);
> +	el1h_64_sync_handler(regs);
> +}
> +
> +asmlinkage void noinstr el1t_64_irq_handler(struct pt_regs *regs)
> +{
> +	el1t_64_check_overflow_stack(regs);
> +	el1h_64_irq_handler(regs);
> +}
> +
> +asmlinkage void noinstr el1t_64_fiq_handler(struct pt_regs *regs)
> +{
> +	el1t_64_check_overflow_stack(regs);
> +	el1h_64_fiq_handler(regs);
> +}
> +
> +asmlinkage void noinstr el1t_64_error_handler(struct pt_regs *regs)
> +{
> +	el1t_64_check_overflow_stack(regs);
> +	el1h_64_error_handler(regs);
> +}
>  
>  static void noinstr el1_abort(struct pt_regs *regs, unsigned long esr)
>  {

-- 
Best regards,
Jinjie