linux-kernel - Re: [PATCH v2 1/2] serial: 8250_platform: Reduce stack usage in serial8250_probe

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Message-ID: <aJO-ApXFIs27couW@smile.fi.intel.com>
Date: Wed, 6 Aug 2025 23:41:38 +0300
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Abinash Singh <abinashsinghlalotra@...il.com>
Cc: arnd@...db.de, gregkh@...uxfoundation.org, jirislaby@...nel.org,
	linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org,
	sunilvl@...tanamicro.com, u.kleine-koenig@...libre.com
Subject: Re: [PATCH v2 1/2] serial: 8250_platform: Reduce stack usage in
 serial8250_probe_acpi()

On Thu, Aug 07, 2025 at 01:40:46AM +0530, Abinash Singh wrote:
> The function serial8250_probe_acpi() in 8250_platform.c triggered a
>     frame size warning:
> drivers/tty/serial/8250/8250_platform.c: In function ‘serial8250_probe_acpi’:
> drivers/tty/serial/8250/8250_platform.c:152:1: warning: the frame size of 1160 bytes is larger than 1024 bytes [-Wframe-larger-than=]
> 
> This patch reduces the stack usage by dynamically allocating the
> `uart` structure using kzalloc(), rather than placing it on
> the stack. This eliminates the overflow warning and improves kernel
> robustness.

...

>  	struct resource *regs;
>  	int ret, line;
> +	struct uart_8250_port *uart __free(kfree) = kzalloc(sizeof(*uart), GFP_KERNEL);
> +
> +	if (!uart)
> +		return -ENOMEM;

For cleanup (__free() in particular) we allow to mix definitions with the code
and it would be natural to have it a bit different

	struct resource *regs;
	int ret, line;

	struct uart_8250_port *uart __free(kfree) = kzalloc(sizeof(*uart), GFP_KERNEL);
	if (!uart)
		return -ENOMEM;

(In your case just a blank line placement is one line above.)

-- 
With Best Regards,
Andy Shevchenko