fbdev: omapfb: avoid stack overflow warning

From: Arnd Bergmann <arnd@arndb.de>

The dsi_irq_stats structure is a little too big to fit on the
stack of a 32-bit task, depending on the specific gcc options:

fbdev/omap2/omapfb/dss/dsi.c: In function 'dsi_dump_dsidev_irqs':
fbdev/omap2/omapfb/dss/dsi.c:1621:1: error: the frame size of 1064 bytes is larger than 1024 bytes [-Werror=frame-larger-than=]

Since this is only a debugfs file, performance is not critical,
so just dynamically allocate it, and print an error message
in there in place of a failure code when the allocation fails.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 drivers/video/fbdev/omap2/omapfb/dss/dsi.c | 28 ++++++++++++++--------
 1 file changed, 18 insertions(+), 10 deletions(-)

Hi Arnd,

On Thu, Dec 15, 2022 at 6:05 PM Arnd Bergmann <arnd@kernel.org> wrote:
> From: Arnd Bergmann <arnd@arndb.de>
>
> The dsi_irq_stats structure is a little too big to fit on the
> stack of a 32-bit task, depending on the specific gcc options:
>
> fbdev/omap2/omapfb/dss/dsi.c: In function 'dsi_dump_dsidev_irqs':
> fbdev/omap2/omapfb/dss/dsi.c:1621:1: error: the frame size of 1064 bytes is larger than 1024 bytes [-Werror=frame-larger-than=]
>
> Since this is only a debugfs file, performance is not critical,
> so just dynamically allocate it, and print an error message
> in there in place of a failure code when the allocation fails.
>
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>

Thanks for your patch!

> --- a/drivers/video/fbdev/omap2/omapfb/dss/dsi.c
> +++ b/drivers/video/fbdev/omap2/omapfb/dss/dsi.c
> @@ -1536,22 +1536,28 @@ static void dsi_dump_dsidev_irqs(struct platform_device *dsidev,
>  {
>         struct dsi_data *dsi = dsi_get_dsidrv_data(dsidev);
>         unsigned long flags;
> -       struct dsi_irq_stats stats;
> +       struct dsi_irq_stats *stats;
> +
> +       stats = kzalloc(sizeof(*stats), GFP_KERNEL);
> +       if (!stats) {
> +               seq_printf(s, "out of memory\n");

I guess this is futile?
No need to increase kernel size for OOM messages.

> +               return;
> +       }
>
>         spin_lock_irqsave(&dsi->irq_stats_lock, flags);

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

On 12/15/22 18:02, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@arndb.de>
>
> The dsi_irq_stats structure is a little too big to fit on the
> stack of a 32-bit task, depending on the specific gcc options:
>
> fbdev/omap2/omapfb/dss/dsi.c: In function 'dsi_dump_dsidev_irqs':
> fbdev/omap2/omapfb/dss/dsi.c:1621:1: error: the frame size of 1064 bytes is larger than 1024 bytes [-Werror=frame-larger-than=]
>
> Since this is only a debugfs file, performance is not critical,
> so just dynamically allocate it, and print an error message
> in there in place of a failure code when the allocation fails.
>
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>

applied to fbdev git tree.

Thanks!
Helge

> ---
>   drivers/video/fbdev/omap2/omapfb/dss/dsi.c | 28 ++++++++++++++--------
>   1 file changed, 18 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/video/fbdev/omap2/omapfb/dss/dsi.c b/drivers/video/fbdev/omap2/omapfb/dss/dsi.c
> index 54b0f034c2ed..7cddb7b8ae34 100644
> --- a/drivers/video/fbdev/omap2/omapfb/dss/dsi.c
> +++ b/drivers/video/fbdev/omap2/omapfb/dss/dsi.c
> @@ -1536,22 +1536,28 @@ static void dsi_dump_dsidev_irqs(struct platform_device *dsidev,
>   {
>   	struct dsi_data *dsi = dsi_get_dsidrv_data(dsidev);
>   	unsigned long flags;
> -	struct dsi_irq_stats stats;
> +	struct dsi_irq_stats *stats;
> +
> +	stats = kzalloc(sizeof(*stats), GFP_KERNEL);
> +	if (!stats) {
> +		seq_printf(s, "out of memory\n");
> +		return;
> +	}
>
>   	spin_lock_irqsave(&dsi->irq_stats_lock, flags);
>
> -	stats = dsi->irq_stats;
> +	*stats = dsi->irq_stats;
>   	memset(&dsi->irq_stats, 0, sizeof(dsi->irq_stats));
>   	dsi->irq_stats.last_reset = jiffies;
>
>   	spin_unlock_irqrestore(&dsi->irq_stats_lock, flags);
>
>   	seq_printf(s, "period %u ms\n",
> -			jiffies_to_msecs(jiffies - stats.last_reset));
> +			jiffies_to_msecs(jiffies - stats->last_reset));
>
> -	seq_printf(s, "irqs %d\n", stats.irq_count);
> +	seq_printf(s, "irqs %d\n", stats->irq_count);
>   #define PIS(x) \
> -	seq_printf(s, "%-20s %10d\n", #x, stats.dsi_irqs[ffs(DSI_IRQ_##x)-1])
> +	seq_printf(s, "%-20s %10d\n", #x, stats->dsi_irqs[ffs(DSI_IRQ_##x)-1])
>
>   	seq_printf(s, "-- DSI%d interrupts --\n", dsi->module_id + 1);
>   	PIS(VC0);
> @@ -1575,10 +1581,10 @@ static void dsi_dump_dsidev_irqs(struct platform_device *dsidev,
>
>   #define PIS(x) \
>   	seq_printf(s, "%-20s %10d %10d %10d %10d\n", #x, \
> -			stats.vc_irqs[0][ffs(DSI_VC_IRQ_##x)-1], \
> -			stats.vc_irqs[1][ffs(DSI_VC_IRQ_##x)-1], \
> -			stats.vc_irqs[2][ffs(DSI_VC_IRQ_##x)-1], \
> -			stats.vc_irqs[3][ffs(DSI_VC_IRQ_##x)-1]);
> +			stats->vc_irqs[0][ffs(DSI_VC_IRQ_##x)-1], \
> +			stats->vc_irqs[1][ffs(DSI_VC_IRQ_##x)-1], \
> +			stats->vc_irqs[2][ffs(DSI_VC_IRQ_##x)-1], \
> +			stats->vc_irqs[3][ffs(DSI_VC_IRQ_##x)-1]);
>
>   	seq_printf(s, "-- VC interrupts --\n");
>   	PIS(CS);
> @@ -1594,7 +1600,7 @@ static void dsi_dump_dsidev_irqs(struct platform_device *dsidev,
>
>   #define PIS(x) \
>   	seq_printf(s, "%-20s %10d\n", #x, \
> -			stats.cio_irqs[ffs(DSI_CIO_IRQ_##x)-1]);
> +			stats->cio_irqs[ffs(DSI_CIO_IRQ_##x)-1]);
>
>   	seq_printf(s, "-- CIO interrupts --\n");
>   	PIS(ERRSYNCESC1);
> @@ -1618,6 +1624,8 @@ static void dsi_dump_dsidev_irqs(struct platform_device *dsidev,
>   	PIS(ULPSACTIVENOT_ALL0);
>   	PIS(ULPSACTIVENOT_ALL1);
>   #undef PIS
> +
> +	kfree(stats);
>   }
>
>   static void dsi1_dump_irqs(struct seq_file *s)