linux-kernel - [PATCH 1/2] drm/omap: dsi: Fix excessive stack usage

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Date:   Fri, 16 Sep 2022 11:22:05 +0300
From:   Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
To:     dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        linux-omap@...r.kernel.org
Cc:     Arnd Bergmann <arnd@...db.de>,
        Linus Walleij <linus.walleij@...aro.org>,
        Tomi Valkeinen <tomi.valkeinen@...asonboard.com>,
        kernel test robot <lkp@...el.com>
Subject: [PATCH 1/2] drm/omap: dsi: Fix excessive stack usage

dsi_dump_dsi_irqs(), a function used for debugfs prints, has a large
struct in its frame, which can result in:

drivers/gpu/drm/omapdrm/dss/dsi.c:1126:1: warning: the frame size of 1060 bytes is larger than 1024 bytes [-Wframe-larger-than=]

As the performance of the function is of no concern, let's allocate the
struct with kmalloc instead.

Compile-tested only.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
Reported-by: kernel test robot <lkp@...el.com>
---
 drivers/gpu/drm/omapdrm/dss/dsi.c | 26 ++++++++++++++++----------
 1 file changed, 16 insertions(+), 10 deletions(-)

diff --git a/drivers/gpu/drm/omapdrm/dss/dsi.c b/drivers/gpu/drm/omapdrm/dss/dsi.c
index a6845856cbce..4c1084eb0175 100644
--- a/drivers/gpu/drm/omapdrm/dss/dsi.c
+++ b/drivers/gpu/drm/omapdrm/dss/dsi.c
@@ -1039,22 +1039,26 @@ static int dsi_dump_dsi_irqs(struct seq_file *s, void *p)
 {
 	struct dsi_data *dsi = s->private;
 	unsigned long flags;
-	struct dsi_irq_stats stats;
+	struct dsi_irq_stats *stats;
+
+	stats = kmalloc(sizeof(*stats), GFP_KERNEL);
+	if (!stats)
+		return -ENOMEM;
 
 	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);
@@ -1078,10 +1082,10 @@ static int dsi_dump_dsi_irqs(struct seq_file *s, void *p)
 
 #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);
@@ -1097,7 +1101,7 @@ static int dsi_dump_dsi_irqs(struct seq_file *s, void *p)
 
 #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);
@@ -1122,6 +1126,8 @@ static int dsi_dump_dsi_irqs(struct seq_file *s, void *p)
 	PIS(ULPSACTIVENOT_ALL1);
 #undef PIS
 
+	kfree(stats);
+
 	return 0;
 }
 #endif
-- 
2.34.1