linux-kernel - [PATCH] hns3: work around stack size warning

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Message-Id: <20250610092113.2639248-1-arnd@kernel.org>
Date: Tue, 10 Jun 2025 11:21:08 +0200
From: Arnd Bergmann <arnd@...nel.org>
To: Jian Shen <shenjian15@...wei.com>,
	Salil Mehta <salil.mehta@...wei.com>,
	Jijie Shao <shaojijie@...wei.com>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	Nathan Chancellor <nathan@...nel.org>
Cc: Arnd Bergmann <arnd@...db.de>,
	Nick Desaulniers <nick.desaulniers+lkml@...il.com>,
	Bill Wendling <morbo@...gle.com>,
	Justin Stitt <justinstitt@...gle.com>,
	Hao Lan <lanhao@...wei.com>,
	Guangwei Zhang <zhangwangwei6@...wei.com>,
	netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	llvm@...ts.linux.dev
Subject: [PATCH] hns3: work around stack size warning

From: Arnd Bergmann <arnd@...db.de>

The hns3 debugfs functions all use an extra on-stack buffer to store
temporary text output before copying that to the debugfs file.

In some configurations with clang, this can trigger the warning limit
for the total stack size:

 drivers/net/ethernet/hisilicon/hns3/hns3_debugfs.c:788:12: error: stack frame size (1456) exceeds limit (1280) in 'hns3_dbg_tx_queue_info' [-Werror,-Wframe-larger-than]

The problem here is that both hns3_dbg_tx_spare_info() and
hns3_dbg_tx_queue_info() have a large on-stack buffer, and clang decides
to inline them into a single function.

Annotate hns3_dbg_tx_spare_info() as noinline_for_stack to force the
behavior that gcc has, regardless of the compiler.

Ideally all the functions in here would be changed to avoid on-stack
output buffers.

Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 drivers/net/ethernet/hisilicon/hns3/hns3_debugfs.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/hisilicon/hns3/hns3_debugfs.c b/drivers/net/ethernet/hisilicon/hns3/hns3_debugfs.c
index 4e5d8bc39a1b..97dc47eeb44c 100644
--- a/drivers/net/ethernet/hisilicon/hns3/hns3_debugfs.c
+++ b/drivers/net/ethernet/hisilicon/hns3/hns3_debugfs.c
@@ -580,8 +580,9 @@ static const struct hns3_dbg_item tx_spare_info_items[] = {
 	{ "DMA", 17 },
 };
 
-static void hns3_dbg_tx_spare_info(struct hns3_enet_ring *ring, char *buf,
-				   int len, u32 ring_num, int *pos)
+static noinline_for_stack void
+hns3_dbg_tx_spare_info(struct hns3_enet_ring *ring, char *buf,
+			int len, u32 ring_num, int *pos)
 {
 	char data_str[ARRAY_SIZE(tx_spare_info_items)][HNS3_DBG_DATA_STR_LEN];
 	struct hns3_tx_spare *tx_spare = ring->tx_spare;
-- 
2.39.5