Re: [PATCH] hns3: work around stack size warning

From: Jijie Shao
Date: Tue Jun 10 2025 - 22:11:16 EST

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on 2025/6/10 17:21, Arnd Bergmann wrote:

From: Arnd Bergmann <arnd@xxxxxxxx>

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.

Hi Arnd:

Thank you for your report.

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.

Would you please help test whether the following changes have solved your problem,
And I'm not sure if this patch should be sent to net or net-next...

From d8d1ec419d45411762dd1c8ba24510e5a40bad08 Mon Sep 17 00:00:00 2001
From: Jian Shen <shenjian15@xxxxxxxxxx>
Date: Tue, 10 Jun 2025 19:35:19 +0800
Subject: [PATCH] net: hns3: clean up compile warning in debugfs

Arnd reported that there are two build warning for on-stasck
buffer oversize[1]. So use kmalloc instead of on-stack buffer.

1: https://lore.kernel.org/all/20250610092113.2639248-1-arnd@xxxxxxxxxx/
Reported-by: Arnd Bergmann <arnd@xxxxxxxxxx>
Signed-off-by: Jian Shen <shenjian15@xxxxxxxxxx>
---
.../ethernet/hisilicon/hns3/hns3_debugfs.c | 37 ++++++++++++-------
1 file changed, 24 insertions(+), 13 deletions(-)

diff --git a/drivers/net/ethernet/hisilicon/hns3/hns3_debugfs.c b/drivers/net/ethernet/hisilicon/hns3/hns3_debugfs.c
index dd86a3f66040..0246d9ef26ab 100644
--- a/drivers/net/ethernet/hisilicon/hns3/hns3_debugfs.c
+++ b/drivers/net/ethernet/hisilicon/hns3/hns3_debugfs.c
@@ -592,10 +592,11 @@ static const struct hns3_dbg_item tx_spare_info_items[] = {
static 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];
+ size_t item_num = ARRAY_SIZE(tx_spare_info_items);
struct hns3_tx_spare *tx_spare = ring->tx_spare;
char *result[ARRAY_SIZE(tx_spare_info_items)];
char content[HNS3_DBG_INFO_LEN];
+ char *data_str;
u32 i, j;
if (!tx_spare) {
@@ -604,12 +605,16 @@ static void hns3_dbg_tx_spare_info(struct hns3_enet_ring *ring, char *buf,
return;
}
- for (i = 0; i < ARRAY_SIZE(tx_spare_info_items); i++)
- result[i] = &data_str[i][0];
+ data_str = kzalloc(item_num * HNS3_DBG_DATA_STR_LEN, GFP_KERNEL);
+ if (!data_str)
+ return;
+
+ for (i = 0; i < item_num; i++)
+ result[i] = &data_str[i * HNS3_DBG_DATA_STR_LEN];
*pos += scnprintf(buf + *pos, len - *pos, "tx spare buffer info\n");
hns3_dbg_fill_content(content, sizeof(content), tx_spare_info_items,
- NULL, ARRAY_SIZE(tx_spare_info_items));
+ NULL, item_num);
*pos += scnprintf(buf + *pos, len - *pos, "%s", content);
for (i = 0; i < ring_num; i++) {
@@ -623,10 +628,11 @@ static void hns3_dbg_tx_spare_info(struct hns3_enet_ring *ring, char *buf,
sprintf(result[j++], "%pad", &tx_spare->dma);
hns3_dbg_fill_content(content, sizeof(content),
tx_spare_info_items,
- (const char **)result,
- ARRAY_SIZE(tx_spare_info_items));
+ (const char **)result, item_num);
*pos += scnprintf(buf + *pos, len - *pos, "%s", content);
}
+
+ kfree(data_str);
}
static const struct hns3_dbg_item rx_queue_info_items[] = {
@@ -793,12 +799,13 @@ static void hns3_dump_tx_queue_info(struct hns3_enet_ring *ring,
static int hns3_dbg_tx_queue_info(struct hnae3_handle *h,
char *buf, int len)
{
- char data_str[ARRAY_SIZE(tx_queue_info_items)][HNS3_DBG_DATA_STR_LEN];
+ size_t item_num = ARRAY_SIZE(tx_queue_info_items);
struct hnae3_ae_dev *ae_dev = hns3_get_ae_dev(h);
char *result[ARRAY_SIZE(tx_queue_info_items)];
struct hns3_nic_priv *priv = h->priv;
char content[HNS3_DBG_INFO_LEN];
struct hns3_enet_ring *ring;
+ char *data_str;
int pos = 0;
u32 i;
@@ -807,11 +814,15 @@ static int hns3_dbg_tx_queue_info(struct hnae3_handle *h,
return -EFAULT;
}
- for (i = 0; i < ARRAY_SIZE(tx_queue_info_items); i++)
- result[i] = &data_str[i][0];
+ data_str = kzalloc(item_num * HNS3_DBG_DATA_STR_LEN, GFP_KERNEL);
+ if (!data_str)
+ return -ENOMEM;
+
+ for (i = 0; i < item_num; i++)
+ result[i] = &data_str[i * HNS3_DBG_DATA_STR_LEN];
hns3_dbg_fill_content(content, sizeof(content), tx_queue_info_items,
- NULL, ARRAY_SIZE(tx_queue_info_items));
+ NULL, item_num);
pos += scnprintf(buf + pos, len - pos, "%s", content);
for (i = 0; i < h->kinfo.num_tqps; i++) {
@@ -827,13 +838,13 @@ static int hns3_dbg_tx_queue_info(struct hnae3_handle *h,
hns3_dump_tx_queue_info(ring, ae_dev, result, i);
hns3_dbg_fill_content(content, sizeof(content),
tx_queue_info_items,
- (const char **)result,
- ARRAY_SIZE(tx_queue_info_items));
+ (const char **)result, item_num);
pos += scnprintf(buf + pos, len - pos, "%s", content);
}
- hns3_dbg_tx_spare_info(ring, buf, len, h->kinfo.num_tqps, &pos);
+ kfree(data_str);
+ hns3_dbg_tx_spare_info(ring, buf, len, h->kinfo.num_tqps, &pos);
return 0;
}
--
2.33.0

Thanks very much!

Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
---
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;

From d8d1ec419d45411762dd1c8ba24510e5a40bad08 Mon Sep 17 00:00:00 2001
From: Jian Shen <shenjian15@xxxxxxxxxx>
Date: Tue, 10 Jun 2025 19:35:19 +0800
Subject: [PATCH] net: hns3: clean up compile warning in debugfs

Arnd reported that there are two build warning for on-stasck
buffer oversize[1]. So use kmalloc instead of on-stack buffer.

1: https://lore.kernel.org/all/20250610092113.2639248-1-arnd@xxxxxxxxxx/
Reported-by: Arnd Bergmann <arnd@xxxxxxxxxx>
Signed-off-by: Jian Shen <shenjian15@xxxxxxxxxx>
---
.../ethernet/hisilicon/hns3/hns3_debugfs.c | 37 ++++++++++++-------
1 file changed, 24 insertions(+), 13 deletions(-)

diff --git a/drivers/net/ethernet/hisilicon/hns3/hns3_debugfs.c b/drivers/net/ethernet/hisilicon/hns3/hns3_debugfs.c
index dd86a3f66040..0246d9ef26ab 100644
--- a/drivers/net/ethernet/hisilicon/hns3/hns3_debugfs.c
+++ b/drivers/net/ethernet/hisilicon/hns3/hns3_debugfs.c
@@ -592,10 +592,11 @@ static const struct hns3_dbg_item tx_spare_info_items[] = {
static 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];
+ size_t item_num = ARRAY_SIZE(tx_spare_info_items);
struct hns3_tx_spare *tx_spare = ring->tx_spare;
char *result[ARRAY_SIZE(tx_spare_info_items)];
char content[HNS3_DBG_INFO_LEN];
+ char *data_str;
u32 i, j;

if (!tx_spare) {
@@ -604,12 +605,16 @@ static void hns3_dbg_tx_spare_info(struct hns3_enet_ring *ring, char *buf,
return;
}

- for (i = 0; i < ARRAY_SIZE(tx_spare_info_items); i++)
- result[i] = &data_str[i][0];
+ data_str = kzalloc(item_num * HNS3_DBG_DATA_STR_LEN, GFP_KERNEL);
+ if (!data_str)
+ return;
+
+ for (i = 0; i < item_num; i++)
+ result[i] = &data_str[i * HNS3_DBG_DATA_STR_LEN];

*pos += scnprintf(buf + *pos, len - *pos, "tx spare buffer info\n");
hns3_dbg_fill_content(content, sizeof(content), tx_spare_info_items,
- NULL, ARRAY_SIZE(tx_spare_info_items));
+ NULL, item_num);
*pos += scnprintf(buf + *pos, len - *pos, "%s", content);

for (i = 0; i < ring_num; i++) {
@@ -623,10 +628,11 @@ static void hns3_dbg_tx_spare_info(struct hns3_enet_ring *ring, char *buf,
sprintf(result[j++], "%pad", &tx_spare->dma);
hns3_dbg_fill_content(content, sizeof(content),
tx_spare_info_items,
- (const char **)result,
- ARRAY_SIZE(tx_spare_info_items));
+ (const char **)result, item_num);
*pos += scnprintf(buf + *pos, len - *pos, "%s", content);
}
+
+ kfree(data_str);
}

static const struct hns3_dbg_item rx_queue_info_items[] = {
@@ -793,12 +799,13 @@ static void hns3_dump_tx_queue_info(struct hns3_enet_ring *ring,
static int hns3_dbg_tx_queue_info(struct hnae3_handle *h,
char *buf, int len)
{
- char data_str[ARRAY_SIZE(tx_queue_info_items)][HNS3_DBG_DATA_STR_LEN];
+ size_t item_num = ARRAY_SIZE(tx_queue_info_items);
struct hnae3_ae_dev *ae_dev = hns3_get_ae_dev(h);
char *result[ARRAY_SIZE(tx_queue_info_items)];
struct hns3_nic_priv *priv = h->priv;
char content[HNS3_DBG_INFO_LEN];
struct hns3_enet_ring *ring;
+ char *data_str;
int pos = 0;
u32 i;

@@ -807,11 +814,15 @@ static int hns3_dbg_tx_queue_info(struct hnae3_handle *h,
return -EFAULT;
}

- for (i = 0; i < ARRAY_SIZE(tx_queue_info_items); i++)
- result[i] = &data_str[i][0];
+ data_str = kzalloc(item_num * HNS3_DBG_DATA_STR_LEN, GFP_KERNEL);
+ if (!data_str)
+ return -ENOMEM;
+
+ for (i = 0; i < item_num; i++)
+ result[i] = &data_str[i * HNS3_DBG_DATA_STR_LEN];

hns3_dbg_fill_content(content, sizeof(content), tx_queue_info_items,
- NULL, ARRAY_SIZE(tx_queue_info_items));
+ NULL, item_num);
pos += scnprintf(buf + pos, len - pos, "%s", content);

for (i = 0; i < h->kinfo.num_tqps; i++) {
@@ -827,13 +838,13 @@ static int hns3_dbg_tx_queue_info(struct hnae3_handle *h,
hns3_dump_tx_queue_info(ring, ae_dev, result, i);
hns3_dbg_fill_content(content, sizeof(content),
tx_queue_info_items,
- (const char **)result,
- ARRAY_SIZE(tx_queue_info_items));
+ (const char **)result, item_num);
pos += scnprintf(buf + pos, len - pos, "%s", content);
}

- hns3_dbg_tx_spare_info(ring, buf, len, h->kinfo.num_tqps, &pos);
+ kfree(data_str);

+ hns3_dbg_tx_spare_info(ring, buf, len, h->kinfo.num_tqps, &pos);
return 0;
}

--
2.33.0

Next message: shao.mingyin: "Re: [PATCH v2] pmdomain: Use str_enable_disable-like helpers"
Previous message: Herbert Xu: "Re: [PATCH] crypto: caam - Set DMA alignment explicitly"
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Next in thread: Arnd Bergmann: "Re: [PATCH] hns3: work around stack size warning"
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