Re: [PATCH] net: hns3: fix hclge_dbg_dump_tm_pg() stack usage

From: "huangguangbin (A)" <huangguangbin2@huawei.com>
To: Arnd Bergmann <arnd@kernel.org>,
	Yisen Zhuang <yisen.zhuang@huawei.com>,
	Salil Mehta <salil.mehta@huawei.com>,
	"David S. Miller" <davem@davemloft.net>,
	Jakub Kicinski <kuba@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>,
	Huazhong Tan <tanhuazhong@huawei.com>,
	Yufeng Mo <moyufeng@huawei.com>,
	Jiaran Zhang <zhangjiaran@huawei.com>,
	"Jian Shen" <shenjian15@huawei.com>, <netdev@vger.kernel.org>,
	<linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] net: hns3: fix hclge_dbg_dump_tm_pg() stack usage
Date: Tue, 28 Sep 2021 16:34:11 +0800	[thread overview]
Message-ID: <bd4871e4-62e6-2cb2-26be-34bda8dcb7dd@huawei.com> (raw)
In-Reply-To: <20210927095006.868305-1-arnd@kernel.org>


On 2021/9/27 17:49, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@arndb.de>
> 
> This function copies strings around between multiple buffers
> including a large on-stack array that causes a build warning
> on 32-bit systems:
> 
> drivers/net/ethernet/hisilicon/hns3/hns3pf/hclge_debugfs.c: In function 'hclge_dbg_dump_tm_pg':
> drivers/net/ethernet/hisilicon/hns3/hns3pf/hclge_debugfs.c:782:1: error: the frame size of 1424 bytes is larger than 1400 bytes [-Werror=frame-larger-than=]
> 
> The function can probably be cleaned up a lot, to go back to
> printing directly into the output buffer, but dynamically allocating
> the structure is a simpler workaround for now.
> 
> Fixes: 04d96139ddb3 ("net: hns3: refine function hclge_dbg_dump_tm_pri()")
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
>   .../hisilicon/hns3/hns3pf/hclge_debugfs.c     | 26 ++++++++++++++++---
>   1 file changed, 22 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/net/ethernet/hisilicon/hns3/hns3pf/hclge_debugfs.c b/drivers/net/ethernet/hisilicon/hns3/hns3pf/hclge_debugfs.c
> index 87d96f82c318..3ed87814100a 100644
> --- a/drivers/net/ethernet/hisilicon/hns3/hns3pf/hclge_debugfs.c
> +++ b/drivers/net/ethernet/hisilicon/hns3/hns3pf/hclge_debugfs.c
> @@ -719,9 +719,9 @@ static void hclge_dbg_fill_shaper_content(struct hclge_tm_shaper_para *para,
>   	sprintf(result[(*index)++], "%6u", para->rate);
>   }
>   
> -static int hclge_dbg_dump_tm_pg(struct hclge_dev *hdev, char *buf, int len)
> +static int __hclge_dbg_dump_tm_pg(struct hclge_dev *hdev, char *data_str,
> +				  char *buf, int len)
>   {
> -	char data_str[ARRAY_SIZE(tm_pg_items)][HCLGE_DBG_DATA_STR_LEN];
>   	struct hclge_tm_shaper_para c_shaper_para, p_shaper_para;
>   	char *result[ARRAY_SIZE(tm_pg_items)], *sch_mode_str;
>   	u8 pg_id, sch_mode, weight, pri_bit_map, i, j;
> @@ -729,8 +729,10 @@ static int hclge_dbg_dump_tm_pg(struct hclge_dev *hdev, char *buf, int len)
>   	int pos = 0;
>   	int ret;
>   
> -	for (i = 0; i < ARRAY_SIZE(tm_pg_items); i++)
> -		result[i] = &data_str[i][0];
> +	for (i = 0; i < ARRAY_SIZE(tm_pg_items); i++) {
> +		result[i] = data_str;
> +		data_str += HCLGE_DBG_DATA_STR_LEN;
> +	}
>   
>   	hclge_dbg_fill_content(content, sizeof(content), tm_pg_items,
>   			       NULL, ARRAY_SIZE(tm_pg_items));
> @@ -781,6 +783,22 @@ static int hclge_dbg_dump_tm_pg(struct hclge_dev *hdev, char *buf, int len)
>   	return 0;
>   }
>   
> +static int hclge_dbg_dump_tm_pg(struct hclge_dev *hdev, char *buf, int len)
> +{
> +	int ret;
> +	char *data_str = kcalloc(ARRAY_SIZE(tm_pg_items),
> +				 HCLGE_DBG_DATA_STR_LEN, GFP_KERNEL);
> +
Hi Arnd, thanks your modification, according to linux code style, should the code be written as follow?
	char *data_str;
	int ret;

	data_str = kcalloc(ARRAY_SIZE(tm_pg_items),
			   HCLGE_DBG_DATA_STR_LEN, GFP_KERNEL);
> +	if (!data_str)
> +		return -ENOMEM;
> +
> +	ret = __hclge_dbg_dump_tm_pg(hdev, data_str, buf, len);
> +
> +	kfree(data_str);
> +
> +	return ret;
> +}
> +
>   static int hclge_dbg_dump_tm_port(struct hclge_dev *hdev,  char *buf, int len)
>   {
>   	struct hclge_tm_shaper_para shaper_para;
>