linux-kernel - [PATCH] dma-buf: support users to change dma

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Date:   Wed, 14 Jul 2021 20:29:54 +0800
From:   <guangming.cao@...iatek.com>
To:     Sumit Semwal <sumit.semwal@...aro.org>,
        Christian König <christian.koenig@....com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        "open list:DMA BUFFER SHARING FRAMEWORK" 
        <linux-media@...r.kernel.org>,
        "open list:DMA BUFFER SHARING FRAMEWORK" 
        <dri-devel@...ts.freedesktop.org>,
        "moderated list:DMA BUFFER SHARING FRAMEWORK" 
        <linaro-mm-sig@...ts.linaro.org>,
        open list <linux-kernel@...r.kernel.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-arm-kernel@...ts.infradead.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@...ts.infradead.org>
CC:     <wsd_upstream@...iatek.com>, <caoguangming34@...il.com>,
        Guangming Cao <Guangming.Cao@...iatek.com>
Subject: [PATCH] dma-buf: support users to change dma_buf.name

From: Guangming Cao <Guangming.Cao@...iatek.com>

User space user can call DMA_BUF_SET_NAME to set dma_buf.name,
also add a kernel api for users to do same thing at kernel side.

Signed-off-by: Guangming Cao <Guangming.Cao@...iatek.com>
---
 drivers/dma-buf/dma-buf.c | 28 ++++++++++++++++++++++------
 include/linux/dma-buf.h   |  1 +
 2 files changed, 23 insertions(+), 6 deletions(-)

diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
index 511fe0d217a0..949af232c644 100644
--- a/drivers/dma-buf/dma-buf.c
+++ b/drivers/dma-buf/dma-buf.c
@@ -331,20 +331,20 @@ static __poll_t dma_buf_poll(struct file *file, poll_table *poll)
  * purpose between different devices.
  *
  * @dmabuf: [in]     dmabuf buffer that will be renamed.
- * @buf:    [in]     A piece of userspace memory that contains the name of
+ * @buf:    [in]     A piece of memory that contains the name of
  *                   the dma-buf.
  *
  * Returns 0 on success. If the dma-buf buffer is already attached to
  * devices, return -EBUSY.
  *
  */
-static long dma_buf_set_name(struct dma_buf *dmabuf, const char __user *buf)
+long dma_buf_set_name(struct dma_buf *dmabuf, const char *buf)
 {
-	char *name = strndup_user(buf, DMA_BUF_NAME_LEN);
+	char *name = kstrndup(buf, DMA_BUF_NAME_LEN, GFP_KERNEL);
 	long ret = 0;
 
-	if (IS_ERR(name))
-		return PTR_ERR(name);
+	if (!name)
+		return -ENOMEM;
 
 	dma_resv_lock(dmabuf->resv, NULL);
 	if (!list_empty(&dmabuf->attachments)) {
@@ -361,6 +361,22 @@ static long dma_buf_set_name(struct dma_buf *dmabuf, const char __user *buf)
 	dma_resv_unlock(dmabuf->resv);
 	return ret;
 }
+EXPORT_SYMBOL_GPL(dma_buf_set_name);
+
+static long
+dma_buf_set_name_user(struct dma_buf *dmabuf, const char __user *buf)
+{
+	char *name = strndup_user(buf, DMA_BUF_NAME_LEN);
+	long ret = 0;
+
+	if (IS_ERR(name))
+		return PTR_ERR(name);
+
+	ret = dma_buf_set_name(dmabuf, name);
+	kfree(name);
+
+	return ret;
+}
 
 static long dma_buf_ioctl(struct file *file,
 			  unsigned int cmd, unsigned long arg)
@@ -403,7 +419,7 @@ static long dma_buf_ioctl(struct file *file,
 
 	case DMA_BUF_SET_NAME_A:
 	case DMA_BUF_SET_NAME_B:
-		return dma_buf_set_name(dmabuf, (const char __user *)arg);
+		return dma_buf_set_name_user(dmabuf, (const char __user *)arg);
 
 	default:
 		return -ENOTTY;
diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h
index efdc56b9d95f..e6612ab59a59 100644
--- a/include/linux/dma-buf.h
+++ b/include/linux/dma-buf.h
@@ -507,4 +507,5 @@ int dma_buf_mmap(struct dma_buf *, struct vm_area_struct *,
 		 unsigned long);
 int dma_buf_vmap(struct dma_buf *dmabuf, struct dma_buf_map *map);
 void dma_buf_vunmap(struct dma_buf *dmabuf, struct dma_buf_map *map);
+long dma_buf_set_name(struct dma_buf *dmabuf, const char *name);
 #endif /* __DMA_BUF_H__ */
-- 
2.17.1