[v6,5/6] staging/android: refactor SYNC_IOC_FILE_INFO

Submitted by Gustavo Padovan on March 2, 2016, 7:52 p.m.

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Message ID 1456948331-7300-5-git-send-email-gustavo@padovan.org
State New
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Series "Series without cover letter" ( rev: 2 1 ) in DRI devel

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Commit Message

Gustavo Padovan March 2, 2016, 7:52 p.m.
From: Gustavo Padovan <gustavo.padovan@collabora.co.uk>

Change SYNC_IOC_FILE_INFO behaviour to avoid future API breaks and
optimize buffer

Now num_fences can be filled by the caller to inform how many fences it
wants to retrieve from the kernel. If the num_fences passed is greater
than zero info->sync_fence_info should point to a buffer with enough space
to fit all fences.

However if num_fences passed to the kernel is 0, the kernel will reply
with number of fences of the sync_file.

Sending first an ioctl with num_fences = 0 can optimize buffer allocation,
in a first call with num_fences = 0 userspace will receive the actual
number of fences in the num_fences filed.

Then it can allocate a buffer with the correct size on sync_fence_info and
call SYNC_IOC_FILE_INFO again, but now with the actual value of num_fences
in the sync_file.

Also, info->sync_fence_info was converted to __u64 pointer to prevent
32bit compatibility issues.

An example userspace code for the later would be:

	struct sync_file_info *info;
	int err, size, num_fences;

	info = malloc(sizeof(*info));

	info.flags = 0;
	err = ioctl(fd, SYNC_IOC_FILE_INFO, info);
	num_fences = info->num_fences;

	if (num_fences) {
		info.flags = 0;
		size = sizeof(struct sync_fence_info) * num_fences;
		info->num_fences = num_fences;
		info->sync_fence_info = (uint64_t) calloc(num_fences,
							  sizeof(struct sync_fence_info));

		err = ioctl(fd, SYNC_IOC_FILE_INFO, info);
	}

v2: fix fence_info memory leak

v3: Comments from Emil Velikov
	- improve commit message
	- remove __u64 cast
	- remove check for output fields in file_info
	- clean up sync_fill_fence_info()

    Comments from Maarten Lankhorst
	- remove in.num_fences && !in.sync_fence_info check
	- remove info->len and use only num_fences to calculate size

    Comments from Dan Carpenter
	- fix info->sync_fence_info documentation

Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
---
 drivers/staging/android/sync.c      | 64 ++++++++++++++++++++-----------------
 drivers/staging/android/uapi/sync.h |  9 ++----
 2 files changed, 38 insertions(+), 35 deletions(-)

Patch hide | download patch | download mbox

diff --git a/drivers/staging/android/sync.c b/drivers/staging/android/sync.c
index dc5f382..3604e453 100644
--- a/drivers/staging/android/sync.c
+++ b/drivers/staging/android/sync.c
@@ -479,13 +479,9 @@  err_put_fd:
 	return err;
 }
 
-static int sync_fill_fence_info(struct fence *fence, void *data, int size)
+static void sync_fill_fence_info(struct fence *fence,
+				struct sync_fence_info *info)
 {
-	struct sync_fence_info *info = data;
-
-	if (size < sizeof(*info))
-		return -ENOMEM;
-
 	strlcpy(info->obj_name, fence->ops->get_timeline_name(fence),
 		sizeof(info->obj_name));
 	strlcpy(info->driver_name, fence->ops->get_driver_name(fence),
@@ -495,28 +491,20 @@  static int sync_fill_fence_info(struct fence *fence, void *data, int size)
 	else
 		info->status = 0;
 	info->timestamp_ns = ktime_to_ns(fence->timestamp);
-
-	return sizeof(*info);
 }
 
 static long sync_file_ioctl_fence_info(struct sync_file *sync_file,
 					unsigned long arg)
 {
-	struct sync_file_info *info;
+	struct sync_file_info in, *info;
+	struct sync_fence_info *fence_info = NULL;
 	__u32 size;
-	__u32 len = 0;
 	int ret, i;
 
-	if (copy_from_user(&size, (void __user *)arg, sizeof(size)))
+	if (copy_from_user(&in, (void __user *)arg, sizeof(in)))
 		return -EFAULT;
 
-	if (size < sizeof(struct sync_file_info))
-		return -EINVAL;
-
-	if (size > 4096)
-		size = 4096;
-
-	info = kzalloc(size, GFP_KERNEL);
+	info = kzalloc(sizeof(*info), GFP_KERNEL);
 	if (!info)
 		return -ENOMEM;
 
@@ -525,29 +513,47 @@  static long sync_file_ioctl_fence_info(struct sync_file *sync_file,
 	if (info->status >= 0)
 		info->status = !info->status;
 
-	info->num_fences = sync_file->num_fences;
-
-	len = sizeof(struct sync_file_info);
+	/*
+	 * Passing num_fences = 0 means that userspace doesn't want to
+	 * retrieve any sync_fence_info. If num_fences = 0 we skip filling
+	 * sync_fence_info and return the actual number of fences on
+	 * info->num_fences.
+	 */
+	if (!in.num_fences)
+		goto no_fences;
 
-	for (i = 0; i < sync_file->num_fences; ++i) {
-		struct fence *fence = sync_file->cbs[i].fence;
+	if (in.num_fences < sync_file->num_fences) {
+		ret = -EINVAL;
+		goto out;
+	}
 
-		ret = sync_fill_fence_info(fence, (u8 *)info + len, size - len);
+	size = sync_file->num_fences * sizeof(*fence_info);
+	fence_info = kzalloc(size, GFP_KERNEL);
+	if (!fence_info) {
+		ret = -ENOMEM;
+		goto out;
+	}
 
-		if (ret < 0)
-			goto out;
+	for (i = 0; i < sync_file->num_fences; ++i)
+		sync_fill_fence_info(sync_file->cbs[i].fence, &fence_info[i]);
 
-		len += ret;
+	if (copy_to_user((void __user *)in.sync_fence_info, fence_info, size)) {
+		ret = -EFAULT;
+		goto out;
 	}
 
-	info->len = len;
+	info->sync_fence_info = in.sync_fence_info;
+
+no_fences:
+	info->num_fences = sync_file->num_fences;
 
-	if (copy_to_user((void __user *)arg, info, len))
+	if (copy_to_user((void __user *)arg, info, sizeof(*info)))
 		ret = -EFAULT;
 	else
 		ret = 0;
 
 out:
+	kfree(fence_info);
 	kfree(info);
 
 	return ret;
diff --git a/drivers/staging/android/uapi/sync.h b/drivers/staging/android/uapi/sync.h
index a6c648c..f064923 100644
--- a/drivers/staging/android/uapi/sync.h
+++ b/drivers/staging/android/uapi/sync.h
@@ -42,21 +42,18 @@  struct sync_fence_info {
 
 /**
  * struct sync_file_info - data returned from fence info ioctl
- * @len:	ioctl caller writes the size of the buffer its passing in.
- *		ioctl returns length of sync_file_info returned to
- *		userspace including pt_info.
  * @name:	name of fence
  * @status:	status of fence. 1: signaled 0:active <0:error
  * @num_fences	number of fences in the sync_file
- * @sync_fence_info: array of sync_fence_info for every fence in the sync_file
+ * @sync_fence_info: pointer to array of structs sync_fence_info with all
+ *		 fences in the sync_file
  */
 struct sync_file_info {
-	__u32	len;
 	char	name[32];
 	__s32	status;
 	__u32	num_fences;
 
-	__u8	sync_fence_info[0];
+	__u64	sync_fence_info;
 };
 
 #define SYNC_IOC_MAGIC		'>'

Comments

Op 02-03-16 om 20:52 schreef Gustavo Padovan:
> From: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
>
> Change SYNC_IOC_FILE_INFO behaviour to avoid future API breaks and
> optimize buffer
>
> Now num_fences can be filled by the caller to inform how many fences it
> wants to retrieve from the kernel. If the num_fences passed is greater
> than zero info->sync_fence_info should point to a buffer with enough space
> to fit all fences.
>
> However if num_fences passed to the kernel is 0, the kernel will reply
> with number of fences of the sync_file.
>
> Sending first an ioctl with num_fences = 0 can optimize buffer allocation,
> in a first call with num_fences = 0 userspace will receive the actual
> number of fences in the num_fences filed.
>
> Then it can allocate a buffer with the correct size on sync_fence_info and
> call SYNC_IOC_FILE_INFO again, but now with the actual value of num_fences
> in the sync_file.
>
> Also, info->sync_fence_info was converted to __u64 pointer to prevent
> 32bit compatibility issues.
>
> An example userspace code for the later would be:
>
> 	struct sync_file_info *info;
> 	int err, size, num_fences;
>
> 	info = malloc(sizeof(*info));
>
> 	info.flags = 0;
> 	err = ioctl(fd, SYNC_IOC_FILE_INFO, info);
> 	num_fences = info->num_fences;
>
> 	if (num_fences) {
> 		info.flags = 0;
> 		size = sizeof(struct sync_fence_info) * num_fences;
> 		info->num_fences = num_fences;
> 		info->sync_fence_info = (uint64_t) calloc(num_fences,
> 							  sizeof(struct sync_fence_info));
>
> 		err = ioctl(fd, SYNC_IOC_FILE_INFO, info);
> 	}
>
> v2: fix fence_info memory leak
>
> v3: Comments from Emil Velikov
> 	- improve commit message
> 	- remove __u64 cast
> 	- remove check for output fields in file_info
> 	- clean up sync_fill_fence_info()
>
>     Comments from Maarten Lankhorst
> 	- remove in.num_fences && !in.sync_fence_info check
> 	- remove info->len and use only num_fences to calculate size
>
>     Comments from Dan Carpenter
> 	- fix info->sync_fence_info documentation
>
> Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
> ---
>  drivers/staging/android/sync.c      | 64 ++++++++++++++++++++-----------------
>  drivers/staging/android/uapi/sync.h |  9 ++----
>  2 files changed, 38 insertions(+), 35 deletions(-)
>
> diff --git a/drivers/staging/android/sync.c b/drivers/staging/android/sync.c
> index dc5f382..3604e453 100644
> --- a/drivers/staging/android/sync.c
> +++ b/drivers/staging/android/sync.c
> @@ -479,13 +479,9 @@ err_put_fd:
>  	return err;
>  }
>  
> -static int sync_fill_fence_info(struct fence *fence, void *data, int size)
> +static void sync_fill_fence_info(struct fence *fence,
> +				struct sync_fence_info *info)
>  {
> -	struct sync_fence_info *info = data;
> -
> -	if (size < sizeof(*info))
> -		return -ENOMEM;
> -
>  	strlcpy(info->obj_name, fence->ops->get_timeline_name(fence),
>  		sizeof(info->obj_name));
>  	strlcpy(info->driver_name, fence->ops->get_driver_name(fence),
> @@ -495,28 +491,20 @@ static int sync_fill_fence_info(struct fence *fence, void *data, int size)
>  	else
>  		info->status = 0;
>  	info->timestamp_ns = ktime_to_ns(fence->timestamp);
> -
> -	return sizeof(*info);
>  }
>  
>  static long sync_file_ioctl_fence_info(struct sync_file *sync_file,
>  					unsigned long arg)
>  {
> -	struct sync_file_info *info;
> +	struct sync_file_info in, *info;
Why put one copy on the stack, and allocate a second?
With sync_file_info now being a fixed size just put 1 copy on the stack from userspace,
run some sanity checks first, put in the new values and copy it back to userspace without additional memory allocation.

The rest looks good now. :)

~Maarten