Op 29-02-16 om 23:08 schreef Gustavo Padovan:
> Hi Maarten,
>
> 2016-02-29 Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx>:
>
>> Op 26-02-16 om 22:00 schreef Gustavo Padovan:
>>> From: Gustavo Padovan <gustavo.padovan@xxxxxxxxxxxxxxx>
>>>
>>> Change SYNC_IOC_FILE_INFO behaviour to avoid future API breaks and
>>> optimize buffer allocation. In the new approach the ioctl needs to be called
>>> twice to retrieve the array of fence_infos pointed by info->sync_fence_info.
>>>
>>> The first call should pass num_fences = 0, the kernel will then fill
>>> info->num_fences. Userspace receives back the number of fences and
>>> allocates a buffer size num_fences * sizeof(struct sync_fence_info) on
>>> info->sync_fence_info.
>>>
>>> It then call the ioctl again passing num_fences received in info->num_fences.
>>> The kernel checks if info->num_fences > 0 and if yes it fill
>>> info->sync_fence_info with an array containing all fence_infos.
>>>
>>> info->len now represents the length of the buffer sync_fence_info points
>>> to. Also, info->sync_fence_info was converted to __u64 pointer.
>>>
>>> An example userspace code would be:
>>>
>>> struct sync_file_info *info;
>>> int err, size, num_fences;
>>>
>>> info = malloc(sizeof(*info));
>>>
>>> memset(info, 0, sizeof(*info));
>>>
>>> err = ioctl(fd, SYNC_IOC_FILE_INFO, info);
>>> num_fences = info->num_fences;
>>>
>>> if (num_fences) {
>>> memset(info, 0, sizeof(*info));
>> Would this memset still be needed if we didn't check for nulls in info->status and info->name ?
>>
>> Seems to me that it could be skipped in that case.
> Yes, I agree.
>
>>> size = sizeof(struct sync_fence_info) * num_fences;
>>> info->len = size;
>>> 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
>>>
>>> Signed-off-by: Gustavo Padovan <gustavo.padovan@xxxxxxxxxxxxxxx>
>>> ---
>>> drivers/staging/android/sync.c | 52 +++++++++++++++++++++++++++++--------
>>> drivers/staging/android/uapi/sync.h | 9 +++----
>>> 2 files changed, 45 insertions(+), 16 deletions(-)
>>>
>>> diff --git a/drivers/staging/android/sync.c b/drivers/staging/android/sync.c
>>> index dc5f382..2379f23 100644
>>> --- a/drivers/staging/android/sync.c
>>> +++ b/drivers/staging/android/sync.c
>>> @@ -502,21 +502,22 @@ static int sync_fill_fence_info(struct fence *fence, void *data, int size)
>>> 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;
>> = 0 unneeded.
>>> int ret, i;
>>>
>>> - if (copy_from_user(&size, (void __user *)arg, sizeof(size)))
>>> + if (copy_from_user(&in, (void __user *)arg, sizeof(*info)))
>>> return -EFAULT;
>>>
>>> - if (size < sizeof(struct sync_file_info))
>>> - return -EINVAL;
>>> + if (in.status || strcmp(in.name, "\0"))
>>> + return -EFAULT;
>> These members always get written by the fence ioctl, I'm not sure it adds value to have them explicitly zero'd out by userspace.
>>> - if (size > 4096)
>>> - size = 4096;
>>> + if (in.num_fences && !in.sync_fence_info)
>>> + return -EFAULT;
>> This check is unneeded, it will happen in the copy_to_user call anyway.
>>> - info = kzalloc(size, GFP_KERNEL);
>>> + info = kzalloc(sizeof(*info), GFP_KERNEL);
>>> if (!info)
>>> return -ENOMEM;
>>>
>>> @@ -525,14 +526,33 @@ 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;
>>> + /*
>>> + * Passing num_fences = 0 means that userspace want to know how
>>> + * many fences are in the sync_file to be able to allocate a buffer to
>>> + * fit all sync_fence_infos and call the ioctl again with the buffer
>>> + * assigned to info->sync_fence_info. The second call pass the
>>> + * num_fences value received in the first call.
>>> + */
>>> + if (!in.num_fences)
>>> + goto no_fences;
>>> +
>>> + size = sync_file->num_fences * sizeof(*fence_info);
>>> + if (in.len != size) {
>>> + ret = -EFAULT;
>>> + goto out;
>>> + }
>> Maybe check for in.len < size, and set set to size?
>>
>>
>>> - len = sizeof(struct sync_file_info);
>>> + fence_info = kzalloc(size, GFP_KERNEL);
>>> + if (!fence_info) {
>>> + ret = -ENOMEM;
>>> + goto out;
>>> + }
>>>
>>> for (i = 0; i < sync_file->num_fences; ++i) {
>>> struct fence *fence = sync_file->cbs[i].fence;
>>>
>>> - ret = sync_fill_fence_info(fence, (u8 *)info + len, size - len);
>>> + ret = sync_fill_fence_info(fence, (u8 *)fence_info + len,
>>> + size - len);
>>>
>>> if (ret < 0)
>>> goto out;
>>> @@ -540,14 +560,24 @@ static long sync_file_ioctl_fence_info(struct sync_file *sync_file,
>>> 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 = (__u64) 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 f0b41ce..9aad623 100644
>>> --- a/drivers/staging/android/uapi/sync.h
>>> +++ b/drivers/staging/android/uapi/sync.h
>>> @@ -42,21 +42,20 @@ 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
>>> + * @len: ioctl caller writes the size of the buffer its passing in.
>>> + * ioctl returns length of all fence_infos summed.
>>> * @sync_fence_info: array of sync_fence_info for every fence in the sync_file
>>> */
>>> struct sync_file_info {
>>> - __u32 len;
>>> char name[32];
>>> __s32 status;
>>> __u32 num_fences;
>>> + __u32 len;
>>>
>>> - __u8 sync_fence_info[0];
>>> + __u64 sync_fence_info;
>>> };
>>>
>>> #define SYNC_IOC_MAGIC '>'
>> Not sure if len adds anything here, userspace knows to allocate num_fences * sizeof(struct sync_fence_info);
> I think of len being useful if we decide to extend struct sync_fence_info in
> the future, so we may use len to help discover the size of each
> sync_fence_info. What do you think?
>
I don't think you could extend it arbitrarily, you could make userspace pass a flag to indicate the struct is extended, so kernel space can choose
whether to use the bigger size struct or not.
something like sync_file_info.flags = FENCE_INFO_V2; -- kernel can reject with -EINVAL if unsupported, or fill in a v2 struct.
~Maarten
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