[PATCH] staging/android: refactor SYNC_IOC_FILE_INFO
Gustavo Padovan
gustavo.padovan at collabora.co.uk
Tue Mar 1 11:55:27 UTC 2016
Hi Maarten,
2016-03-01 Maarten Lankhorst <maarten.lankhorst at linux.intel.com>:
> Op 29-02-16 om 23:08 schreef Gustavo Padovan:
> > Hi Maarten,
> >
> > 2016-02-29 Maarten Lankhorst <maarten.lankhorst at linux.intel.com>:
> >
> >> Op 26-02-16 om 22:00 schreef Gustavo Padovan:
> >>> From: Gustavo Padovan <gustavo.padovan at collabora.co.uk>
> >>>
> >>> 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 at collabora.co.uk>
> >>> ---
> >>> 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.
Fair enough, I'll just remove len then.
Gustavo
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