Hi Maarten,
2016-02-29 Maarten Lankhorst <maarten.lankho...@linux.intel.com>:
> Op 26-02-16 om 22:00 schreef Gustavo Padovan:
> > From: Gustavo Padovan <gustavo.pado...@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.pado...@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?
Gustavo
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