| Message ID | 1440150609-23312-1-git-send-email-a.hajda@samsung.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 08/21/2015 11:50 AM, Andrzej Hajda wrote: > Union v4l2_event::u is aligned to 8 bytes on arm32. On arm64 v4l2_event32::u > is aligned to 4 bytes. As a result structures v4l2_event and v4l2_event32 have > different sizes and VIDOC_DQEVENT ioctl does not work from arm32 apps running > on arm64 kernel. The patch fixes it. > > Signed-off-by: Andrzej Hajda <a.hajda@samsung.com> > --- > Hi Hans, > > It seems there is problem with VIDIOC_DQEVENT called from arm32 apps on arm64 > kernel. After tracking down the issue it seems v4l2_event32 on arm64 have > different field alignment/size than v4l2_event on arm32. The patch fixes it. > But i guess it can break ABI on other architectures. Simple tests shows: > > i386: > sizeof(struct v4l2_event)=0x78 > offsetof(struct v4l2_event::u)=0x4 > > amd64: > sizeof(struct v4l2_event)=0x88 > offsetof(struct v4l2_event::u)=0x8 > > arm: > sizeof(struct v4l2_event)=0x80 > offsetof(struct v4l2_event::u)=0x8 > > arm64: > sizeof(struct v4l2_event)=0x88 > offsetof(struct v4l2_event::u)=0x8 > > Any advices how to fix it in arch compatible way? I noticed a compat_s64 type that knows about the 4-byte alignment on i386. So I think this can be solved by declaring v4l2_event32 as follows: struct v4l2_event32 { __u32 type; union { compat_s64 value64; __u8 data[64]; } u; __u32 pending; __u32 sequence; struct compat_timespec timestamp; __u32 id; __u32 reserved[8]; }; I think that this will force the correct alignment. Can you check this? Good catch BTW. Looking at v4l2-compat-ioctl32.c I suspect that compat_u/s64 will need to be used in more places: v4l2_standard32 (replace the id[2] array by compat_u64 id) and v4l2_ext_control32 are both almost certainly wrong for arm64. I would check those two. Regards, Hans > > Regards > Andrzej > --- > drivers/media/v4l2-core/v4l2-compat-ioctl32.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/media/v4l2-core/v4l2-compat-ioctl32.c b/drivers/media/v4l2-core/v4l2-compat-ioctl32.c > index af63543..a4a1856 100644 > --- a/drivers/media/v4l2-core/v4l2-compat-ioctl32.c > +++ b/drivers/media/v4l2-core/v4l2-compat-ioctl32.c > @@ -739,7 +739,7 @@ struct v4l2_event32 { > __u32 type; > union { > __u8 data[64]; > - } u; > + } u __attribute__((aligned(8))); > __u32 pending; > __u32 sequence; > struct compat_timespec timestamp; > -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/media/v4l2-core/v4l2-compat-ioctl32.c b/drivers/media/v4l2-core/v4l2-compat-ioctl32.c index af63543..a4a1856 100644 --- a/drivers/media/v4l2-core/v4l2-compat-ioctl32.c +++ b/drivers/media/v4l2-core/v4l2-compat-ioctl32.c @@ -739,7 +739,7 @@ struct v4l2_event32 { __u32 type; union { __u8 data[64]; - } u; + } u __attribute__((aligned(8))); __u32 pending; __u32 sequence; struct compat_timespec timestamp;
Union v4l2_event::u is aligned to 8 bytes on arm32. On arm64 v4l2_event32::u is aligned to 4 bytes. As a result structures v4l2_event and v4l2_event32 have different sizes and VIDOC_DQEVENT ioctl does not work from arm32 apps running on arm64 kernel. The patch fixes it. Signed-off-by: Andrzej Hajda <a.hajda@samsung.com> --- Hi Hans, It seems there is problem with VIDIOC_DQEVENT called from arm32 apps on arm64 kernel. After tracking down the issue it seems v4l2_event32 on arm64 have different field alignment/size than v4l2_event on arm32. The patch fixes it. But i guess it can break ABI on other architectures. Simple tests shows: i386: sizeof(struct v4l2_event)=0x78 offsetof(struct v4l2_event::u)=0x4 amd64: sizeof(struct v4l2_event)=0x88 offsetof(struct v4l2_event::u)=0x8 arm: sizeof(struct v4l2_event)=0x80 offsetof(struct v4l2_event::u)=0x8 arm64: sizeof(struct v4l2_event)=0x88 offsetof(struct v4l2_event::u)=0x8 Any advices how to fix it in arch compatible way? Regards Andrzej --- drivers/media/v4l2-core/v4l2-compat-ioctl32.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)