Date: 14 Mar 2003 13:59:26 -0800 From: Eric Anholt <eta@lclark.edu> To: freebsd-hackers@FreeBSD.org Subject: per-open device private data, mmap Message-ID: <1047679166.622.23.camel@leguin>
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To work properly, the DRM needs an area of memory per open of the device which stores information on whether that fd is authenticated and also to have a unique identifier for use in the lock. Currently we use drm_find_file_by_proc to get the private data and use the pid as the unique identifier, but for example this causes problems if a fork occurs (threaded linux programs). This information is needed in the entry points (open, close, ioctl). (read, write, and poll from the current code are being stubbed out because they are unnecessary). To do this, I'm working on following what dev/streams/streams.c does in creating a new struct file and setting its own fileops and using the f_data field for the pointer to the private data. This looks pretty good for open/close/ioctl, but there's a problem with mmap. Currently we use drm_find_file_by_proc in the mmap handler to see if that process is authenticated, but there's no way from the mmap handler to get the private data because the struct file * isn't passed in. My initial thought was to instead check the authentication in the DRM(mapbufs) ioctl, where the vm_mmap is done by the X Server or clients. The problem with this is that a process could still do an mmap() on the fd and avoid the authentication check. What I'm wondering at this point is, is there any way to prevent the mmap() from succeeding (nothing legitimate uses mmap -- it's all done with the mapbufs ioctl), or a way to make it so from the device's mmap handler I can detect whether mmap() or mapbufs made the mapping, or to have different mmap handlers for those two vm_mmap callers. What's the best way to do this? -- Eric Anholt eta@lclark.edu http://people.freebsd.org/~anholt/ anholt@FreeBSD.org To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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