uvideo: replace contigmalloc with OBJT_PHYS vm_object for mmap buffer
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Authored by bapt on Wed, Jul 22, 1:09 PM.

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markj

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rG4c94869c37e1: uvideo: replace contigmalloc with OBJT_PHYS vm_object for mmap buffer

Summary

Allocate the mmap buffer via phys_pager_allocate() and map it into
kernel space with vm_map_find()/vm_map_wire(), instead of a custom
cdev_pager backed by contigmalloc. phys_pager_allocate() is required
over a bare vm_object_allocate(OBJT_PHYS) to initialise un_pager.phys.ops,
otherwise phys_pager_getpages() NULL-derefs during vm_map_wire().

Reported by: markj

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rG FreeBSD src repository

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Event Timeline

bapt created this revision.Wed, Jul 22, 1:09 PM

Herald added a subscriber: imp. · View Herald TranscriptWed, Jul 22, 1:09 PM

bapt requested review of this revision.Wed, Jul 22, 1:09 PM

Harbormaster completed remote builds in B75005: Diff 182453.Wed, Jul 22, 1:09 PM

markj added a subscriber: markj.Wed, Jul 22, 1:28 PM

markj added inline comments.

sys/dev/usb/video/uvideo.c
3588	I believe this vm_object_deallocate() is wrong and should be removed. The vm_map_find() call above consumes a reference to `obj`, and then the vm_map_remove() call releases that reference. See the comment above vm_map_find(). I believe uvideo_vs_free_frame() has the same problem, it calls vm_map_remove(), which releases the original reference, then calls vm_object_deallocate() again.