K 10
svn:author
V 6
andrew
K 8
svn:date
V 27
2019-09-16T15:00:11.566608Z
K 7
svn:log
V 563
MFC r342937:

Fix the location of td->td_frame at the top of the kernel stack.

In cpu_thread_alloc we would allocate space for the trap frame at the top of
the kernel stack. This is just below the pcb, however due to a missing cast
the pointer arithmetic would use the pcb size, not the trapframe size. As
the pcb is larger than the trapframe this is safe, however later in cpu_fork
we include the case leading to the two disagreeing on the location.

Fix by using the same arithmetic in both locations.

Found by:	An early KASAN patch
Sponsored by:	DARPA, AFRL

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