svn commit: r342937 - head/sys/arm64/arm64

[Andrew Turner]

Author: andrew
Date: Fri Jan 11 11:32:46 2019
New Revision: 342937
URL: https://svnweb.freebsd.org/changeset/base/342937

Log:
  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

Modified:
  head/sys/arm64/arm64/vm_machdep.c

Modified: head/sys/arm64/arm64/vm_machdep.c
==============================================================================
--- head/sys/arm64/arm64/vm_machdep.c	Fri Jan 11 09:40:34 2019	(r342936)
+++ head/sys/arm64/arm64/vm_machdep.c	Fri Jan 11 11:32:46 2019	(r342937)
@@ -228,7 +228,7 @@ cpu_thread_alloc(struct thread *td)
 	td->td_pcb = (struct pcb *)(td->td_kstack +
 	    td->td_kstack_pages * PAGE_SIZE) - 1;
 	td->td_frame = (struct trapframe *)STACKALIGN(
-	    td->td_pcb - 1);
+	    (struct trapframe *)td->td_pcb - 1);
 }
 
 void