svn commit: r293063 - head/sys/arm/arm

[Ian Lepore]

Author: ian
Date: Sat Jan  2 22:31:14 2016
New Revision: 293063
URL: https://svnweb.freebsd.org/changeset/base/293063

Log:
  Work around problems that happen when there is ram at the end of the
  physical address space.

Modified:
  head/sys/arm/arm/physmem.c

Modified: head/sys/arm/arm/physmem.c
==============================================================================
--- head/sys/arm/arm/physmem.c	Sat Jan  2 22:04:37 2016	(r293062)
+++ head/sys/arm/arm/physmem.c	Sat Jan  2 22:31:14 2016	(r293063)
@@ -280,10 +280,24 @@ arm_physmem_hardware_region(vm_paddr_t p
 	/*
 	 * Filter out the page at PA 0x00000000.  The VM can't handle it, as
 	 * pmap_extract() == 0 means failure.
+	 *
+	 * Also filter out the page at the end of the physical address space --
+	 * if addr is non-zero and addr+size is zero that means we wrapped to
+	 * the next byte beyond what vm_paddr_t can express.  The calculations
+	 * in vm_page_startup() are going to have the same problem, so just work
+	 * around it by leaving the last page out.
+	 *
+	 * XXX This just in:  subtract out a whole megabyte, not just 1 page.
+	 * Reducing the size by anything less than 1MB results in a NULL pointer
+	 * deref in _vm_map_lock_read() very early in startup.  Better to give
+	 * up a whole megabyte than leave some folks with an unusable system
+	 * while we investigate.
 	 */
 	if (pa == 0) {
 		pa  = PAGE_SIZE;
 		sz -= PAGE_SIZE;
+	} else if (pa + sz == 0) {
+		sz -= 1024 * 1024;
 	}
 
 	/*